IPAS Pro
IPAS CO+
User Manual
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Table of Contents . . . iii
Chapter 1
The IPAS System . . . 1
Introduction . . . 1
Chapter 2
Installation and Configuration . . . 3
System Requirements . . . . 3
Installation . . . 3
License setup . . . 3
Introduction . . . 3
License server setup . . . 4
Application machine setup . . . 7
Configuration of Processor . . . 11
Chapter 3
Getting Started . . . 13
Starting IPAS Pro . . . 13
Launching IPAS Pro . . . . 13
Starting a New IPAS Project . . . 15
The New Project Dialog . . . 15
Chapter 4
IPAS Pro Processing . . . 17
Processing Options . . . 17
Processing Options - IMU Data . . . 18
Processing Options - Using Pre-extracted Data . . . 22
Processing Options - GNSS Data . . . 23
Processing Options - Processor . . . 25
IPAS Pro Processing . . . . 31
Analyzing Data . . . 35
Processed Data Plots . . . 35
Raw Data Plots . . . 37
Real-time Solution Plots . . . 42
Residual Analysis . . . 43
Event Overlay . . . 45
Chapter 5
IPAS PPP . . . 51
IPAS PPP Introduction . . . . 51
Background on precise orbit and precise clock corrections . . . 52
IPAS PPP Installation and Configuration . . . 53
System Requirements . . . 53
Installation . . . 53
Licensing . . . 53
IPAS PPP Processing . . . 54
Step One: Data Preparation . . . 54
Step Two: Data Processing . . . 60
Step Three: Solution Plotting and Quality Check . . . 63
Step Four: Export ASCII solution file . . . 70
Chapter 6
IPAS CO+ . . . 73
Installation . . . 73
License Configuration . . . 73
Introduction to IPAS CO+ . . . 73
Misalignment Angle Calculation . . . 74
Automated Misalignment Calculation . . . 74
Misalignment Calculation with External AT Solution . . . 86
Transform Solution . . . 89
Point File Transform . . . 91
Open and Save . . . 92
Appendix A
GNSS Input Format . . . 93
Appendix B
IPAS CO+ File Format Descriptions . . . 95
Camera Event File . . . 95
Photo ID File . . . 95
AT Files . . . 95
IXYZOPK Format AT File . . . 95
ORIMA PATB AT File . . . 96
Output Files . . . 96
Appendix C
APM setting file Description . . . 101
The IPAS System
Introduction
IPAS (Inertial Position and Attitude System) is an integrated georeferencing system developed by Leica Geosystems AG. It rigorously integrates raw data from a high accuracy GNSS receiver with the raw data from an Inertial Measurement Unit (IMU) using a Kalman filter and outputs position, velocity and attitude data at a high rate.The following figure illustrates the components of a IPAS20 System.
Figure 1-1: IPAS20 System Components
IPAS Pro is a software package that post-processes IMU data together with GNSS data. It provides interfaces for the import and display of the raw data, the post-processing configuration setup, processing of GPS/IMU data,as well as the display and analysis of final computed solutions.
This manual describes how to use the IPAS Pro software.
Where to get assistance and training
Please be aware, that for a complete understanding of the functionality and operation of the system it is necessary to participate in a IPAS20 product training and maintenance course For assistance and training courses please contact your local Leica Geosystems subsidiary or representative.
Headquarter
Internet http://www.leica-geosystems.com
Contact Leica Geosystems AG Business Unit Digital Imaging Heinrich-Wild-Strasse 9435 Heerbrugg Switzerland e-mail: [email protected] Phone: + 41 71 727 3131 Fax: + 41 71 727 4674
Installation and Configuration
System
Requirements
IPAS Pro is a software package that runs under the Microsoft Windows family of operating systems. Basic system requirements are the following:
• IBM PC-compatible computer,
• Windows 2000 or XP Operating Systems, • 128MB or greater RAM,
• 10GB or greater free disk space. Larger disk space is recommended.
Installation
To install IPAS Pro software, double-click the setup.exe file on the IPAS Pro DVD. Follow the instruction provided by the installation program.License setup
Introduction Starting from version 2.0 Leica IPAS Pro and IPAS CO use Leica Geosystems (LGS) FlexNet
licensing.
Entitlements and Activation
With ordering a software product, customer gets an entitlement certificate with an Entitlement-Id.
The Entitlement-Id is the key to the license(s) of a product. It must be entered during the license activation at customer site.
For the license activation user’s computer must be connected to internet.
All issued licenses must be activated on the client license server computer. That means the target machine must be connected online to the FlexNet Operations (FNO) license server at Leica Geosystems through internet for getting the license. The license information is stored in a trusted storage on the client's computer.
Return to FNO function should be used also for expired evaluation licenses.
License Models
There are two major types of models - node-locked and floating licenses. Node-locked license model is used for a fixed license on a single computer, whereas floating license model is used for sharing licenses between different users. The number of concurrent users is defined by the number of available licenses.
IPAS software uses floating licenses.
License Checking
For checking a license, a running application program has to checkout / check-in the corresponding feature(s). The license is searched first in the local trusted storage at the application machine and then on the defined local license servers i.e. on the computer on which the user has activated the licenses by inserting the Entitlement Id(-s).
Application computers using floating licenses must stay connected online to a local license server.
The borrowing of a license (temporary transfer of a single license from the license server to a computer) allows the offline usage of the license for a given period of time. After use, it has to be returned to the floating server; otherwise it expires automatically after ending of the borrowing time.
For using floating licenses in a single computer environment the computer has to be set up for local license server and for application machine.
Licensing software
LGS FlexNet uses:
• on local license server - Client License Manager (CLM) Server SW - (clm_server_package.exe)
• on application machine - Leica License Manager (LLM) SW - (LLM_Installer.exe)
For using ERDAS FlexNet licenses ERDAS-FlexNet_Licensing.exe has to be installed to a local license server. IPAS ABS license, which is required for Leica IPAS CO+ functionality, uses Erdas FlexNet licensing.
1. Install clm_server_package.exe to the local license server. Follow the instruction provided by the installation program.
2. It is recommended to configure the license server for faster return of license features to the free pool with specifying the idle timeout time.
For this configuration step:
• Open the license server option file lgs.opt, located in the servers installation folder (usually C:\Program Files (x86)\Common Files\Leica Geosystems\License-Server\), in text editor. • Add the line TIMEOUTALL 900 to specify the idle timeout for all features, returning it to the free pool for use by another user. 900 seconds is the minimum time system allows. The license server option file lgs.opt should look as follows:
=====
DEBUGLOG lgs.log NOLOG IN
TIMEOUTALL 900
=====
3. Open the CLM Admin Server SW and activate the licenses by entering the Entitlement Id.
For the license activation user’s local license server computer must be connected to internet.
Figure 2-1: Enter Entitlement Id
Click ‘View Licenses in use’ in order to see the activated licenses.
Use ‘Return licenses’ function from ‘View Installed Licenses’ menu in case the rehosting of the licenses to another local license server is intended.
IPAS ABS license setup
IPAS ABS license, which is required for Leica IPAS CO+ Aerial Triangulation funtionality,
uses Erdas FlexNet license server provided with ERDAS-FlexNet_Licensing.exe.
ERDAS-FlexNet_Licensing.exe has to be installed to the local license server.
Application machine setup
Application machine is the workstation with IPAS Pro installation.
1. Install the LLM_License_Installer.exe to the application machine. Follow the instruction provided by the installation program.
2. Open the LLM tool and go to ‘Config’ window for defining from which license server the LGS and ERDAS licenses are used. Browse to or type in the server name. Click ‘Add’ for adding the license server to the list. Click ‘Save’.
In case the whole setup is done with a single workstation and the application machine is acting also as license server then type in 'localhost'.
Figure 2-4: View Floating Licenses
Node Locked Licenses
Leica IPAS Pro and IPAS CO use solely the Floating License model - thus handling of Node Locked Licenses is not the subject for IPAS software.
LLM offers ability to handle Node Locked Licenses.
In order to activate the Node Locked licenses go to ‘Node Locked Licenses’ window, enter the Entitlement ID and click ‘Activate’.
For the license activation user’s computer must be connected to internet. Click ‘Refresh’ for viewing the available node lock licenses.
In order to Return the activated node lock license to FNO pick the license from the list and click ‘Return’. License Return operation requires internet access.
Figure 2-5: Node Locked Licenses
Borrow Floating Licenses
LLM tool allows to Borrow the Floating Licenses from the local license server in order to make the licenses available in application machine(s) for the cases when the network connection between the local server and the application machine will not be available.
Highlight in the list the license to be borrowed. Set the intended number of days and click ‘Borrow’.
License will be returned automatically once the number of the borrowing days has passed. User can return the license earlier by highlighting the borrowed license and clicking ‘Return’. Application machine has to be connected to the local license server for Borrow and Return operation.
Configuration of
Processor
IPAS Pro consists of two main parts: the user interface and the processor kernel. The location of the processor kernel is automatically specified during the IPAS Pro installation process. However it can be changed. To specify a different kernel location, select Tools -> Config Options from the IPAS Pro menu bar. The following dialog allows you to specify the location of the processor kernel.
This dialog also allows the user to specify the locations for IPAS CO and IPAS PPP processor.
Getting Started
Starting IPAS Pro
This chapter provides you with concise descriptions of the functions and utilities of the IPAS Pro software and describes a general procedure used in the GPS/IMU processing.Launching IPAS
Pro
To start the program, double-click on the IPAS Pro icon or its shortcut. After the program is invoked, the splash screen is displayed:
Figure 3-1: The IPAS Pro Startup Splash Screen
Figure 3-2: The Open Project Dialog
The Project field of the dialog displays the location of your IPAS Pro project file. Click the
Browse button to the right to navigate to the location of your project file.
The Recent Projects window displays the recent IPAS post processor projects that have been used. Up to five projects may be displayed. The projects that cannot be found anymore are displayed in red. If your project is not located in the recent project window, click the Browse
button to navigate to it.
When a existing project is opened, if the directory path for any of the data files (IMU data file, GNSS data file, etc) is changed, then a dialog window will be displayed to prompt the user that the file does not exist in that directory as saved in the project file and try to detect whether it exists or not under the current directory where the project file is opened currently. Figure 3-3 shows an example where the IPAS Pro project was copied from Z:\IPAS20_TestData directory to E:\IPAS20_TestData directory. Any file which does not exist in any directory will be displayed in red color. Beside each file, a browse button allows the user to select individual directory for each file. The user can press Continue with Change button to continue so that all new project directory will be saved, or press Continue without Change so that the original directory structure will be maintained, or Cancel to go back to the IPAS Pro menu. This function allows the user to change all the project structure at one window when an entire project is copied into a new directory.
Figure 3-3: The Project File Directory Change Dialog
The New button allows you to create a new IPAS Pro project. This is discussed in the Create A New Project section.
Starting a New
IPAS Project
You can start a new project by clicking the New button on the Open Project dialog. The New Project dialog opens.
Figure 3-4: New Project Dialog
The New Project Dialog
The location of the IPAS Pro project file can be specified by clicking on the browse (...) button and navigating to the desired folder on your computer, or by typing the path of the project directly into the Project Name box. Click the Create button to create a new IPAS Pro project and open the IPAS Pro processing screen.
In the top left-hand corner of the IPAS Pro window, there is a toolbar with three icons.
With this toolbar, you can create a New IPAS Pro project, Open an existing IPAS Pro project, and Save a current project. This toolbar can be accessed at any time when IPAS Pro is active.
IPAS Pro Processing
IPAS Pro uses rigorous Kalman filtering to determine the optimal solution for position, velocity and attitude of an airborne mapping and remote sensing vehicle using GNSS and IMU data. The quality of its solution relies heavily on the quality of the collected IMU and GNSS data. Before processing, the physical references such as the GNSS antenna lever arms and the gimbal frame to IMU reference frame lever arms should be known with great accuracy to reduce the possibility of errors in the processing.
Processing
Options
After creating a new IPAS Pro post processor project, the following dialog opens. This dialog is the main processing area of the IPAS Pro post processor.
Figure 4-1: The IPAS Pro Processing Dialog
This is where you specify raw IMU and GPS data locations, processing options, start the processing, and invoke the plotting functions.
The Project field shows you the projects that are loaded and the location of the IPAS Pro project file.
It is a good practice to organize a project according to the following directory structure:
Project_Directory
... Extract - for extracted data
... Ground - for reference GNSS receiver data ... GNSS - for processed GNSS data
... Raw - for raw IPAS data
... Proc - for processed and final solution files Processing Options -
IMU Data
The Data fields allow you to specify the location of the IMU data file and GNSS data file.
Figure 4-3: Processing Options Data Field
In order for IPAS Pro to function properly, it requires the raw data files from the IPAS system as well as a post-processed GNSS solution file. Clicking the Raw Data button opens the IPAS Pro IMU Data Selection dialog.
Figure 4-4: IPAS Pro IMU Data Selection Dialog
To specify the location of the raw data file, click the Data File browse button (...). Usually, the raw data is located in the <flight_name>/raw directory. Where <flight_name> is the name of the directory you create to contain all of the flight data.
To specify the location of the extracted files, click the Extract Directory browse button (...). A directory named extract is created automatically by IPAS Pro.
Click the Options button to open the IPAS Extract Options dialog. This dialog allows you to select the data to be extracted. If you intend to extract the real-time solution as well as raw measurements, check the RT GNSS solution and RT Navigation Solution check boxes.
To start extracting, click on the Extract button. IPAS Pro reads the raw data file and extracts the data to the folder specified in the Extract Directory field. If the folder does not exist, it will be created automatically.
When extracting multiple raw data files, only the first file needs to be specified, IPAS Pro automatically moves to next files and extracts all raw data files in sequence.
A progress meter opens to inform you of the percentage completed during the extraction process.
Figure 4-6: Raw Data Extraction Progress meter
IPAS Pro informs you when the extraction is complete. The duration of the extraction process depends on the size of the GNSS/IMU data set and computer processing power.
IPAS Pro separates the raw data into up to several separate files. Each file corresponds to a different type of data. A brief description of each file is listed below:
• *.GMB Gimbal data collected during the mission, • *.GPS GNSS data collected during the mission, • *.IMU IMU data collected during the mission,
• *.TM User time file. This file is generated during the extraction process and specific to the Leica ADS40 Airborne Digital Camera system used to collect the imagery.
• *_*. Evt - Input Event File. Each input event will be stored in a separate event file. The file
prefix will be the prefix from the raw data file name. For example,
20050624100053_FlightData_1.evt is the event file from channel one event.
• *_out_*.Evt - Output Event File. Each output event is also stored in a separate event file.
The prefix of the file will be the prefix of the raw data file. • *.RTG - Real-time GNSS solution file.
• *.RNV - Real-time GNSS/IMU integrated IPAS solution file.
Figure 4-7: Extracted File Types
All messages are written into an extraction log file. During the extraction process, the integrity of the files, including their time gaps, is checked and reported in both the message window and the extraction log file.
The resultant file sizes depend on the length of each mission. Generally, *.RNV and *.IMU files are the largest of the four extracted files.
Once the extraction is complete, the IPAS Pro IMU Data Selection dialog looks like the following figure.
• system version, • lever arms, • IMU data file, • GNSS data file, • gimbal data file, • TM file, and
• Gap checking for IMU data, gimbal data and raw GNSS data.
• Gap checking and repairing for TM file. If the gap is smaller than 50 milliseconds, then the gap will be repaired and additional TM records will be interpolated and fill the gaps. If the gap is larger than 50 milliseconds, then a error message will be displayed in the extract window and saved in the extract log file.
Clicking on Save returns you to the IPAS Pro Processing dialog. The file names used in this dialog are automatically saved into the project file.
Some settings in the raw data file, including lever arms, are automatically written to the configuration settings in the project file so that you only need to verify the lever arm values.
Processing Options - Using Pre-extracted Data
IPAS Pro also has the ability to allow you to use pre-extracted GNSS/IMU data in processing. The pre-extracted data must be based on the IPAS Pro extraction file formats and is not interchangeable with other GPS/IMU processing extraction formats.
To verify that your extraction file format is correct, select the file and then click the Check Files
button.
The process for using pre-extracted data is very similar to processing raw data. To begin, click the Raw Data button on the IPAS Pro Processing dialog to open the IPAS Pro IMU Data Selection dialog. Locate the IMU button in the dialog:
Figure 4-9: IMU File Selection Portion of IMU Data Selection Dialog
Click on the IMU button and navigate to the location of the extracted IMU data. Once you have located it, click on the Open button to load the IMU data in IPAS Pro. IPAS Pro will
Processing Options - GNSS Data
Post-processed GNSS solutions are needed in order for IPAS Pro to produce accurate georeferenced results. Many kinds of post-processing software are available, but the software that you are using must be able to export the processed GNSS data to an ASCII file. IPAS Pro post processor requires the input post-processed GNSS file to be in a special format, which is defined in Appendix A “GNSS Input Format”. The IPAS Pro Processing dialog should look like the following:
Figure 4-10: IPAS Pro Processing Dialog After Raw Data Import
Click the GNSS button to open the IPAS Pro GNSS dialog:
IPAS Pro allows you to launch your preferred GNSS processing software from within IPAS Pro. In order to do this, you must first select your preferred GNSS processing program by clicking on the browse button and navigating to the location of the executable file for your GNSS post processing software on your computer. Once this file is selected, click the Launch button to launch the GNSS post processor. For the purpose of this help file, GrafNav from NovAtel Inc. is used as the default GNSS Post-Processing software.
After completing the GNSS processing in GrafNav, a ASCII file is exported using the profile created by IPAS Pro. Select this ASCII file in the ASCII GNSS Solution File field and click on Import File button, this GNSS file will be converted into binary format file used by IPAS Pro and displayed in the IPAS Binary GNSS File field.
Precise Point Positioning (PPP) can also be used to process the GPS data when a reference receiver is not present. To start PPP, click on the Start button under the Precise Point Positioning, follow Chapter 5 for PPP processing. The PPP software will generate the binary GPS Solution file required by IPAS Pro automatically and display the file name in the IPAS Binary GPS File field.
After selecting the proper post-processed ASCII GNSS file, the window should appear similar to the following:
Figure 4-12: IPAS Pro GNSS Dialog After GNSS File Selection
Click the Import File button to convert the ASCII file into a binary file specific to the processing needs of IPAS Pro. A progress meter reports on the progress of the ASCII import.
Click the Close button to return to the IPAS Pro GNSS dialog. Click the OK button to finish the GNSS portion of the IPAS Pro project setup.
Processing Options - Processor
The processing of the GNSS and IMU data can commence once the raw IMU data and post-processed GNSS data have been loaded into IPAS Pro. A properly completed dialog should look similar to the following figure:
Figure 4-14: IPAS Pro Processing Dialog After Raw and GPS Data Imports
Click the Configure button to open the Processor Configuration dialog.
This is the initial page that provides you with setup of the processor configuration. It is important to note the time ranges between the GNSS file and IMU file to ensure that each time range overlaps with one or the other. The time ranges are displayed in GPS week seconds after each file type to the right of the file name. The time range for IMU data has to lie within the time range of the GNSS data.
IPAS Pro will automatically process all data within GNSS and IMU data time window. However, user can change the data time. To set the processing time window, uncheck the All Data check box, and set the GPS week seconds into the corresponding edit boxes.
In this configuration page, you can also select a different output directory. The output format is
IPAS Pro.
After the processing the File Converter Tool can be used in order to convert an IPAS Solution File into a SBET file or into an ASCII file, or convert a SBET file into an IPAS solution file or an ASCII file. Select Tools -> File Converter from the IPAS Pro menu bar to launch File Converter.
Figure 4-16: File Converter Tool Dialog
Processing Options - Processor - GNSS
Click the GNSS tab of the configuration dialog to verify the GNSS lever arm measurements. Lever arm values are automatically extracted from the raw data file and written to the configuration settings in the project file.
A lever arm can be defined as the three dimensional coordinates of a point with respect to a coordinate frame. In IPAS Pro, all lever arms are measured in the reference frame. The referece frame is usually defined by the mapping or remote sensing unit. For example, with the ADS40, a reference frame is defined with the PAV30 mount, with the origin of the reference frame at the PAV30 center while x-axis points to forward, z-axis points downward and y-axis points to right to form a right-hand coordinate system. Usually two lever arms are required to measure in the field when IPAS10 is istalled, one is the GNSS antenna while the other one is the IMU center. Those values are measured during the installation and entered into the IPAS10 system through the IPAS Controller. A field technician should verify the lever arm values whenever there is a change of installation related to reference sensor, IMU, or GNSS antenna.
For each set of flight data to be processed, the values of the lever arms should be verified against the published values provided by the hardware installer or system operator.
Figure 4-17: GNSS Lever Arm Dialog
This dialog is used to verify and correct, if necessary, the GNSS lever arm in the reference frame. As illustrated in the above figure, the lever arm values are measured along the x, y, and z axes of the reference frame from the center of the reference frame to the GNSS antenna phase center.
Processing Options - Processor - IMU
Click the IMU tab to enter the IMU lever arm and boresight measurements.
Figure 4-18: IMU settings Dialog
This configuration page is where you verify and correct, if necessary, the IMU lever arm and boresight angle measurements. As illustrated in the above figure, the IMU lever arm is measured along the x, y, and z axes of the reference frame from the center of reference frame to the IMU center. The boresight angles are also measured as the rotation angles of IMU body frame relative to the reference frame.
IMU Latency value gets detected automatically according to the IPAS system IMU type and is shown in the IMU Latency window as grayed out. Editing of the latency value is normally not required.
When a NUS5 IMU is detected, a data filter list box is displayed. A default filter file is supplied with IPAS Pro to use with all NUS5 systems. The other options for the user would be to select ‘Do not Apply Filter’ or ‘Browse for Filter File’. Leica Geosystems support provides the specific filter files only for the certain NUS5 IMU-s.
Processing Options - Processor - Aircraft
Click the Aircraft tab to enter the aircraft boresight settings.
Processing Options - Processor - Advanced
Click the Advanced tab to enter the advanced processing settings.
Figure 4-20: Advanced settings Dialog
Three types of attitude initialization approaches can be selected from this page:
• Use Static/In-Motion Alignment. This is the default approach. IPAS Pro will automatically compute the initial roll, pitch and heading.
• Use real-time Solution. Attitude computed from real-time IPAS solution are used to intialize the IPAS Pro Kalman filtering.
• User Input Attitude. User can set initial roll, pitch and heading at a specified GPS week seconds. IPAS Pro will start the Kalman filter based on this initial setting.
IPAS Pro
Processing
Once setup is completed, click the GO button to open the Start Processing dialog. The Start Processing dialog allows you to verify that the incorporated GNSS/IMU data is correct and that their time windows overlap.
Figure 4-21: Start Processing Dialog
Click the Output File browse button to specify the location of the output file. By default, all overlapped data is processed. However, you can also specify different start time and end time in GPS week seconds. IPAS Pro will not function properly if the Data Time period does not lie within the time ranges of the GNSS and IMU data sets. Click the Start button to begin processing. A progress meter displays the progress of the job as well as the estimated time of completion.
Figure 4-22: Processing Progress Dialog
Click the >>> button to open the Log window which provides a detailed description of the state of the current progress. Click the <<< button to close the Log window.
Figure 4-23: Expanded Processing Progress Dialog
Once processing is finished, the progress meter looks like this:
Figure 4-24: Finished Processing Progress Dialog
Click the Done button to close the dialog and return to the main IPAS Pro post processor processing dialog. IPAS Pro post processor outputs the processing files into the proc sub-directory under the project sub-directory by default.
Those values are listed in the processing log file for further analysis. A example for this section of log file is given in the following figure.
Figure 4-25: Example of the Portion of Log File with Error Statistics
To analysis more on the statistics of the position residuals and the lever arm values, please refer to the Residual Analysis under Analyzing Data section.
With respect to the statistics of the estimated IMU sensor errors, including accelerometer biases, accelerometer scale factor errors, gyro biases and gyro scale factor errors, these values shall be evaluated against the threshold listed in the following table for each type of IMU used to acquire this dataset. If the estimate IMU sensor error values are larger than the specifications, then other aspects of the processing results, including the residual errors, measurement rejections shall be analysd. If this situation repeatly happens to one system, Leica support shall be contacted and IMU health shall be analysed by Leica support.
Table 4-1: Threshold of IMU Sensor Errors
iIMU-FSAS LN-200 33BM61 MicroIRS
Gyro bias (deg/h) 3.0 2.0 5.0 0.25
Gyro scale factor error (PPM)
1000 1000 500 100
Accelerometer
Note: Only if the estimated IMU sensor errors repeatedly exceeds the specified thresholds, and all other quality analysis are passed, then the IMU health shall be checked. If the estimated IMU sensor errors exceeds the threshold for only one dataset, that can be caused by other factor, and it does not necessarily mean that the IMU is not healthy.
Analyzing Data
Post processing analysis is very important in GNSS/IMU processing because it allows you to visually view and analyze the raw data and processed results. The following data can be visually plotted:• raw IMU data,
• real-time GNSS and GNSS/IMU solutions, • processed GNSS Data,
• processed results from IPAS Pro post processor,
• gimbal data - view and assess the processed position, velocity, attitude, and corresponding accuracies.
The processed results can also be compared against each other and their differences can be plotted. Plots are accessed by clicking the Graphs button in the Analyze section of the IPAS Pro Processing dialog.
Processed Data Plots This portion of the plot shows the processed results and their corresponding standard deviations. These plots may be viewed from several different perspectives thus allowing you to thoroughly analyze the quality of the results.
If the graph dialog is invoked from a processed project, then the processed result from that project is loaded with the North-East plot displayed by default.
Figure 4-26: Available Processed Data Plots
You can zoom in and out of each plot by dragging a box around the desired area using the left mouse button. Click the right mouse button to return the view to the general overview. Those plots with auxiliary standard deviation (SD) plots support synchronized zooming. For example, zooming in the Roll plot automatically zooms to the corresponding area (with respect to time) in the Roll SD plot.
Any IPAS Pro file can be loaded for plotting by clicking the Result File button. Once the file is specified, it is loaded automatically and displayed with the North-East plot by default. The following plots are available for the IPAS Pro processed results:
• North-East: North and East plot, corresponding to vehicle trajectory, • North-Elevation: North and elevation plot,
• East-Elevation: East and elevation plot,
• Heading-Time: Heading verus GPS Time,
• X velocity-Time: North velocity versus GPS Time, • Y velocity-Time: East Velocity versus GPS Time, • Z velocity-Time: Vertical velocity versus GPS Time.
Raw Data Plots Click the Raw Data tab on the left side of the dialog to display the options for plotting raw IMU, GPS and Gimbal data as shown in the following figure:
IMU Raw data
Click on X Gyro Rate, Y Gyro Rate, or Z Gyro Rate to display the raw gyro data in degrees/second.
Click on the X Acceleration Rate, Y Acceleration Rate, or Z Acceleration Rate to display the raw accelerometer data in meter/second2. The following is an example of X acceleration rate.
GNSS data
On the GNSS file tab, following plots can be viewed: • North-East Latitude-Longitude 2D trajectory plot, • North-Elevation Latitude-Height profile,
• East-Elevation Longitude-Height profile,
• Elevation-Time Elevation profile versus GPS Time, • X Velocity - Time North velocity versus GPS Time, • Y Velocity - Time East velocity versus GPS Time, • Z Velocity - Time Up velocity versus GPS Time.
The following figure is the North-East plot which shows the 2D trajectory.
Gimbal Raw data
Under the Gimbal file tab, the following plots can be viewed: • Roll - Time Roll gimbal value versus GPS Time, • Pitch - Time Pitch gimbal value versus GPS Time, • Heading - Time Heading gimbal value versus GPS Time. The following figure is a plot of roll gimbal value versus GPS time.
Real-time Solution Plots
Click on the Real-Time Data tab on the left side of the dialog to display the options for plotting real-time GNSS solution and real-time GNSS/IMU solution plots.
The following plots are available for real-time GNSS solution: • North-East Latitude-Longitude 2D trajectory plot, • North-Elevation Latitude-Height profile,
• East-Elevation Longitude-Height profile,
• Elevation-Time Elevation profile versus GPS Time, • X Velocity - Time North velocity versus GPS Time, • Y Velocity - Time East velocity versus GPS Time, • Z Velocity - Time Up velocity versus GPS Time.
The following plots are available for real-time GNSS/IMU Solution: • North-East: North and East plot, corresponding to vehicle trajectory, • North-Elevation: North and elevation plot,
• East-Elevation: North and elevation plot,
• Elevation-Time: Elevation versus GPS Time in week seconds, • Roll-Time: Roll versus GPS Time,
• Pitch-Time: Pitch versus GPS Time, • Heading-Time: Heading verus GPS Time, • X velocity-Time: North velocity versus GPS time, • Y velocity-Time: East Velocity versus GPS time, • Z velocity-Time: Vertical velocity versus GPS time.
Residual Analysis This function allows you to plot the estimated level arm value as well as the measurement residual error as estimated by the Kalman filter. The following information can be plotted from this selection:
• GNSS Lever Arm X GNSS antenna lever arm in x-axis, • GNSS Lever Arm Y GNSS antenna lever arm in y-axis, • GNSS Lever Arm Z GNSS antenna lever arm in z-axis,
• Position Residual X Estimated residual for GNSS solution in x-axis (latitude) together with the input standard deviation,
• Position Residual Y Estimated residual for GNSS solution in y-axis (longitude) together with the input standard deviation,
• Position Residual Z Estimated residual for GNSS solution in z-axis (height) together with the input standard deviation.
The following figure demonstrates the input and the estimated lever arm values. The blue line is the estimated lever arm value while the green line is the input lever arm value. The input lever arm is always a constant value. The estimated value is usually a constant as well. If the estimated lever arm is not a constant, it usually indicates that there may be issues with this data which needs further investigation.
If the input lever arm is significant different from the true lever arm, it may take a few iterations before IPAS Pro can converge to the correct lever arm values. In this case, the estimated lever arm values should be used as the input values and IPAS Pro processing should be repeated. Note: If lever arm estimation is intended, a trajectory pattern for calibration shall be flown.
The following figure plots position residuals estimated from Kalman filter. The blue line shows the residuals from GNSS solution while the green lines show the positive and negative one-sigma standard deviation values of the input GNSS solution. In general, the residuals shall be within the bounds of the standard deviations. If the residuals go out of bounds of the standard deviation, it usually indicates there are issues with the data set which requires further
investigations. Possible causes are input lever arm values are significantly wrong, IMU data gaps, GNSS data gaps, quality issue from GNSS solution, wrong configuration parameters, IMU out of specifications etc.
Event Overlay IPAS Pro plot function allows you to overlay the evenet mark on the trajectory and other plots. Check the Event check box as shown in the following figure, click on the Event File button to browse the event id file (*.evt file) created during the extraction process. Each event will be displayed on the plot as a gray dot. Check the Show Id check box will display the event ID name on the plot as the same time.
Figure 4-35: Events with ID name Overlayed on the Trajectory
Make Differences This function allows you to compare two solution files between different runs of IPAS Pro processing, or between a IPAS Pro solution file and a current ADS40/ALS50 solution file, or between IPAS real-time solution file and IPAS Pro solution file.
Click the Compare Data button to display the options to make a difference file or to plot a difference file.
Create A Difference file
If a difference file does not exist, then you can make a new one by clicking on the Make File
button to open the Make Difference Plot File dialog:
Figure 4-37: Make Difference Plot File
Use the browse buttons (...) to select a source file and destination file. The source file can be in IPAS Pro output format or in SBET output format. Once the files are specified, click the Make File button to make the difference file. The destination file is created with IPAS calculated differences between the two solution files.
Plot Difference File
Once the difference file is made, it is automatically loaded and the north differences are displayed by default. You can view another difference file by clicking on Difference File and loading the file.
The following differences can be viewed: • dNorth Latitude differences, • dEast Longitude differences, • dElevation Height differences, • dRoll Roll differences, • dPitch Pitch differences, • dHeading Heading differences, • dXVelocity North velocity differences, • dYVelocity East velocity differences, • dZVelocity Upward velocity differences.
Figure 4-38: Latitude Differences Between an IPAS Pro Solution File and a Real-time Solution File
IPAS PPP
IPAS PPP, which stands for Inertial Position and Attitude System (IPAS) Precise Point Positioning (PPP), is a post-processing software package developed by Leica Geosystems AG for high accuracy position and velocity determination using data from a single Global Positioning System (GPS) receiver.
IPAS PPP
Introduction
Through the processing of GPS satellite signals, along with precise satellite orbit (hereinafter called precise orbit or just called orbit) and precise satellite clock corrections (hereinafter called precise clock or just called clock) information, the IPAS PPP software can produce high accuracy position and velocity results for kinematic objects using the observations from a single GPS receiver. The most advantageous aspects of using this product are: (1) eliminating the requirement of a reference receiver, as in traditional double-differencing positioning technique, (2) producing high accuracy position and velocity solutions and (3) the use of this product is straightforward, requiring minimum user interaction and a priori experience.
In order to obtain the best position and velocity accuracy for which this product has been developed, several prerequisites should be met:
(1) Geodetic-grade dual-frequency GPS receiver and antenna should be used to collect the observation data. Doppler observations are required in order to obtain velocity solution in addition to the position solution.
(2) Precise orbit and precise satellite clock information should be supplied when running this software. High-rate (e.g. 30-second interval) satellite clock corrections is preferred to low-rate ones (e.g. 5-minute interval). The IPAS PPP software can retrieve this data for the user.
(3) GPS observation data should be continuously collected for a long enough period of duration. The recommended minimum observation period is 60 minutes. In addition, it is suggested that the GPS signal tracking cutoff angle shall be set to smaller than 5 degrees.
Background on precise orbit and precise clock corrections
International GNSS (Global Navigation Satellite System) Service (IGS) offers two products, namely precise orbit data and precise clock correction data, to the GNSS community for better position and navigation accuracy. The typical names for precise orbit and precise clock correction files are "igswwwwd.sp3.Z" (or igswwww.sp3c.Z if the precise orbit file is in sp3c format) and "igswwwwd.clk.Z", respectively, where "igs" represents the agency that generates the product files, "wwww" represents the 4-digital GPS week number and the "d" represents the day in the GPS week and ".Z" is the suffix of a compressed file. The interval of the precise orbit data is usually 15 minutes while the interval for precise clock correction data is 5 minutes.
The IGS provides different categories of products based on the product's availability latency. One category is the FINAL product, which has a latency of about 13 days after the GPS observation. Another is the RAPID product, which has a latency of about 17 hours after the GPS observation. To distinguish the RAPID products from the FINAL product, the IGS uses the names "igrwwwwd.sp3.Z (or igrwwwwd.sp3c.Z) for precise orbit file and "igrwwwwd.clk.Z" for precise clock file. Both categories of products have same format except their different latencies and accuracies. FINAL category products generally have better accuracy and reliability than the RAPID ones.
To use the FINAL category products in IPAS PPP for the best accuracy, it is advised to plan your flight missions in advance to make sure that you collect the mission data at least 13 days before your project deadline.
Under the organization of International GNSS Service, there are several data analysis centers, such as Jet Propulsion Laboratory (JPL), Center for Orbit Determination in Europe (CODE), National Geodetic Survey (NGS), etc. These analysis centers also generate their own precise orbit and precise clock corrections products. The products from those analysis centers have the same format as the IGS products. However, some analysis centers, such as JPL and CODE, produce precise clock corrections at a higher rate (30-second interval) than the IGS ones (5-minute interval). IPAS PPP recommends the use of high-rate precise clock data files whenever possible. Unlike the IGS organization, the individual data analysis centers do not generate RAPID category precise orbit (clock) data files. They produce precise orbit and precise clock corrections data only in FINAL category.
NOTE: In order to produce consistent IPAS PPP solutions, the precise orbit and precise clock corrections used for GPS data processing should come from the same agency.
For example, if the precise clock corrections data are generated by JPL, the precise orbit data used for IPAS PPP should also come from JPL. The name convention for the data analysis centers' products is quite similar to the IGS products. For example, JPL products usually have file names as "jpl13984.sp3.Z or jpl13984.sp3c.Z" and "jpl13984.clk.Z" for the precise orbit and precise clock correction files, respectively.
IPAS PPP
Installation and
Configuration
System Requirements IPAS PPP is a software package that runs on a PC with Microsoft Windows family of operating
systems. Basic system requirements are: • IBM PC-compatible computer,
• Windows 2000 or XP Operating Systems, • 128MB or greater RAM,
• 100 MB or greater free disk space. Larger disk space is recommended.
Installation IPAS PPP can be installed separately or installed together with IPAS Pro. When IPAS PPP is
installed together with IPAS Pro, please follow the IPAS Pro installation procedure and no additional installation for the IPAS PPP is required. When IPAS PPP is installed separately, the followings steps should be followed:
• Locate the installation file "IPAS_PPP.EXE"
• Double-click on the installation file, following the subsequent installation instructions. Once IPAS PPP is installed, it can be started under "Program Files\Leica Geosystems\IPAS PPP".
Licensing A license is required to run IPAS PPP. A USB dongle that contains the license information will
be provided to the users by Leica Geosystems.
NOTE: In order for the USB dongle to work properly with IPAS PPP software, a SafeNet USB SuperPro/UltraPro driver Version 7.3.0.0 or higher is required.
IPAS PPP
Processing
The use of IPAS PPP software consists of three steps, namely Data Preparation, Data Processing and Solution Plotting with Quality Check. The first step is to prepare the GPS observation data file and precise orbit and precise satellite clock correction data files. The GPS observation data file can be in either NovAtel raw (BINARY) format or RINEX (ASCII) format. If last letter of the GPS data file name is capital 'O' or small case 'o', IPAS PPP will regard the GPS observation data file is in RINEX format. Otherwise, the GPS data file is considered as in NovAtel raw (BINARY) format. The second step is to execute the data processing and obtain position and velocity results. The third step is to plot the IPAS PPP results and check the quality of the results. IPAS PPP also provides a feature to allow the users to convert IPAS GPS solutions to an ASCII format.
Step One: Data Preparation
Once the IPAS PPP software is started, a user interface will be presented with a main program window as shown in Figure 5-1: “IPAS PPP User Interface” .
The data preparation can be described in the following steps:
• Preparing the GPS data file. Clicking on the Data tab, the users will see the screen that
asks the users to specify the location of the GPS data file. When IPAS PPP is used together with IPAS Pro, this GPS data file name will be automatically extracted from the IPAS Pro project file. In the example as shown in Figure 5-2: “Loading GPS data file to IPAS PPP”
the GPS file is "20061026_010813_rover_raw.GPS" and it is stored under the directory "D:/My_Project". This file is in NovAtel raw binary format since its last letter in the file name is "S" not "O" or "o", which indicates RINEX file format is used. Once the file is loaded, the information on the observation starting and ending time will be displayed in the format of GPS week seconds, GPS week number, and the day of the week. In this example, the GPS data collection started at GPS second 349694 in the GPS Week 1398. The Day of Week (DoW) of the starting time is 4 (ie. Thursday in the GPS Week 1398). The GPS data collection stopped at GPS second 356284 in the GPS Week 1398. The Day of Week of the stopping time is 4 (ie. Thursday of the GPS Week 1398). Please note that the GPS second counts from 0 at each week's Sunday 00h:00m:00s.Input the camera event offset time if there is any.
• Preparing the precise orbit and precise clock files. The precise orbit and precise clock
files can be directly imported to IPAS PPP software at this step, if both files are already available in your computer - this means, in case both files have previously been downloaded from the internet or obtained from somewhere else.
Figure 5-3: Loading precise orbit and precise clock data files to IPAS PPP
In most cases, however, the users do not have the precise orbit or precise satellite clock files. In this case, IPAS PPP will help the users automatically download both files from ftp sites. First, pull down the arrow to select one from the multiple ftp sites, as indicated in
Figure 5-4: “Select the internet source of precise orbit and precise clock data files” . In this example, the IGS ftp site is selected.
Figure 5-4: Select the internet source of precise orbit and precise clock data files
It is recommended that precise orbit and clock files from CDDIS ftp site be used whenever available since this site provides precise clock file with 30 seconds interval.
Click the Check Ephemeris Availability button to check what types of precise orbit and precise clock data are available from the particular ftp site that you have just selected. The IPAS PPP will link to that ftp site and check the availabilities for you. As shown in Figure 5-5: “Check the availability and select one type of precise data files”
, two types of precise orbits and clocks are available: final orbit (clock) and rapid orbit (clock), at the IGS ftp site for the date corresponding to the GPS data given in Step
Preparing the GPS data file. By default, the IPAS PPP automatically selects the final
orbit and clock files, because the final precise data have higher accuracies than the rapid data. In this example, the final category of orbit (clock) data files, e.g.
To eliminate the possibility of using different categories precise data files in the data processing, it is recommended to select only one category of precise data files at one time. It is highly recommended that the same type of precise orbit and precise clock data files should be selected. It is always NOT recommended to use mixed type of precise orbit and precise clock data files, e.g. mix final orbit data file with rapid clock data file.
NOTE: The rapid orbit will be available 17 hours after the time of data collection. The final orbit and clock are available 13 days after the data collection.
Figure 5-5: Check the availability and select one type of precise data files
Click the Download button to download both files to the specified directory, after the type of the precise orbit and precise clock data is selected. Under the directory where the GPS file is stored, IPAS PPP automatically creates a directory called "PPP", if it does not exist. The downloaded precise orbit and clock files are stored to the "PPP" directory. In this example, the directory where the GPS file is stored is "D:/My_Project", thus the precise orbit and precise clock data files are stored to "D:/My_Project/PPP". If the downloaded
Figure 5-6: Download and import precise data files to IPAS PPP
After the orbit and clock files are imported, their time span information is extracted and displayed. Make sure the time span covers the time span of the GPS observation data. At this stage GPS data, precise orbit data and precise clock data have all been prepared for IPAS PPP processing. Go to Step Two: Data Processing to continue the processing.
Step Two: Data Processing
By clicking the Process tab, as shown in Figure 5-7: “Process GPS data using IPAS PPP” , the users can start to process the GPS data using IPAS PPP.
Figure 5-7: Process GPS data using IPAS PPP
In the top panel of the screen, a summary of the basic information such as GPS data file name, precise orbit file name, precise clock file name, the start date & time (hereinafter, time always means the seconds in week in GPS time system, unless specifically stated otherwise) and end date & time of each data file are displayed. In this example, the GPS file name is
"20061026_010813_rover_raw.GPS", the precise orbit file name is "igs13984.sp3", and the precise clock file name is "igs13984.clk". The start time and end time for GPS data are 349694 seconds and 356284 seconds, respectively. The start time and end time for precise orbit data are 345600 seconds and 431100 seconds, respectively. The precise clock file has the same start time and end time as the precise orbit file. The date for all the three data files is the 4th day of GPS week 1398.
In the middle panel, there are several options available for user to modify, although the modification is not necessary in most cases.
The first option is the initial coordinate of the GPS receiver. By default, this information is automatically extracted from the GPS data. If the users want to change it, the new values can be entered here. The latitude and longitude are in the format of degree, minute, second. The sign convention for latitude and longitude is that latitude north and longitude east are "+" and that latitude south and longitude west are "-". The unit of height is in meters.
The second option is the start time and end time for processing. By default, the entire GPS data set is processed. If only a portion of the GPS data set rather than the entire data set needs to be processed, the users can specify the start time and end time. The user specified time should not exceed the time span of the GPS data its own.
It is highly recommended that the users process the entire GPS data set in order to achieve the highest possible position and velocity accuracy.
The third option that users can modify is the path and name of the IPAS PPP output file. By default, the output file has the same file name as the GPS data except that its extension is .ppp. The output file is stored by default under the PPP directory.
Clicking on the Start Processing PPP button will start the IPAS PPP processing once all the options are gone through. If the project has not been saved, a window will come up to prompt the users to enter the IPAS PPP project file name, as shown in Figure 5-8: “Save IPAS PPP project information” . If IPAS PPP is started from IPAS Pro, then the IPAS Pro project file will include the IPAS PPP project information. In this case, no window will pop up to ask for the IPAS PPP project name. After the users enter the IPAS PPP project file name and click the Save button, all the information such as: GPS data file name, precise orbit file name, precise clock file name, initial coordinates of the GPS receiver will be saved to the project file.
Meanwhile, the IPAS PPP data processing will start, as indicated in Figure 5-9: “Progress of IPAS PPP data processing” . The GPS data will be processed until it is finished. The data processing can be terminated by clicking the Stop Job button.
Figure 5-9: Progress of IPAS PPP data processing
IPAS PPP processing consists of forward processing, backward processing and refined processing. During these steps, a progress bar indicates the percentage of the data processing which has been completed. If there are important messages, then these will be displayed in the Log window. Log window can be activated by clicking ">>>" button. The log window can be deactivated by clicking on "<<<" button.
Once the data processing is completed, The Stop Job button will automatically change to Done button. The user shall go to 3.3 Step Three to plot the solutions and to check the quality of the
Step Three: Solution Plotting and Quality Check
The checking of the quality of IPAS PPP solution is an important step in the use of the software. In order to make sure the IPAS PPP produces high quality solutions, the users are suggested to check several quality indicators by looking at the graphical plots or examining the numerical results after processing the GPS data. By clicking the Plot Results button as shown in Figure 5-10: “Start quality check” , the users can start the quality check procedure.
Figure 5-10: Start quality check
Specifically, the following steps should be checked:
1. Check the differences between backward and forward solutions
The users plot the differences between the backward and forward solutions for latitude, longitude and height components. Normally, the horizontal differences between backward and forward solutions should be bounded within 0.20 m during the entire period of observation time. Generally, the vertical differences between backward and forward solutions should be within
Shown in Figure 5-11: “Differences between backward and forward solutions” are the backward and forward differences for the example data in this manual. In the figure, the x-axis is GPS time in unit of week seconds and the y-axis is the differences for latitude, longitude and height components in unit of meters. The corresponding standard deviations and RMS of the differences are displayed on the bottom of the plot.
Figure 5-11: Differences between backward and forward solutions
2. Check the statistics of the differences between backward and forward solutions
Generally, both the standard deviation (1 sigma) and root-mean-squares (RMS) for horizontal component should be at the level of less than 0.10 m. For vertical component, both the standard deviation (1 sigma) and root-mean-squares (RMS) should be at the level of less than 0.15 m. The three-dimensional standard deviation (1 sigma) and root-mean-squares (RMS) should be less than 0.20 m. For the example data, the statistics of the differences are shown in Table 5-1: “Statistics of the differences”
3. Check the Backward and Forward Zenith Tropospheric Delay Estimate
The differences between the backward and forward zenith tropospheric delays generally are very small during the entire observation period. The maximum magnitude of the differences is normally about a few centimeters. Under exceptional circumstances, this maximum magnitude might be as large as 0.08 m. The standard deviation and RMS of the differences generally should not exceed 0.02 m.
For the example data of this manual, the differences between forward and backward zenith tropospheric delay are shown in Figure 5-12: “Differences between backward and forward zenith tropospheric delay” , where the standard deviation of the differences is 0.004 m and the RMS of the difference is 0.007 m, the maximum difference is 0.015 m. In the figure the top panel is the magnitudes of the zenith tropospheric delays in backward and forward processing. The bottom panel is showing the differences of the zenith tropospheric delays between the backward and forward processing. The standard deviation and RMS of the differences are displayed in the middle of the plot.
The magnitude of the absolute zenith tropospheric delay is usually in the range of 1.5 ~ 2.5 m. Under no circumstances should this magnitude exceed 3.0 m.
4. Check the DOP Values and Number of Satellites
Under normal conditions, the PDOP, HDOP and VDOP values should not exceed 5.0, 3.0, and 4.0, respectively. If significantly large DOP values are found in the plot, it might indicate that the PPP solution potentially have a problem at those epochs where large DOP values occur. Normally, IPAS PPP should have at least 6 useable satellites for each epoch's data processing. If the number of satellites is less than 6, it might indicate that the PPP solution potentially have a problem at those epochs with less satellites.
Shown in Figure 5-13: “The DOP values and number of satellites” are the DOP values and the number of satellites for the example data set of this manual.
