To begin collecting the first transect, scroll to LOG DATA and hit enter.

3. Hit Enter twice to start data collection. Drag the conductivity meter slowly across the ground making sure to maintain contact with the surface until you reach the end of

the survey grid. Once the orange button is aligned with the end survey grid line, hit F1 to put the machine on standby.

4. Hit F1 to create a new survey line. The new transect information (including what meter mark you are at on the grid, what direction you are now walking, etc.) will appear on the screen. If all information is correct, hit F1 again. Move the

conductivity meter to the new meter location, and hit enter to begin collecting data along the next transect. Repeat steps until the grid is complete.

5. At the end of the grid, hit F2 to exit out of the data logging phase. Exit out of the program.

6. Data can be uploaded to a computer using Microsoft Activesync or the conductivity software DAT38BW.

GPS

Use of a Global Positioning System when collecting geophysical data is vital; especially when you are integrating your data into GIS. It is important to record the corners of your survey

grids in a GPS unit so that you may geo-rectify your processed data in the GIS software.

Specific tasks such as geo-rectification will require their own web-pages that include step by step procedures .

GPS surveying uses satellite triangulation/trilateration to locate a receiver (satellites are the transmitters).

14. Most handheld units (e.g., Garmin and Magellan) are capable of only 10-20meter resolution. The use of WAAS correction in the United States can bring the

resolution of handheld units to 3-5 meters. This is usually not accurate enough to map outlines or distributions but can be useful for generally positioning oneself on the landscape.

15. Submeter accuracies are possible in several ways:

a. Two receivers, one maintained at a public location. This can be

accomplished using a public base station that generates correction data on a daily basis. Data are recorded in the field and compared with logs made at a public base stations. Data are download via the internet and the

Pathfinder software.

i. In the case of SEMO, the National Geodetic Survey runs a base station in Memphis, TN (http://www.ngs.noaa.gov/CORS/cors- data.html) that can be used to correct data. Other public basestations can be found at:

http://www.trimble.com/trs/findtrs.asp?Nav=File- 14444&Detail=Arkansas

ii. Note that the Trimble Pathfinder software will automatically search available databases for the closest reference station when points are post-processed and corrected.

iii. The Pathfinder Pro XRS system is capable of this kind of sub meter resolution.

iv. Note that submeter accuracies using post-processing and data from a public base station are only possible in a non-realtime basis – usually the next day.

b. Two receivers, one at a known location that actively transmits correction factors. This is known as Real Time Kinematic (RTK) surveying.

i. The Trimble Ag 214 system is capable of survey. This consists of a rover unit with receiver and radio and a base station with receiver and radio.

ii. Resolutions of up to 1-cm XY (2-cm Z) are possible using RTK. iii. This resolution is available in realtime – the rover unit is constantly

updated in terms of the correction factor.

iv. Accuracies are relative to the fixed base station. If the base station is known accurately, the rover unit will not be accurate. However, the rover unit will always be precisely located relative to the base station. This situation works well with archaeological field surveys where distances within areas need to be known very precisely but between areas, small differences are tolerable.

v. Like all GPS units, RTK is subject to decrease precision with satellite configuration, obscured satellite visibility due to leaf cover,

topography, etc.

vi. The Ag214 system is excellent for integration with the geophysical equipment.

vii. Use of the Ag214 for generating locational information without the geophysical equipment requires the use of the hand held data collector/computer (the Juniper).

c. A single receiver and commercial satellite differential correction service. i. The Trimble Ag132 and Trimble Pathfinder PRO XRS is capable of

satellite correction using the OMNISTAR service

(www.omnistar.com). This service give the Pathfinder Pro XRS a resolution (precision and accuracy) of 50-100 centimeters. ii. OmniSTAR VBS is a "sub-meter" level of service. A typical 24-

hour sample of VBS will show a 2-sigma (95%) of significantly less than 1 meter horizontal position error and the 3-sigma (99%) horizontal error will be close to 1 meter.

iii. This service must be purchased and turned on in advance of the survey. This can be done over the phone and in about 30 minutes. iv. The corrections are done in real-time so this service is useful for the

geophysical equipment when 50-100cm accuracies are adequate. This works well for wide transects and the resistivity unit.

GPS Measurements made with the Ag132, Pathfinder Pro XRS or handheld units.

A. You must have a more or less unobstructed view of the sky to obtain a location; the equipment is robust in this regard (i.e., it will not deliver a location if insufficient satellites are available).

B. Since the resolution of these units is on the order of a meter or greater, GPS units should not to be used where topographic information is required as useful topographic information cannot be obtained from this GPS configuration.

C. As each location is done from a preexisting reference system, much time is saved over conventional surveying by eliminating the instrument station; the instrument is transported to each data point.

D. The survey notebook is transported to each data point and the instrument readings as well as the number (sequential by tract/date) and description of point are recorded.

E. Obtain at least three readings at all reference locations (e.g., field corner, collection boundaries, etc.) and at least two at all data points (to exclude blunders and to provide minimum error term).

F. Be certain to record the Datum and reference grid used by the GPS unit – i.e., WGS-1984, NAD-1983, etc. Standard usage in North America is to use the NAD-1983 datum point.

G. Set the GPS unit to use UTM coordinates (not lat/long). H. If you are using the satellite corrected

I. Otherwise proceed as in electronic or optical surveying. J. When using the GPS units with the geophysical gear:

1. Make certain that that you have cables connected correctly

2. Check the baud rate on the GPS unit – it must match what the geophysical equipment is expecting.

3. The Mag/Res units require the use of a NULL MODEM connector to link the GPS cables with the RS-232 input of the Geometrics 858. This little connector is easily lost or misplaced. DO NOT LOSE THIS ITEM.

GPS Measurements made with the Ag214 Base Station .

A. Like other GPS systems, you must have a more or less unobstructed view of the sky to obtain a location; the equipment is robust in this regard (i.e., it will not deliver a location if insufficient satellites are available).

a. In the case of the Ag214 Base Station, you must also make sure the Base Station has an unobstructed view.

B. The radio of the Ag214 is good for up to 6 miles in diameter. However, that kind of distance requires line-of-sight between rover and base station. In practice, distances of only several kilometers are recommended.

C. The base station can be placed anywhere but should be over a fixed point that can be relocated (if you wish to resurvey any area).

a. Ideal location, however, has an unobstructed view of the sky from all sides. b. The radio portion of the base station should be placed as HIGH as possible. It

does not have to be in a fixed location and can be placed on top of a truck, etc. D. Since the resolution of the RTK system is on the order of 1 cm over most

distances, the Ag214 CAN be used to collect topographic information (Z values are typically +/- 2 cm.).

E. Use as large a battery as possible for the base station. Since it is unattended you want to make sure it will have power for the entire time you are running the mobile unit. Thus a car battery works best for the base station. This will last several days without recharging.

F. When setting up the base station:

a. If you are setting up on a known position, you will enter the coordinates of the position into the base station receiver

b. If you haven’t previously used the location as a base station, you should generate a point by averaging the location for at least 30 seconds. Record this information in the field notebook for future reference.

c. Note that location of the base station point will be only accurate to 10-20 meters from the actual point However, all points made with the rover unit will be accurate to within 1-cm of THIS point.

d. See the Appendix for the Ag214 Base Station set up procedures.

e. Test that the base station is working by referring to the rover station. When the system is working, the rover unit will report that it is using “carrier phase.”

Integrating Geophysical Data in ArcGIS Introduction

One of the most powerful and dynamic tools for interpreting processed geophysical data is GIS programs such as ArcGIS. Geophysical data may be integrated into GIS by directly importing processed data as image files or interpolating raw data within ArcGIS itself. Either way different datasets may be overlain on top of one another as layers. These layers may then be compared using statistical processes located in the programs toolbox.

The website will include step by step instruction on ways to incorporate geophysical data into ArcGIS as well as various techniques for analyzing the data. These instructions will be located within the tutorial section and will include streaming video that show the user exactly what to do on their own computer to work with geophysical data in ArcGIS.

Below we have listed just some of the information that will be available on the website. The information will be presented in a more dynamic and instructional format. The tutorial will use the data sets collected in Zzyzx, CA.

Methodology for Integrating Geophysical Data

GPR Slice Vector

Different Elevations

Create Layer File

Artifacts in low elevations and near Subsurface Features Artifacts within 2 m of Subsurface Features Artifacts located in low elevations Areas of High Dielectric Values Elevation Countours Select By Attribute Select By Location Select By Attribute Select By Location Slope of Elevation Contours Select by Attribute Different Slope Gradients Surface Tool  Slope

The first step after collecting data in the field is to process the data and import it all into ArcGIS. All of the data from the GPS unit and the geophysical instruments must be extracted and imported into ArcGIS. The data can be directly imported into ArcGIS or imported as Raster or Shape files via a program called Surfer. Regardless of how the data is imported from the geophysical instrument it must be georeferenced to the points collected on the GPS. Because we recorded the locations of the corners of our survey grid we can then georeference the corners of the geophysical data sets so that the data is overlain on the base data (topographic maps, satellite images, aerial photos, etc.).

Georeferencing can be easily performed by using the georeference toolbar. The corners of the images imported into ArcGIS including the images that we captured of the area with the aerial camera rig and raster datasets including the GPR data must be referenced to the known coordinates of our grid points. After the corners are tied to the correct coordinates then you must update the georeferencing or rectify the image. If you rectify the image you risk loosing some clarity in the image. The image can also become distorted. Rectifying the image creates a new file and layer, whereas simply updating the georeferencing orients and size the original image properly and a world file is created that is associated with the image. After georeferencing the image, a projection should be defined for the image that corresponds to the projection associated with the reference points.

The next step that is necessary in order to perform our spatial analysis is to convert the raster layer associated with our GPR data to a vector layer. This can be done by using the Conversions Toolbox. The “From Raster to Polygon” function allows you to simply change the color values associated with the pixels in the raster to individual polygons. We were interested in the areas of the GPR raster that were represented by red because they represented areas of high dielectric values within the subsurface of our grid. These high values are probably

associated with subsurface features that are much harder and compact than the surrounding soils suggesting that they might have previously been used for sedentary activities.

Figure 1: Conversion of Raster to Vector w/ areas of interest highlighted

After generating a shapefile, the areas of high dielectric values were selected by the numerical value associated with them and a layer file was created from the selection. This isolated the desired features into their own shapefile. Then the artifacts layer was queried and a selection of all artifacts within 2 meters of the subsurface features was highlighted. The results of this query selected a large percentage of artifacts within our grid. The majority of the artifacts and artifact clusters that we had recorded locations for in our GPS were located within at least 2 meters of subsurface features with high dielectric values. This tells us that there is a possible non-random relationship between the spatial distribution of the artifacts on the surface and characteristics of the underlying subsurface.

Figure 2: Selection of High dielectric Values

Because the relationship between the spatial distributions of the artifacts on the surface seemed to be non-random with respect to the location of the subsurface features, we sought to explain the distribution of the artifacts in relation to the subsurface feature with respect to topography.

In order to prove that the local topography plays a role in how the artifacts were

distributed we need to show that the artifacts align themselves along key topographical gradients. Since we wanted to examine the relationship between the elevational differences and the artifact distribution we decided to import the topographical GPS points we took with our Trimble unit and bring it into ArcGIS. Since the Trimble Pathfinder software does not import directly export into a .dbf file (at least not in a straightforward way that we were aware of), we exported the data under the setting “Sample Configurable ASCII Setup” as a tab delimited text file. In this menu of Pathfinder were able to select the projection and coordinate system we were going to export our data under as well as any critical details of the features we wanted to examine.

From here we opened up the text file under excel and then saved it as a .dbf (IV) file to import in ArcGIS. I then added the flat file into ArcView. From here we went into the “Tools” menu function and clicked “Add X/Y Data”. From here I got to choose which column was the X and the Y as well as define the spatial reference that the points were going to be under. The spatial reference we chose was the Projected Coordinate System UTM Zone 11N with the WGS 1984 datum since the original data was also exported under the same constraints.

The geographic data was then imported as a series of points as shown below.

From here we added the “Spatial Analyst” extension in ArcGIS in order to create a contour map of the area. First I clicked “Spatial Analyst” and then selected “Interpolate to Raster.” We then selected the Kriging method since I preferred this interpolation method over that of inverse distance. We then set the Z field heading in the attribute table as my “Z value field” and hit “OK”. The resulting map presented below was okay but did not sufficiently highlight the differences we wanted to see between gradients. We then right clicked this layer in the table of

contents and opened up its “properties”. Under the Symbology and Classified tabs I then hit the “Classify” button and set the intervals under the “Quantiles” method since the “Equal Distance” intervals did not visually highlight what I was trying to see. We then switched the GPS point layer on and off to see where the interpolations were going to be the most precise. Naturally the contour map was going to be the most accurate at the areas with the most points. Once that was done we turned off the GPS point layer

While the raster data helped me see the overall gradients in elevation we also wanted a more definitive and structured look at the elevation. For this we wanted a line contour map. Again we went into the “Spatial Analyst” extension and went into the “Surface Analyst” function and selected the “Contour Option”. For the “Z factor” we chose 0.25 since 0.5 and 1 drew too many lines to see anything clearly.

Slope

After viewing the elevational data it also occurred to us to try and examine the slope of the elevational gradient as well. To do this we once again went into the “Spatial Analyst” extension and selected the “Surface Analyst” function. This time chose “Slope” instead of “Contour”.

We then added in the artifact distribution data and examined the relationship between the artifact distribution, the geophysical data, the elevational differences, as well as the slope gradient. Once we positioned the data we wanted displayed and messed with the color settings to both our satisfaction we then went into the “View” menu and chose to display our data in the layout view in the form of a map and added in the symbols, legend, text, orientation, and scale. We then went into “File” and clicked “Export Map” to move our analysis into a readily transferable format. We then high-fived each other and proceeded to celebrate heartily.

Software Page Introduction

There are a variety of ways to process and render geophysical data. Some are proprietary and are