GEOGRAPHIC INFORMATION SYSTEMS Lecture 20: Adding and Creating Data

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1 GEOGRAPHIC INFORMATION SYSTEMS

Lecture 20: Adding and Creating Data

Adding Existing Data Into ArcGIS

- there are many different ways to get data into ArcGIS

Add Data

- normally we use the Add Data button on the Standard Toolbar and browse to a file … - we can add: - shapefiles (vector points, lines or polygons)

Esri shapefile format (.shp)

- feature classes from a “file geodatabase” Esri file geodatabase format (.gdb) - feature classes from a “personal geodatabase”

Microsoft Access format (.mdb)

- feature classes from an enterprise “geodatabase” e.g. Microsoft SQL format or other RDMS - continuous or discrete raster layers

ARC/INFO GRID format - image layers

.tiff, .img, .sid, .jpg formats - map services

data layers hosted by Esri or others online - layer files

A file that contains symbology and a path (eg c:\data) to the data

Table Joins and Relates

- once we have a shapefile or feature class added to ArcMap

- we can append or access additional attribute information (tabular data) with joins and relates

1) Joins (a ‘table join” appends data from a table to the attribute table) a) one-to-one relationship

- attribute information is added to features by joining data from a table with same number of records - e.g. we can join a U.S. county census table to U.S. county polygons

b) many-to-one relationship

- attribute information is added to multiple features by joining data from a table with fewer records - e.g. we can join data from a U.S. states table to multiple county polygons

2) Relates (a “table relate” provides access to tabular data related to features) c) one-to-many relationship

- attribute information associated with a feature can be accessed (but not directly joined) - e.g. list of tenants living at a single address

- most commonly, we bring tabular data into ArcMap in a dBase IV (.dbf) or Excel format - dBase IV is the native format for shapefile attribute tables (the .dbf part of a shapefile)

Import Data

- we can also import data into ArcGIS (using tools in ArcToolbox) - import implies that we have to go through a file conversion process

1) can import layers created using other GIS software - e.g. MapInfo (business GIS software) 2) can import layers created using AutoCAD

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Creating Your Own Data

- in many cases the data we are interested in simply does not exist and we have to create our own data - the three most common methods of creating data are:

- digitizing - heads-up digitizing of scanned maps or digital imagery - digital image processing - requires the use of remote sensing software - mobile field mapping - most commonly involves the use of GPS

1) Digitizing

- most GIS data are created by digitizing either scanned paper maps or digital remote sensing imagery - in older times, paper maps were digitized directly on a digitizing table using a digitizing puck

- today, we use heads-up digitizing - the process of tracing features on the computer screen using the mouse

- to digitize features, the process is fairly straight forward:

- open ArcCatalog and create a new empty shapefile or feature class in a geodatabase - the new shapefile or feature class can be a point, line or polygon layer

- the layer must be assigned a coordinate system (either geographic or projected) - the assigned coordinate system must match the coordinate system of the image layer - open ArcMap and add the image layer (either a georeferenced scanned map or digital imagery) - add the new empty shapefile or feature class to the Table of Contents

- use the Editor toolbar and Start Editing to begin an edit session

- select a template and a tool and use mouse clicks to trace the feature of interest - double click to finish - the new feature is created – then select Save Edits (good practice)

- we can now add attribute information to the records in the attribute table - repeat the process for each feature

- finally, select Stop Editing and Save Edits

2) Digital Image Processing

- digital image processing requires the use of specialized remote sensing software - example software includes: ERDAS Imagine, ER Mapper, ENVI

- the image processing software is used to classify the features in a digital satellite or airborne image - the software classifies the features based upon a unique image signature (multiband reflectance) - imagery can be classified to map land use, vegetation, crop types, water bodies, urban areas, etc - two examples of data layers derived from image processing include:

- the National Land Cover Dataset (NLCD - available from the USGS) - the National Cropland Data Layer (available from the NRCS)

3) Field Mapping with GPS (Global Positioning System)

- today, GPS is the most widely used method of field data collection

- we can add GPS data (lat, long) to ArcMap using Add X,Y data from the File > Add Data pulldown menu - if we Add X,Y data, the points are drawn directly from a table (e.g. Excel) and displayed as a Event layer - an Event layer looks like a point feature class in ArcMap, but points are displayed directly from the table - to use the x,y data, we must export the Event layer to either a shapefile or feature class

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Geographic Information Systems

GIST 3300 / GEOG 5300

Geographic Information Systems

Adding Existing Data and

Creating Your Own Data

Adding data into ArcGIS

- Add data

- Join and relate tabular information - Import spatial and tabular data

Creating your own data

- Digitizing

- Digital image processing - Mobile field mapping with GPS

Getting Data Into ArcGIS

Add Data

- normally we use the Add Data button on the Standard toolbar - we can add:

- shapefiles (.shp) (vector points, lines and polygons) -feature classes from a “file geodatabase” (.gdb) - feature classes from a “personal geodatabase” (.mdb) - feature classes from an enterprise “geodatabase”

e.g. Microsoft SQL format or other RDMS - raster layers (either continuous or discrete)

ARC/INFO GRID format

- image layers (airborne or satellite imagery) .tiff, .img, .sid, .jpg

- map services

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Joins and Relates

- once we have a shapefile or feature class added to ArcGIS - we can append additional attribute information with a “table join”

1) Joins

- works if we have: - one-to-one relationship

- attribute information is added to features by joining data from a table with the same number of records

- e.g. we can directly join a U.S. county census table to U.S. county polygons - many-to-one relationship

- attribute information is added to multiple features by joining data from a table with fewer records

- e.g. we can join data from a U.S. states table to multiple county polygons in a U.S. county layer

Joins and Relates

- once we have shapefile or feature classes added to ArcGIS - we can access additional attribute information using a “table relate”

2) Relates

- works if we have: - one-to-many relationship

- attribute information associated with features can be accessed (but not directly joined)

- e.g. list of tenants living at a single address, or one parcel has many owners

Tabular Data Formats

- most commonly we join or relate tabular data in a dBaseIV (.dbf) or Excel format

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Import Data

- we can also import data into ArcGIS (using tools in ArcToolbox) - import implies that we have to go through a file conversion process - we can import:

1) layers created using other GIS software

- for example MapInfo (business GIS software) 2) layers created using AutoCAD:

- for example .dxf or .dwg files - often with limited success

3) raster layers in either binary or ASCII formats

Geographic Information Systems Three most common methods of creating GIS data:

1) Digitizing

- heads-up digitizing 2) Digital image processing

- involves the use of remote sensing software 3) Mobile field mapping

- Global Positioning System (GPS)

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1) Digitizing Creating Your Own Data

- involves tracing features from an existing source - usually hardcopy air photos or a hardcopy map

Digitizing Table – dated hardware

1) Digitizing (heads-up digitizing) Creating Your Own Data

- today, paper maps are scanned with a large format scanner to create a digital map image

- the digital map image is then georeferenced

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1) Digitizing (heads-up digitizing) Creating Your Own Data

- in Catalog or ArcCatalog– create a new, empty feature class in a geodatabase - the new feature class can be a point, line or polygon layer

- the layer must be assigned a coordinate system (geographic or projected) - the coordinate system must match the image layer that is being digitized - open ArcMap and add the image layer (scanned map or digital imagery)

- add the new feature class to the Table of Contents - use the Editor toolbar and Start Editing

- select a template and a tool and use mouse clicks to trace the features - once a new feature is created – then Save Edits

- add attribute information to the records in the attribute table - repeat the process for each feature

- finally, select Stop Editing and Save Edits

2) Remote Sensing and Digital Image Processing Creating Your Own Data

- image processing software can be used to classify imagery

- the classified image is a raster dataset that can be added to ArcMap - most often, imagery is classified in order to map land use

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Creating Your Own Data

3) Mobile Field Mapping with GPS

- today, GPS is the most widely used method of field data collection - we can add GPS data directly into ArcMap using Add X, Y Data

from the File > Add Data pulldown menu