Exercise 3: GIS data on the World Wide Web

Transcription

1 Exercise 3: GIS data on the World Wide Web These web sites are a few examples of sites that are serving free GIS data. Many other sites exist. Search in Google or other search engine to find GIS data for your own state or country. US and worldwide data: Maps on Google is an interactive map display where you can zoom in to any part of the world displaying either map features or remote imagery. Geography Network ESRI (geographic census data. American Factfinder (tabular census data) USGS Seamless Elevation Data Northwestern US Data: Idaho data: Interior Columbia River Basin Project Washington Geographic Information Council Oregon Portland State University, Population Research Center The INSIDE server is located in the library at the University of I. Among other data this site provides 1m color photography for the entire state of Idaho. Look for NAIP 2004 data! Idaho Water Resources Idaho Department of Lands Idaho GAP data + Great GIS links RSGIS lab at U of I contains many useful links to GIS web sites. 26

2 Step 1: Download NAIP 2004 color photography for the Craig Mountain area from the INSIDE Idaho web site. Go to then click on Geodata Find Data Popular Data. Go to the bottom of the page and select 2004 Digital Ortho Images NAIP. At the middle of the page, select Click here for an IMAGE MAP from which to download. Select Nez Perce County. Click Download data and save the data to your computer in the REM402 folder. Compressed file formats Data downloaded from the Internet come in many file formats such as.tgz,.exe.zip.z and.e00..tgz,.exe,.zip and.z files are compressed to save space on the web server. You can use Windows utilities such as Winzip to uncompress these files. If Winzip is loaded on your computer you can simply double-click on the downloaded file and Winzip will automatically uncompress the file. During the uncompression process you will be asked where on the computer you want to save your file remember where you save it!! Download Winzip: If Winzip is not loaded on your computer you can access it for free from (search on WinZip). Step 2: Use My Computer or Windows Explorer to locate the downloaded Nez Perce county NAIP photography file. Then Double-click on the downloaded compressed NAIP photography and uncompress the file. Click Extract and specify what file folder you would like to extract the image to. Make sure to remember where on your computer you are storing the unzipped photo!!!!! There are many files associated with the NAIP photo. Do not delete any of the files since some of the files are necessary for correct display of the photo. The actual image file has the extension.sid. 27

3 Step 3: Add the NAIP photography to your Craig Mountain ArcGIS project. Two files have been downloaded from the Internet. They are all located in the folder c:\rem402\downloads bvbfirlc.exe fire start locations in the Interior Columbia River Basin gwma.exe ground water management units Idaho Water Resources Arc export files -.e00 metadata was also downloaded.e00 files are ArcInfo export files and cannot be uncompressed using utilities such as Winzip. You can import these files to GIS using data conversion tools in ArcToolbox. Import functions in ArcToolbox (ArcGIS 9.3) ArcToolbox includes Conversion tools that allow you to import and export various file formats to files readable in ArcGIS. Data Management Tools are used for defining map projections for shapefiles or geodatabases and for projecting GIS layers. Step 4: Double-click on the file c:\rem402\downloads\bvbfirlc.exe to uncompress the file. Remember where you save the file! The compressed file contains two files: bvbfirlc.dat and bvbfirlc.e00. You cannot view these files through ArcCatalog since they are not in a GIS format, however you can view them through Windows Explorer or My Computer. Step 5: Use the ArcToolbox sequence Coverage Tools - Conversion To Coverage - Import from Interchange file, to import the bvbfirlc.e00 file to an ArcInfo coverage that is readable in ArcGIS. 28

4 Step 6: The input file is c:\rem402\downloads\bvbfirlc.e00. Save the output coverage in the c:\rem402\downloads directory Step 7: Start ArcCatalog and view the metadata spatial reference data for the bvbfirlc coverage. The new coverage is in an Albers projection. All our other data is in a UTM projection, zone 11, units meters, datum nad27. Data layers in different map projections may not overlay properly in ArcMap because the data is in a different coordinate system. 29

5 Information about map projections can also be found in the metadata on the web site where the data layer was downloaded from. ArcGIS 9.3 is capable of Projecting on the Fly which means that data in different map projections can be viewed simultaneously without going through a Projection procedure in ArcToolbox. Projection on the fly only works if the map projection is properly defined for the datasets. In Lesson 4 you will learn how to define map projections. Map projections can be defined in ArcCatalog and spatial data layers can be projected (change projection) in ArcToolbox. Step 8: Add the bvbfirlc coverage (fire start locations) to the Craig Moutnain project. Also add the Idaho boundary (boundary) from c:/rem402/idaho_utm as a reference. The fire point locations from bvbfirlc covers the entire northwestern USA. If you overlay the Idaho state boundary over the fire points your maps should look like the display to the left. Notice that you can move layers in the table of contents by clicking on the layer and hold down the left mouse button while you drag the layer towards the top of the screen. The Display tab in the lower left must be selected in order for the drag and drop to work. In the next section you will extract another data layer (groundwater management areas for Idaho) and display with the Craig Mountain data. This exercise will demonstrate what happens if the map projection of a data layer is not defined and how you can solve this problem to correctly display the data. Step 9: Extract the Idaho Groundwater Management units from the file c:/rem402/downloads/gwma.exe by double-clicking on the file. Remember where you save the extracted files. The files gwma.shp, gwma.shx and gwma.dbf will be extracted. 30

6 These three files must always be kept together as a unit one by one they are useless! Add gwma to your ArcMap project and realize that we have a projection problem. Idaho counties in UTM projection Groundwater Management Units in IDTM projection The groundwater management areas should be located in southern Idaho, however they appear off the map Save your project!!! There is no assignment to turn in for Exercise 3, continue to Exercise 4. 31