Lab 3: Projections, Data Acquisition and Data Transfer

 

Part I: Projections

Do the tutorial exercises in Chapter 13 of Getting to Know ArcGIS Desktop. Answer the following questions and produce the following outputs.

 

Chapter 13 

  1. What is a spheroid and how does it relate to a geographic coordinate system?
  2. What is a projected coordinate system?
  3. What properties of features are distorted when changing from a geographic coordinate system to a projected coordinate system?
  4. What is "on-the-fly" projection?
  5. At the end of exercise 13a put your name on the map using a text box, switch to a layout view, and print the map.
  6. What is a prj file in ArcGIS?
  7. At the end of exercise 13b put your name on the map using a text box, switch to a layout view, and print the map.
  8. What is different about using the Define Projection tool in ArcToolbox compared to doing "on-the-fly" projection?
  9. Find the Project tool in ArcToolbox (there is a different tool for features and rasters). What is the difference between this tool and the Define Projection tool?
  10. The Project tool for features has an optional geographic transformation selection. What is that selection used for?
  11. If you use the Project tool for rasters, you must specify a resampling technique. Explain the difference between the available options.

 

Part II: More Projections

Download the file Lab3.zip to a drive you have access to. Right click on the file, select Extract All, and follow the prompts for the extraction wizard. When you are done you should have three shapefiles: Willamette Valley boundary, streams for the Willamette Valley and highways for the Willamette Valley. Note: The boundary file is in a projected coordinate system of NAD 1983 (feet) State Plane Oregon North. The highways file is in a projected coordinate system of NAD 1983 UTM Zone 10N.

Open a new empty map in ArcMap and add first the boundary shapefile, then the highways and streams shapefiles.

 

  1. You will see that the different layers do not overlay each other and display together. Explain why not.
  2. Click on the full extent button (the globe). Only two layers are shown. Why can you not see the third layer? (If you select zoom to layer, you will see that it is on the map.)
  3. Next, define the projection for the highways layer. Did the position of the layers change? Why or why not?
  4. Now open a new empty map in ArcMap, and this time add the datasets in the following order: First, highways, then streams, then boundary. Explain why two of the datasets now align and other does not?
  5. Now change the projection and coordinate system of the data frame. To do this, right click on Layers (the yellow icon) in the table of contents, and select Properties then Coordinate System. You will see that it is currently set to the projected coordinate system of the highways layer. Why? Change it to the projected coordinate system of the boundary layer (you will find it in the predefined folder). Explain what happened on your map after you made this change. Put your name on the map with a text box and print it.
  6. Do you need to have all the datasets in the same spatial reference system to display them together? Why or why not?

 

Part III: Data Acquisition and Transfer

GIS data are available online in a number of different formats. All datasets will be in some sort of compressed (zipped) format and will need to be extracted. However, all zip formats are not readable by all compression/extraction software. Windows XP will extract .zip files. A different compression/extraction program is needed to extract .gz, and .tar files.

 

Many datasets are available in ESRI ArcView shapefile format. You will also see E00 files which are ESRI ArcInfo interchange files (also called Export files). Unlike a shapefile, if you download an E00 file and unzip it, you STILL cannot view it directly in ArcMap; it must be converted to the ArcInfo coverage format. To do that, open the ArcToolbox window and choose Coverage Tools, Conversion, Import from Interchange File. The Input file is the E00 file and the Output Dataset is what you want to call the coverage. (This option is only available with ArcInfo at the university, not with the ArcView program that came with your book.)  You can then add the ArcInfo coverage to ArcMap.

 

Many digital elevation models (DEMs) also cannot be viewed directly in ArcMap. After you download and unzip a DEM, you can translate the files into the ESRI raster format. Open the ArcToolbox window and choose Conversion Tools, To Raster, DEM to Raster, and under Input USGS DEM file navigate to and choose the unzipped DEM file. Under Output Raster choose the filename you want. DEMs may also be available as SDTS files (use the SDTS to coverage tool) or ASCII files (use the ASCII to Raster tool) or interchange files (see process described above).

 

 

Visit two different websites listed on the Spatial Data Links. A link to this page is also found in the course syllabus under the projects section.

 

  1. Describe the kinds of datasets available at each of the websites you visited. What data formats are they available in?
  2. Download two datasets from each of the sites you visit, add them to ArcMap, and print the resulting maps. Make sure that you use a text box to add your name and somehow describe what the datasets are and where you found them.
  3. Many websites have GIS-produced maps as well as GIS data. What is the difference between the two? If you downloaded a map, what data format would it be in?