Fall 2008 SO432, GIS

Lab--Raster GIS Processing

We will look at the following raster GIS data sets.  They are in a ZIP file.  Download it and unzip it anywhere (as long as you remember where, since you will have to open the files individually).  One good place to unzip would be in c:\mapdata, and you would have a directory for "raster_data_lab".

• NLCD for Annapolis (annap_nlcd\51395573.tif).  MICRODEM considers this to be an image, so you must open it with the "Image" option.
• NLCD classification of the US, 2.5' cell size, percentage of land cover to 21 categories. (nlcd_atlas\*.dem)  This is not the actual NLCD data, but a statistical summary of it. MICRODEM considers these to be DEMs or raster data sets, so you must open with the "DEM" options.  This was created with the 30 m NLCD data from USGS, such as the one for Annapolis.

MICRODEM has a "raster gis" menu choice, which has most of the options we want. You might want to look up NLCD, and Raster GIS in the MICRODEM help.

Answer the 4 questions in Bold type below:

1. NLCD-- see the MICRODEM help file for definitions of the 1990 NLCD categories.  

• Open the NLCD of Annapolis, using the Open Image command.. 
  • Find the World file for it (TFW extension), and open that in NotePad or WordPad.  What is the meaning of the various lines?  Is there a datum in the world file?
  • Open the TIF file, using the Analyze, Metadata, Geotiff menu choice.  Is there information on the projection?  The datum?
• Use the Open DEM command to open all of the NLCD statistical summary maps that cover "forest", and create a new raster layer with all forest. Use the add multiple grids menu option on the Raster GIS menu. What is actually stored in this file?
• Open all the NLCD maps that cover man-made cultural features, and create a single grid with the percentage disturbed. You might want to read the definitions of the categories in case you do not think the same way that someone at USGS does.
• Interpret the two maps you created. You can overlay states boundaries from the Overlay, US properties menu in the lab, picking either "States" or "world outlines".
• Try filters on your two summary grids.  Use both a smoothing and coarsening filter.  What effect do the filters have?  Are they good or bad?

Metadata:

1. The NLCD  classification grids were created by Prof. Peter Guth.  NLCD covering the entire US was downloaded from seamless.usgs.gov.  Within each 2.5x2.5' cell, percentage of terrain in each of the 21 categories was computed and stored in the grid.
2. The NLCD map of Annapolis was downloaded from seamless.usgs.gov and uncompressed.  It has an associated metadata file.