Spatial Analysis Based on Raster Data Processing - Introducing Geographic Information Systems with ArcGIS - page 485

3. Start ArcMap with a new blank map. In ArcToolbox locate the ASCII to Raster (Conversion) tool
and start it. For the Input ASCII file, browse to Raster_Experiments and select Forty_Two_Cells.txt.
4. Click the Output Raster text box. Use Browse to navigate to Raster_Experiments > Ras_Expr.
gdb, and type Basic_Raster for the name.)
5. The Output data type should be INTEGER. OK the ASCII To Raster window. Watch the lower right
of the window to see the progress. When the tool has finished, Basic_Raster will be added to
the map.
6. Use the mouse cursor to determine the extent of the raster. (If the cursor slips off into the
Pan mode, as it seems to sometimes, click Select Elements.) Round your readings off to the
nearest 100.
Y_Maximum _______.
X Minimum _______. X Maximum _______.
Y Minimum _______.
Considering the specification coordinates of the center of the lower-left cell (x=4150 and
y=1150) and the cell size (100), does it appear that the raster is in the correct position?
______ Move the cursor to the approximate center of the lower-left cell to verify your conclusion.
7. Look at the Table Of Contents (T/C). What is the smallest value in the raster? ____. The
largest? ______. Use the Identify tool to check out some cell values. Bring back the textfile
window: Forty_Two_Cells.txt. Verify that the values you find in the map are in the appropriate
position relative to their locations in the text file that created them—for example, the two cells
showing 24 are in the third row, cells 6 and 7. Close Identify. Close the text file.
8. Bring up the Layer Properties window of Basic_Raster. Under Symbology > Show, pick Stretched.
Examine the window, then click Apply and OK.
This “stretches” values over a color ramp. The default is black to white, so you get a grayscale
representation of the values—low (black) to high (white).
9. Open the attribute table of Basic_Raster and put it where you can see both it and the map.
Using the table, pick a record and highlight it. Verify that the Count field in the selected record
in the table represents the number of cells highlighted. How many cells have value 23? ______.
Deselect all records and close the attribute table.
It would be nice if each cell could be labeled with its value. That capability is not a part of ArcMap per se,
but there is available an unsupported tool, called CellTool, that does the job. It is provided on the DVD
that accompanies this topic. You can add the CellTool with the following step. (This process assumes that
you have the right to add software to your computer. If you don't have that right, contact your instructor or
computer system administrator.)
10. Using the CD-ROM that came with the topic, find the CellTool folder with the operating system
of the computer. Navigate to esriCellTool.dll. Copy the DLL to your personal folder ___IGIS-
Arc_ YourInitials . In ArcMap click Customize on the Main menu. Pick Customize Mode to bring
up a Customize window. Under the Toolbars tab click Add From File. Navigate to the DLL in