GIS in H2O Resource Engineering
Hw 4 Process Summary
Jake McDermott
1) Downloaded 3 DEM quads from (http://rgis.unm.edu). Files were downloadee from the arc export column.
2) Files downloaded were zipped and so needed to be unzipped which was done by highlighting the file > open with>withCompressed (zipped) Folders
3) I then copied these unzipped files to my workspace.
4) To import the unzipped DEMs via the arc toolbox by clicking: Coverage Tools > Conversion > To Coverage > Import From Interchange File
a. In the dialogue box that comes up you must select the file you wish to input—input interchange file. In this case, one of the 3 unzipped quad files.
b. In the next drop down—output dataset--within the same widow, choose the browse button and select where you would like converted file stored.
c. Click okay.
5) To add the DEMs to a new map click the add data button and connect to the workspace folder. Select all 3 file and click add.--at this point the quads should be displayed.
6) Enable the Spatial Functions
a. Make the Extension active by going to Tools > Extensions and checking the box next to the spatial analyst..
b. Enable the Analyst Toolbar by going to Tools > Customize.
7) Once the toolbar is enabled, click the toolbars dropdown box and select options. The Dialogue box that comes up has 3 tabs: (general, extent, and cell size)
i. general tab – browse for the file folder you have set up as your workspace as your working directory.
ii. Extent tab – choose same as display
iii. Cell size – select maximum of intputs
- now the spatial analyst function are enabled
8) To connect the 3 DEM quads more seamlessly
a. Click the spatial analyst dropdown menu and select raster calculator
b. In the raster calculator dialogue box type in the function given in the HW instructions then click evaluate
- the quads will now be consistent with regards to color coating, but there are still a few blank spaces were no data exosts.
9) The file the cells with no data: select raster calculator in the spatial analyst dropdown menu and type the following command
con(isnull([Calculation ]),focalmean([Calculation ],rectangle,4,4),[Calculation ]) then click evaluate.
- the cells that had no data should now be filled, but are not filled with grid data. They are filled with a calculation.
10) To fill the data cells with grid data, right click on the calculation two in the table of contents click data > make permanent and save the new grid file to the work space created earlier.
11) Once there is a fully mosaiced grid close out all the other calculations and grid quads
12) Fill the spurious pits by clicking Spatial analyst tools > Hydrology > Fill
a. Select the grid created as the input surface raster then choose the appropriate workspace as the output surface raster.
13) Make the extent and cell size the same as the grid file created.
14) Then several calculation are done using the raster calculator, each calculation builds on previous ones. For the first calculation it appeared to work better to perform the calculation on the Fill_jmABQgrid rather than the jmABQgrid layer.
*It seemed to work best when any operators were entered using the operator buttons rather than typing them in.
*All calculations appeared to work but there were a few problems with the final results: the flow direction and watersheds especially looked wrong. And I noticed the counts did not match the values in the screen capture of the example shown in the directions. Attempt to recondition with AGREE was unsuccessful.
Below is a presentation of calculation results.
