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We will be using a program called ArcView for this
exercise. Hopefully by this time you are relatively familiar with ArcView,
however you can refer back to the notes from Lab 3 for general instructions
in how to use it. Instructions for this lab will also help you gain
more familiarity with ArcView's capabilities.
This lab is intended to show you a different approach of combining habitat mapping with species presence/absence data to delineate the distribution of a species. |
Use the Windows File Manager to copy all files and subdirectories from k:\wlf\448\arcmaps2 to your zip disk or personal directory on the H: drive. If you don't know how to do this, we will show you again! If you do not have enough room on your H: drive, then you will have to copy the maps to a ZIP disk. As a last resort you can use the temp T: drive, but remember everything on the T: drive is erased each night!
Log on to the Novell network
Click on the Start Menu; Analytical; ArcView 3.3; ESRI ArcView 3-3 SP1
Open the program. This may take awhile, depending on the server's workload.
Click on "File" in the main menu and select "New Project." (will happen automatically when you first open the program)
Click on "Views" in the project window if it is not framed, and click on "New" (will happen automatically when you first open the program)
Click on "View" in the ArcView main window and select "Add Theme" (will happen automatically when you first open the program)
In the next window, click on "Drives" in the lower part of the window and select the Zip drive or the H: drive.
Double-click on "arcmaps2" (assuming you copied or created the subdirectory arcmaps2).
If no themes appear on the left side of the add theme window, you will need to add the Spatial Analyst extension. To do that, click on "File" in the main menu and go to "Extensions". A list of available extensions will appear. Use your mouse to go down the list and check the box next to 'Spatial Analyst'. Click 'OK'. You might notice a few more menus appear across the top of your ArcView window. Try adding a theme again and change the 'Data Source Type' to "Grid Data Source". Hopefully when you do this, you will see a theme appear in the left side of the add theme window.
Double-click on "idveg_resamp." The theme name will appear in the View window with a check box. This is a grid theme, which means it is raster data. This is the Idaho Gap Analysis Project vegetation map, which has been resampled from a 30 meter grid cell size to 90 m cell size. This was done for our lab because the resampled map is smaller in size and easier to work with.
Click on the check box next to 'idveg_resamp' and the map theme should appear.
Let's load the legend file for this theme. Double-click on the symbol under 'idveg_resamp' and the Legend Editor window appears.
In the Legend Editor, click on the "load" button at the top right of the Legend Editor window. A new window should appear. Select the file named 'idveg.avl' and then click 'OK'. Another window will appear you want to make sure the field that is selected is 'Value' and that there is a check by 'All'. Click 'OK'. You will now see the new legend loaded in your Legend Editor window.
Once your legend is loaded in the Legend Editor, click "Apply" to apply your changes to the current view. Then close the Legend Editor window by clicking on the upper right corner (the "x" sign).
It is a good idea to save your "map" as a project. It is not uncommon to run into segmentation errors or other errors that kick you out of the program. Consequently, save early and save often!
Go to the main window (project window or "untitled1" window) and select "Save Project As" from the "File pull-down menu." Give your project a name (keep the "apr" extension). Make sure it is saving the file to your arcmaps2 directory on your Zip or H: drive.
V. Choosing habitat types based on species information:
The map you have displayed includes all the vegetation types that occur in Idaho. At this time, open the 'idveg' MS Word file in the arcmaps2 directory. This document provides details about what grass, shrub, or tree species occurs within each of the idveg_resamp vegetation types. Explore this document by selecting a vegetation type from your map and reading about the species included. For example, what species are included in the vegetation type 'curlleaf mountain mahogany'?
Next open the MS Word file 'species_info' under arcmaps2. This file provides information regarding what habitat types 3 Idaho species (Mountain lion, tailed frog, and black chinned hummingbird) occur within. For this In-class exercise we will be using the tailed frog and in your Problem set you will be using either the mountain lion or black-chinned hummingbird.
Read over the habitat description for the tailed frog in the 'species_info' file. Use this information to select the appropriate habitat types for this species from the vegetation type list (i.e., idveg).
What vegetation types would you choose for the tailed frog?
Once you have decided upon the vegetation types that are used by the tailed frog, select them from the 'idveg_resamp' theme. Do this by opening the attribute table for the theme. You will see 2 fields in the table, 'Value' and 'Count'. You want to match up the numerical code from the 'idveg' word file with the number in the 'Value' column. Select all the 'Value' records that correspond with your vegetation types. Remember to use the shift key to select muliple records.
Your map should now show the all the vegetation types that tailed frogs use in Idaho. We want to save this map and overlay the presence/absence data based on hexagons for tailed frogs. On the main menu bar, click 'Theme' and the choose 'convert to grid'. This will save just the vegetation types you have selected. You will need to provide a name for the new file and be sure to save it to your directory where you have all the arcmaps2 files. Click 'OK'. You will be asked if you want to add the new grid theme to your view-say 'yes'. You can add the legend file for 'idveg_resamp' again (see instructions in III, steps 9-11).
To see your new map, click on the box next to 'idveg_resamp' to turn it off and then click on the box next to your new theme to turn it on. You have created a tailed frog distribution map based on habitat. You can also close the attribute table for 'idveg_resamp'.
VI. Incorporating presence/absence data:
Let's add the hexagon theme to our habitat map. Go to 'View', 'add theme' and then find the folder 'cov'. Open the folder and find the theme called 'hexagon'. Be sure your 'Data Source Type' is set to 'Feature Data Source'.
Click on the box in the View window to display the hexagon map for Idaho.
To see the hexagons in which there is presence data for the tailed frog, we need to open a new table. Click on the project window and then click on 'Tables'. Click on the 'Add' button. Navigate to /arcmaps2/spreadsheet/herphex.dbf. Select that file and then click 'OK'. You will also want to open the attribute table for the 'hexagon' map.
In both these tables (i.e., herphex.dbf & hexagon attributes), you will see a field called 'hexagon-id'. We need to link these 2 tables by 'hexagon-id'. To do this successfully, the tables and fields have to be selected in a specific order.
First, select the 'hexagon' attribute table (the top bar will be purple when the table is selected) and then highlight the 'hexagon-id' field by clicking on the field name (it should turn a darker gray with white text when it is highlighted). Second select the 'herphex.dbf' table and highlight the 'hexagon-id' field.
Third, go up to the main menu under 'Table' and click on 'Link'. You will not notice anything change, but if you select any record in the 'herphex.dbf' file, a record with the same 'hexagon-id' value will also be selected. This is how you will know you did the link successfully.
There are no species names in the 'herphex.dbf' file, but instead there are element codes (Elcode is the field name), which identify each species. Look back at your 'species_info' file to determine the element code for tailed frog.
Select the 'herphex.dbf' file and then do a query on it using the element code for tailed frog. To do a query, choose the hammer button on the toolbar and then select 'Elcode = "AAABA01010" (Be sure to use capital letters because the query is case sensitive.).
If done successfully you should have 283 of 8398 records selected in herphex.dbf and you should also have 164 of 404 records selected in the hexagon attribute table and on the hexagon map.
Close both tables and make sure the 'hexagon' map is highlighted in the View window (it will appear raised).
Now we want to save the tailed frog hexagon map. On the main menu bar, click 'Theme' and the choose 'convert to shapefile'. This will save just the hexagon that are selected. You will need to provide a name for the new file and be sure to save it to your directory where you have all the arcmaps2 files. Click 'OK'. You will be asked if you want to add the new shapefile to your view-say 'yes'. The 'hexagon' map can now be closed.
VII. Making the final distribution map:
Now you have a habitat map and a presence/absence map for the tailed frog. We want to combine these to make a distribution map for the tailed frog in Idaho.
Open the attribute table for the tailed frog hexagon map. Under 'Table' on the main menu select 'Start editing'. Then under 'Edit' on the main menu select 'Add Field'. A 'Field Definition' window will pop up. Name the new field 'tailed frog' and choose 'number' for type and 4 and 0 for width and decimal places, respectively. Click 'OK'.
Make sure your new 'tailed frog' field is highlighted and click on the calculate button (it looks like a calculator on the toolbar). A field calculator window should appear. It should already say [tailed frog] =. Just type 1 in the text box and click OK. All the records in the field 'tailed frog' should now equal 1.
Under 'Table' on the main menu select 'Stop editing' and say 'yes' to 'Save edits?'.
Select your View window and be sure that your tailed frog hexagon theme is highlighted (it will appear raised). Go under 'Theme' and select 'convert to grid'.
Select a new file name and make sure it is being saved in your arcmaps2 directory. Click 'OK'.
A 'Conversion Extent' window will appear. Choose 'idveg_resamp' for both the 'Output grid extent' and the 'Output grid cell size'. The cell size should change to 90. Click 'OK'.
Another window will appear. Pick 'tailed frog' as the field for cell values. Click 'OK'.
Click 'yes' to 'Join feature attributes to grid?' and 'yes' to 'Add grid as theme to View?'.
Turn on your new theme.
The last step involves clipping your vegetation map to the extent of your hexagon map.
Under 'Analysis' on the main menu choose 'Map Calculator'. A new window will appear.
Double click on your hexagon map for the tailed frog (it should be the file name with no extensions), then click on the multiply button (*) and double click on your vegetation map for the tailed frog. Then click 'Evaluate'.
A new grid will be created. When the analysis is complete, close the 'Map Calculator' window (click in upper right corner on x).
Your new distribution map will be categorized by vegetation. You can load the vegetation legend from 'idveg_resamp' (see instructions in III, steps 9-11).
Remember to save your project before closing ArcView. You can use the instructions from Lab 3 to print out a map of your tailed frog distribution.
Return to Lab Notes Revised: 19 August 2008