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Geomedia-Pro/Geomedia GridLaboratory Exercises

Prof. Cyrus B. DawseyAuburn University

Phase 1:DEM Display and Mosaic

Objectives:1. Analyze elevation data for East Alabama for later use in temperature study.2. Improve basic GIS skills using vector and raster-based applications.3. Learn to use attribute filtering capability in Geomedia Pro.4. Learn to use various Geomedia Grid Study Area and Layer capabilities. 5. Learn how to use the “Mosaic” capability available in Geomedia Grid.

Input files/folders:1. USSampleData.mdb: Access database including a variety of attributes for the United States.This file is provided with a standard instalation of Geomedia-Pro.

East_Alabama_Dems: Folder including four DEM files at 1:250,000 covering east Alabama.Obtained from the USGS.

Hydrology_access.mdb: Access database including hydrology vector data for Alabama.Obtained from the USGS.

Required Applications:Microsoft AccessGeomedia-Pro v.5.0 or 5.1Geomedia-Grid

General description of the workflow:We will initiate Geomedia-Pro, establish warehouse read-only connections to the necessary data,and create a separate Access warehouse for output. This will be followed by selection ofcounties from Alabama and hydrology for a display backdrop. The DEM files will be imported,resampled to a common resolution. The mosaic command will be used to combine the DEMfiles for display with the other features of the state.

Detailed Steps:

Basic input and display:1. Create a new Geomedia-Pro workspace using the default “normal.gwt” template.2. Browse to locate “USSampleData.mdb” and open a read-only warehouse connection.

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3. Browse to locate “Hydrology_access.mdb” and open a read-only warehouse connection.4. Create a new Access warehouse named: DEM_Project.5. Go to (Legend/Add Feature Class) and select counties and cities to display a map of the US(Image1).

Select Alabama counties:

1. Go to (Analysis/Attribute Query) to open the new query dialogue window.2. Select “Access Connection 1" and then “Counties” in the feature pull-down window.3. Click “Filter” to display the attribute filter dialogue.4. On the attribute list, scroll down and select the variable “STATE_NAME”5. Click the arrow to place it in the query box.6. Click the “=” sign.7. Click the “Show Values” buttons and answer “Yes” when asked if you want to continue.8. Select “Alabama” and click the down arrow.9. Click “OK” to move forward.10. Change the query name to “Alabama_Counties”, leave checks in the display boxes, and OK.11. Examine the data window to confirm that Alabama county data was selected, and close.12. On the display map of the US, use the right mouse button to turn off the display for“Counties” and “Cities”13. That should leave only “Alabama_Counties displayed. Use the “Fit-All” to increase themap size.

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Add Hydrology:1. Go to (Legend/add Feature Class) and select “Access Connection 2) from the pull-down.2. Hold the shift key down and select both “lakes” and “rivers”; then OK.3. After the features are displayed in the legend, right-click in the Legend box and selectproperties. This brings up the “Legend Properties” dialogue box.4. Select the left-most button and highlight (in yellow) all of the row for “lakes.”5. Click the style button, and for the primary color, pick a bright blue. Then OK/OK.6. Repeat steps 4 and 5 above for “rivers.” and then close the “Legend Properties” box.7. Close the “Legend Properties” dialogue.

Reproject to UTM:(Though not necessary, this step will match the display map to the projection used for theDEMs.)1. Go to (View/Geoworkspace Coordinate System)2. Click on the “Projection Space” tab and under the “Projection algorithm” scroll down andpick: “Universal Transverse Mercator”3. Click the “Projection Parameters” and choose Zone 16 in the Northern Hemisphere.4. Close with OK/OK.(Image2)

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Import the DEM files:1. Import the raster DEMs by going to: (Grid/Study Area/Import File(s)). The Connection in thedialogue box should read: “DEM_Project” (the only connection open for writing output).2. In the “Study area name” blank, write: “East_Alabama_DEMs”3 Click “Add Files” and browse to the “East_Alabama_Dems” folder. Select all 4 files andopen.4. On the Import Files dialogue, click OK and examine the Imported file results. Note that theprojection name for each is “Cylindrical Equirectangular” and the Datum is NA-27. Close.5. Go to (Grid/Study Area/List) and confirm that under the “DEM_Project” connection, onestudy area named “East_Alabama_DEMs - Cylindrical Equirectangular” was created with 4layers corresponding to the imported maps. The projection type is added automatically to thestudy area name when it is created by importing files. 6. To display in the map window, select (Grid/Layer/Display in Map Window), shift-select all 4files, and click OK. With the left mouse button, select and drag each of the new entries in thelegend down to the bottom of the legend box so that counties and hydrology appear on top.

Resample the DEM files:1. Open (Grid/Layer/Information) and examine each of the DEM layers. Note that the cellresolution of the “Atlanta-W” and “Birmingham-E” files is the same, but that those two fileshave a slightly different resolution from the “Phenix City-W” and “Montgomery-E” files. Thisis because the DEMs cover one degree of arc, and because each degree of longitude covers anever smaller ground distance as you move toward the poles. Files must have the same resolutionto be suitable for the mosaic command. So the northern two can be merged and the southerntwo merged, but the two sets cannot be combined unless all are given the same resolution (afterclosing the information dialogue, try the (Grid/Layer/Mosaic) command selecting differentcombinations of layers and see what happens). Close the information dialogue box.2. Define a new study area by selecting (Grid/Study Area/Define New) and dragging the mouseacross a rectangle on the map window at least as large as the displayed DEMs. In the “Set upraster study area” dialogue, write “100_Meter_E_Alabama” in the “Study area name” field, andmake sure that the Connection is “DEM_Project” (no other option should be possible). Set thecell resolution to 100 meters. Click set.3. Now we are going to resample (copy at a new resolution) the DEM files into the new studyarea. Select (Grid/Study Area/List), and in the dialogue, make sure that the“EastAlabama_DEMs-Cylindrical Equirectangular” study area is highlighted in the Study AreaList..4. Go to (Grid/Study Area/Reproject/Copy) and highlight all 4 Grid layers. Since we areresampling two-dimensional data, we will opt for the Bilinear Interpolation method, so pick thatradio button. The destination connection should read DEM_Project, and the destination studyarea should be “100_Meter_E_Alabama” (pick from the drop-down). Click OK.5. After the computation (may take a bit longer than previous computations), you can viewinformation about the new files containing the resampled data. Making certain that the“100_Meter_E_Alabama” study area is highlighted on the “Study Area List” (if the list is notdisplayed, you can view it by opening (Grid/Study Area/List)), open the layer informationdialogue (Grid/Layer/Information). In turn, examine each of the DEMs and notice that the

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resolution for all 4 is now 100 meters. Close the information dialogue.6. Making certain that the “100_Meter_E_Alabama” study area is highlighted in the Study AreaList, go to (Grid/Study Area/Select) to view information about the study area containing the newDEM layers. Though the source DEMs came from a Cylindrical-Equirectangular projection, thenew files now match the UTM projection and WGS84 datum associated with the baseGeomedia-Pro map in the display. Close the “Select Study Area Information’ dialogue.7. Display the new DEMs in the map window. Before looking at the new files, remove theoriginal DEMs from the map and legend by right-clicking the mouse on the legend, selecting“Properties”, highlighting in yellow all of the raster-DEM files, and deleting. Then, makingcertain that “100_Meter_E_Alabama” is the selected study area, go to (Grid/Layer/Display inMap Window), and highlight all 4 DEM files. Click OK.

Mosaic the DEM files:1. Since all DEMs in the “100_Meter_E_Alabama” study area are now of the same resolution,they can be combined in a mosaic. Making certain that “100_Meter_E_Alabama” is the selectedstudy area in the Study Area List, open (Grid/Layer/Mosaic) Mosaic Layers dialogue. Highlightall 4 layers and click “>” to select them. Check the “Interpolate gaps” box.2. In the expanded “Mosaic Layers” dialogue, set an output precision of 1 meter, set the searchradius to 5 cells, and leave the Inverse Weighting method button selected (accept the defaultmethod). Name the layer “DEM_Mosaic” and leave the “Place results in map window” selected. Click OK.3. Examine the mosaic layer in the edit window by going to (Grid/Layer/Edit Window) andpicking “DEM_Mosaic”(Image3)

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4. Expand the window and use the “Query Raster Values” tool to look at actual elevations. Notethe prominence of Cheaha mountain with elevation values ranging above 720 meters.5. With the map displayed in the Geomedia-Pro window, examine the patterns of light and darkwith the rivers and lakes in the foreground.(Image4)

6. Save your workspace and exit Geomedia-Pro.

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Phase 2East Alabama Temperature Evaluation

Objectives:1. Evaluate Long-term temperature data for East Alabama2. Improve basic GIS skills using vector and raster-based applications.3. Continue to develop Geomedia Grid knowledge by rasterizing a feature class, interpolatingamong sparse points using ordinary Kriging, and the spatial calculator.4. Evaluating temperature patterns across east Alabama.5. Forecasting January low temperatures for selected locations in East Alabama.

Input files/folders:Files used in Phase 1.Alabama_weather.mdb: access database including weather data for east Alabama.The data were obtained from the Web site maintained by the Southeast Regional Climate Center:http://www.sercc.com/products/historical/historical_al.html

Required Applications:Microsoft AccessGeomedia-Pro v.5.0 or 5.1Geomedia-Grid

General Description of the Workflow:Pre-processing.In order to arrive at a predictive temperature map of East Alabama, the long-term data requiredcompilation and pre-processing which was done using Microsoft Excel and Access. Averagemonthly temperatures were copied from the SRCC web site for locations in East Alabama; andadditional variables depicting elevation-corrected temperatures for the January high, Januarylow, July high, and July low were computed. It is estimated that 1,000 feet in elevationtranslates roughly into a reduction of 3 degrees Fahrenheit. Therefore, 4 additional variablesidentifies as: Elev_stand_Jan_max, Elev_stand_Jan_min, Elev_stand_Jul_max, Elev_stand_Jul_min whichpresented the temperatures that might be expected if the station elevation were sea-level. Additionally, a code number of “999" was inserted if valid temperature data were not available. Two Access tables include 1) all weather data; and 2) only those stations that have validtemperature data.

GIS workflow:Building on the project completed in Phase 1, we will establish a new connection to the weatherdata, import and map the valid temperature data, and rasterize the weather station locations. Thiswill be followed by Kriging to interpolate a raster surface for January lows and computing asurface of predicted lows combining temperature and elevation data.

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Detailed Steps:(note: Phase 2 builds on Phase 1)

Add Warehouse connection and study area:1. If not already done, open the GIS project completed in Phase 1.2. Browse to locate “Alabama_weather.mdb” and open a read-only warehouse connection.3. Add “Valid_Temps” to the map by going to (Legend/Add feature class) and selecting from“Access Connection 3.”4. Increase the visibility of the feature by right-clicking on the legend, highlighting the“Valid_Temps” row in the Legend Properties dialogue, clicking “Style,” selecting “Color” andpicking a bright red. OK/OK/OK to close.5. Create a new Grid study area by going to (Grid/Study Area/define New) and dragging themouse pointer to form a rectangle incompassing the displayed Dem_Mosaic. Make certain thatDEM_Project is the Connection, input “Temperature_Study” in the “Study area name” field, setthe Cell Resolution to 100 Meters, and click “Set.”

Rasterize the “Valid_Temps” feature.1. Open the Study Area List by selecting (Grid/Study Area/List). Highlight“Temperature_Study.”2. In the map legend highlight “Valid_Temps.3. Select (Grid/Layer/Rasterize Feature Class) to create a new raster layer. Check and makecertain that the new layer appears in “Temperature_Study” rather than one of the other studyareas.

Interpolate by Kriging:1. Making certain that “Temperature_Study” is highlighted in the “Study Area List” window,select (Grid/Interpolation/Ordinary Kriging).2. In the dialogue box, make certain that “Valid_Temps” is the shown layer name (it should bethe only one available), and in the drop-down list of Attributes, find: “Elev_stand_Jan_min). Leave the “Mask layer” with the default “(None). Set Output precision to 0.1 (our surface willinclude steps for each 0.1 degree Fahrenheit change), and leave “None” set in the box for units. The model should be “Spherical,” and do not change the Range setting. In the Layer name field,type in: “Sea_level_Jan_min,” and leave a check mark in the “Place results in map window” box.3. Once the image appears on the map, go to the legend and drag the new raster layer(“Sea_level_Jan_min”) down to the bottom so that the stations and hydrology will be visible. You may want to delete the “DEM_Mosaic” legend entry by right-clicking on the legend,selecting properties, highlighting its row, and clicking “Delete.”(Image5)

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View the Interpolated layer in the Edit Window: 1. With “Temperature_Study” highlighted in the Study Area List, open (Grid/Layer/EditWindow). Select “Sea_level_Jan_min” and click “Edit.”2. Zoom out to about a 4:1 ratio and observe the overall pattern of dark and light colors. Scrollthrough the legend and note that temperatures range from just over 25 degrees to almost 36degrees, with the coldest values occurring in the northeast and the warmer areas in thesouthwest. Zoom in and use the “Query Raster Values” tool to sweep across the surface and lookat cell values. 3. You may also want to experiment with different color range settings. Using the shift key,scroll and highlight all of the legend entries. Right-click, pick “Color Sequence” and try differentcolor combinations for the lowest and highest values. 4. Close the edit window, answering “No” when asked if you want to save the changes.

Make a predictive January minimum temperature map.1. Whereas elevation was removed as a confounding variable in the pre-processing of the data, itwill now by re-included. It can be expected that the predicted minimum temperature in Januaryat a given location will by the value shown in the “Sea_level_Jan_min” layer minus the amountassociated with an increase in elevation above the base sea level. As noted above, it is estimatedthat temperature increased by 1 degree for every 333.3 feet in elevation. We will use the GridCalculator to create this new predictive surface. Since our DEM_Mosaic indicates elevations in

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meters, we will first determine the temperature change per meter. The value of 333.3 feet equalsabout 102 meters.2. In order to perform computations combining information from different layers, both layersmust be in the same study area. Therefore we will copy our DEM_Mosaic layer into the“Temperature_Study” study area. 3. Highlight “100_Meter_E_Alabama” in the Study Area List. Select (Grid/StudyArea/Reproject/Copy) to open the Reproject/Copy dialogue box.4. Highlight “DEM_Mosaic,” pick “Bilinear” radio button, and select “Temperature Study” asthe destination study area. The Connection cannot be changed from “DEM_Project.” Click OK.5. Open (Grid/Calculator). Double-click on “Sea_level_Jan_min;” click “-” to subtract; click on“(“ to open a set of parentheses; double-click on DEM_Mosaic; click on “/” to divide by; typethe value of 102 into the equation line; and click “)” to close the parenthesis. The equation lineshould look as follows: “Sea_level_Jan_min” - (“DEM_Mosaic”/102). For the output layername, type “Temperature_Prediction” in the Layer name field, leave the box checked to view theresults in the map window, and click “Evaluate.”6. Open the Edit window (Grid/Layer/Edit Window) by selecting the “Temperature_Prediction”layer, and look over the values. This layer shows what you might expect as a minimum Januarytemperature given observed temperatures and elevation.

Overall Assessment:1. In the map window look at the pattern in the context of the hydrology. Note the apparentmoderating effect of the Coosa river and Lake Martin. As an additional task, you may want toplot major cities such as Birmingham and see if this appears to be related to the temperaturepredictions. (Image6)

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2. Finally, using the Edit Window, you might actually predict the value for a specific location. For example, if you have a farm in Lee county located at the exact UTM coordinates of:662118.40 E and 3613756.55 N, then your predicted January minimum temperature will be 27.8degrees Fahrenheit. 3. Save your work and close Geomedia-Pro.