3d_surface_contour_aerial.pdf

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Creating a 3-Dimensional Surface Diagram Based on a Two-Dimensional Contour Map & an Aerial Photograph

Table of ContentsIntroduction ...................................................................................................................................................................2 Step 1: Select the RockWorks Screen Digitizer ............................................................................................................2 Step 2: Load the raster image ........................................................................................................................................3 Step 3: Calibrate the map...............................................................................................................................................3

Step 4: Calibrate using three points (optional) ..............................................................................................................3 Step 5: Zoom into the map.............................................................................................................................................4 Step 6: Set the digitizing mode......................................................................................................................................4 Step 7: Enter the contour elevation................................................................................................................................4 Step 8: Digitize the contour line ....................................................................................................................................4 Step 9: Repeat for other contours ..................................................................................................................................5 Step 10: Export the data.................................................................................................................................................5 Step 11: Create a grid model of the digitized contour data............................................................................................5 Step 12: Drape the photograph over the grid model ......................................................................................................6

Table of Figures

Figure 1: Bitmap (BMP) based on a scanned USGS topography map. ........................................................................2 Figure 2: Bitmap (JPEG) of aerial photograph. .............................................................................................................2 Figure 3: Grafix / Digitize from Bitmap menu item......................................................................................................2 Figure 4: Load Bitmap menu option..............................................................................................................................3 Figure 5: Screen digitizer calibration screen .................................................................................................................3 Figure 6: Screen digitizer Size setting ...........................................................................................................................4 Figure 7: Digitizing contour lines..................................................................................................................................5 Figure 8: 3D surface for the grid model generated from the digitized contours ............................................................5 Figure 9: Graphix / 3D-Utilities / Images / Drape menu settings ..................................................................................6 Figure 10: 3D view of aerial photo draped over the grid model ....................................................................................6


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IntroductionThis case study describes how to create a three-dimensional surface diagram based on a scannedtopography map and an aerial photograph as shown within the following example.

Figure 1: Bitmap (BMP) based on a scannedUSGS topography map.

Figure 2: Bitmap (JPEG) of aerial photograph.

Step 1: Select the RockWorks Screen DigitizerIn the RockWorks Utilities, go to Graphix/Images/Digitize from Bitmap.

Figure 3: Grafix / Digitize from Bitmap menu item


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Step 2: Load the raster imageSelect the File/Load Bitmap option from within the "On-Screen Map Digitizer".

Figure 4: Load Bitmap menu option

When prompted for the file name, select the file that contains the topography image and click on the OK button.

Step 3: Calibrate the mapGo to File/Calibrate. RockWorks offers you two methods for calibrating the map; if you know thecoordinates at the edges of the map, select the option labeled "Min/Max Calibration" and enter thecoordinates represented by the edges of the map. Skip to step 5.

Figure 5: Screen digitizer calibration screen

Step 4: Calibrate using three points (optional)

If you don't know the map border coordinates, select the option labeled "3-Point Calibration". Enter thecoordinates for three known points and select the "Ok" option. You will then be prompted to digitizethose three points within the map display. If you don't know the coordinates for three points or the mapedges, you're out of luck.


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Step 5: Zoom into the map

Enlarge the map to the desired size (using the Size option).

Figure 6: Screen digitizer Size setting

Step 6: Set the digitizing modeSet the Mode option (located at the top/middle of the screen) to "Points".

Step 7: Enter the contour elevation Notice the Elevation option location at the top-right corner of the screen. As you digitize contours, youmust remember to change this to the appropriate contour level each time you change lines. Set this to agiven contour interval.

Step 8: Digitize the contour lineStart clicking on points along a given contour line. Notice how the xyz coordinates for these points aredisplayed along the right side of the screen. Later on, we'll be using these points to generate a grid modelof the topography. Also notice how small "x" symbols will be plotted along the points that you'vedigitized. These points help you to keep track of what you've already digitized. Don't be afraid to enlargeand reduce the diagram as you digitize; the program will keep track of the coordinates - the program willnot modify your original bitmap file. If you make a mistake, move the cursor to the data window anderase the mistake.


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Figure 7: Digitizing contour lines

Step 9: Repeat for other contoursRepeat this process for all of the contours. Don't forget to change the elevation setting when you changecontours. Also remember that you can edit the data within the data window.

Step 10: Export the dataWhen you've finished digitizing the contours, select the File/Export/RockWare Utilities Datasheet option.This will transfer the digitized points into the Utilities datasheet.

Step 11: Create a grid model of the digitized contour dataIn the RockWorks Utilities, select the Map/Grid-Based-Map option and create a grid model based on thedigitized points. This case-study will not go into the details of this operation. Please see yourRockWorks manual or on-line help for more information about the gridding options.

Figure 8: 3D surface for the grid model generated from the digitized contours

The diagram that is produced by Grid-Based-Map program will not be used within the following steps --we'll be using the grid model instead. But ... while you're here, have a look at the surface and make surethat it's a good representation of the original contour map.


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Step 12: Drape the photograph over the grid modelSelect the Graphix/3D-Utilities/Images/Drape option. Enter the name for the aerial photograph and thegrid and select the "Ok" option.

Figure 9: Graphix / 3D-Utilities / Images / Drape menu settings

The resulting diagram should show the aerial photo draped over the grid surface.

Figure 10: 3D view of aerial photo draped over the grid model

3d_surface_contour_aerial.pdf

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