Quick Guide to Making 3-D Views from DEMs

More Information about DEMs

• Return to Digital Elevation Models
• USGS Digital Elevation Models
• DEM Viewing Software

This page outlines a simple step by step process for making 3-dimensional views using a Digital Elevation Model (DEM) file and a free software package called MicroDEM.

To make your own views you will need:

1. A copy of MicroDEM. The version we used is version 10.36. You can get that here.
2. A DEM. - We have several DEMs available free for download.

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How to Make a Perspective View

Steps:

1. Open a new DEM in MicroDEM.
2. Select perspective under the view menu.
3. Choose reflectance.
4. Double click on the point you wish to view from. Hint: Select a point with a good view shed, like a hill top. A contour map will now appear. The contour map is a zoomed in view of the area you just selected. Double click again in the location you want as your view point.
5. A triangle now appears that you can drag to create the view direction and vanishing point. Moving the triangle about two screen inches should provide for a good view.
6. Double Click again and the perspective will be drawn.
• If you don't like the view point you have chosen, you can redo the above steps till you get a better view. If this is the case, close the perspective window and return to step 2.
• If you like the location of the view point, but are not happy with the way the perspective was rendered you can, right click on the image to change the settings of the view.
• The vertical angles control the upper and lower extent of what you will see. Zero is horizontal. Positive numbers are for up, and negative numbers are for down. It works better to use a large look angle, like 40-degrees(i.e. 20 up ,-20 down), for near views and a small look angle, like 20-degrees, for far views.
• The view width is also a factor of the distance of the view. Use a low number like 40 for long views and 60 for short views.
• In the observer above ground box you can change the elevation from which the view is built. If you change the elevation, your view angles will have to compensate. You can use a high elevation to get aerial perspectives.
• Points per radial changes the resolution of the perspective image. A high number takes more time to compute, but the resulting image is visually smoother.
• You can ignore the observer elevation.
7. Once you are satisfied with the changes, click OK and the image will redraw. Repeat this process until you are satisfied with the result.
8. To save the results go to the file menu and then select save image. You will have to save the view as a BMP file. You can then edit the view in a bitmap editor like Corel Photo-Paint or Adobe Photo-Shop and then resave it.

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How to Make an Oblique View

Steps

1. Open a new DEM into MicroDEM.
2. Select oblique under the view menu.
3. Choose DEM reflectance.
4. The oblique will be made from a square area. Double click on one of the corners of an area you wish to portray.
5. A square now appears that you can drag to create the oblique viewing area. Choose a size that covers the area you would like to see, but you can only select an area that is completely within the boundary of the DEM.
6. Double Click again and the oblique will be drawn.
• If you aren't satisfied with the represented area, you may want to close the perspective window and return to step 2.
• If you like the location, but are not happy with the rotation or the appearance of the terrain, you can right click on the image and change the settings for the oblique view.
• The vertical exaggeration controls how much the elevation is exaggerated. A setting of 1 is normal and any other number is an exaggeration or a reduction. A multiplier of two or three is usually adequate to help reveal some of the more subtle variations in most Wisconsin terrains. Negative numbers will make the slopes negative, which reverses the DEM. If you want to reduce the exaggeration you will need to use a fraction in decimal form like 0.75 for example.
• Rotate allows you to rotate the view around the images ceteral point. You can only rotate in increments of 90-degrees.
• Method changes how the oblique is rendered. Reflectance is the shaded relief method currently used. Feel free to experiment with the other methods on your own.
• The number by a number represents the resolution for the oblique view in pixels.
• If you want to change the shaded relief effect, click the reflectance button. From here you can change the sun's position in the sky as well as its angle. The location of the sun will change the shaded appearance of your view. The azimuth is the compass direction of the sun's location. The elevation is the sun's angle above the horizon.
7. After making changes to these settings, click OK and the image will redraw. Repeat this process until you are satisfied with the result.
8. To save the results go to file and then select save image. You will have to save the view as a BMP file. You can then edit the view in a bitmap editor like Corel Photo Paint or Adobe Photo Shop.

MicroDEM has many other features that you may want to explore on your own. Some of these features include: making a fly through, draping line files on the DEM, and draping an aerial photograph or satellite image on the DEM. These techniques are for a more advanced user. We suggest you read the help file that comes with MicroDEM. The help file includes the information necessary to assist you with these, and other more advanced features of the program.

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