Creating a 3D Terrain Model by 2Um1O0QL

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									Creating a 3D Terrain Model
        and Flyover
        Bonnie J. Brown
  CAST – University of Arkansas,
          Fayetteville
First you need to figure out what data you need. This is sort of like getting
    the ingredients together for a recipe. The basic data you are going to
    need for this is elevation data, which is in raster format. You may wish to
    add vector data or a DOQ into it.

The instructions here will take you through using digital elevation model
   (DEM) data from the National Elevation Dataset.

        If you are from Arkansas, follow the instructions for data
          download and preparation here:
    http://www.cast.uark.edu/east/support_info/Arkansas_elev_data.htm

        If you are from any state follow the instructions for data download
          and preparation here:
        http://www.cast.uark.edu/east/support_info/elevation_data_anystate
        .htm
3. Once you have downloaded and prepared your data, go to the Add
Theme button. It looks like a plus-sign sitting on a diamond. You can
also go to the View menu and click, “Add Theme.”

4. Change the data source type to Grid. Browse for the data you just
prepared and select that as the theme you want to add. Your view will
look similar to the one below.
5. The numbers to the side of the
different shades, are the values for the
elevations. Elevation is measured in
number of meters above sea level. In
the example above, the darker reds
represent higher elevations.

6. Double click on the legend and
change the color ramp (located at the
bottom of the Legend Editor) to Terrain
Elevation #3. (This step is optional,
you can make it any color scheme you
wish. The terrain elevation schemes
however, generally allow for a nice
visualization) Close the Legend editor.
Now go to the View menu and select 3D Scene. You have a choice to add it as
a theme or an image. Choose Image and click OK. Your 3D scene will be
similar to the image below. Don’t worry about the white around the DEM.




        Navigating around the 3D scene is a bit different than
        the 2D. Use the icon that looks like a ship to move and
        rotate the scene.
 NOTE: There is a button that will make your 3D
 scene spin around.



 Do NOT click that button until you have your main ArcView window maximized.
You will not be able to stop it from spinning if you can’t get to the Stop button in
the lower right corner of the screen. You won’t be able to see that Stop button
unless the main ArcView window is maximized.
You may have noticed that your 3D scene looks pretty much 2D. That’s
because we haven’t added the third dimension yet.
 Go to the theme menu and select 3D properties. In the “Assign base
heights by:” section select surface and then click the browse button next to
the white box.




                                    When the Get Source window pops up.
                                    Select your elevation data. It should be a
                                    Grid source type
The Z factor determines the amount of exaggeration to your elevation. Its
something you will need to adjust to get the visualization you are looking for.
Start out by changing your Z Factor to a number between 1 and 10. Then make
your adjustments according to the look you want. Click OK.




                                     Now you have a basic 3D terrain model.
                                     The next section will show you how to
                                     create a “flyover,” of your terrain model.
            The “Flyover.”
To create a flyover you will need to
 download a special extension for ArcView
 3D Analyst. The next few slides will cover
 the download and installation process for
 an extension called 3D InControl. It is
 freeware so you don’t need to worry about
 licensing.
First go to the following web page. http://arcscripts.esri.com/ Change the search
parameters from “All ESRI Software” to “ArcView GIS. In the “Search For” box,
type “3d AND fly.” When the search is complete, Click on 3DInControl.
Click the download button. The next page has information regarding
public domain, copyright, etc. Scroll down and accept the agreement



                                        When you get the file download
                                        window. Click save. The file will
                                        come to you zipped. You will
                                        need to use an application such
                                        as ultimate zip, winzip or the like
                                        to unzip or extract the file
                                                 Unzip the file to the path specified

                                                 C:\ESRI\AV_GIS30\ARCVIEW\EXT
                                                 32

                                                 IMPORTANT: 3DInControl comes
                                                 with a Read Me file that has some
                                                 specific information on how to use
                                                 the extention. You will need to get
                                                 it out of the EXT32 folder once you
                                                 have extracted the file.

Go back to ArcView. If you still have your 3D scene up close it. Go to the File
menu and select Extensions. Check 3DInControl. Go back and open up your 3D
scene again.

Click the Add Theme button.


Add the grid file for your elevation data but do not click the check box next to it.
Click once on the grid them you just added so as to make it the active theme.
Go to the Theme menu and select 3D Properties.




Assign base heights
by Surface. Then
browse for your grid
theme as you did
with your image
theme.
Set your Z factor to
the same value as
your image theme.


Click OK
                     Click the blue button to
                     the far right. After you
                     click it you should see a
                     little control panel pop up.




Click the button that looks like a little globe.
Arrange the windows so that you
can see the 3D scene, the 3D
Scene PlanView, and the Control
panel.
                               Observer


                             The PlanView is the window
                             where you will draw your flight
                             plan. The target (in red) is the
    Target                   location where you, the observer
                             (in black) will be looking.



    Target

             To change the observer location, click the blue
             and black button. Then click the location in the
             PlanView.

             To change the target location, use the button
Observer     with the circle and crosshairs.
Click the button with the
squiggly to draw your flight
path in the PlanView.
Once you have your flight plan drawn, you will need to check other settings in the
control panel. You can change any of the numeric values by clicking the up or down
arrows.

Step: Controls your speed of flight.

Observer: The altitude must be set higher than the highest elevation in your DEM.

Target: Should be equal to or lower than your observer. You may find that every
time you change your flight path, you must reset your target and observer values.

Angle, Roll and Rotate. These should be set to your personal preferences

Try first looking at the Target at a Constant altitude. (If you look In Front and have
your altitude Above Terrain, you will find it a bit jerky.)
When you are ready to fly, click the little running man.

								
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