Making 1-meter Heightmaps for RT3
The following is a step-by-step set of instructions for making a heightmap for RT3 that will have 1-meter resolution . It assumes the reader has very little familiarity with Microdem. You will need the special version of Microdem that supports Elevation Tables containing more than 1024 entries. The updated program and complete elevation table can be obtainedHERE. This tutorial can be obtained in PDF format HERE. Rename your old Microdem.exe (i.e. Microdem.old) and unzip the three files in the ZIP archive into the Microdem program directory
The GTOPO30 Digital Elevation Model (DEM) dataset contains data that are spaced at 1km intervals measured at the equator; resolution increases as one moves away from the equator. The data are supplied in tiles and can be obtained from USGS athttp://edcdaac.usgs.gov/gtopo30/gtopo30.asp. The following example will use the E60N40 tile, which contains nearly the full range of elevations found on Earth, from the Indian Ocean to Mt. Everest. Unzip the data into the "mapdata\DEMs" folder on the drive that contains the Microdem program.
Start the Microdem program. If you haven't already done so, turn off the grid markers and marginal information.
Click on "Options" on the menu bar and select the "Maps" tab:
Set the Default display to "Elevation" and uncheck "Marginal information". Then click on the "Grid" Button:
Set the Grid to "Neither" and click "OK", then change the Latitude/Longitude units to be in decimal degrees. Click on the "Units" tab:
and click the "Decimal degrees" radio button. Click "OK" and then close the "Options" dialog box by clicking "OK".
The first step is to generate a DEM file of the exact area you want to convert. Load the DEM that contains the area you want to map. Click on "File" and then "Open DEM".
Click on the "Files of type" dropdown arrow
DEM data from the GTOPO30 set are opened through their "header" file (.hdr). Select the DEM you want to use and click "Open"
Click on the "Subset and Zoom" button (fourth from the left, at top of map) and click and drag to select an area a little bigger than the area you want for your final map. Position the pointer in the upper left of the area you want, hold down the mouse button and drag to the lower right corner. Then release the mouse button.
The selected area will now be shown. You could also select an area by Latitude and Longitude. Click "Modify" on the menu bar, then "Map Area" then "Keyboard corners".
This brings up a dialog box that allows you to manually set the boundaries of the map.
Click "OK" to move to the SE corner and click "OK" again to close the box.
Continue taking subsets of the data until you have the area you want to use for your map. It helps if the area is a little bit larger than you actually want so that you have some data in case you need to tweak the dimensions of your map a little. The final dimensions of the map will be set in the next few steps.
Save the subset and reload it: Click "File", "Save DEM" and "Current subset, MD DEM :
Then type in a name for the new DEM that will contain only the data for your map:
Type in a name and click "Save". Close the window with the current map (click on the "X" in the upper right corner of the window) and open the DEM you just saved. If you want to further refine the area for your map, take a subset of the currently displayed map as decribed above. When you are satisfied with the result, expand the map to give a 1:1 image (click the magnifying glass with the "1" in it or Click "Modify" "Map area" "1:1 view" on the menu bar. Bring up the Information box to see what the dimensions of the displayed map are:
Decide the number of horizontal cells (East/West) you want on your final map. Say you want the RT3 map to be 448 cells from left to right (64 x 7). Zoom out to give a view of the displayed map that has 448 pixels in the horizontal direction. Start the Windows Calculator (from the Start menu) and divide the number of pixels that the map currently has by the number you want (in this case 830 / 448). Copy this number to the clipboard (Ctrl-C) and then click on the "Zoom out" button (the magnifying glass with the red "-" sign) or click "Modify", "Map area", "Zoom out", and paste the number into the "zoom out factor" box:
The numbers you see in the box are the rightmost digits in the value copied from the calculator, although the entire number has been copied into the calculator. Click on "OK" to resize the map:
As the Information box shows, the map has been rescaled to be 448 pixels across. The vertical dimension, however is not an even multiple of 64. The nearest even multiples of 64 are 704 (64 x 11) and 768 (64 x 12). We can either reduce the range of Latitudes slightly to make the range map 704 pixels, or we can add pixels to the map to bring the image size to 768 (assuming that the current DEM contains the data). Since the bottom of the map is all ocean, we will do the former, that is crop the Latutude range down by 44 pixels, although a similar method would be used to enlarge the map.
Find the difference in Latitude between the top and the bottom of the map and divide by the number of pixels to obtain the degrees of Latitude per pixel. To see the limits of the current map, begin by clicking "Calculate", "Map window corners":
To bring up a box that shows the Latitude and Longitude of the four corners of the map:
Here we see that the Latitude at the top of the map is 32.4291696 degrees and the bottom of the map is 16.4208354 degrees. The difference between the two is 16.0083342 degrees. If we divide this number by 748 pixels (height of map) we get the number of degrees per pixel, and if we multiply by the number of pixels to crop (44) we get 0.941667 degrees. If we wanted to add a few pixels we would multiply the degrees/pixel by the number of pixels to add to get the amount, in degrees, to expand the map. In this example, we can take the 0.941667 degrees away from the top, the bottom or both. We'll start by taking it away from the bottom, which is mostly ocean anyway. Since we are removing pixels from the bottom of the map, we want to add 0.941667 degrees to the Latitude of the SE corner. We can do this with the "Keyboard corners" used before. Click on "Modify". Map area", "Keyboard corners" and click "OK" for the NW corner values. Type in the new value for Latitude (16.4208354 + 0.941667) or 17.3625021 degrees.
And click "OK". The new map should now be 448 x 704 pixels. Recalculate the map corners to bring up the new values for the four corners of the map. You may want to print them out at this point for later reference.
Click "OK" to clear the Information box. Save the new map coodinates for later use. It is important to do this if you want to go back and exactly reproduce the map you just made. First click "Modify", "Map area", "Save" and type in a name (be sure that it is saved in the \mapdata\DEMs folder:
Now we need to recolor the map.
Click on "Modify", Elevation", "colors" and then click the "Colors from table" radio button, and then the "Elevation table" button:
Select "ELEV_COLORS_0-9999.dbf" and click on "Open". If you want the ocean to be recognized, it must be colored Red. The GTOPO30 datasets do not contain data for ocean elevation; the data are "missing". To get the map colored correctly click on the "Missing" button and choose the bright red color box:
then click "OK" to close the "color" box and then click "OK" to recolor the map.
Save the colored map. Click on "File" and "Save image":
And save the file in the RT3\Data\GrayscaleMaps folder:
You can exit the Microdem program and Open Irfanview. Open the file you just saved:
The file should open as a bitmap:
Then click "File" and "Save as" and select "Save as type TGA - Truvision Targa" in the dropdown menu. Select the RT3\Data\GrayscaleMaps as the "Save in" folder:
Then click "Save". You can now quit Irfanview.
The map is now ready to be imported into the RT3 editor. Start RT3 and make sure you're in Windowed mode (if the first menu covers the whole screen, press the "F9" function key.:
Click on "Extras" then "Editor" then "New Map" then "From Heightmap":
Select your heightmap and click "Open".
Change the "Overall Height Modifier" to 1.431 and click "OK"
Click "OK" to keep the "mountain top height modifier" at 1.0
And either keep the "Smoothing Modifier" value at 1 or change it to 0. If you have a lot of sharp peaks, you may want to use a smoothing factor of 1. If your original map does not have any steep elevation changes you can change the value to 0. Then click "OK" to make the map.
As you can see, this map has very steep mountains, so a smoothing factor of 1 would probably be better:
The drawback is that the elevations are now smoothed and are not exactly accurate. Most maps will not have the dramatic elevation changes in this example, so a smoothing factor of 0 will work fine.
If you are satisfied with the result, save your RT3 map.