A small cli tool to download heightmap-images from Geoportal Bayern's Bayernatlas
Just running the program with dotnet run displays this help:
Usage: bayernatlas-heightmapper [-h] [-v] [-S] [-r] [-u <units>] [-s <size>] [-t <step>] centerX centerY [outputFile]
Download heightmap images or heightmap values from Bayernatlas.
centerX: Longitude in GK4-Coordinates.
centerY: Latitude in GK4-Coordinates.
Options:
-h, --help Display this help
-u, --units Units per pixel (meters). Default is 20
-v, --verbose Print occurring exceptions
-S, --simple Use a simplified downloading algorithm (not necessary in most cases)
-s <size>, Specify size (two-value tuple) in GK4 units in each direction from the center.
--size <size> Example: 12000,12000
Default: 5000,5000
-x <by>, Scale the resulting image by that factor
--scale <by> Example: 5
Default: 1
-r, --raw Don't render an image; output raw numeric height values instead
-t <step>, Instead of saving the image as a heightmap, draw a simplified topographical map
--topo <step> The lines will be separated by 'step' meters of height.
Example: 22.5
outputFile:
Write the output to a file.
When not using '-r' or '--raw', this must be set.
The website and its api use GK4-Coordinates. One unit in this coordinate system is equivalent to 1 meter in real life.
- Get the GK4 coordinates of the location you want to have at the center of the image.
Simply right click on the website:
- The fourth row contains the required coordinates. (marked with the text
GK4)
Of course, the dialog layout might change in the future if the website gets updated.
- Then, download a heightmap using the following command:
dotnet run 4466640 5418104 heightmap.png
By default, a pixel will represent an area of 20x20 meters.
This can be changed by using --units 100, to change it to 100x100 meters for example, etc.
The lower the value, the higher the resolution, but the longer the image will take to download.
The resolution is also limited by the server. --units 20 is approximately the minimal value.
Below that you don't really get any more precision as the server itself interpolates the values internally.
The physical size the image is covering can be changed by using --size. For example to capture an area
of 10000x8000 meters, you would have to use --size 5000,4000, as it specifies how far the region extends into each direction
from the center. I.e. 5000m north, 5000m south and 4000m west, 4000m east. So the resulting area will always be double that of size.
By default, size is set to 5000,5000.
dotnet run 4511300 5378491 heightmap2.png --units 30 --size 10000,8000
dotnet run 4481536 5422592 heightmap3.png --units 200 --size 130000,180000
This is a map showing the entirety of bavaria.
The server does not have data outside the state borders, thus looking a bit chipped at the edges.
At the end of each download you will see a summary of some parameters:
Final Parameters:
Minimum Height: 370.53
Maximum Height: 518.14
Size-X: 10000
Size-Y: 8000
Center-X: 4511300
Center-Y: 5378491
Units per pixel: 30
Final image size: 666x533 pixels
Important are the Minimum Height and Maximum Height values, as they directly correspond to a pixel value of 0 and 255 respectively. All values are interpolated linearly within this range.
When importing the image as terrain in 3D software or a game engine, you need to specify this height range.
By using the argument --raw, instead of rendering an image, the raw height-values in meters will be saved.
It is a simple collection of space-separated values, where each line contains the "pixels" of the image row-by-row.
These values are not interpolated to fit any particular range, allowing more precision than the image version, as the raw numbers are outputted.
By using the argument --topo, instead of outputting a grayscale heightmap, a simplified
topographic map will be rendered.
Specify the height-spacing of lines after the --topo argument.
The coloring is chosen according to this hardcoded table:
| Height (m) | Color |
|---|---|
| < 0 | black |
| 0 | rgb(120, 170, 255) |
| 200 | rgb(240, 255, 200) |
| 350 | rgb(170, 255, 120) |
| 450 | rgb(170, 200, 50) |
| 600 | rgb(140, 160, 50) |
| 1000 | rgb(255, 200, 120) |
| 2000 | rgb(255, 240, 200) |
| > 10000 | rgb(255, 255, 255) |
The output is linearly interpolated for any height between two values.
Examples:
dotnet run 4307200 5538368 topo1.png --topo 10 --scale 5 --size 6000,6000
dotnet run 4613664 5409312 topo2.png --topo 12.5 --scale 5 --size 15000,15000
(The image shown has been scaled down to 1500x1500 from its original resolution of 7500x7500)