Thank you Storm Rider.
ORIGINAL: storm rider
Unless you plan to further process the heightmap in some other apps, you should export it to BMP.
It is not necessary to export with a sample spacing of 30m at this point because you can always resize it to 2048px in photoshop or gimp later on.
Thanks to let me know. Could you let me know how can I use QGIS to export map bmp in 30m/px, or 2048px for 61.440km?
Also, before you export, you need to make sure that your raster map is properly configured in the right color gradient.
Check this post for more info:
This is the exactly the one that I was curious. Each wargames have their own format for contour. It seems that I miss that part in my files.
But I still couldn't get it. Above example of north east Hamburg region only contains -13m ~ 115m. I just round them to 0 to 100m, but I think I shouldn't do that rounding. Anyway, I think I just can use red channel in this case since the highest height is only 115m, inside the red channel range of 0 to 255m, right?
But I'm still not sure how much color gradient I need to choose in this case for QGIS.....
Formula is (Red Channel) + (Green Channel * 255).
For example: if a pixel value is RGB (171,1,0) then the height is (171) + (1 * 255) = 426
Another example: if a pixel value is RGB (107,2,0) then the height is (107) + (2 * 255) = 617
Is QGIS possible to use the same option like those from Global Mapper?
I don't really use QGIS. I much prefer Global Mapper. From the QGIS (OSGeo4W package) I mostly use SAGA because of its simplicity and easy to use. I find QGIS and GRASS to be all very stupidly hard to use finicky with every little detail, clunky unfriendly and Python interface based (I hate Python and Github!)
The way to do it in global mapper is to create a rectangular polygon w/ specify coordinates, than choose the one option which allows you to specify the length in meters = 61440m.
Then with the digitizer tool, right click on this square and move it around the map to where you want. Select the proper raster gradient to be displayed, then make sure to have square selected. Go to File>Export Raster to bmp, 30 sample spacing and select crop to the selected feature (which is the polygon). It will extract only the area inside the polygon which is 61.440km at 30m/px = 2048px in length. Ideally this exported heightmap, depending on the region's characteristics and data source, be post processed to smooth the ground out of all the noise or even to remove the elevation anomaly caused by the canopy of vegetation.
It sounds simple, but I know that every little thing in these gis programs are all a real pain in ass. Once I have some time and have figured the best settings for post processing, I'll make a little easy guide.
< Message edited by storm rider -- 11/24/2018 9:35:23 PM >