02-13-2018 04:29 AM - edited 02-13-2018 04:30 AM
I'm trying to extract the snow cover from a raster satellete picture.
Any hint how to vetorize a raster file with geomedia desktop or other component in order to filter the pixels with specific values ?
If not possible, any hint how to achieve this ?
Solved! Go to Solution.
02-13-2018 04:59 AM
unfortunately it is quite difficult to give more specific answer. The Grid is a complex bundle of commands and to work with it, it is the best to start from beginning with the tutorials. If you want a shortcut, you can look at GeoMedia Help > Overview of GeoMedia > Grid Analysis > Layer Menu > Vectorize to Feature. But I am afraid you will need to learn more about Grid anyway.
By the way, there are more tools in Grid than Vectorize, and some of them like edge detection may also be useful for you. So it would be good to get some overview of Grid first.
02-13-2018 05:32 AM
I used the function output to geotiff for my georeferenced snow cover raster, And it worrked perfectly.
I tried to import my geotiff file using import function in the grid tab.
Although my raster file has a square cell resolution , I got this error:
Error description: The x and y resolutions are not equal. GeoMedia Grid does not support non-square cells.
Any clue how to solve this issue ?
02-13-2018 05:53 AM
OK, I don't know in this case. I told you that you would have to learn GM Grid in more details. One more idea - make sure that the coordinate system used is the one native for the raster image. The grid should be rectangular then.
03-09-2018 01:44 AM - edited 03-09-2018 01:45 AM
After some research, I managed to find a solution...
Here is a solution in case someone needs it :
The georeferencing tool of Geomdia desktop turns square cells of a raster file to non square cells when the transformation is not linear, meaning that any rotation or polynomial transfomation of the raster file will result in non square cells that unfortunately can't be imported into Grid using the import tool of the Grid menu, hence it's not possible to vectorise the raster file...
On the other hand, It's possible to Georeference the raster file in a different GIS software( I used QGIS with polynomial transformation), and the output raster file will remain a square cell raster that can be imported into Geomedia using the import Raster tool of the Grid menu. The output file will be a .mfm grid file that can be vectorized using the vectorize to feature tool in the Grid menu.
All the best,