Hexagon Geospatial
MENU

Support GeoMedia

Search for an answer, post a question, or answer other users' questions in our GeoMedia support discussions. This discussion board is a great way to collaborate with industry peers around the world. It is intended for discussion and support of the GeoMedia Desktop and Add-on applications.
Showing results for 
Search instead for 
Do you mean 
Reply
Highlighted
Contributor
Posts: 60
Registered: ‎10-10-2017
Accepted Solution

Vectorize raster

[ Edited ]

Hi, 

 

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 ?

 

 

Thank u 

Phoenicia

 

Technical Evangelist
Posts: 492
Registered: ‎09-11-2015

Re: Vectorize raster

Hi Phoenicia,

 

this is typical task for GeoMedia Grid.

 

Pavel

Contributor
Posts: 60
Registered: ‎10-10-2017

Re: Vectorize raster

Thanks Pavel, 

 

Can u be more specific in the steps ?

 

Thank u 

Phoenicia

 

Technical Evangelist
Posts: 492
Registered: ‎09-11-2015

Re: Vectorize raster

Hi Phoenicia,

 

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.

 

Pavel

Contributor
Posts: 60
Registered: ‎10-10-2017

Re: Vectorize raster

Hi, 

 

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 ?

 

Thank u 

Phoenicia

 

 

 

 

Technical Evangelist
Posts: 492
Registered: ‎09-11-2015

Re: Vectorize raster

I think in this case it will be safetier to rasterize the feature class first - even if it is a raster feature class, then vectorize.

 

Pavel

Contributor
Posts: 60
Registered: ‎10-10-2017

Re: Vectorize raster

Hi, 

 

the rasterize function gives u only access to vector feature classes to rasterize them.

How to rasterize a raster feature class ?

 

Phoenicia

 

Technical Evangelist
Posts: 492
Registered: ‎09-11-2015

Re: Vectorize raster

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.

 

Pavel

Contributor
Posts: 60
Registered: ‎10-10-2017

Re: Vectorize raster

[ Edited ]

Hi,

 

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,

Phoenicia

 

Do you need immediate support?
If you encounter a critical issue and need immediate assistance please submit a Service Request through our Support Portal.