Subset terrain corrected GRD products in Graph Builder

Hi, everyone!

I am trying to subset an area from S1 GRD files using the following graph builder and WKT coordinates.

POLYGON ((68.38 40.25, 68.55 40.25, 68.55 40.4, 68.38 40.4, 68.38 40.25))

The GRD files are projected to UTM coordinate, and I want to subset them by Lat/Lon. But when I click the update button, it cahnges to the WKT like this.

POLYGON ((68.37999725341797 40.25, 68.55000305175781 40.25, 68.55000305175781 40.400001525878906, 68.37999725341797 40.400001525878906, 68.37999725341797 40.25, 68.37999725341797 40.25))

For I need to get a area with fixed pixel size, it seems a little different from what I want. And I try to batch process 156 S1 products, so I prefer Graph Builder. If anyone has any advice, I would greatly appreciate it!

I think the changes of the coordinates are caused by the pixel size of your raster because SNAP cannot cut the pixels in half. So what is suggested as wkt is probably the closest to your entered geometry which is possible.
Could that make sense?

Yes, I tried to enter a closer wkt coordinate. Like this:

POLYGON ((68.38000274658203 40.25, 68.54999694824219 40.25, 68.54999694824219 40.39999847412109‬, 68.38000274658203 40.39999847412109‬, 68.38000274658203 40.25, 68.38000274658203 40.25))

But it seems a invalid parameters in SNAP. What’s more, I used the Raster-Subset Tool to do it, it works. So I really want to konw the reason.

What kind of error message do you get?

Is the problem that the coordinates change or that you get no result?

Just like this:

this is the WKT in UTM 42N coordinates
POLYGON((447270 4455689, 447270 4455689, 447386 4472339, 461813 4472252, 461728 4455602, 447270 4455689))

As your data is already projected, it might be worth a try.

Thanks a lot! :blush: