Reproject and collocateWith graph example


#1

Hi,

I’m new to snap and trying to automate some data conversions with gpt. I’ve tried to understand the tutorial and the most helpful thread I’ve found on this topic so far ([here] (Best practice to convert and reproject Sentinel-3 radiances to reflectance)), along with gpt -h and gpt Reproject -h.

I can successfully extract a band (using BandExtract) and reproject the data using the Reproject example from the two links above. However, I cannot figure out the correct XML to reproject using collateWith and an existing HDF5 file I have.

In the GUI GraphBuilder and Reproject, I can’t find a way to set a collocateWith option. Am I missing something there? I only see “Custom” and “Predefined” CRS options.

In the GUI GraphBuilder and Collocate (is this even what I should be using?), I see an error (red text) that states, "Error: [NodeID Collocate] Operate ‘CollocateOp’: Mandatory source product (field ‘masterProduct’) not set.

Can someone provide a working example for this?

Thank you,

-k.


#2

It seems that the UI for the Reprojection in the GraphBuiler is only half-way implemented and the collocateWith option is missing.

If you go to Raster -> Geometric Operations -> Reprojection you get the “main” Reprojection GUI.
Here you have the collocateWith option. It is only named as “Use CRS of”.
So this is not a real collocation but it brings both products to the same CRS.
Combining both product into one would be done with the Collocate operator. I would also suggest that you also use the one in Raster -> Geometric Operations.


#3

Could you tell me where I can find the mathematics behind collocation tool ?


#4

This is described in the Help


You can find more details in the code: