Automated GPT Parameters


When filling in parameters with an XML file to use with GPT how does it work when you need to fill in automated parameters?

For example, the “Multilook” tool for Radar has inputs for “Number Range Looks” and “Number of Azimuth Looks”. When I’m using the SNAP software, the azimuth input cannot be selected and only updates when you input for number of range looks. Meanwhile, in the XML there are these parameters:


If i want to modify the XML by myself, should I just leave nAzLooks empty? Does that mean that the GPT tool will automatically fill that in?


I do not know if i understand the question correctly, but i will give you my answer as i understand it.
I think what you need to do is to look at parameter substitution.



A yo can see in the example above, we replaced the fixed values with our parameters. You can run the GPT loading the xml file and replacing the placeholders with the actual value in the command line

I do not know if that makes sense

Hi sorry for the confusion, that was not what I was asking for. I’m familiar with parameter substitution. Let me try again. I can see that my initial post can be confusing.

When I’m using the tools in the SNAP software there are some parameters where SNAP will automatically calculate the parameter for you. My example is using the Azimuth looks parameter in “Multilook”. This parameter is automatically updated when using the graph builder. I cannot change this parameter. It only changes when I change “Number of Range Looks”. I do not know exactly what is the formula for the change for some of these automated parameters.

My question is: if I use the GPT command line tool, can I leave the automated parameters empty? Will the GPT tool fill it in automatically like when I’m using the graph builder? I ask because I save and copy the XML files from the graph builder. But when i inspect, the XML files include the input for the automated parameters. So I’m confused if that is required or not to use the GPT command line tool.

Hopefully that is easier to understand. Thanks.

Maybe @lveci or @jun_lu can answer how the operator behaves.

The automated parameter value will be computed based on other parameters you provided in the command line. For example, you only need to specify the “Number of range looks”, the “Number of azimuth looks” will be computed automatically. The GPT tool should work like the graph builder.

Thank you for the clarification jun_lu!

I am building an external tool to automate SNAP software and I wanted to make sure the parameters would work correctly if a user would customize them :slightly_smiling_face: