ALOS OALSAR1 SICD Format Support

[syu-tan]

Thank you for the great SAR repository.

I would like to apply the SICD format for ALOS PALSAR1.
I have confirmed it with subaperture. I would be happy if i pull request. I would love to contribute.

I don't have permission when pushing, so I get a 403 error.
Please grant me permission.

[pressler-vsc]

@syu-tan, thanks for the offer! SARPy uses the fork and pull request model for contributions, which means no additional permissions are necessary.

There's some information regarding SARPy contributions scattered in a few READMEs (apologies for the current scattered nature of the "Contributing" documentation...):

• Pull Requests
• About integration branches
• tests README

Please reach out with any further questions and we look forward to your contribution!

[utwade]

Note that there is one irreconcilable difference between the current SICD spec and ALOS1, as I understand it. What I have been told by others who know more than me about that sensor is that ALOS1 data is in a native Doppler geometry, which isn't really a grid currently supported by SICD (as opposed to a zero Doppler geometry that is used in SICD and many modern sensors). That said, it may still effectively be able to get you most of the way there for much of the functionality you may be looking for (as you have shown in your results.) It is possible that geolocation will be a bit off though.

[syu-tan]

Thank you for sharing this important information.
The distortion of iso doppler has not been corrected. I haven't done the calculations, but I think that if the difference in squint angle is large, the change in the azimuth direction cannot be reproduced in the SICD format.
Still, I thought the attempt to unify it to NGA was great.