[gdal-dev] gdalwarp problems with MODIS L1B

[Michael Sumner]

Thank you Rutger, it was me who was missing things - I've been confused
about to what level the GDAL warping is appropriate, and every part of this
discussion has been very helpful. It seems very much like the
orthorectification process where you need a DEM as well as details on
camera geometry, but my understanding on the relationship here is very dim.

I'd love for lower level techniques like the MODIS Swath to grid and Seadas
L1A to L2 chain to be available via GDAL, but I have a lot to learn about
all the steps. I have no idea how appropriate it is for GDAL to aspire to
these things, but I'm very keen to learn.

Cheers, Mike

On Thu, 21 May 2015 at 17:48 Rutger <kassies at gmail.com> wrote:

> Hey,
>
> Maybe i'm missing something, but for as far as i know, the MODIS MOD021KM
> product is still a 'swath', and therefore still containing the bow-tie
> effect as the result of the scanning sensor. Wouldn't this mean that
> gdalwarp will never work? The lat/lon arrays aren't continuous, so any
> fitting (GCP/TPS) wont be accurate. And upsampling the arrays with cubic,
> like Even did, will result in interpolating pixels which are next each
> other
> in the array/file, but aren't next to each other 'on the ground', wont work
> well.
>
> I think you need to either use a dedicated algorithm (like gradient
> search),
> or something very generic (like the KDTree of Pyresample) to overcome the
> bow-tie effect.
>
> I have spend alot of time experimenting with this in GDAL, since i try to
> do
> as much with GDAL as possible. But projecting a swath file from a scanning
> sensor (like MODIS or VIIRS) is something i have never gotten to work. For
> some historic discussion about this see for example:
>
> http://osgeo-org.1560.x6.nabble.com/gdal-dev-reproject-python-numpy-binary-swath-lat-lon-td4978609.html
>
>
> Regards,
> Rutger
>
>
>
> --
> View this message in context:
> http://osgeo-org.1560.x6.nabble.com/gdal-dev-gdalwarp-problems-with-MODIS-L1B-tp5206583p5206825.html
> Sent from the GDAL - Dev mailing list archive at Nabble.com.
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20150521/84f52296/attachment.html>