[gdal-dev] gdal translate/warp goes16

[Beale, Steven]

Hi Zac,
I tried to be as explicit as possible setting the source srs, including the semi-major/minor axes:
gdalwarp -s_srs "+proj=geos +a=6378137 +b=6356752.31414 +lon_0=-75 +h=35786023 +x_0=0 +y_0=0 +ellps=GRS80 +units=m +no_defs  +sweep=x" -t_srs EPSG:4326 -dstnodata -999.0 -tr 0.009 0.009 -te 290 40 320 65 -r near <in> <out>

But I still have the longitude shifting.
Out of curiosity I tried +sweep=y, just to see what would happen, and that didn’t do anything either… could the sweep be getting ignored entirely?
Just to verify that the srs was being interpreted at all, I tried adjusting lon_0, which did work. Not very helpful though.
Thinking there could possibly be some conflict in setting ellps=GRS80 and setting parameters by hand, I omitted that the +ellps. Same result.
Any other thoughts?

Thanks,
Steve

From: Zachary Flamig [mailto:zac at weatherwary.com]
Sent: Wednesday, March 21, 2018 4:04 AM
To: Steven Beale <steven.beale at woodplc.com>
Cc: gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] gdal translate/warp goes16

Hi Steven,

So the issue here is that gdal_translate doesn’t properly store the +sweep=x in the geotiff.

See http://geotiff.maptools.narkive.com/3CqwNeMd/geos-projection-sweep-parameter<https://urldefense.proofpoint.com/v2/url?u=http-3A__geotiff.maptools.narkive.com_3CqwNeMd_geos-2Dprojection-2Dsweep-2Dparameter&d=DwMFaQ&c=ZWY66qCYUTYUcOev9C2GlDEcKuYKzoWDVNR_L93Z9mQ&r=xGAbC1Ogv9duClaR3TChYqg_fGB4xrhak7uN1kZcfR8&m=zVXU4kc36wijhVLYDg1WghqZOoFePzeG6PQfNC150tU&s=f466QSOBNcqeD3kETK3-K2-4KeUmCONhKlY6J9t4dMU&e=> for some relevant discussion. I believe the best solution right now is to specify the s_srs in the gdalwarp command like -s_srs "+proj=geos +lon_0=-75 +h=35786023 +x_0=0 +y_0=0 +ellps=GRS80 +units=m +no_defs  +sweep=x"

This is a bit of a mess, sorry about that.

Zac


On Mar 20, 2018, at 9:37 PM, Steven Beale <steven.beale at woodplc.com<mailto:steven.beale at woodplc.com>> wrote:

Hi gdalers,

I'm a little out of my field here, usually I work with weather/climate data,
but I need to warp some goes16 satellite data. (source is aws s3:
https://noaa-goes16.s3.amazonaws.com/ABI-L2-CMIPF/2018/079/12/OR_ABI-L2-CMIPF-M3C01_G16_s20180791200447_e20180791211214_c20180791211280.nc<https://urldefense.proofpoint.com/v2/url?u=https-3A__noaa-2Dgoes16.s3.amazonaws.com_ABI-2DL2-2DCMIPF_2018_079_12_OR-5FABI-2DL2-2DCMIPF-2DM3C01-5FG16-5Fs20180791200447-5Fe20180791211214-5Fc20180791211280.nc&d=DwMFaQ&c=ZWY66qCYUTYUcOev9C2GlDEcKuYKzoWDVNR_L93Z9mQ&r=xGAbC1Ogv9duClaR3TChYqg_fGB4xrhak7uN1kZcfR8&m=zVXU4kc36wijhVLYDg1WghqZOoFePzeG6PQfNC150tU&s=wpMH3kBCq917DTkCCXLtN0FpDoYrz6Xbmh4KZvNmrSM&e=>
- the link should work for a few months then it will be glaciered and
unavailable)

source data is netcdf, I'm using nco tools & gdal for the processing.

My work flow is:
1. clip the data to the region of interest (north atlantic):
ncks -d x,5424,8678 -d y,0,2170 <raw.nc> step1.nc
2. deflate & unscale
gdal_translate -ot float32 -unscale -CO COMPRESS=deflate NETCDF:step1.nc:CMI
step2.tiff
3. warp (in this case data is 1km resolution : ~0.009 degrees)
gdalwarp -t_srs EPSG:4326 -dstnodata -999.0 -tr 0.009 0.009 -te 290 40 320
65  -r near step2.tiff step3.tiff
4. convert back to nc
gdal_translate -ot float32 -of NETCDF step3.tiff output.nc

The problem i have is that the output has the longitude shifted to the west
by about 10 degrees.
The issue seems related to the ncks clipping, if I exclude the x clip,
everything works out fine, but takes significantly longer.
Here's an example once it's loaded into an erddap server;
<http://osgeo-org.1560.x6.nabble.com/file/t382897/GOES16_L2CMIPF_M3C01_201803201200.png>
You can see greenland to the west of it's map underlay.

I'm using gdal v2.3.0, netcdf v4.4.1.1, nco v4.7.3 & proj4 v5.0.0





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