[postgis-users] Reference vrt datasets in postgis raster

[David Haynes]

Hello,

You might want to try this projection:
http://spatialreference.org/ref/sr-org/6842/postgis/
This the most accurate projections, despite the description on the spatial
reference site. I am doing related work and found this calculator at the
following url
http://landweb.nascom.nasa.gov/cgi-bin/developer/tilemap.cgi
There is no projection accuracy error when using SRID 6842.



On Fri, Jul 11, 2014 at 9:33 AM, Christian Yrrman <yrrman at gmail.com> wrote:

> Hi All,
>
>
> I'm a newbie to this group, so hello everyone and thanks in advance for
> letting me participate :-)
>
> After several tests and searching on the net I'm a little stuck with the
> following problem:
>
> I have downloaded a bunch of MODIS tiles (MOD13A1) from [0] that I want to
> (only) reference in a postgis raster database. These tiles come in hdf
> containers with several layers in it
> .
> - For a start,  I'm only interested in the EVI layer, so I created EVI vrt
> files with command [1]
> - This gives me several EVI*.vrt files referencing EVI with the original
> sinusoidal projection. According to spatialreference.org, the closest SRS
> match is sr-org6974 [2].
> - As this is not in postgis, I've imported this into spatial_ref_sys [3]
> - Next, I'm using the following command to insert the data into raster
> table "modistest" with the following command:
>
> for i in `find / -name "EVI_origSRS*.vrt"`; do
>         raster2pgsql -s 96974 -R -F -f rast -a $i modistest;
> done
>
> where:
> "-s 96974" - use the freshly imported MODIS SRS from [2]
>   -R  Register the raster as an out-of-db (filesystem) raster.  Provided
>       raster should have absolute path to the file
>   -F  Add a column with the filename of the raster.
>   -f <column> Specify the name of the raster column
>      -a  Appends raster into current table, must be
>          exactly the same table schema.
>
> I've built the index on rast in a separate step (not using switch -I)
>
> This populates table modistest (using | psql...), so it looks fine.
> However when I want to retrieve data from the raster, e.g. via
>
> SELECT ST_AsTiff(rast) from public.modistest where id=1158;
>
> I get an error message like this
> ERROR:  rt_raster_from_gdal_dataset: Unable to get data from transformed
> raster
> CONTEXT:  PL/pgSQL function "st_astiff" line 20 at RETURN
>
> and in the postgresql log I get
>
> ERROR 4:
> `HDF4_EOS:EOS_GRID:"MOD13A1.A2012065.h35v10.005.2012082112322.hdf":MODIS_Grid_16DAY_500m_VI:500m
> 16 days EVI' does not exist in the file system,
> and is not recognised as a supported dataset name.
>
>
> So it looks like the layers were not correctly referenced - however I
> cannot see a mistake. I'm actually using "find / -name "EVI_origSRS*.vrt"
> to get the full path for the loop (not "for i in *vrt")
>
>
> Any help/advice is highly appreciated! In a next step, I would even like
> to transform the sinusoidal tile afterwards with ST_transform to epsg:4326.
> That would be fantastic, I'd have all tiles in original format in the file
> system and let postgis do all the rest.. :-)
>
>
>
> Thanks in advance and greetings!
>
>
>
> Chris
>
>
>
>
>
> [0] MODIS download website
> http://e4ftl01.cr.usgs.gov/MOLT/MOD13A1.005/
>
> [1] command to create vrt files:
> #!/bin/bash
>
> for i in *hdf; do
>         echo Processing $i
>         j=`gdalinfo $i| grep SUBDATASET_2_NAME | cut -d '=' -f 2`
>         echo Extracted $j
>         gdal_translate -of VRT "$j" EVI_origSRS_$i.vrt
>
> done
>
> [2] SRS projeciton for MODIS
> http://spatialreference.org/ref/sr-org/6974/
>
> [3] SQL command to insert MODIS SRS
>
> INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext)
> values ( 96974, 'sr-org', 6974, '+proj=sinu +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs ',
>
> 'PROJCS["MODIS Sinusoidal",
> GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],
> AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
>
> UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]],
> PROJECTION["Sinusoidal"],
> PARAMETER["false_easting",0.0],
>
> PARAMETER["false_northing",0.0],
> PARAMETER["central_meridian",0.0],
> PARAMETER["semi_major",6371007.181],
> PARAMETER["semi_minor",6371007.181],
> UNIT["m",1.0],AUTHORITY["SR-ORG","6974"]]');
>
>
>
>
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