Wed, Aug 17 2005
11:43:26
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Request created by neteler@itc.it
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Wed, 17 Aug 2005 11:43:14 +0200
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From |
Markus Neteler <neteler@itc.it>
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To |
Kenneth Waight <ken@meso.com>
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GRASSLIST@baylor.edu, grass-bugs@intevation.de
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Subject |
Re: [GRASSLIST:7929] Problem using r.in.gdal to import geoTIFF of US NDVI
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<20050817094314.GC13041@thuille.itc.it>
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Kenneth Waight <ken@meso.com>, GRASSLIST@baylor.edu, grass-bugs@intevation.de
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(cc bugtracker)
On Tue, Aug 16, 2005 at 03:39:45PM -0400, Kenneth Waight wrote:
> I'm using r.in.gdal to import a geoTIFF file of U.S. NDVI data. The
> import is performed, but this message is displayed and the data
> doesn't seem to be projected correctly:
>
> GRASS_INFO_WARNING(20541,1): Datum
> 'Not_specified_based_on_Authalic_Sphere' not recognised by GRASS and
> no parameters found. Datum transformation will not be possible using
> this projection information.
> Over-riding projection check.
> Proceeding with import...
>
> CREATING SUPPORT FILES FOR ndvi.2004113.test
> SETTING GREY COLOR TABLE FOR ndvi.2004113.test (8bit, full range)
>
>
> It's close but is a few km off when I reproject to a lat-lon grid.
> Here's the dataset information:
>
> http://glcf.umiacs.umd.edu/data/modis/ndvi/guide.shtml
> U.S.16 day Vegetation Index User Guide
>
> * Projection: Alber's Equal Area Conic Conformal
> reprojected from native MODIS projection: Sinusoidal
> Central Meridian used was 96d W
> std Parallels of 29d 30' 0" and 45d 30' 0"
> Latitude of Origin is 0d 0' 0"
> Easting & Northing are 0.0000000000 m
> Datum: sphere (a sphere of radius 6370997 m)
> Resolution is 250 meters
> ***NOTE*** - When you load the geotiff, many programs may not
> correctly recognize the datum and report a wrong datum (i.e., WGS
> 1984). THE DATUM IS THE SPHERE USED IN MODIS DATA, WITH A RADIUS OF
> 6370997 METERS!!!
>
>
> Any ideas?
I have downloaded such a file and tested with gdalinfo:
gdalinfo US.Albers.2005145.ndvi.tif
Driver: GTiff/GeoTIFF
Size is 21000, 13000
Coordinate System is:
PROJCS["unnamed",
GEOGCS["Unknown datum based upon the Authalic Sphere",
DATUM["Not_specified_based_on_Authalic_Sphere",
SPHEROID["Sphere",6370997,0,
AUTHORITY["EPSG","7035"]],
AUTHORITY["EPSG","6035"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4035"]],
PROJECTION["Albers_Conic_Equal_Area"],
PARAMETER["standard_parallel_1",29.5],
PARAMETER["standard_parallel_2",45.5],
PARAMETER["latitude_of_center",0],
PARAMETER["longitude_of_center",-96],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]]]
Origin = (-2356750.000000,5769500.000000)
Pixel Size = (250.00000000,-250.00000000)
Metadata:
AREA_OR_POINT=Point
TIFFTAG_SOFTWARE=hdf2geotiff v0.1.5
Corner Coordinates:
Upper Left (-2356750.000, 5769500.000) (128d59'15.31"W, 49d50'21.28"N)
Lower Left (-2356750.000, 2519500.000) (118d30'25.87"W, 21d47'47.16"N)
Upper Right ( 2893250.000, 5769500.000) ( 56d16'50.11"W, 48d 0'54.53"N)
Lower Right ( 2893250.000, 2519500.000) ( 68d37'26.12"W, 20d30'41.05"N)
Center ( 268250.000, 4144500.000) ( 92d52'8.97"W, 38d54'34.96"N)
Band 1 Block=21000x1 Type=Byte, ColorInterp=Gray
Actually I don't understand the phrase "THE DATUM IS THE SPHERE USED IN MODIS
DATA,
WITH A RADIUS OF 6370997 METERS!!!" on the GLCF page as the MODIS sphere is
with radius 6371007.181 according to
http://edcdaac.usgs.gov/landdaac/tools/mrtswath/info/ReleaseNotes.pdf
http://s2k.gsfc.nasa.gov/html_pages/groups/sat/modis_land_overview.html
Moreover, 6370997.0 is the Normal Sphere, not the MODIS sphere:
cs2cs -le | grep 6370997
sphere a=6370997.0 b=6370997.0 Normal Sphere (r=6370997)
But who cares, we can only trust the metadata here.
Importing within Spearfish into a new location I can reproduce
the error message:
r.in.gdal in=US.Albers.2005145.ndvi.tif out=ndvi2005145 loc=albers_usa
WARNING: Datum 'Not_specified_based_on_Authalic_Sphere' not recognised by
GRASS and no parameters found. Datum transformation will not be
possible using this projection information.
Restarting GRASS with ther new location, I get
GRASS 6.1.cvs (albers_usa):/tmp > g.proj -p
-PROJ_INFO-------------------------------------------------
name : Albers Equal Area
proj : aea
a : 6370997
es : -inf
lat_1 : 29.5
lat_2 : 45.5
lat_0 : 0
lon_0 : -96
x_0 : 0
y_0 : 0
no_defs : defined
-PROJ_UNITS------------------------------------------------
unit : metre
units : metres
meters : 1
GRASS 6.1.cvs (albers_usa):/tmp > g.proj -w
ERROR: Invalid ellipsoid descriptors (a, rf, es or b) in file
This doesn't look good. Apparently fix is needed.
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Wed, Aug 17 2005
11:44:08
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User changed to ken@meso.com,neteler@itc.it by mneteler
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Wed, Aug 17 2005
11:44:18
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Area changed to grass6 by mneteler
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Wed, Aug 17 2005
11:44:32
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Subject changed to Sphere: Problem using r.in.gdal to import geoTIFF of US NDVI by mneteler
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Tue, Aug 23 2005
20:53:54
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Mail sent by pkelly
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It is my opinion that the WKT projection description in the metadata is
wrong. In WKT the ellipsoid is described by two parameters: the semi-major
axis and the inverse flattening. For a sphere the flattening is 0 and so the
inverse flattening is infinity. If the metadata is modified to read
SPHEROID["Sphere",6370997,"inf",AUTHORITY["EPSG","7035"]]
instead of
SPHEROID["Sphere",6370997,0,AUTHORITY["EPSG","7035"]]
then GRASS creates a valid PROJ_INFO file.
The problem can be worked around by editing the line b: -inf in the
PROJ_INFO to read either "b: 6370997" or "es: 0".
Perhaps we could change GRASS to accept 0 as well as "inf" as representing a
sphere to allow for other broken software if this is common. Suggestions /
opinions on the most appropriate course of action are welcome.
This is all very complicated and hard to get my ahead around so please
challenge/question this if it looks like I've made a mistake.
Paul
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Wed, Aug 24 2005
02:53:23
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Mail sent by pkelly
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It is my opinion that the WKT projection description in the metadata is
wrong. In WKT the ellipsoid is described by two parameters: the semi-major
axis and the inverse flattening. For a sphere the flattening is 0 and so the
inverse flattening is infinity. If the metadata is modified to read
SPHEROID["Sphere",6370997,"inf",AUTHORITY["EPSG","7035"]]
instead of
SPHEROID["Sphere",6370997,0,AUTHORITY["EPSG","7035"]]
then GRASS creates a valid PROJ_INFO file.
The problem can be worked around by editing the line b: -inf in the
PROJ_INFO to read either "b: 6370997" or "es: 0".
Perhaps we could change GRASS to accept 0 as well as "inf" as representing a
sphere to allow for other broken software if this is common. Suggestions /
opinions on the most appropriate course of action are welcome.
This is all very complicated and hard to get my ahead around so please
challenge/question this if it looks like I've made a mistake.
Paul
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Thu, Aug 25 2005
13:27:33
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Status changed to resolved by pkelly
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Thu, Aug 25 2005
13:27:33
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Mail sent by pkelly
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I made a change to lib/proj/convert.c to accept an inverse flattening of 0
as meaning flattening was 0. So it should now handle the broken metadata.
Paul
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Thu, Aug 25 2005
15:02:12
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Mail sent by neteler@itc.it
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Date |
Thu, 25 Aug 2005 15:02:06 +0200
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From |
Markus Neteler <neteler@itc.it>
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To |
Paul Kelly via RT <grass-bugs@intevation.de>
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Cc |
ken@meso.com
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Subject |
Re: [bug #3526] (grass) Sphere: Problem using r.in.gdal to import geoTIFF of US NDVI
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<20050825130205.GB7528@thuille.itc.it>
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On Thu, Aug 25, 2005 at 01:27:33PM +0200, Paul Kelly via RT wrote:
> I made a change to lib/proj/convert.c to accept an inverse flattening of 0
> as meaning flattening was 0. So it should now handle the broken metadata.
Thanks, Paul.
I have made a test
GRASS 6.1.cvs (albers):/tmp > g.proj -p
-PROJ_INFO-------------------------------------------------
name : Albers Equal Area
proj : aea
a : 6370997
es : 0
lat_1 : 29.5
lat_2 : 45.5
lat_0 : 0
lon_0 : -96
x_0 : 0
y_0 : 0
no_defs : defined
-PROJ_UNITS------------------------------------------------
unit : metre
units : metres
meters : 1
GRASS 6.1.cvs (albers):/tmp > g.proj -w
PROJCS["Albers Equal Area",
GEOGCS["unnamed",
DATUM["unknown",
SPHEROID["unnamed",6370997,"inf"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433]],
PROJECTION["Albers_Conic_Equal_Area"],
PARAMETER["standard_parallel_1",29.5],
PARAMETER["standard_parallel_2",45.5],
PARAMETER["latitude_of_center",0],
PARAMETER["longitude_of_center",-96],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
UNIT["metre",1]]
r.colors ndvi col=byg
v.proj roads loc=spearfish60
I feel that it looks as expected.
Markus
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Thu, Aug 25 2005
15:02:12
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Status changed to open by _rt_system
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