I started with a tiff image, in Albers projection. Imported in a new location in GRASS - the tiff region is rectangular with no nulls in the region, so the GRASS region follows the tiff region exactly.
Then I projected to a latlong location. The tiff is off to one side of the central meridian, so the projected image appears rotated and stretched, as expected:
Ugh - tried it with GRASS 6.4 and I get the nulls. Looks like a GRASS 6.5 bug.
On Jun 5, 2009, at 3:43 PM, William Kyngesburye wrote:
I started with a tiff image, in Albers projection. Imported in a new location in GRASS - the tiff region is rectangular with no nulls in the region, so the GRASS region follows the tiff region exactly.
Then I projected to a latlong location. The tiff is off to one side of the central meridian, so the projected image appears rotated and stretched, as expected:
<unprojected.png>
But the the triangular areas outside the original tiff region are white, not null. My latlong region is larger than the image - I'm going to merge multiple tiled and overlapping tiffs - and there are nulls outside the extents of the projected area of the image.
Is this expected behavior? I usually go from latlong to projected location, and the source latlong region is larger than the projected region so I don't see this.
GRASS 6.5svn
-----
William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
http://www.kyngchaos.com/
"Oh, look, I seem to have fallen down a deep, dark hole. Now what does that remind me of? Ah, yes - life."
- Marvin
I'm an idiot. It was the r.mapcalc in my script that wasn't taking nulls into account.
On Jun 5, 2009, at 3:52 PM, William Kyngesburye wrote:
Ugh - tried it with GRASS 6.4 and I get the nulls. Looks like a GRASS 6.5 bug.
On Jun 5, 2009, at 3:43 PM, William Kyngesburye wrote:
I started with a tiff image, in Albers projection. Imported in a new location in GRASS - the tiff region is rectangular with no nulls in the region, so the GRASS region follows the tiff region exactly.
Then I projected to a latlong location. The tiff is off to one side of the central meridian, so the projected image appears rotated and stretched, as expected:
<unprojected.png>
But the the triangular areas outside the original tiff region are white, not null. My latlong region is larger than the image - I'm going to merge multiple tiled and overlapping tiffs - and there are nulls outside the extents of the projected area of the image.
Is this expected behavior? I usually go from latlong to projected location, and the source latlong region is larger than the projected region so I don't see this.
GRASS 6.5svn
-----
William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
http://www.kyngchaos.com/
"History is an illusion caused by the passage of time, and time is an illusion caused by the passage of history."
- Hitchhiker's Guide to the Galaxy