[GRASS5] [bug #2537] (grass) aitoff/winkel tripel fails on rasters

[William K]

No good.  I was hoping to use GRASS 5.7 - I tried r.to.vect to both 
point and area but I ran into some odd limit - both quit at 1105902 
features.  The error was that it couldn't insert a new row into the 
values.

So, your suggestion to use sites in GRASS 5.3 didn't work either.  Even 
dividing the globe into 4 quarters.  The conversion to sites worked, no 
problems with feature limits.  They also projected fine.  But I get a 
bus error in s.surf.rst after a while.  (I've never had luck with 
s.surf.rst, maybe I'm using too much data).  I was even using a cell 
size 1/4 of the original unprojected data (latlong 30" GLOBE DEM to 
4000m projected).


A question about the inverse projection thing - is that a PROJ 
limitation, or a general limitation of the Aitoff/Winkel Tripel 
projection?

Kinda interesting sidenote - it seems ArcInfo & ArcGIS do a forward 
projection of rasters, so it doesn't have this problem.  BUT, ArcInfo 
(that is, the old workstation stuff) has problems when anything but 0 
deg is used as the central meridian - it cuts off the west 1/4.  bleh.  
ArcGIS (that is, desktop stuff) is supposed to have fixed the problem, 
but you must use the new 'geodatabase' storage, which requires ArcSDE.  
Arrrrgggghhhhh!

Well, finally got it done by using Arc to convert to points and project 
and to raster (topogridtool 16 hrs!).  Did the masking and relief with 
GRASS.  phew!


On Jul 15, 2004, at 3:53 AM, Glynn Clements wrote:

>
> Request Tracker wrote:
>
>> this bug's URL: http://intevation.de/rt/webrt?serial_num=2537
>
>> Subject: aitoff/winkel tripel fails on rasters
>
>> When trying to project a raster from geographic (or any other
>> projection) to a Winkel Tripel or Aitoff, r.proj spews out VERY many
>>
>> pj_transform() failed
>> cause: non-convergent inverse meridinal dist
>>
>> errors, then gives up with:
>>
>> ERROR: Input map is outside current region
>>
>> and stops. The region is correct - I use proj (or m.proj2 in
>> grass53) to determine the extents needed. And it projects vectors
>> (v.proj) just fine.
>
> Neither Aitoff nor Winkel Tripel have defined inverse projections, so
> you can't project to those projections with r.proj; you can project
> from them, though. v.proj and s.proj use forward projections, so they
> don't have this problem (they have the opposite problem: you can
> project to such projections, but not from them).
>
> For projections which don't have an inverse, you can use a sequence of
> r.to.sites, s.proj and s.surf.rst.
>
> Although, we should make r.proj (or PROJ itself) handle this situation
> better.

-----
William Kyngesburye <kyngchaos at charter.net>
http://webpages.charter.net/kyngchaos/

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