[GRASS-dev] Re: [bug #4877] (grass) d.grid -g, ps.map: incorrect

[Paul Kelly]

On Wed, 19 Jul 2006, Hamish wrote:

>>> this bug's URL: http://intevation.de/rt/webrt?serial_num=4877
>>> -------------------------------------------------------------------
> ..
>>> "d.grid -g" and ps.map's geogrid command are not calculating the
>>> correct grid lines for me. (lines are drawn 90m to the north)
>>>
>>> Perhaps it is only doing the projection, and not the datum transform
>>> ?!!?
>>
>> Looking at the code, this seems quite possible. I have applied a patch
>> in  CVS - can you test? If it's working now, I expect we should be
>> able to  apply a similar patch to ps.map.
>
> umm, now it is twice as bad. the 'd.grid -g' line is now drawn 180m
> north of the expected location.

For me (I've tried with a test NZMG/nzgd49 location) before the patch the 
lines were about 90m *south* of where they'd be expected to be from the 
d.where -l output, and after the patch they agree :/ d.grid is supposed to 
show lines of latitude&longtiude on the current ellipsoid, not WGS84, 
right?

> I take it that in this case the LL datum was the one missing?

Yes the way it was being done was ll was set as the projection and the 
ellipsoid parameters were copied over to the new parameters, but not the 
datum. I've double-checked and am fairly confident that particular problem 
is fixed now, but perhaps there was something else in the code that 
compensated for this bug and so something else needs changed? I'm not sure 
where to look.

Paul