[GRASS-dev] Re: [GRASS GIS] #163: g.transform no longer calculating error for 2nd order transformation

[Martin Landa]

Hi Michael,

> Yes. This has 6 points like it is supposed to. But the transformation
> doesn't work. Doesn't work with more than 6 either.

from

g.transform g=roads_streams o=2 f=src,dst,rev,fwd,fd,rd
 274.000000 462.000000 598064.018692 4927655.934580 274.000000
462.000000 598064.018692 4927655.934580 0.000000 0.000000
 ....

I get what I would expect with min number of GPSs for the given order,
when I add some other GPSs to the points file I get non-zero fwd/rev
errors

g.transform g=roads_streams o=2
 0.004227 0.007915
 0.132068 0.006500
 0.047218 0.003247
...

Maybe I don't understand your point here,

Regards, Martin

2008/6/17 Michael Barton <michael.barton at asu.edu>:

>
> Michael
>
>
> On 6/17/08 3:44 AM, "GRASS GIS" <trac at osgeo.org> wrote:
>
>> #163: g.transform no longer calculating error for 2nd order transformation
>> -----------------------+----------------------------------------------------
>>   Reporter:  cmbarton  |       Owner:  grass-dev at lists.osgeo.org
>>       Type:  defect    |      Status:  new
>>   Priority:  major     |   Milestone:  6.3.1
>>  Component:  default   |     Version:  svn-develbranch6
>> Resolution:            |    Keywords:  g.transform georectify
>> -----------------------+----------------------------------------------------
>> Comment (by martinl):
>>
>>  Replying to [ticket:163 cmbarton]:
>>> Sometime recently, g.transform stopped calculating forward and backward
>>  error for 2nd order transformations. It simply returns 0's. 1st order
>>  transformations still work fine AFAICT.
>>
>>  The 2nd order transformations requires at least 6 GCPs. Your input POINTS
>>  file contains 6 points. Then forward/reverse error is 0.0's.
>>
>>  Martin
>
> __________________________________________
> Michael Barton, Professor of Anthropology
> Director of Graduate Studies
> School of Human Evolution & Social Change
> Center for Social Dynamics & Complexity
> Arizona State University
>
> phone: 480-965-6213
> fax: 480-965-7671
> www: http://www.public.asu.edu/~cmbarton
>
>
>



-- 
Martin Landa <landa.martin gmail.com> * http://gama.fsv.cvut.cz/~landa *