Fwd: Re: [GRASS-dev] VTK export for lat-long locations

[Benjamin Ducke]

Wow, that explains the result I got!
So I guess you need to know exactly how many meters a lat/long cell
dimension is in the current projection, so you can scale the Z axis
accordingly?
Does this vary between cells? Does GRASS have a function to calculate
metric lengths between two points in a lat-long system? If so, I guess
you would need to take the the metric distance between corner points of
a lat-long cell and use the value for Z axis scaling?

Sören Gebbert wrote:
> -------- Original-Nachricht --------
> Datum: Tue, 06 Mar 2007 16:06:18 +0100
> Von: "Sören Gebbert" <soerengebbert at gmx.de>
> An: Benjamin Ducke <benjamin.ducke at ufg.uni-kiel.de>
> CC: 
> Betreff: Re: [GRASS-dev] VTK export for lat-long locations
> 
> Hi Benjamin,
> please dont use the vtk export modules with lat/lon projections.
> The vtk export modules in grass are not 
> usable with lat/lon projections right now.
> I think i should put this info to the html docs.
> 
> The lat/lon coordiantes are used to define the coordinates for each point.
> VTK interpret these coordinates as planimetric and not as lat/lon.
> This is not that bad for x,y coordinates, but for the height (z coordinate).
> Because if x and y lat/lon coordiantes are of type [54.001/34.002] and the
> height varies from 0m - 500m you will get a senseless result.
> 
> I still dont know exactly how to implement a meaningful 
> lat/lon ->planimetric coordinate transformation to get rid 
> fo this behaviour.
> 
> Any suggestions are welcome.
> 
> Best regards
> Soeren
> 
> 
> -------- Original-Nachricht --------
> Datum: Tue, 06 Mar 2007 15:57:17 +0100
> Von: Benjamin Ducke <benjamin.ducke at ufg.uni-kiel.de>
> An: GRASS devel <grass-dev at grass.itc.it>
> CC: 
> Betreff: [GRASS-dev] VTK export for lat-long locations
> 
>> Hi everyone,
>>
>> I just tested r.out.vtk in a lat-long location and all I got when I
>> loaded the VTK file in Paraview (2.6.0), was a single line of data
>> projecting through the origin of the coordinate system.
>>
>> Does anyone have any experiences with VTK/Paraview and lat-long data?
>>
>> Thanks,
>>
>> Benjamin
>>
>>
>> -- 
>> Benjamin Ducke, M.A.
>> Archäoinformatik
>> (Archaeoinformation Science)
>> Institut für Ur- und Frühgeschichte
>> (Inst. of Prehistoric and Historic Archaeology)
>> Christian-Albrechts-Universität zu Kiel
>> Johanna-Mestorf-Straße 2-6
>> D 24098 Kiel
>> Germany
>>
>> Tel.: ++49 (0)431 880-3378 / -3379
>> Fax : ++49 (0)431 880-7300
>> www.uni-kiel.de/ufg
>>
>> _______________________________________________
>> grass-dev mailing list
>> grass-dev at grass.itc.it
>> http://grass.itc.it/mailman/listinfo/grass-dev
> 

-- 
Benjamin Ducke, M.A.
Archäoinformatik
(Archaeoinformation Science)
Institut für Ur- und Frühgeschichte
(Inst. of Prehistoric and Historic Archaeology)
Christian-Albrechts-Universität zu Kiel
Johanna-Mestorf-Straße 2-6
D 24098 Kiel
Germany

Tel.: ++49 (0)431 880-3378 / -3379
Fax : ++49 (0)431 880-7300
www.uni-kiel.de/ufg