[vtk-developers] Geocoordinate System Filter, 2D Text Manager, 2D Text Preformance, and Buffered Hardware Picking

[Thompson, David C]

I had a quick glance at vtkGeography and it looks like it just uses PROJ.4 under the hood. I don't know of any Swiss datums for PROJ.4 but I'll keep my eyes open. I'll also see if I can't find a home for the OSGB36->WGS84 code as I'm a pack rat with code... I just *know* I'll find a use for it sooner or later. :-)

    David

________________________________________
From: vtk-developers-bounces+dcthomp=sandia.gov at vtk.org [vtk-developers-bounces+dcthomp=sandia.gov at vtk.org] On Behalf Of John Biddiscombe [biddisco at cscs.ch]
Sent: Thursday, December 20, 2007 02:09
To: Thompson, David C
Cc: vtkdev; a.maclean at cas.edu.au
Subject: Re: [vtk-developers] Geocoordinate System Filter, 2D Text Manager, 2D Text Preformance, and Buffered Hardware Picking

I was (naively?) hoping to hide all the different coordinate systems in
a utility library like PROJ.4 instead of implementing each one (there are
*tons* of them) as its own distinct subclass of vtkCoordinateSystem the


Absolutely. I made the class that I referred to because we needed to drive around in a van with a GPS receiver and display the map data around us, including the 3D buildings etc for measurements - where all was specified in OSGB coords. The UK transformation is annoying because the 1997 version includes special 'lookuptables' which correct for errors which were made in the 1936 'official' mapping where grids were not completely regular. This kind of 'exception' to the standard projection/ellipsoid/nonsense makes it hard to create a very general purpose any to any coordinate transformation.

My experience with proj.4 is limited I remember reviewing it in the late 1990s when I was working in that field - I suspect it can do most stuff that the majority of users need. If you poke around with any of these vtkGeography classes etc and there is a swiss grid transformation implemented, please let me know. We have terrain data and climate stuff that would look good blended.

cheers

JB


way vtkGeography appears to. My (to date cursory) review of PROJ.4
made me think that many of these datums can be compiled into the library
but perhaps it doesn't choose the most numerically stable way to transform
coordinates from one system to another?

     David





--
John Biddiscombe,                            email:biddisco @ cscs.ch
http://www.cscs.ch/about/BJohn.php
CSCS, Swiss National Supercomputing Centre  | Tel:  +41 (91) 610.82.07
Via Cantonale, 6928 Manno, Switzerland      | Fax:  +41 (91) 610.82.82