[Therion] Calibration of co-ordinate systems

[Wolfgang Zillig]

Hi Andrew,

I'm not sure if I understand your problem correctly. There is on issue 
with the EPSG codes for OSGB36, see:
http://osgeo-org.1803224.n2.nabble.com/EPSG-27700-td4469120.html
and
http://www.osgeo.org/pipermail/grass-user/2009-July/051494.html

But this could explain your uneven numbers in the calibrate command. Can 
it be that the coordinate fix misses some leading numbers? The skipping 
is sometimes common to avoid huge numbers. Can you check this by 
converting some coordinates from WGS84 (for instance) to OSGB36?

Best regards
Wolfgang

Am 17.05.2010 23:17, schrieb Andrew Atkinson:
> Hi
>
> I am having a little bit of difficulty with the various different 
> helps on co-ordinate systems. I am building an area survey map from 
> data from various different sources, so having to 'adapt' it, but 
> really do not want to have to convert it all. It would be nice to have 
> one of the outputs as .kml for google earth and the like.
>
> Lots of the data is in Survex, with Local OSGB 6 figure grid 
> references. These I have been importing eg
>
> import Great_Swallet.3d -surveys use -filter great_swallet -cs 
> EPSG:27700 -calibrate [0 0 0 299912 99991 0]
> #Should be -calibrate [0 0 0 300000 100000 0]
>
> (goodness knows why the calibrate is not right, the bodge is to align 
> it on goodle earth, probably my ignorance)
>
>
> As most of the new data is in Pockettopo imported, into therion, is 
> attached to the survex data this has worked well.
> One cave entrance has been done in therion direct but I just dealt 
> with that by doing the calibrate manually
>
> I have now been sent lots of data with lots (60 fix #ed points or 
> more) of cave entrances, all in therion with local 6 figure grid 
> references.
>
> I can set the coordinate system to EPSG:27700 by adding it within the 
> centreline/endcentre, but that puts the cave in the Atlantic 
> somewhere. So using
> centreline -cs EPSG:27700 -calibrate [0 0 0 299912 99991 0]
> gives the error
>
> not enough option arguments -- -calibrate -- must be 2
>
> Which is fair enough as calibrate is already used in the centreline 
> for correcting a zero error.
>
> Not to be easily put off I tried it the other way round, remove the 
> calibrate from the centreline and use
>
> cs EPSG:27700 in the config files to get therion to output in these 
> coordinates, however although I can get the caves relatively next to 
> each other, the kml puts them in the Atlantic again and
>
> cs EPSG:27700 -calibrate [0 0 0 299912 99991 0]
>
> gives error
>
> output coordinate system specification requires single parameter
>
>
> and
>
> cs EPSG:27700
> calibrate [0 0 0 299912 99991 0]
>
> gives error
>
> unknown configuration command -- calibrate
>
> Have I missed something or do I need to go through and add 300000 and 
> 100000 to all the fixed points. If this is so, could we have a 
> calibratecs to use with the cs command to overcome localised 
> coordinates on a national grid, the UK cannot be the only country with 
> this problem, and it must be easier to work mainly in the more 
> localised coordinates and calibrate it on output
>
> hope this all makes sense,
>
> Andrew
>
> _______________________________________________
> Therion mailing list
> Therion at speleo.sk
> http://mailman.speleo.sk/mailman/listinfo/therion