On 27/05/10 13:29, Martin Budaj wrote: > Hi, > > On Mon, May 17, 2010 at 11:17 PM, Andrew Atkinson<andrew at wotcc.org.uk> > wrote: >> 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) > > Which therion version are you using? Recent versions include geodetic > datum shift parameter which should eliminate the 90-m difference.
5.28 on ubuntu. Wookey has said that he is trying to update the repository, so I am waiting to be the crash dummy...... But the datum shift would explain one of the jumps we got, however we still seem to get jumps (google earth), on the same version with no change to the cs, calibration (3d files) or the fixed points. This is something I do not understand. Generally all the entrances are off by the same amount, so I can go and adjust them, but it is tedious, especially when the jump a few months latter (possibly when google earth is updated?) Maybe this indicates a calibrate for cs when used as output will still be needed, even with the solution below, although in reality it should not be. > >> cs EPSG:27700 -calibrate [0 0 0 299912 99991 0] >> >> gives error >> >> output coordinate system specification requires single parameter > > It is not possible to modify cs using 'calibrate' option. > > I guess your problem could be solved by defining custom Proj4 > coordinate system. For ST square it should be > > +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=100000 > +y_0=-200000 +ellps=airy +datum=OSGB36 +units=m +no_defs > > Currently the 'cs' command doesn't accept custom Proj4 specifications > like the one given above (this funcionality will be added as soon as > possible), so the easiest way to add this projection is to modify > thcsdata.tcl and recompile therion. > > In thcsdata.tcl just duplicate line 52 (s-merc projection) and replace > 's-merc' with e.g. OSGBST and proj4 specification with the > specification given above. > > Then use cs OSGBST in your data. > Thanks Martin, sounds like another good solution. I think that I will wait for the ability to customise proj4. I have already been through an adjusted them by hand. Plus this is a project spread over lots of cavers and clubs (SVN is wonderful, most of the time!) and everyone having to compile from source would be a pain (I have to go round and install the software as it is...) thanks Andrew
