ETRS89 UTM zone 30N : EPSG:25830 preferred to EPSG:3042

[Warren Family]

An ah-ha (!) moment... I was doing some more investigation and found 
that there is in fact a crucial difference between EPSG:3042 and another 
co-ordinate system EPSG:25830, both of which are ETRS89 UTM zone 30N 
except the former (EPSG:3042) has data interchange in the order 
(northing, easting) whereas the latter (EPSG:25830) has it in the more 
usual (easting, northing) order.  See:
https://gis.stackexchange.com/questions/224238/whats-the-difference-between-epsg-3043-and-epsg-25831

I checked that replacing *cs out EPSG:3042 with *cs out EPSG:25830 not 
only fixes the problem I had, but in addition leaves the *fix stations 
with the exact same co-ordinates :-).

So maybe survex IS working as it is supposed to be, and all one has to 
do is avoid co-ordinate systems with the (easting, northing) data 
interchange the 'wrong way around'.  Then for ETRS89 UTM zone 30N one 
can and should use *cs out EPSG:25830 rather than *cs out EPSG:3042.

Patrick


On 26/10/2023 21:50, Warren Family wrote:
> Thanks Olly for getting to the bottom of this.  I'll update the 
> DowProv case study to follow your suggestions. -- Patrick