Hello
The software I am using to build models recognises several coordinate systems for survey point CSV files, for OSGB specifically it has the option of using OSGB36 EPSG:4277 (Geographic) and OSGB36 EPSG:27700 (projected)
I’ve noted in Emlid Flow that that EPSG:27700 is listed as an option but classed as `legacy’, the other option OSGB36 does not state an EPSG code.
What would be the workflow to achieve a .csv that has the coordinates in EPSG:4277?
I have already taken points on a project using the standard OSGB36 option in Emlid Flow, would I be able to run that through some kind of conversion tool?
As a side note, the height values the above option resulted in were in the 130m range whereas when looking at the same place on OS Maps it shows an altitude in the 79m range. The Reach unit was connected to a UK based NTRIP correction service. Have I done something wrong here?
Thank you
Hi @PLLNM001 ,
What would be the workflow to achieve a .csv that has the coordinates in EPSG:4277?
I have already taken points on a project using the standard OSGB36 option in Emlid Flow, would I be able to run that through some kind of conversion tool?
You can’t get EPSG:4277 in EF. The bases are placed in ETRS89 in the UK, and you’ll get ETRS89 as Global coordinates for a project based on OSGB36. Once you have completed the survey, you can convert your results to the targeted coordinate systems using a converter tool or GIS software.
I’ve noted in Emlid Flow that that EPSG:27700 is listed as an option but classed as `legacy’, the other option OSGB36 does not state an EPSG code.
I recommend you choose the one without the “legacy” tag because it’s in our registry, and it will work well with our future app versions. It is exactly the same coordinate system.
As a side note, the height values the above option resulted in were in the 130m range whereas when looking at the same place on OS Maps it shows an altitude in the 79m range. The Reach unit was connected to a UK based NTRIP correction service. Have I done something wrong here?
Such differences are usually related to different vertical datums that define where your zero value is. The default option is Ellipsoidal height, but you can use several Vertical datum for OSGB36 EPSG:27700.
OS Maps also use a geoid model called Ordnance Survey National Geoid Model (OSGM15) as a vertical datum. You can find different OSGM15 geoids in Emlid Flow, as you can see in our guide. There are some, especially for the biggest islands and one to the mainland called ODN height. If the vertical datums match, the point’s elevation should match too.
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