I’m new to HEC-RAS and having problems with projected coordinate systems of my HEC-RAS (5.0.3) geometry and the WMS maps in RAS Mapper. I imported georeferenced cross sections via a .CSV file (i.e. not using GIS), however, they are offset by ~120m from the river seen on WMS maps (Google, Open Streetmap etc).

I've used .prj files (27700: OSGB 1936/British National Grid) I downloaded (

http://spatialreference.org/ref/epsg/27700/) as well as those generated by QGIS, leading to the same results.

I found a workaround by manually editing the Easting & Northing in the .prj file which aligned my geometry and the WMS correctly - however, I'm wondering if this may affect 2D modelling e.g. generating misprojected flood maps. I'd be grateful for any suggestions please?

**.prj file**PROJCS["OSGB 1936 / British National Grid",GEOGCS["OSGB 1936",DATUM["D_OSGB_1936",SPHEROID["Airy_1830",6377563.396,299.3249646]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",49],PARAMETER["central_meridian",-2],PARAMETER["scale_factor",0.9996012717],PARAMETER["false_easting",400000],PARAMETER["false_northing",-100000],UNIT["Meter",1]]