Basemap Shifting

KateYoung

On a couple of occasions I have opened Arcmap Pro, loaded one of the base maps and used a feature class to digitise an area. When I have printed the maps the base map and my feature class have shifted out of alignment (up to 10m).

I am very careful to make sure that the map is set to British National Grid before starting to digitise the area.

I think this is a transformation issue, as when I open the feature class in Arcmap 10.3.1 it is in the wrong (shifted) position, but I cant work out what I am doing wrong in Arcmap Pro.

Has anyone else experienced something like this?

Jeremy Wright

Kate,

Just a guess, but to use the proper datum transformation with BNG (if using OSTN02 or some variant thereof) you'll need to copy the appropriate gsb file into the pedata folder of your installation.  Unfortunately this means you have to do it twice - once for ArcMap, and once for ArcGIS Pro.  This may explain the disparity between ArcGIS Pro behavior and ArcMap behavior.

Here are some references (the data file itself, and an article from EsriUK on picking a datum transformation for your data:

OSTN02 – NTv2 format | Business and government | Ordnance Survey​

geoXchange - geoXchange - Understanding which Transformation to choose in ArcGIS 

The pedata folder in ArcGIS Pro is in the \Resources\pedata subfolder of your Pro installation.