So I am using
ArcGIS 10 and trying to work in British National Grid. My shape file is in WGS84 UTM30N. By chance I passed the shape file across to a colleague and we both transformed into BNG.
When we compared the data there was a significant difference in our results. I have since cross checked with QGIS, Global mapper and a website or two and got a whole range of results but in general the most common is the result my colleague got.
My question I guess is three-fold:
- What have I done wrong?
- Why is there such a variation (~150m) in values? (1 or 2m error is probably ok for what I am looking at.)
- Which value is "right"?
Bit of a beginner-ish question I fear but help would be much appreciated!