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I'm changing raster layers in ArcMap from WGS84 to BTM (Bangladesh Transverse Mercator). I first set my data frame to be in BTM

[BTM Projection: Transverse_Mercator False_Easting: 500000.0 False_Northing: -2000000000.0 Central_Meridian: 90.0 Scale_Factor: 0.9996 Latitude_Of_Origin: 0.0 Linear Unit: Meter (1.0)]

When I add the layers I'm asked to do a datum transformation apparently. I found two transformation datum which differ in ΔZ. Which one is accurate?

First one: ΔX -283.729m ΔY -735.942m ΔZ -261.143m

Second: ΔX -283.729m ΔY -735.942m ΔZ -161.143m

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  • The BTM seems to be a custom one, did you used the project tool to convert from WGS to BTM? Dec 21 '20 at 15:32
  • yes it's a custom one, and yes I used the project raster tool but that's a later step, this transformation window appeared to me once I entered the layers since they are in WGS84. Then I did the transformation using the X,Y,Z above. Then I used project raster tool to convert them from WGS84 to BTM.
    – Areej
    Dec 21 '20 at 16:25
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When I've processed data in Bangladesh and it has been supplied to me in BTM (Bangladesh Transverse Mercator) it sometimes comes with the datum set to GCS_Everest_Bangladesh. I have found if I set the datum to be GCS_Gulshan_303 I generally get better alignment.

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  • Yes I agree, even I had a few projects involving India-Bangladesh borders, there the data used to be in the UTM zone(45 & 46) with their datum in WGS 84, for BTM the datum was Everest Bangladesh, and for Gulshan 303 it was the same datum Gulshan 303 with spheroid Everest Bangladesh Adjustment 1937 Dec 21 '20 at 19:09

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