Natter
Posts: 1
Joined: Thu Jun 11, 2009 10:50 pm
Location: Norway

What datum should be used for old coordinates?

Thu Jun 11, 2009 11:12 pm

I have a list of geographical positions (given in "standard" degrees/minutes/seconds format) for numerous sites in Norway, taken from various english and german WWII-documents (ie: dated between 1940-1945). I have no information about what datum these positions are based on though, and using the positions with a current datum (WGS84) will lead to an error varying from a few metres to a couple of kilometres.

I have tried searching anywhere for information about what datum to use (or even any kind of "offset-values" to use), but no luck so far.

I can't find any suitable datums in CoordTrans either, so I thought it might be worth trying a question here: Does anyone have an idea of how I can set a correct datum for these positions (or suggestions to what datums english/ german military were most likely to use at the time), or maybe converting them to a current value for use with WGS84?

A couple of examples:

Position 1 (WGS84): E 16°28'33" / N 68°31'47"
Position 1 in a german 1945-document: E 16°29'06" / N 68°31'42"

Position 2 (WGS84): E 14°58'18" / N 67°58'15"
Position 2 in a german 1945-document: E 14°59'06" / N 67°58'07"

Position 3 (WGS84): E 4°57'18" / N 60°32'57"
Position 3 in an english 1944-document: E 4°57'30" / N 60°32'50"

Position 4 (WGS84): E 7°30'13" / N 60°36'07"
Position 4 in an english 1944-document: E 7°30'30" / N 60°36'08"

ensoco
Posts: 1
Joined: Fri Jun 19, 2009 9:17 pm
Location: USA

RE: What datum should be used for old coordinates?

Fri Jun 19, 2009 9:24 pm

Suggest you try the EPSG database which is an oil & gas sponsored repository of coordinate reference system information. You can access it at www.epsg.org. Your data is likely in a local datum and ellipsoid. There may be transformation parameters from local to WGS-84. You can do an area of interest search on Norway and see what is archived.

If you have known points in WGS-84 which you can correlate to your old maps, then it is possible to derive a datum shift between the unknown and WGS-84 on a per map basis.

John

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