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All you need is the Lat/Lon converted to decimal format There are 60 minutes in a degree and 60 seconds in a minute so it is just a bit of slightly fiddly maths degrees + minutes/60 + seconds/3600 so N50 21' 15" becomes 50 + 21/60 + 15/3600 = 50 + 0.35 + 0.004166 = 50.354166 If your data is in "degrees and decimal minutes" format (N50 21.25) then the maths is even simpler degrees + decimalminutes/60 50 + 21.25/60 = 50 + 0.354166 Remember that west and south are negative so add a minus sign to the result for them