My homebrew GPS uses ddd.dddddd internally, for feeding data into it I type it in a spreadsheet as dd mm ss for the simple reason that I'm an old-fashioned person. Spreadsheets are great for converting data between different formats or units.
The format dd mm.mmmm seems to be a standard, used in several countries' AIP's. To me it looks like a particularly unhappy compromise between dd mm ss (traditional, and quite natural to use if one gets indeed used to it) and dd.dddddd (by far the most logical). But to be really logical, there should be 100 degrees rather than 90.
NB before talking of ss.s, first consider the distance one second corresponds to (30 yards or so, on a great circle?). I cannot imagine a single reason a pilot should ever need to go into the decimals.
Last edited by Jan Olieslagers; 4th Sep 2011 at 02:01.