I have no experience in mapping, so please excuse me if this sounds foolish.

I'm trying to use Microsoft MapPoint (2004) software to geocode a number of addresses in Excel. However, my version of MapPoint does not have a nice, neat way to return the latitude and longitude of an address; it has to be calculated.

The method I've found to calculate latitude and longitude, in a nutshell, uses the great-circle distances from the location to the North Pole and the prime meridian. These distances are calculated using spherical coordinates, so they're fairly accurate, but they're not as precise as I'd like.

Is there a way to tweak these, let's call them "spherical" coordinates, so that they better represent true "elliptical" coordinates?

  • 2
    Can you provide an example of the coordinates you get from MapPoint, as well as an example of the coordinates you want to convert to?
    – nagytech
    Jun 24 '12 at 8:43
  • This thread explains some of the many kinds of latitude in use: gis.stackexchange.com/q/25982. This one may give you some insight about the nature of the inaccuracies: gis.stackexchange.com/q/25494. It would help if you could provide details of your calculation, because longitudes are not great-circle distances to the prime meridian, not even approximately (except for points close to the prime meridian itself). (Lines of latitude, which are swept out as the longitude varies, are geodesic circles, not geodesic lines: see gis.stackexchange.com/a/6824, e.g.)
    – whuber
    Jun 24 '12 at 14:41

Here's one way to easily transform the lat/long on a sphere to WGS84 (true lat/long as you say)

The open source PROJ4 library comes with a utility called cs2cs. Easiest way to run it is to grab FWTools http://fwtools.maptools.org/ and run the following commandline

cs2cs +proj=latlong +ellps=sphere +towgs84=0,0,0 +to +proj=latlong +ellps=WGS84 +towgs84=0,0,0

Then enter your coordinates as LONGITUDE LATITUDE

-170 60

Would give you something like

170dW 60d9'58.076"N 8918.648

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