The US' National Geophysical Data Center maintains a magnetic declination model called the International Geomagnetic Reference Field Model[1] and also provides a program[2] that can give you the declination for a given set of coordinates on the planet given this data.
Here's some sample output from that program: Model: IGRF2005 Latitude: 64.14 deg Longitude: -21.91 deg Altitude: 0.00 km Date of Interest: 2008.00 ------------------------------------------------------------------------------- Date D I H X Y Z F (yr) (deg min) (deg min) (nT) (nT) (nT) (nT) (nT) 2008.00 -16d 32m 75d 34m 13057.2 12517.3 -3716.2 50705.2 52359.4 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Date dD dI dH dX dY dZ dF (yr) (min/yr) (min/yr) (nT/yr) (nT/yr) (nT/yr) (nT/yr) (nT/yr) 2008.00 17.7 -0.8 18.4 36.7 59.3 23.3 27.1 ------------------------------------------------------------------------------- I think it would be awesome to have a declination overlay on OSM similar to the contour map the cyclemap uses. If I want to make this happen I guess I'd have to do it myself. I have no experience producing custom renderings of OSM data or producing contour-like overlays on the map from a set of coordinates/elevation data. I guess a very similar technique could be used to get declination data on the map basically by swapping out elevation for declination. If someone here has any pointers on how I'd go about getting started on such a project that would be most useful. 1. http://www.ngdc.noaa.gov/geomag/declination.shtml 2. http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html _______________________________________________ talk mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk
