[OSM-newbies] How to convert NAD83 to latitude/longitude?

[Kelly Jones]

I found some public domain data I want to upload to OSM, but can't
seem to convert the NAD83 format it's in to latitude/longitude. I know
it should be easy, but even things like:

http://www.ngs.noaa.gov/cgi-bin/spc_getgp.prl

are giving me ridiculous answers.

Here's the header from ogrinfo -al

PROJCS["NAD_1983_HARN_StatePlane_New_Mexico_Central_FIPS_3002_Feet",
    GEOGCS["GCS_North_American_1983_HARN",
        DATUM["NAD83_High_Accuracy_Regional_Network",
            SPHEROID["GRS_1980",6378137.0,298.257222101]],
        PRIMEM["Greenwich",0.0],
        UNIT["Degree",0.0174532925199433]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["False_Easting",1640416.666666667],
    PARAMETER["False_Northing",0.0],
    PARAMETER["Central_Meridian",-106.25],
    PARAMETER["Scale_Factor",0.9999],
    PARAMETER["Latitude_Of_Origin",31.0],
    UNIT["Foot_US",0.3048006096012192]]

and a sample item:

OGRFeature(schoolLocation):23
  SCHOOLTYPE (String) = HIGH
  SCHOOLNAME (String) = RIO GRANDE
  POINT (1507003.249 1473733.624)

I know the correct answer for this item is approximately latitude
35.052536, longitude -106.69394, but am not sure how to do this
translation for all items in the shapefile.

I played around with subtracting (and even adding) the "False_Easting"
value, converting feet to meters, using NAD27 (on the NOAA page
above), but nothing seemed to work.

Any help appreciated: I suspect it's just a linear transformation, but
want to make sure I have it right before uploading.

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