Most of the descriptions I have seen for converting Lat/Long into UTM have some method of estimating ellipse arc lengths mixed into the formulas (e.g. see http://www.linz.govt.nz/geodetic/conversion-coordinates/projection-conversions/transverse-mercator-preliminary-computations/index.aspx) .
I want to be able to use the arc length formulas provided by a separate library. Can anyone point me to a description of Lat/Long -> UTM conversion which just treats the ellipse arc length formulas generically without specifying a particular estimation method? I'm not clear on what is the GIS stuff and what is the ellipse stuff with these methods.