I don't know if this will help at all. o_lon_p and o_lat_p define the new pole
for the latitude and longitude values. So the lat/lon values are converted
to a new, rotated sphere, then projected. I assume the values you set
for the projection should be based on the new spheroid. John Snyder
talks about this theoretically in _Map Projections: A Working Manual_, pp 29-32.
ASU libraries reports that there's a copy in "Hayden US Documents", I 19.16:1395.
Michael and I are trying to learn about the ob_tran projection in order to
facilitate use here at the Mars Space Flight Facility. We need more
information about the o_lon_p and o_lat_p parameters. Could someone give an
exact English description of how they operate or a URL to such. We
understand the notion of an oblique projection, but we're having a hard time
understanding how these parameters define the "obliqueness". We applying
these to eqc (Platte Caree) if that simplifies your answer at all.