Open ctslater opened 4 years ago
Hi, are there any updates on this? Looking at the functions calcGnom()
and degToGnom()
and the conversion gnom_dist = degToGnom(r)
( gnom_dist = tan(rad(r)) ), could this be a gnomonic projection? Is there something in the documentation or in other external sources that explains the method and the formulas used to determine the distance?
If we take the Gnomonic projection equations and set phi_1 and lambda_0 both to zero, (and also substitute lambda for abs(ra_2-ra_1) and phi for abs(dec_2-dec_1)), that would be as though the projection is centered on ra_1 and dec_1. That's what was implemented. I hope that makes sense for you?
Yes, thank you very much @zecevicp . I was also wondering, is there a particular reason why the UDFs are written in Scala? Wouldn't be possible to implement calcGnom() directly in Python as a PandasUDF or using the built-in SQL functions? Thanks again
Ernesto Castillo asks a very good question: what are the units on axsdist? This seems to be computed by
calcGnom
inFrameFunctions.scala
, but I can't follow what the final formula is producing.