Hi Does anyone know of a way to transform an sf from equatorial (RA, DEC) into galactic (b, l) coordinates please? Thanks Eugene This email originated from TU Dublin. If you received this email in error, please delete it from your system. Please note that if you are not the named addressee, disclosing, copying, distributing or taking any action based on the contents of this email or attachments is prohibited. Is ? OT Baile ?tha Cliath a th?inig an r?omhphost seo. M? fuair t? an r?omhphost seo tr? earr?id, scrios de do ch?ras ? le do thoil. Tabhair ar aird, mura t? an seola? ainmnithe, go bhfuil dianchosc ar aon nochtadh, aon ch?ipe?il, aon d?ileadh n? ar aon ghn?omh a dh?anfar bunaithe ar an ?bhar at? sa r?omhphost n? sna hiat?in seo.
astrophysics - transform sf from equatorial to galactic coordinates
2 messages · Eugene Hickey, Barry Rowlingson
1 day later
Eugene, I don't think this can be done using the PROJ library that does most coordinate transformations for sf objects. The `astrolibR` package has functions for converting coordinates on various astronomical systems https://cran.r-project.org/web/packages/astrolibR/astrolibR.pdf but you have to feed it vectors of RA and declination rather than entire spatial objects. This isn't much of a problem if you are dealing with points (extract coords with st_coordinates, convert, make a new geometry) but for lines of polygons you need to extract all the vertex points, convert them, then rebuild the features. You might also have problems if you have lines or polygons going across the cosmic coordinate equivalent of the -180/+180 longitude line... Having another look, it *might* be possible to do this with PROJ by constructing an appropriate spherical rotated coordinate system, and you might even be able to convert degrees to RA hours with a +units parameter... Barry On Sat, Mar 21, 2020 at 6:06 PM Eugene Hickey <Eugene.Hickey at tudublin.ie> wrote:
Hi
Does anyone know of a way to transform an sf from equatorial (RA, DEC)
into galactic (b, l) coordinates please?
Thanks
Eugene
This email originated from TU Dublin. If you received this email in error,
please delete it from your system. Please note that if you are not the
named addressee, disclosing, copying, distributing or taking any action
based on the contents of this email or attachments is prohibited.
Is ? OT Baile ?tha Cliath a th?inig an r?omhphost seo. M? fuair t? an
r?omhphost seo tr? earr?id, scrios de do ch?ras ? le do thoil. Tabhair ar
aird, mura t? an seola? ainmnithe, go bhfuil dianchosc ar aon nochtadh, aon
ch?ipe?il, aon d?ileadh n? ar aon ghn?omh a dh?anfar bunaithe ar an ?bhar
at? sa r?omhphost n? sna hiat?in seo.
[[alternative HTML version deleted]]
_______________________________________________ R-sig-Geo mailing list R-sig-Geo at r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo