Awesome thanks Steve, and great to see ya again Chris. Martin, take it away :)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Chris Mattmann, Ph.D. Chief Architect Instrument Software and Science Data Systems Section (398) NASA Jet Propulsion Laboratory Pasadena, CA 91109 USA Office: 168-519, Mailstop: 168-527 Email: [email protected] WWW: http://sunset.usc.edu/~mattmann/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Adjunct Associate Professor, Computer Science Department University of Southern California, Los Angeles, CA 90089 USA ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -----Original Message----- From: "Hughes, John S (398B)" <[email protected]> Date: Wednesday, October 28, 2015 at 5:40 PM To: jpluser <[email protected]>, "[email protected]" <[email protected]> Cc: "Christopher E Isbell ([email protected])" <[email protected]> Subject: RE: Note about usage of SIS for planets other than Earth >Hi Chris, > >I am ccing Chris Isbell, the current lead on the PDS4 Cartography working >group, a team of experts who have been working on the cartography >dictionary. His team should be interested in Martin's work. > >Thanks, >Steve > > >-----Original Message----- >From: Mattmann, Chris A (3980) >Sent: Wednesday, October 28, 2015 5:14 PM >To: [email protected] >Cc: Hughes, John S (398B) <[email protected]> >Subject: Re: Note about usage of SIS for planets other than Earth > >I wonder if it would make sense to talk about some of this stuff with >Steve Hughes, CC’ed here, Martin. Steve, meet Martin Desruisseaux who is >working on Apache SIS. Martin, meet Steve who is the Planetary Data >System (PDS) System Engineer and a JPL principal. This sounds useful >potentially to PDS. > >Cheers, >Chris > > >++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >Chris Mattmann, Ph.D. >Chief Architect >Instrument Software and Science Data Systems Section (398) NASA Jet >Propulsion Laboratory Pasadena, CA 91109 USA >Office: 168-519, Mailstop: 168-527 >Email: [email protected] >WWW: http://sunset.usc.edu/~mattmann/ >++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >Adjunct Associate Professor, Computer Science Department University of >Southern California, Los Angeles, CA 90089 USA >++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > > > >-----Original Message----- >From: Martin Desruisseaux <[email protected]> >Organization: Geomatys >Reply-To: "[email protected]" <[email protected]> >Date: Wednesday, October 28, 2015 at 4:29 PM >To: Apache SIS <[email protected]> >Subject: Note about usage of SIS for planets other than Earth > >>Hello all >> >>A note in case some peoples are interested in planetary mapping. Often, >>the methods for going from Cartesian coordinates (e.g. map projection >>or geocentric system) to geographic coordinates have no exact formulas. >>The solution is approximated in various ways, but two common approaches >>are: >> >> * iteration until the error become sufficiently small, >> * or series expansions. >> >>The series expansions are often preferred since they are faster than >>iterations (at least twice faster for Lambert Conic Conformal according >>my measurement) for equivalent precision. They can be found in the EPSG >>guidance notes for instances, and their accuracy are quite good. >>However precision of series expansions depend on the number of terms, >>and that number is usually chosen for a planet having an eccentricity >>like Earth. >>Empirical tests suggest that for a planet having an eccentricity twice >>larger than Earth, series expansion precision become lower than >>iteration. >> >>Apache SIS currently focus about Earth. However I opportunistically >>made some provisions for planetary usages when I could identify a >>possible issue with high eccentricities. The strategy is: >> >> 1. Begin with series expansion. For geographic coordinates on Earth, >> this is the only step. >> 2. Only if we know that series expansion may not be enough (e.g. >> eccentricity is above some threshold), continue with iteration. >> >>For Lambert Conic Conformal projection this was relatively easy. For >>the "Geocentric to Geographic conversion" just committed today it is >>more difficult, because the precision is impacted by two parameters: >> >> * high eccentricity (e) >> * high altitude (h) >> >>I did not tried to resolve how those parameters interact with each >>others. However if there is any peoples in this list who have an >>interest for extraterrestrial planetary mapping, this is an area where >>some research could be done. A first step could be to maintain a wiki >>page listing known issues like this one. >> >> Martin >> >> >
