Hi All, Ed Davies wrote: > I'd strongly urge the use of WGS-84 whereever high precision is > required. Apart from it being the basis of GPS and pretty much the > world standard it also has the advantage that the least badly defined > transformations between datums exist with respect to it. Most > transformations between other datums go via WGS-84 anyway. In case anyone cares, SkyMap and IRIDFLAR have always used WGS-84. So if the orbital elements used with SkyMap or IRIDFLAR are WGS-72 (or some other datum), then that will introduce a small systematic error in the predictions. Likewise, if you supply SkyMap or IRIDFLAR with observer coordinates in a datum other than WGS-84, that will also introduce an error (primarily in longitude). The maximum positional error between these two datums occurs at the equator, with a longitude difference of 17.1 meters (or about .00015 degrees) and a latitude difference of 4.5 meters (.000040 degrees). The longitude error is always .00015 degrees, but in terms of meters it is 17.1 * COS(Latitude). --Rob ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Fri Aug 17 2001 - 10:59:05 PDT