hi, this is really very interesting. e.g. when I quote my position I am referring to Mapblast.com :-) and I do not know the geoid they are using. our local maps say I am 60 m above sea level ... now: as you say the same location differs about 124 m according to different géoids. I am asking: what precision do we actually need here ? for the normal observer - like me an "aficionado" - I think I do not really need the referring geoid ... but that may not be the case in every instance. But then we have some real problems: - the elsets what geoid do they require? - how can we transform - in case we need that precision - data from one geoid to the other in order to make data comparable ? just food for thinking Jörg Allen Thomson schrieb: > > > As a newcomer to the List, from the background of being a Geodesist, > > I've been wondering about the apparent precision of some List members' > > declared co-ordinates and to what geodetic framework they refer. > > A most interesting discussion. In many cases, I suspect the > answer to "which datum?" is "nary a clue." In my own case, > pre-NIMA and pre-Heavens Above, I scrounged coordinates > from atlases, airport and weather site databases, wherever. > Few if any of those gave the datum used. > > - Which datum is preferred today and should be used when possible? > (I'd guess WGS84.) > > - If the datum is unknown, what level of accuracy should be reported and > used? I.e., where do the coordinates given in decimal degrees diverge > in the commonly used systems? The current standard in this community > seems to be four places after the decimal point, 10 meters, around GPS > accuracy. Does that demand specifying the datum? > > > ----------------------------------------------------------------- > 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 -- ===================================================================== Dr. Jörg Kampmann - IBK-Consult for Real-Time and Embedded Systems D-31228 Peine - Tel.:+49-177-276-3140 - Fax: +49-5171-13385 http://www.ibk-consult.de ===== QNX is the better Choice for Real-Time: http://www.qnx.com ==== ----------------------------------------------------------------- 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 : Thu Aug 16 2001 - 14:53:40 PDT