Google maps are notoriously incorrect on co-ordinates. Even their own road map overlay does not align perfectly with the scenery. You can check the accuracy yourself if you have a GPS receiver and visit a set of easily identifiable points like road junctions.
My understanding is that they stitch their photos together and then produce tiles. These tiles are fitted to a spheroid using an array of reference points. Any position that you try to measure that is not close to one of these reference points will have an interpolation error. The photography and stitching process is bound to introduce a degree of distortion. Point positions of aeronautical navaids and airfields have mostly been well surveyed and their positions should therefore be accurate. Alan -----Original Message----- From: Martin Spott Sent: Sunday, September 11, 2011 11:39 PM Newsgroups: list.flightgear-devel To: [email protected] Subject: Re: [Flightgear-devel] Openstreetmap vs. G**gl HB-GRAL wrote: > I am just curious why FlightGear and OSM have the same "accurate" > position, and Google map shows another one. I might not have entirely understood your question (it's late and I'm tired), but one cause to be considered could be that OSM folks might simply have imported from the good old NIMA airport database - the same source which has built the basis of the X-Plane aiport collection. > Beside of that, where does this inexisting taxiway to the left come from > ? Is this a FlightGear feature ? Something like > "we-have-no-taxiways-so-there-is-probably-one-to-the-left" ? Exactly, that's a default in Robin's collection. Cheers, Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -------------------------------------------------------------------------- ------------------------------------------------------------------------------ Using storage to extend the benefits of virtualization and iSCSI Virtualization increases hardware utilization and delivers a new level of agility. Learn what those decisions are and how to modernize your storage and backup environments for virtualization. http://www.accelacomm.com/jaw/sfnl/114/51434361/ _______________________________________________ Flightgear-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/flightgear-devel ------------------------------------------------------------------------------ Doing More with Less: The Next Generation Virtual Desktop What are the key obstacles that have prevented many mid-market businesses from deploying virtual desktops? How do next-generation virtual desktops provide companies an easier-to-deploy, easier-to-manage and more affordable virtual desktop model.http://www.accelacomm.com/jaw/sfnl/114/51426474/ _______________________________________________ Flightgear-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/flightgear-devel
