From: Alex P. <ale...@ie...> - 2011-01-25 18:54:23
|
Tides? Ocean with LOD? On Tue, Jan 25, 2011 at 10:13 AM, Curtis Olson <cur...@gm...> wrote: > Quick explanation: the world is curved (oblate spheroid) so if in order to > have an ocean that measures zero MSL at all points, it would have to be > curved. To do this perfectly requires a *lot* of polygons. We have been > using large polygons for the ocean so that leads to some errors depending on > where you are within the polygon. Near the verticies will be pretty > accurate, near the middle could be off by a few meters. > Regards, > Curt. > > > On Tue, Jan 25, 2011 at 11:57 AM, Peter Brown <smo...@ad...> > wrote: >> >> In attempting to place an item on the ocean surface, I came to realize >> that it's not the Nimitz that is "hovering" above MSL, it's that the "ocean >> surface" is about 7 meters below MSL. I was going to suggest simply >> dropping the carriers to match, but then looking around I discovered that it >> was not constant, as the ocean surface is different from front to back of >> the Nimitz. >> So the ocean surface is not flat. Where it meets the terrain north of the >> Golden Gate Bridge the water is at zero MSL. It then slopes down as it you >> head out to sea, to -8.72 meters below sea level, before starting to come >> back up again. I did not continue out to see if it continues to rise and >> fall, or if it's purely a dip in this area. This is different from the >> ocean surface being curved to match the earth, as it actually has a dip, at >> least in this spot. >> See screenshots - >> Terrain intersection north of Golden Gate >> >> [URL=http://s512.photobucket.com/albums/t325/barefootr/?action=view¤t=Screenshot2011-01-24at102804PM.png][IMG]http://i512.photobucket.com/albums/t325/barefootr/th_Screenshot2011-01-24at102804PM.png[/IMG][/URL] >> At the Nimtiz >> >> [URL=http://s512.photobucket.com/albums/t325/barefootr/?action=view¤t=Screenshot2011-01-24at100253PM.png][IMG]http://i512.photobucket.com/albums/t325/barefootr/th_Screenshot2011-01-24at100253PM.png[/IMG][/URL] >> West of Nimitz >> >> [URL=http://s512.photobucket.com/albums/t325/barefootr/?action=view¤t=Screenshot2011-01-24at103120PM.png][IMG]http://i512.photobucket.com/albums/t325/barefootr/th_Screenshot2011-01-24at103120PM.png[/IMG][/URL] >> >> Anyone know why? Or, more importantly, can we set the carriers at an >> altitude appropriate for their default location, so they are no longer >> "hovering"? I'd prefer to do it globally so everyone was at the same >> altitude. >> >> Thanks, >> Peter >> >> ------------------------------------------------------------------------------ >> Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! >> Finally, a world-class log management solution at an even better >> price-free! >> Download using promo code Free_Logger_4_Dev2Dev. Offer expires >> February 28th, so secure your free ArcSight Logger TODAY! >> http://p.sf.net/sfu/arcsight-sfd2d >> _______________________________________________ >> Flightgear-devel mailing list >> Fli...@li... >> https://lists.sourceforge.net/lists/listinfo/flightgear-devel >> > > > > -- > Curtis Olson: > http://www.atiak.com - http://aem.umn.edu/~uav/ > http://www.flightgear.org - http://www.flightgear.org/blogs/category/curt/ > > ------------------------------------------------------------------------------ > Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! > Finally, a world-class log management solution at an even better price-free! > Download using promo code Free_Logger_4_Dev2Dev. Offer expires > February 28th, so secure your free ArcSight Logger TODAY! > http://p.sf.net/sfu/arcsight-sfd2d > _______________________________________________ > Flightgear-devel mailing list > Fli...@li... > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > > |