On Wed, 5 Jan 2011, Tom Browder wrote: > On Wed, Jan 5, 2011 at 17:03, klaatu <kla...@earthops.org> wrote: >> >> Greetings, all, > > Hello again, klaatu--and Happy New Year!
Hi, Tom, good to see you're still on the job! >> As a long-time user of BRLCAD, I recently had reason to build and install >> it, and I have to say that it's far easier now than it was in, say, 1997 >> or so. ;) > > Sean and crew have been very busy--fruitfully so. They've done a great job. ;) > >> The problem? Knowing the decimal degrees of latitude and longitude (x,y), >> give a bearing and distance, and get a result in latitude/longitude (x,y). > ... >> For what it's worth, the best reference I could find for this was at: >> http://williams.best.vwh.net/avform.htm#Triangle > > Doesn't the "Lat/lon given radial and distance" formulae on that site > do what you want? In some cases, it gives a rough approximation. In other cases, it's incredibly wrong. I think his math is good -- he's highly recommended -- but his javascript implementation seems to have major problems in some areas. Using input from google maps (lat/long) and giving bearing and distance, I've gotten errors in results, which seem to be about 170 degrees off. I've triple-checked and in those certain cases it is very repeatably wrong. I suppose I should write to him, rather than to the BRLCAD folks. I don't know that there is much use in BRLCAD for computations of "great circle" problems, however large the universe or however small the ruler, to reference a nice paper that used to be distributed with the download. Still, a lot of things have come to me along with the main BRLCAD distribution, for instance the little app 'loop (start/limit interval)' which is most useful in 'bash' for incrementing in scripts. :D I don't know if BRLCAD in the developer community, or the user community, would have much use for this function. I expect that it is already to some degree calculated, for example, in a combinatorial geometry of the intersection of an extruded triangle with the surface of a sphere. However that calculation is probably in the RT and most likely occurs as an artifact of the process, rather than as an intentional result towards that specific goal. It might be nice if there was a way to pick a spot on a sphere and then enter a "follow surface at bearing to distance, return x,y" function. The generic case in that code could doubtless be applied elsewhere. I suppose that this is all very "old hat" in the military, especially in the Navy and the artillery divisions. I'm not asking for the latest in secret stuff, but maybe a 100 year old solution would do the trick for me. ;) Regards, -- Be kind to your neighbors, even though they be transgenic chimerae. ------------------------------------------------------------------------------ Learn how Oracle Real Application Clusters (RAC) One Node allows customers to consolidate database storage, standardize their database environment, and, should the need arise, upgrade to a full multi-node Oracle RAC database without downtime or disruption http://p.sf.net/sfu/oracle-sfdevnl _______________________________________________ BRL-CAD Users mailing list brlcad-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/brlcad-users
