AirTalk.org Aviation discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Great circle calculations. Help rqd. Goto page 1, 2  Next          AirTalk.org Forum Index -> Planes, gliders and flying in Australia View previous topic :: View next topic   Author Message Jarod (the puppy) Guest Posted: Fri Aug 26, 2005 11:15 pm    Post subject: Great circle calculations. Help rqd. Hello there again folks. Thanks much to all who helped me with my Wind vector problems earlier. Now I would like a bit of help to calculate the distance and track between two points. Given I have both point's lat/long. I know how to do it for flat surfaces, but as the earth isn't flat I believe there is a slight trick to it. (waiting for the reply exclaiming - "Gad! The earth isn't flat?".) Anyway, if someone out there wouldn't mind helping me please. Thanks in advance. -- ======== Thanks..... Jarod Back to top Paul Slater Guest Posted: Fri Aug 26, 2005 11:36 pm    Post subject: Re: Great circle calculations. Help rqd. Try http://gc.kls2.com/ HTH, Paul "Jarod (the puppy)" <dog_kennel_alias (AT) zeta (DOT) org.au> wrote Quote: Hello there again folks. Thanks much to all who helped me with my Wind vector problems earlier. Now I would like a bit of help to calculate the distance and track between two points. Given I have both point's lat/long. I know how to do it for flat surfaces, but as the earth isn't flat I believe there is a slight trick to it. (waiting for the reply exclaiming - "Gad! The earth isn't flat?".) Anyway, if someone out there wouldn't mind helping me please. Thanks in advance. -- ======== Thanks..... Jarod Back to top John Ewing Guest Posted: Fri Aug 26, 2005 11:37 pm    Post subject: Re: Great circle calculations. Help rqd. "Jarod (the puppy)" <dog_kennel_alias (AT) zeta (DOT) org.au> wrote Quote: Hello there again folks. Thanks much to all who helped me with my Wind vector problems earlier. Now I would like a bit of help to calculate the distance and track between two points. Given I have both point's lat/long. I know how to do it for flat surfaces, but as the earth isn't flat I believe there is a slight trick to it. (waiting for the reply exclaiming - "Gad! The earth isn't flat?".) Anyway, if someone out there wouldn't mind helping me please. Thanks in advance. -- ======== Thanks..... Jarod Jarod - unless you want it all explained from first principles why not enter "great circle calculations" in Google, and you can take your choice of easy-to-use programs. Cheers, John Back to top Nick Guest Posted: Fri Aug 26, 2005 11:37 pm    Post subject: Re: Great circle calculations. Help rqd. Jarod (the puppy) wrote: Quote: Hello there again folks. Thanks much to all who helped me with my Wind vector problems earlier. Now I would like a bit of help to calculate the distance and track between two points. Given I have both point's lat/long. I know how to do it for flat surfaces, but as the earth isn't flat I believe there is a slight trick to it. (waiting for the reply exclaiming - "Gad! The earth isn't flat?".) Anyway, if someone out there wouldn't mind helping me please. Thanks in advance. Google for great circle calculator, there are thousands of sites. -- Nick Back to top veritas Guest Posted: Fri Aug 26, 2005 11:47 pm    Post subject: Re: Great circle calculations. Help rqd. Jarod (the puppy) wrote: I found this in a folder where I was fooling about. Might give some insight into the problem. I know I have completed (working) algorithms somewhere - I will look..... theta = lon2 - lon1 dist = acos(sin(lat1) × sin(lat2) + cos(lat1) × cos(lat2) × cos(theta)) if (dist < 0) dist = dist + pi dist = dist × 6371.2 Back to top veritas Guest Posted: Sat Aug 27, 2005 2:44 am    Post subject: Re: Great circle calculations. Help rqd. veritas wrote: Quote: Jarod (the puppy) wrote: I found this in a folder where I was fooling about. Might give some insight into the problem. I know I have completed (working) algorithms somewhere - I will look..... theta = lon2 - lon1 dist = acos(sin(lat1) × sin(lat2) + cos(lat1) × cos(lat2) × cos(theta)) if (dist < 0) dist = dist + pi dist = dist × 6371.2 =============================================== This would run in Clipper 5 - but dB is needed I wrote it in '88 ans as far as I can recall, the calculations worked fine. Anyhow - the principle is there..... +++++++++ clear store ' ' to T1,T2 set exact off *do navndx select 1 use nav index navid select 1 @ 6,10 say 'Input LOC1' get T1 pict '!!!!!' read seek T1 ida=id lna=ln @ 6,30 say lna lata=(ltd*60)+ltm lona=(lgd*60)+lgm @ 8,10 say 'Input LOC2' get T2 pict '!!!!!' read seek T2 idb=id lnb=ln @ 8,30 say lnb latb=(ltd*60)+ltm lonb=(lgd*60)+lgm chlat=lata-latb chlon=lona-lonb if lata>latb midlat=lata+chlat/2 else midlat=latb+chlat/2 endif if lona>lonb midlon=lona+chlon/2 else midlon=lonb+chlon/2 endif adj=1-((60*(((midlat/60)/90)/2))*.01) *adj=1-(adj*.01) *chlon=chlon*adj dist=sqrt(chlat^2+(chlon*adj)^2) @ 12,10 say int(dist+.5) pict '99,999' @ 12,18 say 'Nautical Miles.' @ 14,10 say int((dist*1.82)+.5) pict '99,999' @ 14,18 say 'Kilometres.' * suspend cancel Back to top J Mac Guest Posted: Sat Aug 27, 2005 3:59 am    Post subject: Re: Great circle calculations. Help rqd. Quote: Now I would like a bit of help to calculate the distance and track between two points. Given I have both point's lat/long. Go to this Website. It has all navigation formulas you could need. http://williams.best.vwh.net/avform.htm#Changes Back to top J Mac Guest Posted: Sat Aug 27, 2005 4:01 am    Post subject: Re: Great circle calculations. Help rqd. Change that Web address to: http://williams.best.vwh.net/avform.htm Back to top Jarod (the puppy) Guest Posted: Sat Aug 27, 2005 11:26 pm    Post subject: Re: Great circle calculations. Help rqd. "JE" == "John Ewing" writes: JE> Jarod - unless you want it all explained from first principles JE> why not enter "great circle calculations" in Google, and you JE> can take your choice of easy-to-use programs. Well John, and Paul, it isn't that I don't appreciate your help, but I would like the formulars not the programs. When I asked about wind vectors to calculate drift and heading, I got the formulars, and I was happy. I am trying to write my own spreadsheet to help me design (for lack of better word) my flights. Sometimes I am flying between "nominal" points on the map and so it is - I thought - just as easy to get the two point's lat/long and do the maths to get the distance and track. I know there is no second prize for re-inventing the wheel, but I am not really wanting to do that either. I just want to get an understanding on the formular and then apply it to my sheet. Fair enough? Happy flying. -- ======== Thanks..... Jarod Back to top Jarod (the puppy) Guest Posted: Sat Aug 27, 2005 11:28 pm    Post subject: Re: Great circle calculations. Help rqd. "v" == "veritas" writes: v> This would run in Clipper 5 - but dB is needed v> v> I wrote it in '88 ans as far as I can recall, the calculations v> worked fine. v> v> Anyhow - the principle is there..... v> Thanks much. Going to be an uphill battle for me to convert that to work on Excel. But I'll try. ;-) I'm guessing the first post is really the crux of it - Yes? -- ======== Thanks..... Jarod Back to top Jarod (the puppy) Guest Posted: Sat Aug 27, 2005 11:33 pm    Post subject: Re: Great circle calculations. Help rqd. "JM" == "J Mac" writes: JM> JM> Change that Web address to: JM> http://williams.best.vwh.net/avform.htm JM> Thanks thanks thanks. Got the whole page and cached it. I'm in pig heaven - kinda. Now for the fun to impliment the formulars into my sheet. Fun Fun Fun! Happier flying! <8-) -- ======== Thanks..... Jarod Back to top veritas Guest Posted: Sun Aug 28, 2005 1:07 am    Post subject: Re: Great circle calculations. Help rqd. Jarod (the puppy) wrote: Quote: "v" == "veritas" writes: v> This would run in Clipper 5 - but dB is needed v v> I wrote it in '88 ans as far as I can recall, the calculations v> worked fine. v v> Anyhow - the principle is there..... v Thanks much. Going to be an uphill battle for me to convert that to work on Excel. But I'll try. ;-) I'm guessing the first post is really the crux of it - Yes? Well, I can't recall much about the origin of the first post but I believed that it might be something to start with. I had a good one in basic. That would have been ideal to convert into excel. I will continue to search - but I have gone through many computers and HDD's since the 80's It may have gone where all good HDD stuff goes (software Valhalla). Back to top Brian May Guest Posted: Sun Aug 28, 2005 5:22 am    Post subject: Re: Great circle calculations. Help rqd. Quote: "Jarod" == Jarod (the puppy) <dog_kennel_alias (AT) zeta (DOT) org.au> writes: Jarod> Now I would like a bit of help to calculate the distance Jarod> and track between two points. Jarod> Given I have both point's lat/long. Jarod> I know how to do it for flat surfaces, but as the earth Jarod> isn't flat I believe there is a slight trick to it. Are you sure you want the great circle distance? Remember, while this is the shortest distance, it is also the most complicated to navigate by (without a navigation computer[1]) as the magnetic heading is probably not constant. Maybe a compromise is possible, but I don't fly such long legs to make it matter. A better strategy (depending on length of leg) might be to project the coordinates onto a flat map (i.e. make it a map), and then you can use standard calculations to determine constant heading and distance. This is essentially the same as drawing a line on a map and calculating the track and distance. Obviously the method you use for projecting the map is also important. This may not give the shortest distance, but I suspect this may not matter (unless you want this to work with long flights). There was an algorithm to do something like this in the flight planner excel spreadsheet I think I posted earlier - I haven't yet tried to understand the algorithm though - it is not simple. Disclaimer: [1] I am not an airliner pilot, so I don't know what methods they use to navigate by great circle routes. -- Brian May <bam (AT) snoopy (DOT) apana.org.au> Back to top AA Guest Posted: Sun Aug 28, 2005 10:50 am    Post subject: Re: Great circle calculations. Help rqd. "Jarod (the puppy)" <dog_kennel_alias (AT) zeta (DOT) org.au> wrote Quote: "JM" == "J Mac" writes: JM JM> Change that Web address to: JM> http://williams.best.vwh.net/avform.htm JM Thanks thanks thanks. Got the whole page and cached it. I'm in pig heaven - kinda. Now for the fun to impliment the formulars into my sheet. Fun Fun Fun! Jarod, I've done an excel spreadsheet using the formulae from this site and am happy to send it to you if you want. If not, I do remember some of the pitfalls. Convert the degreees to radians. Angles used in excel - start with a circle - 0 radians is at 3 o'clock on the circle and moves anticlockwise for positive radians - so p/2 (90°) is at 12 o'clock. If you want my spreadsheet send your email to sirronnala AT yahooooooo cot com cot au and I'll forward it. Only two o's in yahoo and change cot to read dot AA Back to top AA Guest Posted: Sun Aug 28, 2005 10:52 am    Post subject: Re: Great circle calculations. Help rqd. "AA" <someone (AT) yahoo (DOT) com.au> wrote Quote: "Jarod (the puppy)" <dog_kennel_alias (AT) zeta (DOT) org.au> wrote in message news:l1.h1.vc2A9h661Za3yyd.NR (AT) zeta (DOT) org.au... "JM" == "J Mac" writes: JM JM> Change that Web address to: JM> http://williams.best.vwh.net/avform.htm JM Thanks thanks thanks. Got the whole page and cached it. I'm in pig heaven - kinda. Now for the fun to impliment the formulars into my sheet. Fun Fun Fun! Jarod, I've done an excel spreadsheet using the formulae from this site and am happy to send it to you if you want. If not, I do remember some of the pitfalls. Convert the degreees to radians. Angles used in excel - start with a circle - 0 radians is at 3 o'clock on the circle and moves anticlockwise for positive radians - so p/2 (90°) is at 12 o'clock. If you want my spreadsheet send your email to sirronnala AT yahooooooo cot com cot au and I'll forward it. Only two o's in yahoo and change cot to read dot AA That p/2 -bloody outlook converted my pi symbol to a p AA Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AirTalk.org Forum Index -> Planes, gliders and flying in Australia All times are GMT Goto page 1, 2  Next Page 1 of 2   Jump to: Select a forum Aviation----------------alt.aviationAviation safety EnhancementPlanes, gliders and flying in AustraliaAviation et pilotage (Français)rec.aviationAviation (Aerobatics)Hot air, gas balloons and airshipsHang-gliding, paragliding, foot-launched flightAircraft Design & BuildingInstrument Flight RulesAviation (Classifieds)Military AircraftNaval AviationAviation (Miscellaneous Topics)Owning AirplanesAviators (General Discussions)Aviation related productsAircraft RestorationHelicopters and rotary wing aircraftsFlight SimulationSailplanesAviation (Students)Light aircraftFlying related activities in the UK Airports----------------alt.airportsEdinburgh Airport Glasgow Airport Humberside Airport Luton Airport Aberdeen Airport Glasgow Prestwick Airport  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.