On Thu, 16 Nov 2000, Fernando Cabral wrote: >Hello Friends > >It's been a long, long time since I last disturbed you with my novice >questions. >I was just acculating credits do be entitled to ask the following >question >that has more to do with navigation than any other thing: > >a) If I am using UTM coordenates, what is the easiest way to calculate > the bearing from point A to point B in the chart; >b) Same questions if am using latitude and longitude > >When using UTM I have come accross a solution that works but I must >confess I hate it because I don't think it is elegant and it takes a lot >of >time so I am sure there must be a better solution. > >For the UTM it is much simpler because I can always create a Pythagorean > >triangule whose sides are the difference of Northing and Easting of the >points, >so I have three sides and an angle. Now, if I make the origin point the >origen >of a Cartesian system I can find the Azimuth adding together the angle I >found >plus 0, 90, 180 or 270 if the destination point is on the first, second, >third or >fourth quadrant. > >I does work, but there must be a simpler way to do it.
Nothing realy wrong with your approach but if you use the ATAN2 Fortran function (or the equivalent in other programming languages or the Cartesian to polar coordinate function on many calculators), you can specify the sign of delta x and delta y and the azimuth will then be automatically reported in the correct quadrant. >If what I have are the geographic coordinates it takes me much more time > >with the spherical triangles and I am never sure I've done the right >thing. > >I've read some books on celestial navigation and position astronomy. I >can see >the solution is there, but it does not seem I have the expertise to >convert all those >useful information in a simple formula for this specific calculation. > >And I feel very unhappy when I have to fill out a couple of pages with >ugly >calculations just to find out an azimuth I can easily find with a GPS or >with >a protactor and a map! The use of plane trigonometry to find distances and angles is an important feature of UTM. But for highest accuracies one has to be careful about the differences between geodetic and grid azimuth. See my article in the February 1998 issue of GPS World magazine for more details. -- Richard Langley Professor of Geodesy and Precision Navigation >Best regards > >- fernando > > > > > >-- >Fernando Cabral Padrao iX Sistemas Abertos >mailto:[EMAIL PROTECTED] http://www.pix.com.br >Fone Direto: +55 61 329-0206 mailto:[EMAIL PROTECTED] >PABX: +55 61 329-0202 Fax: +55 61 326-3082 >15? 45' 04.9" S 47? 49' 58.6" W >19? 37' 57.0" S 45? 17' 13.6" W > > > =============================================================================== Richard B. Langley E-mail: [EMAIL PROTECTED] Geodetic Research Laboratory Web: http://www.unb.ca/GGE/ Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142 University of New Brunswick Fax: +1 506 453-4943 Fredericton, N.B., Canada E3B 5A3 Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/ ===============================================================================
