One other thing which may be a problem once you've surmounted this one: For certain combinations of the distance, the latitude and longitude, the product of those sin and cos functions that you are dividing by might equal 0.
-- Emily At 01:26 PM 8/30/05 -0700, you wrote: >> Jamey Saunders wrote: >> > I have a bit of a problem with a pretty complicated mathematical >> > expression. Basically, I'm trying to determine the initial heading >> > between two points on the globe using latitude and longitude of the >> > two points. I already know the distance between the two ($miles). >> > >> > Here's the expression: >> >$Hdg=2*M_PI-acos((sin($lat2)-sin($lat1)*cos($miles))/(sin($miles)*cos($lat1))); >> > >> > When I echo $Hdg, I see: >> > >> > -1.#IND >> > >> > If the expression was working, I should see something like 134.9 for >> > the following latitude/longitude combinations: >> > >> > $lat1 = 33.9780761 >> > $lon1 = -83.9623772 >> > $lat2 = 32.1950556 >> > $lon2 = -81.8695556 >> > $miles = 172.7381359 >> > >> > I can't find any references to what #IND means, so if anyone out there >> > has any ideas, I'd be grateful. >> > >> > -JS > > >--- Brian Cummiskey <[EMAIL PROTECTED]> wrote: >> >> Only thing i can thinkg of off the top of my head is that you are trying >> to plug in degrees and minuets, but the sin,cos, and other trig >> functions in php take on a parameter in radians-- not degrees. > > >Degrees vs. radians can certainly be a factor. Make sure you are giving the >functions a value in radians. > >Also, you have this item: > > 2*M_PI > >Have you defined a constant called M_PI or do you expect it to be a variable? > >Here are some links which may be helpful for determing the bearing (or heading) >between two latitude and longitude points: > > http://www.movable-type.co.uk/scripts/LatLong.html > > http://mathforum.org/library/drmath/view/55417.html > >This sounds like a Google Map application :) > >James >_____ > > >James D. Keeline >http://www.Keeline.com http://www.Keeline.com/articles >http://Stratemeyer.org http://www.Keeline.com/TSCollection > >http://www.ITeachPHP.com -- Free Computer Classes: Linux, PHP, etc. >Fall Semester Begins Sep 7 -- New Classes Start Every Few Weeks. > > > >Community email addresses: > Post message: [email protected] > Subscribe: [EMAIL PROTECTED] > Unsubscribe: [EMAIL PROTECTED] > List owner: [EMAIL PROTECTED] > >Shortcut URL to this page: > http://groups.yahoo.com/group/php-list >Yahoo! Groups Links > > > > ------------------------ Yahoo! Groups Sponsor --------------------~--> Fair play? Video games influencing politics. Click and talk back! http://us.click.yahoo.com/T8sf5C/tzNLAA/TtwFAA/HKFolB/TM --------------------------------------------------------------------~-> Community email addresses: Post message: [email protected] Subscribe: [EMAIL PROTECTED] Unsubscribe: [EMAIL PROTECTED] List owner: [EMAIL PROTECTED] Shortcut URL to this page: http://groups.yahoo.com/group/php-list Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/php-list/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
