Hi Rogier, I wanted to try this forumla out. Could you possibly help me by spelling out the formula in more word terms, like
i.e. Take initial latitude number, and divide it by X then divide that by the cosign of the XX ... which should result in XYZ something like that. Basically I hope to generate a bounding box based on a Lat/Lon coordinate :) I am on a steep learning curve, and not too sure when I need to divide or where the numbers come from :) :) ----- Original Message ----- From: "Rogier Wolff" To: "David Earl" Subject: Re: [OSM-dev] Question about Calculating Radius from GPS cord Date: Fri, 8 Aug 2008 17:44:11 +0200 On Fri, Aug 08, 2008 at 04:02:10PM +0100, David Earl wrote: > On 08/08/2008 14:30, Fire Girl wrote: > > I am working with OSM data, and would like to be able to spec > out 5 mile > bounding boxes from certain GPS points. > > > After research into this problem, I am to understand that > each degree of > latitude is approximately 69 miles (111 > kilometers) apart with a slight > variance (68.703 - 69.407 > miles) between the equator and the poles, and > that each degree > of longitude is widest at the equator @ 69.172 miles > (111.321 > kilometers) and gradually shrinks to zero at the poles. : ) :) > > > So what does this mean? If I want to take a input point, like lets say, > > > 167.9 lat > > -29.1 lon > > > or > > > -63.1 > > 18.1 > > > Can someone say with authority, what the 'calculus' would be > to > definitivly construct a NSWE bounding box with a 5 mile > radius around > those points?.... that would be basically close > enough or accurate? :) A degree longitude is about 40000km / 360 * cos (lat). A degree lattitude is about 40000km / 360. So 5 miles would be in longitude: 5 / (40000 / 1.609 / 360 * cos (lat)) km/circle degrees/circle mile km/mile and about 5 / (40000 / 1.609 / 360) km/circle degrees/circle mile km/mile lattidude. This comes to about 0.0725, 0.0725/cos(lat) degrees for 5 miles (lat, lon). This defines an almost-square where the circle would be almost completely inside. This especially doesn't work near the poles. Roger. -- ** [EMAIL PROTECTED] ** http://www.BitWizard.nl/ ** +31-15-2600998 ** ** Delftechpark 26 2628 XH Delft, The Netherlands. KVK: 27239233 ** *-- BitWizard writes Linux device drivers for any device you may have! --* Q: It doesn't work. A: Look buddy, doesn't work is an ambiguous statement. Does it sit on the couch all day? Is it unemployed? Please be specific! Define 'it' and what it isn't doing. --------- Adapted from lxrbot FAQ -- Be Yourself @ mail.com! Choose From 200+ Email Addresses Get a Free Account at www.mail.com
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