----- Original Message ----- From: "David Cantrell" david@cantrell.org.uk To: "Discussion of development on the OpenGuides software" openguides-dev@openguides.org Sent: 28 November 2003 12:21 Subject: Re: [OpenGuides-Dev] Location data for non-UK cities [Was: Re: Newarrivals]
On Fri, Nov 28, 2003 at 11:54:53AM +0000, Kate L Pugh wrote:
Working out distance between places specified by latitude and longitude may be trickier. There is Geo::Distance on CPAN but its docs warn:
"The formula used for [great] circle distances is also somewhat unreliable for small distances (for locations separated less than about five degrees) because it uses arc cosine which is rather ill-conditioned for values close to zero."
And that's not so good when you consider that we're working out distances within a city.
Within a city you can ignore the curvature. Just assume that the grid is square. Or maybe rectangular for the far north/south. It helps that there are very few significant or big places in the arctic, and none in the antarctic.
Strangely enough, Earle and I were discussing doing just that in the pub after the london.pm tech meet.
I feel a module coming on. How about Geography::Grid