Re: decimal longitude and latitude problem

"steve" <steve@xxxxxxxxxx> wrote in message
news:1163683958.762379.136400@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Please help...I need to know the formula for calculating a particular
distance from a specific decimal longitude and latitude. For exampl,
for a house located at -77.209528 ,38.716728, what is the latitude and
longitude range for all houses withing .25 miles or .5 miles

If the distances are short relative to the curvature and diameter of the
earth, you can just use a variation of Bresenham's circle algorithm to see
if a specific other point is inside or outside a circle of a certain
diameter.

The equation for a circle is of course:

(x-x0)**2 + (y-y0)**2 = r**2

However, the implication also holds that:

(x-x0)**2 + (y-y0)**2 < r**2 --> (in circle)

You would need to adjust for the way the distance of a degree of longitude
varies with latitude, but that is a relatively simple thing.

Dave.



.

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