How to Find Distance Between Two Points on the Earth

One of the Newton 2.x OS Q&As
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This document was exported on 7/23/97.

How to Find Distance Between Two Points on the Earth (6/7/96)

Q: Is there an API which calculates the distance between two points on the Earth?

A: Yes. In the Newton 2.0 ROM there is a global function called CircleDistance which takes two longitude/latitude pairs and the units to use in reporting the distance, and CircleDistance returns the distance between the two points. NTK may give a warning about "Unknown global function 'CircleDistance'". This warning can be safely ignored so long as you're writing a package for a Newton 2.0 OS device.

CircleDistance (firstLong, firstLat, secondLong, secondLat, units)

Returns the distance between the two points. The distance is an integer. Currently CircleDistance rounds the distance to the nearest ten miles or ten kilometers.

firstLong: The longitude for the first point on the Earth.
firstLat: The latitude for the first point on the Earth.
secondLong: The longitude for the second point on the Earth.
secondLat: The latitude for the second point on the Earth.
units: A symbol specifying the units in which the distance will be calculated. Currently the options are 'miles or 'kilometers.

Note: the longitude and latitude arguments need to be integer values of the type used by NewCity. Check the section titled "Using the Time Zone Application" in the Built-In Applications and System Data chapter of the Newton Programmer's Guide for information on how to convert a longitude or latitude in degrees, minutes & seconds to an integer for CircleDistance.