# Two-Point Equidistant

## Description

This projection shows the true distance from either of two chosen points to any other point on a map.

## Projection method

Modified planar.

## Points of contact

None.

## Linear graticules

Normally none.

## Properties

### Shape

Minimal distortion in the region of the two chosen points, if they're within 45° of each other. Increasing distortion beyond this region.

### Area

Minimal distortion in the region of the two chosen points, if they're within 45° of each other. Increasing distortion beyond this region.

### Direction

Varying distortion.

### Distance

Correct from either of two chosen points to any other point on the map. Straight line from either point represents the correct great circle length but not the correct great circle path.

## Limitations

Does not represent great circle paths.

## Uses and applications

Used by the National Geographic Society for maps of Asia.

Adapted form used by Bell Telephone system for determining the distance used to calculate long distance telephone rates.

## Parameters

### Desktop

- False Easting
- False Northing
- Latitude of 1st point
- Latitude of 2nd point
- Longitude of 1st point
- Latitude of 2nd point

Supported on spheres only.

### Workstation

- Longitude of point A
- Latitude of point A
- Longitude of point B
- Latitude of point B

Point A must be west of point B.

Supported on spheres only.