# Chamberlin Trimetric

## Description

This is the standard projection developed and used by the National Geographic Society for continental mapping. The distance from three input points to any other point is approximately correct.

## Projection method

Modified planar.

## Linear graticules

None.

## Properties

### Shape

Shape distortion is low throughout if the three points are placed near the map limits.

### Area

Areal distortion is low throughout if the three points are placed near the map limits.

### Direction

Low distortion throughout.

### Distance

Nearly correct representation of distance from three widely spaced points to any other point.

## Limitations

The three selected input points should be widely spaced near the edge of the map limits.

Chamberlin Trimetric can only be used in ArcInfo as an OUTPUT projection because the inverse equations (Chamberlin Trimetric to geographic) have not been published.

You can't project an ArcInfo grid or lattice to Chamberlin Trimetric because the inverse equations are required.

## Uses and applications

Used by the National Geographic Society as the standard map projection for most continents.

## Parameters

### Workstation

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

Supported on spheres only.