Understanding distortion
In this
topic, we'll look closer at spatial properties and how they are distorted in
projections. We'll pay special attention to Tissot indicatrices as a technique for assessing distortion on a
map.
Remember
the four spatial properties that are subject to distortion:
·
Shape
·
Area
·
Distance
·
Direction
No map can
preserve all four. (Only a globe can do that.)
Some maps
preserve one property, and some preserve two, but none preserves more than two.
Some maps don't preserve any properties perfectly, but compromise a little bit
on all of them.
If a map
preserves two spatial properties, one of them is always true direction.
Any spatial property
can be preserved alongside direction. Direction and distance are preserved in
the Azimuthal Equidistant projection. Direction and
shape are preserved in the Stereographic projection. Direction and area are
preserved in the Lambert Azimuthal Equal Area
projection.
The
following properties can't be preserved together:
No property can be
preserved along with a property other than direction. There are no conformal
equidistant projections, no equal area equidistant projections, and no
conformal equal area projections.