Map Scales and Distortions

Find area distortion; trim data to quadrangle

Distortions are inherent in flattening the sphere. Each projection creates a different distortion of one or more characteristic properties of the map. For any given projection, however, the smaller the area being mapped, the less distortion it introduces if properly centered.

It is useful to be able to estimate the degree of error in direction, area, and scale for a particular projection type and parameters used. Several Mapping Toolbox™ functions help you to quantify and visualize projection distortions.

Functions

clipdataClip data at +/-pi in longitude, +/-pi in latitude
distortcalcDistortion parameters for map projections
maptrimsTrim regular data grid to latitude-longitude quadrangle
mdistortDisplay contours of constant map distortion
tissotProject Tissot indicatrices on map axes

Topics

Visualize Spatial Error Using Tissot Indicatrices

A standard method of visualizing map projection distortion is to project small circles spaced at regular intervals across the globe.

Visualize Projection Distortions Using Isolines

This example shows how to visualize map projection distortions using contour lines of constant map distortion.

Quantify Map Distortions at Point Locations

You can calculate quantitative position-specific map error statistics, such as area scale, angular deformation of right angles, and directional scale distortions along meridians and parallels.