www.gusucode.com > map 案例源码 matlab代码程序 > map/VisualizeProjectionDistortionsUsingTissotIndicatricesExample.m
%% Visualize Projection Distortions using Tissot Indicatrices % This example shows how to add Tissot indicatrices to a map display. %% % Set up a Sinusoidal projection in a skewed aspect, plotting the % graticule. figure axesm sinusoid gridm on framem on setm(gca,'Origin',[20 30 45]) %% % Load the coast data set and plot it as green patches. load coastlines patchm(coastlat,coastlon,'g') %% % Plot the default Tissot diagram. Notice that the circles vary % considerably in shape. This indicates that the Sinusoidal projection is % not conformal. Despite the distortions, however the circles all cover % equal amounts of area on the map because the projection has the % equal-area property. Default Tissot diagrams are drawn with blue unfilled % 100-point circles spaced 30 degrees apart in both directions. The default % circle radius is 1/10 of the current radius of the reference ellipsoid % (by default that radius is 1). tissot %% % Clear the Tissot diagram, rotate the projection to a polar aspect, and % plot a new Tissot diagram using circles paced 20 degrees apart, half as % big as before, drawn with 20 points, and drawn in red. In the result, % note that the circles are drawn faster because fewer points are computed % for each one. Also note that the distortions are still smallest close to % the map origin, and still greatest near the map frame. clmo tissot setm(gca,'Origin',[90 0 45]) tissot([20 20 .05 20],'Color','r')