www.gusucode.com > map 案例源码 matlab代码程序 > map/CalculateTheAreaOfContinentalUnitedStatesExample.m
%% Calculate Geographic Area for Vector Data in Polygon Format % This example shows how to calculate geographic areas for vector data in % polygon format using the |areaint| function. |areaint| performs a % numerical integration using Green's Theorem for the area on a surface % enclosed by a polygon. Because this is a discrete integration on discrete % data, the results are not exact. Nevertheless, the method provides the % best means of calculating the areas of arbitrarily shaped regions. Better % measures result from better data. For more information, see % <docid:map_ref.br4uguf>. %% % Load the continental United States MAT-file, |conus.mat| , and calculate % the radius of the Earth. % Copyright 2015 The MathWorks, Inc. load conus earthradius = almanac('earth','radius'); %% % Calculate the area of the continental United States, along with the area % of Long Island and Martha's Vineyard. |areaint| like the other area % functions, |areaquad| and |areamat|, returns the area as a fraction of the % entire planet's surface, unless you provide a radius. Because the default % Earth radius is in kilometers, the area is in square kilometers. area = areaint(uslat,uslon,earthradius) %% % Calculate the areas of the Great Lakes using the same variables, this % time in square miles. |areaint| returns three areas: the largest for the % polygon representing Superior, Michigan, and Huron together, the other % two for Erie and Ontario. earthradius = almanac('earth','radius','miles'); area = areaint(gtlakelat,gtlakelon,earthradius)