MATLAB Answers

Determining whether a point on earth (given latitude and longitude) is on land or ocean

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Soumyadeep Chatterjee
Soumyadeep Chatterjee on 9 Feb 2011
Edited: Amy Haskins on 1 Apr 2015
I am looking for a quick way to determine whether a point on earth's surface (given latitude and longitude) falls on one of the continents or on an ocean.
Any help is greatly appreciated.
Thanks, Deep

Answers (4)

Brett Shoelson
Brett Shoelson on 9 Feb 2011
I think this will do it. It is a binary classifier: Ocean/Land.
coast = load('coast.mat');
[Z, R] = vec2mtx(coast.lat, coast.long, ...
1, [-90 90], [-90 270], 'filled');
figure; worldmap(Z, R)
geoshow(Z, R, 'DisplayType', 'texturemap')
colormap([0 1 0;0 0 0;0 1 0;0 0 1])
lat = 38.53;%N
lon = -57.07;%W
plotm(lat,lon,'ro')
val = ltln2val(Z, R, lat, lon);
isOcean = val == 2
%isLand = ~isOcean
Cheers,
Brett

Amy Haskins
Amy Haskins on 1 Apr 2015
Edited: Amy Haskins on 1 Apr 2015
You could also try the inpolygon function.
% Load the coastline
coast = load('coast.mat');
ax = worldmap('world');
geoshow(coast)
% Grab a point from the map
[lat,lon] = inputm(1,ax);
% Determine if it's within the coast polygon
isInland = inpolygon(lat,lon,coast.lat,coast.long);

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