cannot get a rectangle with linem

I am trying the draw a rectangle on the world map. The our vertices in (latitude, longitude) are [-60, -140] [-60, 140] [60, 140] [60, -140].

I used the following command:

linem([-60;-60], [-140;140], 'm-'); 

linem([-60;60], [140;140], 'm-');

linem([60;60], [-140;140], 'm-');

linem([60;-60], [-140;-140], 'm-');

It seems that I can only get two vertical lines. Does anyone have any suggestion?

Thanks!

Answer 1

[Chad Greene]

I get the same problem using Matlab 2012b. I've been finding a number of weird behaviors with Mapping Toolbox plotting functions lately. The first thing I always try as a workaround is to manually perform coordinate transformations, then plot using standard plotting functions. To do this,

1. Initialize a map,
2. Transform coordinates, then
3. plot using standard (non-mapping toolbox) plotting functions. Here's an example:

% Using these coordinates for your bounding box: 
lat = [-60 -60 60 60 -60]; 
lon = [-140 140 140 -140 -140];

% Initialize a map: 
worldmap('world') 

% Perform coordinate transformation: 
[x,y] = mfwdtran(lat,lon); 

% Plot using line instead of linem: 
line(x,y,'color','m')

However, the bounding box does not follow the curves of the projection, so you might want to densify the lines before doing coordinate transformation:

lat = [-60 -60:60 60:-1:-60]; 
lon = [-140 140*ones(1,121) -140*ones(1,121)];
worldmap('world') 
[x,y] = mfwdtran(lat,lon); 
line(x,y,'color','m')