Problem with Web Map

Question

Roberto Revelli 2022-7-13

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https://ww2.mathworks.cn/matlabcentral/answers/1758820-problem-with-web-map

编辑： Siraj 2023-9-15

Hello, I'm trying to upload several gpx traces on a web map. The basic code is

webmap('worldimagery')
for i=1:n_route
    wmline(route{i});
end

whre route is a cell array with n_route gpx traces.

The for-loop cracks after 12-15 loops and the following error appears "The web map page has not finished loading."

Many thanks for any suggestion!

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Geoff Hayes 2022-7-14

@Roberto Revelli - perhaps you need to pause on each iteration of the loop to give the app time to draw the line...rather than trying to draw each line one after the other. I'm just guessing here as I don't have the Mapping Toolbox to reproduce the behaviour.

Roberto Revelli 2022-7-14

Thanks @Geoff Hayes.

I've already tried with pause(...) in the for-loop after the wmline command, but error comes anyway. I'd like to find a more stable solution.

Roberto

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Answer 1

Siraj 2023-9-15

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https://ww2.mathworks.cn/matlabcentral/answers/1758820-problem-with-web-map#answer_1310746

编辑：Siraj 2023-9-15

在 MATLAB Online 中打开

Hi!

It is my understanding that you want to draw multiple lines on a web map using the "wmline" function in MATLAB. However, when the number of lines becomes larger, the following error is encountered.

"The web map page has not finished loading."

I suspect that it is a memory issue. As the number of lines to be drawn on the web map increases, it consumes more memory and eventually leads to the error.

As a workaround you can put all the line coordinates into a “geoshape” and then use one call to “wmline”. This is significantly faster.

Refer to the provided code for a clearer understanding and feel free to modify it according to your specific requirements. In this example, the code draws 500 circles on a web map.

% Define the center coordinates 
lat0 = 51.50487; 
lon0 = 0.05235; 
% Open the web map using OpenStreetMap as the base map 
webmap('OpenStreetMap') 
% Initialize an empty array to store azimuth values 
az = []; 
% Define the reference ellipsoid 
e = wgs84Ellipsoid; 
% Start measuring the execution time 
tic 
% Loop to create circles with increasing radii 
for i = 1:500 
    % Calculate the radius based on the loop index 
    radius = 10 * i; 
    
    % Calculate the latitude and longitude coordinates of the circle 
    [lat, lon] = scircle1(lat0, lon0, radius, az, e); 
    
    % Generate a name for the circle based on its radius 
    name = sprintf('%d Meters', radius); 
    
    % Create a geoshape object representing the circle 
    s(i) = geoshape(lat, lon, "Name", name); 
end 
% Draw all the circles as a single line on the web map 
wmline(s, 'Color', 'k', 'OverlayName', '1:500 lines (meters)') 
% Stop measuring the execution time and display it 
toc 

For more detailed information about the "geoshape" object and the "wmline" function, you can refer to the following links:

https://www.mathworks.com/help/map/ref/geoshape.html

https://www.mathworks.com/help/map/ref/wmline.html

These resources provide comprehensive explanations and usage examples for the "geoshape" object and the "wmline" function in MATLAB.

Hope this helps.

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