Contours on Geoaxe with addCustomBasemap

Question

Asaf Schuldenfrei 2023-10-2

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https://ww2.mathworks.cn/matlabcentral/answers/2028174-contours-on-geoaxe-with-addcustombasemap

回答： Alan Garger 2023-12-24

Hi,

I Plan on using a High Resolution map data (OpenStreet & Sat Images) for a project and draw on them contours of heights or population density or other GIS information.

For the maps the best solution is using addCustomBasemap to draw the map tiles from a map server (as the data is too huge to load into a mapaxe with mapshow or other method).

But then I can't draw the contours (lines and fills & lines labels) on that map as counturem or contourfm cant be a chiled of Geoaxe.

Is there a method to do it? If not, is there a schedule to add this functionality to a later release of MATLAB?

Thanks

Asaf Schuldenfrei

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Answer 1

Kevin Holly 2023-10-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2028174-contours-on-geoaxe-with-addcustombasemap#answer_1329454

在 MATLAB Online 中打开

getContourLineCoordinates.m

You can use the getContourLineCoordinates function from the File Exchange.

Create contours with contourf

[X,Y,Z] = peaks;

[M, h] = contourf(X,Y,Z,20);

Custom Basemap:

figure
ax = geoaxes;
name = 'googleSat'; url = 'https://mt1.google.com/vt/lyrs=s&x={x}&y={y}&z={z}';
addCustomBasemap(name,url)
geobasemap(ax,name)

Use getContourLineCoordinates

hold(ax,"on")

cTbl = getContourLineCoordinates(M);

nContours = max(cTbl.Group);

colors = autumn(nContours);

for i = 1:nContours

gidx = cTbl.Group == i;

geoplot(ax, cTbl.Y(gidx), cTbl.X(gidx), ... % note: x & y switched

'LineWidth', 2, 'Color', colors(i,:))

end

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Answer 2

Alan Garger 2023-12-24

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https://ww2.mathworks.cn/matlabcentral/answers/2028174-contours-on-geoaxe-with-addcustombasemap#answer_1376947

在 MATLAB Online 中打开

I had a very similar issue for one of my own projects, and I utilized a similar method to the one above. But instead of just plotting the contour lines, I also included a part to plot each layer region so that I could see the filled contour plot.

[X,Y,Z] = peaks;
figure()
ax = geoaxes(); 
geobasemap('satellite')
hold on
contdata = contourc(X,Y,Z,25); 
cTbl = getContourLineCoordinates(contdata); % from the file exchange
hold(ax,'on')
nContours = max(cTbl.Group); 
%finding every unique level
ltable=cTbl.Level;
levs=unique(ltable);
gpart=[];
%for loop that splits countour data into groups and adds a NaN after every
%group, then recombines the data. NaNs are added to be able to plot shapes
%with holes
for i=1:nContours
    temp=cTbl(cTbl.Group==i,[1,3,4]);
    temp=temp{:,:};
    temp=[temp;temp(1,1),NaN,NaN];
    gpart=[gpart;temp];
    
end
%converts the data into a table for a comparison in the next for loop
gpart=array2table(gpart,'VariableNames',["Level","Long","Lat"]);
%creates a cell array that will be useful later
lpart=cell(length(levs),1);
%for loop that separates groups by their layer, ie, its value for the
%"Z" axis
for i=1:length(levs)
    
    temp=gpart(gpart.Level==levs(i),:);
    temp=temp{:,:};
    lpart(i)=mat2cell(temp,height(temp),3);
end
%color array that will be used to color the contour. Change "autumn" to
%change color gradient
colors = autumn(length(lpart));
%for loop to actually plot the contour 
for i=1:length(lpart)
    %coordinates of the ith layer
    shapemat1=cell2mat(lpart(i));
    %coordinates of the next layer up, if statement for if there is no next
    %layer
    if i==length(lpart)
        shapemat2=[];
    else
        shapemat2=cell2mat(lpart(i+1));
    end
    %combines this layer with the next layer
    shapemat=[shapemat1;shapemat2];
    %plots the shape from above. By combining the ith layer with the i+1
    %layer, the ith layer get plotted and then the i+1 layer is then taken
    %out. This is why I did the NaN stuff from before, to split the data up
    %into something geopolyshape can recognize.
    cshape=geopolyshape(shapemat(:,3),shapemat(:,2));
    %actually plots the shape onto the map. alpha values are transparency
    geoplot(cshape,'FaceColor',colors(i,:),'FaceAlpha',.25,'EdgeAlpha',.5)
end
geolimits([40.4,41], [-75.9,-75]);
% Add colorbar
colormap("autumn")
colorbar(ax)