Contours on Geoaxe with addCustomBasemap

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

Answer 1

[Kevin Holly]

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

[Yair Dayan]

Thanks,

In both answers you lose the smart labeling option within contour function.

How can I create labels that are visually like the ones contour function creates?

Answer 2

[Alan Garger]

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)

This solution is likely very inefficient, but I got it to run in my own code. Note that I also use the getContourLineCoordinates function

[Yair Dayan]

Thanks,

In both answers you lose the smart labeling option within contour function.

How can I create labels that are visually like the ones contour function creates?