Using scatterm to plot points on Globe Projection of world map (spherical)

Hi all,

I am trying to plot points on the map using the Mapping toolbox. I am using the "Globe Projection", which gives me a 3D spherical map, however the "scatterm" function does not work. I have tried this on other map projections and it works fine.

A sample code for the 2-D case (which works) is below:

lat = rand(1,100)*100;
lon = rand(1,100)*100;
temp = rand(1,100)*20;
load coastlines;
worldmap world
plot3m(coastlat,coastlon,.01,'k','LineWidth', 1.5)
gridm('GLineStyle','-','Gcolor',[.7 .7 .7],'Galtitude',.02)
hold on
scatterm(lat, lon,10, temp, 'filled');
colorbar

Now if i try to do the same using the globe projection, i get the error " Not enough input arguments"

lat = rand(1,100)*100;
lon = rand(1,100)*100;
temp = rand(1,100)*20;
load coastlines;
ax = axesm('globe');
gridm('GLineStyle','-','Gcolor',[.7 .7 .7],'Galtitude',.02)
plot3m(coastlat,coastlon,.01,'k','LineWidth', 1.5)
hold on
scatterm(lat, lon,10, temp, 'filled');
colorbar

the "plotm" function seems to work on the globe projection, but i cannot specify the color for each point based on the value of "temp", the same way as scatterm.

Any thoughts on this?

Answer 1

[Chad Greene]

You pose the question well. I was able to replicate the problem. Here's a fix:

mstruct = gcm;
[x,y,z] = mfwdtran(mstruct,lat,lon,zeros(size(lat)));
scatter3(x,y,z,20,temp,'filled')

[Amir]

Thanks Chad, great solution. does exactly what i was looking for.

[Chad Greene]

Excellent, I'm glad it helped. I occasionally run into issues with Mapping Toolbox plotting functions, but often the problem can be circumvented by performing the coordinate transformation myself with mfwdtran, then plot using standard plotting functions.

[Amir]

I actually received an email from Matlab Support, there developers have been notified of this limitation and are working on it. They have proposed the following alternative solution, which works fine, but is very slow for high number of points.

 lat = rand(1,100)*100;
lon = rand(1,100)*100;
temp = rand(1,100)*20;
p = geopoint(lat,lon,'Temp',temp);
load coastlines;
ax = axesm('globe');
gridm('GLineStyle','-','Gcolor',[.7 .7 .7],'Galtitude',.02)
plot3m(coastlat,coastlon,.01,'k','LineWidth', 1.5)
hold on
colorbar
 colorRange = makesymbolspec('Point',...
                            {'Temp',[0 20],'MarkerFaceColor',parula(21),'Marker','o','MarkerEdgeColor','none'});
 geoshow(p,'SymbolSpec',colorRange);

is still prefer your solution though, it is very fast. thanks again