MATLAB: (mapping toolbox) Map axes xdata, ydata and zdata meaning

Mapping Toolboxplot handle

Hi,

I am using plot3m to plot the geographical location:

hplot = plot3m(lat,lon,h)

but to update the plot in the map it requires xdata, ydata, zdata

unfortunately there is not any documentation about the coordination of these fields in mapping toolbox?

how can I calculate xdata,ydata and zdata in the following code from lat,lon,h:

set(hplot,'xdata',xdata,'ydata',ydata,'zdata',zdata)

thanks in advance.

abblah

Best Answer

Map axes apply a geographic transform to convert the geographic coordinates to the projection used by the map axis. You can perform this transform manually using mfwdtran:

ax = worldmap('world');
lat = [0 45];
lon = [0 45];
hln = plotm(lat, lon, '-ro');
% Compare the line's X/YData to manually transformed data
hln.XData
hln.YData
[x,y] = mfwdtran(lat, lon)
% The results you should see...
ans =
            0   3.8059e+06
ans =
            0   4.7997e+06
x =
            0   3.8059e+06
y =
            0   4.7997e+06

To go the opposite direction (i.e. convert from projected x/y to lat/lon, use minvtran).

Related Solutions

MATLAB: How to define a Mapping Toolbox stereographic projection using the information from a projection file (.prj)

The ability to automatically parse a projection file and create a projection is not available in the Mapping Toolbox.

To work around this issue, you can manually parse the projection file and use the parameters to create a stereographic projection. For example, a stereographic projection file has the following contents:

 PROJCS["WGS_1984_Stereographic_South_Pole",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Stereographic_South_Pole"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",0.0],PARAMETER["Standard_Parallel_1",-71.0],UNIT["Meter",1.0]]

You can create a Mapping Toolbox stereographic projection structure from the parameters in the .prj file as follows:

mstereo = defaultm('stereo')
mstereo.geoid = [6378137.0, flat2ecc(1/298.257223563)] ; 
mstereo.falseeasting  = 0; 
mstereo.falsenorthing = 0; 
mstereo.nparallels = 1; 
mstereo.mapparallels = -71; 
mstereo.origin = [-90 0]; 
mstereo = defaultm(mstereo);

To use this projection structure to display latitude and longitude coastline vector data, you can use the following commands:

figure
axesm(mstereo)
load coast
plotm(lat, long)

To transform map coordinate data (given x,y coordinate arrays) to latitude and longitude, use:

[lat,lon] = minvtran(mstereo, x, y);

MATLAB: How to control elevation of geoshow() contour lines

Hi Mike,

I had a similar problem trying to overlay the build-in "states" map on my 3D surface plot. Your question helped me solve my problem, so I hope I can be of help.

My initial formulation was a little different since I was using the 'SymbolSpec' option of the geoshow function. Still, I think you can solve your issue assigning an array to A.Children.ZData instead of a scalar.

C = 8;  %some arbitrary height you want place your map at
A.Children.ZData = C*ones(size(A.Children.XData)));

I think the issue was that XData, YData, and ZData need to be the same size. So you just need to create an array of all "8s" and assign it to ZData.

I hope this is of help.

Best regards,

Tom

Best Answer

Related Solutions

MATLAB: How to define a Mapping Toolbox stereographic projection using the information from a projection file (.prj)

MATLAB: How to control elevation of geoshow() contour lines

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