# (mapping toolbox) Map axes xdata, ydata and zdata meaning?

7 views (last 30 days)
abblah abblah on 31 Aug 2019
Commented: abblah abblah on 5 Sep 2019
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)
abblah

Kelly Kearney on 5 Sep 2019
Edited: Kelly Kearney on 5 Sep 2019
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).

#### 1 Comment

abblah abblah on 5 Sep 2019
% Thanks for your exact and fast response.
% I recommend that the meaning of xdata,ydata,... in map axes
% be documented in mapping toolbox, in the next version.
% best regards.

dpb on 31 Aug 2019
The map is still an axes underneath the hood so the internal property names are the same. But, the property name is just a name, the data are what are associated with the particular axis direction...just use
set(hplot,'xdata',lat,'ydata',lon,'zdata',h)

abblah abblah on 4 Sep 2019
Unfortunately you are wrong.
Matlab directly sets the xdata,ydata and zdata to lat,lon and h,
and does not consider any projection in setting these properties.
I tested it, the marker in the map after the first creation by plot3m,
disapeared when I used your proposed code!
Why matlab does not have any documention about in which cartesian coordinate 'xyz' in map axes are????
I am also waiting for the hero to answer my question.
dpb on 4 Sep 2019
I don't have mapping TB so can't do more than read the doc...
Did you use hold on before trying to add more to the existing plot?
Submit support request to Support if joy doesn't ensue...