MATLAB Answers


Plotting data on curvilinear coord projection

Asked by mashtine on 1 Jul 2016
Latest activity Edited by Jonathan Eliashiv on 18 Oct 2016
I have two lat and lon matrices, each 622x810 and they are of a curvilinear projection. I previously just used vectors of lon and lat to plot my data with surfacem (see below) but I am not sure how to do this with lat and lon as a matrix of curvilinear coordinates.
Any suggestions?
ax = worldmap(latlim, lonlim);
S = shaperead('landareas','UseGeoCoords',true);
surfacem(lat, lon, inpdata)
shading interp
geoshow([S.Lat], [S.Lon],'Color','black');


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3 Answers

Answer by KSSV
on 1 Jul 2016

As you have matrices in hand, it shall be very easy to plot what you want. If you want to get vectors of lon, lat from 622x810 matrices of each, try using unique(); this will give you the vectors.

  1 Comment

Thanks for the reply. This won't be as simple because the projection of the map needs to change. When I use geoshow for instance, the coastline will not match up with where it should be for the UK as the data is in one projection and the geoshow is putting the coastline in another.

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Answer by José-Luis
on 1 Jul 2016

It is not clear to me how you want those arrays displayed. If you only want to show the points:
geoshow(S.Lat(:), S.Lon(:),'Color','black');


Hi Jose-Luis,
I have another 622x810 matrix of data (inpdata) with values for each grid cells that I would like to plot. Basically, the lon and lat are coordinates of the UK and inpdata is a parameter that I would like to plot to show the pattern across the UK domain.
Makes sense? I need to use surfacem as shown in my code
I don't know what a matrix of curvilinear coordinates is.

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Answer by Jonathan Eliashiv on 18 Oct 2016
Edited by Jonathan Eliashiv on 18 Oct 2016

Super simple actually.
Go ahead and reshape your coordinates and data into 1-d vectors:
X_curvi = reshape(lon,[],1);
Y_curvi = reshape(lat,[],1);
data_curvi = reshape(inpdata,[],1);
Make a meshgrid that you want to interpolate into:
[lon_grid,lat_grid] = meshgrid(minlon:dx:maxlon,minlat:dy:maxlat)
and then you can use the griddata function:
[~,~,data_rectilinear] = griddata(X_curvi,Y_curvi,data_curvi,...
and plot away
pcolor(lon_grid,lat_grid,data_rectilinear); shading flat


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