Making a Map Image from a Matrix

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John Ziggs
John Ziggs on 13 Mar 2021
Commented: Chad Greene on 14 Mar 2021
Hi all, I am trying to make a map based off data from a text documents containing daily surface air temperature. I attached 2 txt files as a sample. I am trying to create a map based off this.
This is my code:
inputdirTA = 'C:\Users\john\Desktop\TA2004daily'; %directory of folder containing data
S = dir(fullfile(inputdirTA,'*.txt'));
for k = 1:numel(S)
fnm = fullfile(inputdirTA,S(k).name);
vector = load(fnm);
mtx = reshape(vector,72,144);
if k == 1;
DataTA = [mtx];
else
DataTA = [DataTA mtx];
end
end
figure(1);
rv = [0.4 90 0];
worldmap('world');
geoshow(DataTA, rv, 'displaytype', 'texturemap');
C = load('coast');
plotm(C.lat, C.long, 'k');
title('Map of Surface Air Temperature');
I am getting this map:
But I am trying to get this kind of map:
I understand the concept of having to create 3 planes of the matrix, but I am having troubles understanding the syntax.
Any help or advice is greatly appreciated.
Thanks.

Accepted Answer

Chad Greene
Chad Greene on 13 Mar 2021
Edited: Chad Greene on 13 Mar 2021
With the Climate Data Toolbox you could do it like this:
T = flipud(reshape(load('TS20040101.txt'),[72 144])); % loads, reshapes, and orients the data correctly
[lat,lon] = cdtgrid(2.5); % creates a 2.5 degree global grid
pcolor(lon,lat,T) % plots the grid
shading interp
cmocean thermal % sets the colormap
borders('countries','color',rgb('gray'))
xlabel longitude
ylabel latitude
You could even take it one step further and interpolate to a high-resolution grid, then plot with hillshaded topography:
% Create a 0.1 degree grid:
[lati,loni] = cdtgrid(0.1);
% Interpolate the temperature data to the high-res grid:
Ti = interp2(lon,lat,T,loni,lati);
% Get elevation data on the high res grid:
Zi = topo_interp(lati,loni);
% Set ocean elevations to zero:
Zi(Zi<0) = 0;
figure
surf(loni,lati,Zi,Ti)
shading interp
view(2)
axis tight equal
cmocean thermal
shadem(-10) % applies hillshade
  3 Comments
Image Analyst
Image Analyst on 14 Mar 2021
Very cool Chad. I voted for it to give Chad additional reputation points. John, you can also vote, to award Chad extra points.
Chad Greene
Chad Greene on 14 Mar 2021
Thanks, Mark! That means a lot coming from you!

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