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Creating a map using x/y data

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Louise Wilson
Louise Wilson on 4 Apr 2022
Answered: Harshit on 15 Sep 2023
I have X, Y, Z data where X and Y are lon and lat coordinates and Z is value of interest. All variables are 12500*1800 (too large to attach here).
I would like to plot these variables on map axes so I can add shape files with additional info., aswell as a scale bar.
clf
axesm('MapProjection','mercator') %define axis
surfm(y,x,z) % plot X/Y data
S = shaperead('study_site.shp','UseGeoCoords',true); %add shapefile on top of X/Y data
info = shapeinfo('study_site.shp');
crs = info.CoordinateReferenceSystem
geoshow(S,'FaceColor','white');
Apart from needing to adjust the axes limits, this looks good. But, I am struggling to add a scale bar. When I try to do this, the plot is just replaced with a scale bar:
hold on
scaleruler on
How do I do this properly?
Also, how do I add lat and lon information to the frame?

Answers (1)

Harshit
Harshit on 15 Sep 2023
Hi,
I understand that you want to plot the latitudes and longitudes onto the map axes.
For such large variables of "X", "Y", and "Z", I suggest creating a meshgrid of lon and lat coordinates first. Then, you can use the "pcolorm" function to plot the "Z" variable on the map.
Additionally, you use the "scaleruler" function to add a scale bar to the frame.
Here's an updated version of your code incorporating the above suggestions:
clf
axesm('MapProjection', 'mercator')
% Create a meshgrid of lon and lat coordinates
[lon_grid, lat_grid] = meshgrid(x, y);
% Plot the Z variable using pcolorm
pcolorm(lat_grid, lon_grid, z);
S = shaperead('study_site.shp', 'UseGeoCoords', true);
info = shapeinfo('study_site.shp');
crs = info.CoordinateReferenceSystem;
geoshow(S, 'FaceColor', 'white');
% Adjust axes limits if needed
% xlim([lon_min, lon_max]);
% ylim([lat_min, lat_max]);
% Add scale bar
scaleruler('RulerStyle', 'patches', 'Units', 'km', 'FontSize', 10);
% Add latitude and longitude information to the frame
framem on;
gridm on;
mlabel on;
plabel on;
To find more about the functions used here, kindly refer to the following documentation pages:
Hope the above information resolves your issue.
Regards,
Harshit

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