Change the aspect ratio of x,y to plot Longitude and Latitude correctly ( I have the conversion needed- need help implementing it)

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P_L 2019-3-12

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https://ww2.mathworks.cn/matlabcentral/answers/449614-change-the-aspect-ratio-of-x-y-to-plot-longitude-and-latitude-correctly-i-have-the-conversion-need

评论： P_L 2019-3-13

采纳的回答： Jan

在 MATLAB Online 中打开

Hi there,

I am wanting to change my x,y axis to reflect true longitude and latitude scales.

The conversion is: 1 degree of longitude (x-axis) is equal to 111cos(latitude). Latitude being the Y-axis. I need this in order to create a single scalebar rather than 2 seperate ones.

this is the code I have but I do not know how to implement it - any help would be much appreciated!

Many thanks!

load('x_data.mat')
load('y_data.mat')
load('z_data.mat')
h = pcolor(X,Y, Z);
shading interp
%% map personalising
xlabel('Longitude (deg, E)');
ylabel('Latitude (deg, N)')
axis equal
% set axis limits 
xlim([30.3 30.45])
ylim([40.7 40.8])
hold on 

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P_L 2019-3-13

在 MATLAB Online 中打开

Hi Jan,

Please see atched the result i am wanting to change ( the x and y axis to reflect geographic scales) .The image shows the result I have now so you get an idea of one of the types of plots I am making- as some of them are in 3D as below. Please also see attached example code so you understand what I have been doing. Axesm - I can't get to project properly and display all the ticks- I have just been trying this just in 2D and world map doesn't dispaly anything evewn if I use pcolorm. I will be using cellfun to plot data as well. I initially tried plottinmg onto a map that I couldn't get to work for eveything - This is why I wanted to see if I could change the aspect ratios myself. I have also tried xyz2ell.m from https://uk.mathworks.com/matlabcentral/fileexchange/15285-geodetic-toolbox?focused=6513492&tab=function but still not working.

Many Thanks

% I have read in aseries of X,Y,Z topographic data 
h = pcolor(X,Y, Z); %shading the topography
shading interp;
% map personalising
xlabel('Longitude (deg, E)');
ylabel('Latitude (deg, N)')
demcmap([0 1000], 30 );
% I am now wanting to plot these co-ordinates for example in 3-D
x_dat = [29.2 29.6 29.4 29.8 29.5 29.6 29.7]; 
y_dat = [30.4 30.5 30.5 30.4 30.3 30.2 30.2];
z_dat = [10.2 12.1 11.5 7.6 8.9 10.2 11.5]/111;  %km /deg
% as I am plotting in 3-D using scatter3 I don't believe yiu can use this
% with the geographic maps matlab produces. 
%% other attempts I have made are: 
%axesm('MapProjection','mercator','MapLatLimit',[40.7 40.8],'LabelUnits','degrees')
%axesm('MapLonLimit',[30.3 30.5],'LabelUnits','degrees','MapLatLimit',[40.7 40.8])
%worldmap([40.5 40.9],[30.3 30.5])
%[lat,lon,h]=xyz2ell(X,Y,Z)

Jan 2019-3-13

@P_L: Please take into account, that I cannot read the code on your screen, if you do not post it here.

"Axesm - I can't get to project properly and display all the ticks- I have just been trying this just in 2D and world map doesn't dispaly anything evewn if I use pcolorm."

I cannot follow this description. Your code contains two calles of axesm, but they are commented - which one are you talkinh of.

"I will be using cellfun to plot data as well."

Why? Is this a part of the question?

"I initially tried plottinmg onto a map that I couldn't get to work for eveything"

Then please post the code and the error message, or a detailed description of the difference between your expectation and the results.

I have also tried xyz2ell.m from https://uk.mathworks.com/matlabcentral/fileexchange/15285-geodetic-toolbox?focused=6513492&tab=function but still not working.

"Still not working" does not allow to give you any advice how to fix the code.

P_L 2019-3-13