How to plot height information in Matlab using surf?

1
votes

I have obtained the latitude, longitude and height information from a TIFF image into Matlab and plotting it using the surfc function as surfc(X,Y,Z).

surfc output:

surfc output

Image of the tree: image of tree

But how do I get Z to display as a contour (something like a cone) corresponding to the height of an object in the image?

Thanks for any answers

2
imagematlabtiffcontour
Is there height (altitude) information stored for each pixel of the TIFF image? Is the height of the pixel code in the color of each pixel some how? Is there a height information of each tile? Normally there is a single height information for entire image, so you can't use it for display contour. - Rotem
Hi, Yes. The height information is stored in the geotiff image itself. I'm using the surf function but all I'm getting is a blank plot with only the coordinates. Actually I wanted to plot the height of a tree contained in the geotiff image. - Sack11
Could you provide us a minimal reproducible example - Yvon
@Yvon I'm using these two codes. 'surfc(x,y,z); axis tight'. But after plotting I'm getting a blank plot with the x,y and z. I want the height information to be displayed/plotted corresponding to the height of a tree in the geotiff image - Sack11
Unfortunately we don't have the geotiff image. - Yvon

2 Answers

0
votes

You can change the color mapping of the surf. Example: 

clear;clc;close all
tif4 = imread('RzwK3.tif');
THeight = rgb2gray(tif4(:,:,1:3));
imshow(THeight)

x = 1:size(THeight,1); % can be changed to coordinates
y = 1:size(THeight,2);
[X,Y] = ndgrid(x,y);

% make contour color on the surface
M = 4; % # color in contour
Cvec = parula(M); % any Mx3 RGB triplet
hs = surf(X,Y,THeight,'EdgeAlpha',.1);
colormap(Cvec)
colorbar

If parula or other color generation function is not available in your Matlab version, you can assign Cvec manually. Each row of the matrix is a RGB color triplet with values between 0 and 1 (you can divide a web RGB color by 256) and there should be M rows in the matrix. Example: the following is the output of parula(4), which can be manually input by replacing the line of code. 

Cvec = [
    0.2081    0.1663    0.5292; % R1 G1 B1
    0.0265    0.6137    0.8135; % R2 G2 B2
    0.6473    0.7456    0.4188; % R3 G3 B3
    0.9763    0.9831    0.0538]; %R4 G4 B4

example output

0
votes

If you have the pionts as cartesian coordinates use plot3

plot3(X,Y,Z,'.');

If X and Y are the independent variables and Z the dependent one (The corresponding height for a given X and Y) then use surf or mesh

surf(X,Y,Z);
mesh(X,Y,Z);

Otherwise put some sample of your data and results so we can better understand your problem.

EDIT: You are actually obtaining a contour plot, but surfc should also plot the surface. Take a look at the documentation of surfc and you will see that it combines two plots in one figure (the surface and the contour)

[X,Y,Z] = peaks(30);
figure
surfc(X,Y,Z)

enter image description here