How to adjust resolution in Hough transform?

I'm trying to interpret potential linear trends in a map op volcanic centers using the Hough transform. Attached is the image used with hough lines on it. As you can see, the lines are only very short. How do I change the sensitivity so that more points are considered in the transform?

Code used:

RGB = imread('NVP_WP_ONLY.tif');
I = rgb2gray(RGB);
BW = edge(I,'canny');
[H,T,R] = hough(BW);
subplot(2,1,1);
imshow(RGB);
title('Newer Volcanic Province Eruption Points');
subplot(2,1,2);
imshow(imadjust(mat2gray(H)), 'XData',T,'YData',R,'InitialMagnification','fit');
title('Hough transform eruption points all Default settings');
xlabel('\theta'),ylabel('\rho');
axis on, axis normal, hold on;
colormap(hot)
P = houghpeaks(H,100);
imshow(H,[], 'XData',T,'YData',R,'InitialMagnification','fit');
xlabel('\theta'),ylabel('\rho');
axis on, axis normal, hold on;
plot(T(P(:,2)),R(P(:,1)),'s','color','white');
lines = houghlines(BW,T,R,P);
figure, imshow(RGB), hold on;   %expect a figure size warning
max_len = 0;
for k = 1:length(lines) xy = [lines(k).point1; lines(k).point2];
plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green');
end

[Walter Roberson]

We might need NVP_WP_ONLY.tif as well.

[Korien Oostingh]

Thanks for responding. Attached is the tif as .zip

[Walter Roberson]

It did not seem to get attached. Remember to click on "Attach File" after you select the file.

[Korien Oostingh]

I'm very sorry. This should work.

Answer 1

[Walter Roberson]

Perhaps in your hough() call you need to adjust your RhoResolution or ThetaResolution?

[Korien Oostingh]

Hi Walter,

thanks for your response. I've adjusted the rho and theta resolution, but I don't understand the implications of changing them. Attached is a zip folder with a bunch of figures I've created varying the rho and theta. The interpretation differs a lot. Could you please explain to me what Rho and Theta exactly do? I know their theoretical background (length and angle of line in polar coordinates), but I don't understand their implications for my data. Thanks