To use the 'pol2cart' function the radii and angle vectors need to be of equal size, as they define the coordinates of the points. The 'rr' and 'bearings' variables are possible values for the radii and angles, so they can be used to make a polar grid using the 'meshgrid' function. This grid then can be used by the 'pol2cart' function to convert into a cartesian grid. Here's some sample code:
clc
clear
r = 0:1:2028; % 1 X 2029
theta = linspace(0,pi,180); % 1 X 180
zPolar = r'*sin(theta); % 2029 X 180
[rGrid, thetaGrid] = meshgrid(r,theta);
[x,y,z] = pol2cart(thetaGrid,rGrid,zPolar');
Here's the documentation to the 'meshgrid' and 'pol2cart' functions: