Measurement time step and integration time step

Hi,

 i saw people using measurement time step and integration time step when performing the algorithmm using Matlab. What's the differences between these two?

Eg: T = 0.5; % measurement time step

tf = 30; % simulation length (seconds)

dt = 0.001; % time step for integration (seconds)

for t = T : T : tf % Simulate the system. 
  for tau = dt : dt : T 
    xdot(1,1) = x(2); 
    xdot(2,1) = rho0 * exp(-x(1)/k) * x(2)^2 / 2 * x(3) - g; 
    xdot(3,1) = 0; xdot = xdot + sqrt(dt * Q) * [randn; randn; randn]; 
    x = x + xdot * dt; 
    end
.....