In lab 4 we did ground truthing. This involves checking and comparing the land use that we determined in Lab 3 to the actual land usage. This is done in a number of ways, but with the limitation we had (such as this being an online course) we used Google Maps. For most features in the mapped area street view was sufficient to determine the actual land usage. Some areas not adjacent to the road required zooming in really close and using associated features to determine actual land usage.
The points that were ground truthed were chosen randomly, though there are other, more methodical ways to select points for ground truthing.