I have a problem. I have a digital map that I have drawn of a fictional city in my paint program. I used a paint tool to measure the width of one of the roads (7.0 pixels). Now I know that a standard two lane road is 20 feet in width. So I figure 7.0 pixels = ~20 feet. The map image is 1488x1062 pixels.
Now, using this information how can I figure out the distance of the entire width of the city map in feet?