Render size-UV map image

utilities map.zip (644 KB) I am mapping the entire county that I live in and in this map will be included all the culverts and signs. My problem is the camera size. For the signs to be visible and readable in the render the camera has to be so close that when I am finished and am ready to make a poster size image of the map to hang on the wall of the shop, I’m going to have to piece together way too many images. How can I modify the camera or what do I have to change to include at least 6 or 8 square miles or more of the image and still have all the signs readable?
Thanks!