All About Aerials

All About Aerials
Posted by on November 15, 2016
Posted in: environment, imaging, legal, mapping, real estate, tips and tricks

Investigating a motor vehicle crash or crime? Planning a trip? Shopping for a new home? For these, and countless other activities, aerial photography is a valuable source of information. You probably already know how to get it: Google Maps, right? That’s a great place to start, but dig a bit deeper, and you stand to discover much more.

Historical Imagery

Google archives aerial photo sets going back more than ten years. This provides a good way to see how a location has changed over time and also look for cleaner imagery of your area of interest. All you need to do is download Google Earth and click the Historical Imagery icon. Many cities have their own database of aerial imagery that can be viewed online for little or no cost. For example, check out PortlandMaps to browse images of a property going back as far as 1996.

Perspective

In a perfect world, aerial photos would show all land a 90° angle, looking straight down with no sides of buildings visible. In reality, for every image, only a small portion has that elusive 90° angle. The further you get from the center of the image the more you see the sides of buildings, and that error of a few degrees can cause objects on the ground to be obscured by the tops of buildings. This is especially problematic in large cities, and another good reason to hunt for an image with the best perspective.

Intersection of 6th and Arch (Source: Philadelphia GIS)

Intersection of 6th and Arch (Source: Philadelphia GIS)
Google photo of same location exhibits building perspective problems

Google photo of same location exhibits building perspective problems

Another option to consider is aerial oblique imagery, a.k.a. 45°, or birds-eye view. This is useful when you want to see the the sides of buildings or see what’s underneath trees. One long-time source of birds-eye imagery is Pictometry, which, as of this writing, can still be seen on Bing Maps. These images are getting rather dated, however. The more modern approach is to use birds-eye imagery in combination with Lidar surface maps to create the “3d” aerial views that can be seen in Google and Apple Maps.

Resolution

Google brings together imagery from many different sources to make a seamless picture of the Earth. In some areas, you can zoom in very close before the image gets blurry. In other areas, not so much. There are sources for higher resolution aerial photos if you are willing to pay. Fat Pencil Studio subscribes to NearMap, which offers frequent high-res aerial photo updates for most major cities in the United States. The quality is often better than the best Google has to offer, and they also provide Spring and Fall season images which can be useful if you want to see trees without leaves.

Best image of SW Naito Pkwy at Yamhill available from Google

Best image of SW Naito Pkwy at Yamhill available from Google
NearMap photo show same location in more detail

NearMap photo show same location in more detail

One final option is to hire a company to take exactly the aerial photos you need. With careful planning you it’s possible to capture the exact location and details needed, and the pricing can be quite reasonable. We’ve used a company called SkyShots in the past that takes photos from a helicopter, and there are many new drone operators popping up that can provide similar services.

Stay tuned next month for a tutorial on Street View imagery!

About Joshua

Joshua Cohen founded Fat Pencil Studio in 2004. Read more