Wednesday, June 26, 2013

Oblique imagery for police work

I'm blogging this week about the value of oblique aerial photos for public safety agencies. Today, I am going to describe a typical use case for policing. My example deals with the planning and execution of an arrest warrant (hypothetical, that is) for an individual who is believed to be in a house in south-central Springfield, MO.  This is a common activity in police agencies all over the country, and one that usually involves pre-planning, including a briefing for the officers who will be involved in the warrant service.

Gathering information about the premise is always part of the preparation. An undercover drive-by would reveal the home's appearance from the street.  The view would be much like this screenshot from Google Streetview. It is a two story frame house with columns on the front stoop supporting an overhang above the front door. There is an asphalt driveway along the left side of the house.

A conventional aerial orthophoto would shed a little more light on the target  (the house in the center with the green shingles). The parcel is long and narrow. The driveway goes back to a sizable concrete apron at the back, where a  large white-roofed outbuilding sits. If you go under cover of darkness, take care not to fall in the neighbor's swimming pool.

The oblique image from Pictometry (via Bing Maps) shows the arrangement of these buildings even better. This view is oriented towards the north, showing the alpha face of the house. Note the front columns. There are several windows visible on the south side of that outbuilding.  That might be an indication that it is an apartment or guest house, rather than a garage. There is a small above-ground pool at the northwest corner of the lot.

Rotating around to the bravo side and viewing from the west shows more significant detail.  The outbuilding appears to be composed of a one story section on the south with a door and a chimney (a guest house or apartment, perhaps?), and a double garage in the north portion. Above the garage is a second story with windows.  This could be part of a second residence, or it might be something like a workshop above the garage. There is a low shed attached to the north side of the garage. The small yard between the main house and the "guest house" is enclosed by a substantial fence. We could continue to rotate around to the other two compass points and gather even more information.

I don't know about you, but if I'm going to this place to look for a bad guy, these oblique images are providing me with a lot of very important detail that I wouldn't get from just driving by for a peek, or from a standard aerial orthophoto. Why on earth would I just draw a freehand diagram of this property on a dry erase board, when I could pull up these images and show everyone involved in the case more precisely what we will be dealing with at the scene? And yet, exactly that is going to happen dozens of times today in police departments all over the country.

This is just one example. Hopefully, you can see that oblique imagery would be valuable in many other circumstances: setting up a search area for an Alzheimer's patient who has walked away from home, establishing a perimeter around a building with a barricaded suspect, planning a special event at a public park, visualizing the area around a string of storage unit burglaries, and so forth.

When you've got a little time to prepare, it's hard to beat the oblique imagery from Pictometry, Bing, or Google for getting the lay of the land.


Anonymous said...

Is there some significance to the house, or did you pick it randomly?

Tom Casady said...


Our home from 1959-1964--first through fifth grade. Looks like it hasn't changed at all.

Anonymous said...

Totally off-topic, so post or delete as you see fit. This wasn't my bike, not that of anyone I know, but since this is a city parking cage, and supposedly secure, I think it should be publicized that a bike got ripped off from there:

1730 06-25-2013