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More Than Aerial Photography

Written by TR Staff

When planning a tactical operation, maps are good, aerial photos are better, and having both is great, although it doesn't happen very often. When aerial photos are available, they are usually outdated, taken from directly overhead of the objective, and are not detailed enough to show man-on-the-ground features. What if you could have aerial photos that were tied to a computerized mapping program, not more than two years old, showed detail as small as six inches, and offered views from all four compass points?

The image sets offered by Pictometry® do just that. Using proprietary methods and technologies, Pictometry produces extremely detailed sets of aerial images of an entire county, with every feature and landmark photographed from multiple angles and resolutions.

The images are all digital, and are linked to a computer-based map of the entire surveyed area. By clicking a mouse on the area of the map to be viewed, the user is taken to a screen showing all available views of that area, and can then select the ones best suited for the task. Users can zoom in on any image to pick up additional detail.

Orthogonal and Oblique

The images from any one county make up one complete set. When they are contracted to produce the image set, a Cessna 172 light aircraft overflies the county in strips, collecting digital photos with specially designed cameras. Overflights are made at approximately 5,000 and 2,500 feet, and from all four compass directions.

The images are also from two views. The orthogonal view (straight down) is like a map or traditional aerial image, and is useful for planning and orienting against a standard map. Oblique (angled) views are from a perspective of about 45 degrees, and show detail of the sides of buildings, signs, and other visual information that might not be so obvious when seen from directly overhead.

The value of these oblique views should not be underestimated. Even though very tall buildings are obvious when viewed from the conventional ground-level perspective, there is no sense of their height when viewed from directly overhead. It is virtually impossible to distinguish a 20-story building from a one-story building with a similar perimeter, unless there are shadows or other cues that give it away. With the oblique view, the difference between structures becomes instantly evident.

The resolution of the images is extremely high. Images taken from the higher altitude, called community views, resolve to about two feet per pixel, where the neighborhood view images from the 2,500 foot altitude are at about six inches per pixel. This is plenty sufficient to see the placement of doors, windows, clotheslines, doghouses, and other details that would be useful in tactical planning, but not be a threat to personal privacy.

License plates, faces, and other similarly small details are not discernable even at the greatest resolutions and magnifications. Neighborhood images are about 0.5 mile long by 0.25 mile wide, where community view images are about 1.25 miles long and 0.75 miles wide.

In order to reduce costs, rural areas, where there is less need for detail, are imaged at the higher altitude, whereas urban, built-up areas will have the full range of images available. The end result is that every square foot of the county will have at least three and as many as 20 different views available to all users, with an average around 12.

User Interface

The user interface to the Pictometry software is fairly intuitive. On an overview map of the entire county (and surrounding counties, where those images are available) shown in the main workspace window, a blue outline placed by the user identifies the area of interest. A pane to the right of the main workspace has thumbnail views of all the images available for the area identified. Clicking on one of the thumbnails brings it into the main workspace.

For each image, a compass-rose alongside the thumbnail shows the view angle, so that the user does not become disoriented. Icons on a tool bar at the top of the screen allow the user to switch angles with a single click, bringing the new view into the main workspace. By clicking on all four directional perspectives, the user can navigate any perimeter.

When the user picks a line tool to draw on the map, the length of the line is displayed in the lower right of the workspace, and can be shown on the image itself, if desired. Similarly, using a closed-loop tool to draw a perimeter on any image shows not only the length of the perimeter line, but also the area enclosed by that perimeter.

One use for this tool is to instantly determine the square footage of a building by drawing a perimeter and multiplying it times the number of floors in the building. The units of measure for length and area are user-selectable. Once a line or perimeter is drawn, switching to another view will keep the line or perimeter displayed on the image, even though it is shown from a different perspective.

Since all of these views are from an angle of approximately 45 degrees, apparent dimensions of objects can be deceptive. The software automatically compensates for the view angle and delivers a true dimension of the line. In a demonstration, a sales rep for the company drew a line from home plate to the pitcher's mound in a city baseball stadium, showing that the two landmarks were exactly the required 60 feet, six inches apart.

This drawing and measurement tool can also be used to define safety or evacuation zones. If an incident commander wants to define a safety zone of 500 feet from a point of origin, all he need do is place the cursor on the point depicted in the image, and tell the software how big a circle to draw. The circle will appear on the image, giving a clear picture of the area and properties to be evacuated.

Another drawing and measurement feature, called "the walking man," describes a linear path on an image, or one that spans several images. As the user draws segments of the path with the cursor, the software shows a running tally of the line's distance. One application for this would be to direct officers to the precise location to set up road spikes during a pursuit. The visual cues supplied by the overhead pictures are much more intuitive than a map for this purpose, and the images will also show terrain features that can be used to hide the officers from the view of the suspect while they prepare the barrier.

The cost of a Pictometry survey is surprisingly reasonable. The city and county of San Francisco (the city and county share the same borders), an area of 47 square miles, was imaged at a cost of $60,000. Because the county is entirely urbanized, almost every square foot of the city has between 12 and 20 views available.

Once the image set is created, it and the Pictometry software associated with it are licensed to every local government agency in the county for two years, regardless of the number of users there might be. This means that the same software and imagery available to police is also available to the fire service, to EMS, 911 communications, tax assessors, urban planning, streets department, and any other local government entity.

No distinction is made between county, city, or special district governmental bodies in providing access to the images and software, so that the cost can be spread over the budgets of multiple departments, if desired. Moreover, if neighboring counties are also Pictometry customers, they can share the imaging sets across the county borders in the same manner.

The ability to share this resource so freely makes Pictometry a highly defensible resource for funding purposes. In fact, it is well-positioned for funding through Department of Justice and Homeland Security grants because of the way that it enhances interoperability between agencies and can be deployed for all types of emergencies, from natural disasters to the apprehension of fugitives.

The two-year license is intended to encourage a re-fly of the county on at least a two-year interval, as many features will change over that time. The overflights can be done more frequently, as needed. Depending on the size of the area imaged, the turnaround time can be very short. Pictometry was involved in the post-9/11 investigation of the attacks on the World Trade Center. Operators had the images in their hands within 48 hours. The Arlington, VA Fire Department used Pictometry images at the Pentagon site to measure the degree of penetration to the building. This came from images taken earlier in the year.

A complete county set of Pictometry images can take up 120 GB or more of hard drive space, which is considerably more than most portable computers contain. An image database in use in Monroe County, NY started out as 120 GB, but was successfully compressed to 45 GB for mobile use. It is also possible to create subsets of image data when it isn't necessary to load an entire set onto a single computer.

Applications

Pictometry images have proven to be very useful in the courtroom. Rather than use diagrams drawn in court by officer witnesses with limited artistic talents, prosecutors can show actual photos of the crime scene, and from multiple angles. Jurors can see how likely it would be that a suspect could gain entry or exit via a window or door, and how long it might take him to get from point A to point B. The measurement tool described above can be superimposed on an image to get the dimensions of windows and doors, or the height of a wall or fence.

Users have found applications for Pictometry that were not anticipated. 911 operators can bring up an image of the site of a call based on the address associated with the telephone number, and then direct responders verbally based on that image, or have them view the same image on their in-car computers by relaying an XY coordinate. Because everyone has access and is using the same data set, there is less confusion and better teamwork.

When officers in the field have the imagery loaded on in-car computers, they can get a view of the site of a call for service before actually entering a danger zone. When GIS data is available from the city or county planning or assessor's office, the data can be linked with the Pictometry images, tying a street address and/or apartment number to every residence in the county.

Officers applying for and executing search warrants can use Pictometry images to illustrate the warrant affidavit and at the pre-service briefing. Many agencies do a drive-by of a building targeted for a search warrant prior to its execution, so that all members of the entry team will have a preview as to what the premises look like.

Using Pictometry images allows the team to see the building to be entered, the buildings on all sides of it, and any open areas in the vicinity. The savings in litigation and damages from a single wrong house search warrant lawsuit could fund the cost of an image set several times over. In planning for a night warrant service, officers have the advantage of seeing the site in daylight conditions to scope out potential hazards and obstacles.

Gwinnett County, GA is a Pictometry customer, and used the imagery to plan the takedown of fugitive Brian Nichols after he killed several people and escaped from an Atlanta courthouse in March 2005. Tactical teams were able to view the apartment building where Nichols was holding a hostage, and plan approach routes and fields of fire, all without exposing themselves to fire and alerting the suspect to their presence.

Patrick O'Flynn is the sheriff of Monroe County, NY which is also the home of Pictometry's headquarters. The Monroe County Sheriff's Office has been one of the test beds for Pictometry, and the relationship has been a profitable one for law enforcement. "The county bought the system mainly for public safety use, but the planning and water departments both use it extensively," said Sheriff O'Flynn.

"County workers can pre-inspect property without having to go to the sites, because they could see the siting of the properties with Pictometry. We've used it on many occasions for our special weapons team to identify safe paths for hostages, or for gridding areas in searches. We've also run training scenarios on laptops for tactical and WMD exercises."


Published in Tactical Response, Jan/Feb 2006

Rating : Not Yet Rated


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