Oblivision . . . A Lateral Imaging Technique

Joseph Freund

Imagine that you are an intelligence officer charged with mission planning for a rescue operation, hostage situation, preemptive strike, or special-forces combat mission. You would probably use an ortho­photo to obtain a “straight-down” view of every point on the terrain.
Figure 1 shows the proposed route of a task force from point T1 to point P1 and, from there, to points B1 and T2. The route looks easy enough—the force will approach the main road, cross it, proceed through the bush to the dirt road on the other side, and continue on to the destination.
In reality, however, the situation is quite different. Along the main road, at point P1, lies a concrete wall that is 3.5 meters tall and is totally invisible on the orthophoto, even at high magnification. Furthermore, the orthophoto gives no indication of how tall the building is at point B1 and which parts of the access route are visible from that building.
The wall is readily discernible on a regular aerial photograph shot at an angle—an oblique photo—as can be seen in Figure 2. But some of the buildings obstruct others in the ob­lique photo, and it does not permit accurate measurement. Clearly, an ortho­photo is more appropriate for obtaining a general impression rather than for gathering the details required for mission planning.
A company in Israel, Idan Computers Ltd. (www.idan.com), has created a solution for merging the types of data provided by orthophotos and oblique photos into one comprehensive, interactive tool—Oblivision. Figure 3 gives the Oblivision view of the terrain seen in Figure 1.
In the background is the ortho­photo. The photos in the corners show the relevant areas of the oblique photo and provide four views of point P1, each from a different direction. Each of the corner photos has a colored spot (blue, green, red, or cyan) that represents point P1. The colored lines on the orthophoto correspond to the colored spots and indicate the direction from which each oblique photo was shot.
The bottom line? You’ve got the accuracy of an orthophoto along with the details of an oblique photo.
Oblivision isn’t new, and neither is Idan Computers. Idan customers in Israel, including the Israel Defense Forces, police force, forestry services, and Israel Electric Company, have been using Oblivision technology for years. For the Israel Electric Company, Oblivision is an essential tool for planning maintenance operations of high-tension lines, as it enables technicians to measure the distance from a power line to the top of the trees as well as to detect all nearby obstacles.
Remember the building at 1 point B? In the Oblivision view in Figure 4, you can see that the building is semicircular, consists of three stories, and has a structure on the roof. The red line, drawn by two mouse clicks on the photo in the upper right-hand corner, shows that the building’s height is 8.3 meters.
Oblivision technology reflects the origin of Idan Computers—a company with a civil engineering orientation that has added complex imaging capabilities to its base offerings. Oblivision includes many analytic capabilities inherent in civil engineering software. In the mission-planning scenario, for example, one would be able to obtain an elevation and slope analysis of the route from T1 to T2 Figure 5.
With such capabilities, the Oblivision software is already used in many diverse applications. The Forestry Authority and fire brigade in Israel use it for obtaining data on hydrants, fire lines, and the height of trees. Government agencies take advantage of the technique for analyzing flood patterns and preventing floods. For mining companies, it is ideal for maintaining an inventory of open mines and planning future activity. Municipal inspection agencies use Oblivision images for devising and enforcing construction codes.
A major benefit of the Oblivision technology is that it opens up the field of photographs that are available for analysis. You can apply Oblivision to photos taken by large, professional, airborne cameras as well as by simple handheld cameras—not to mention photos shot by intelligence drones. Neither the settings on the camera nor its exact position and direction are necessary for “solving” the oblique photo. You just select four control points on the orthophoto and the oblique photo, and the Oblivision Solver module does the rest.
Because Oblivision has a small memory footprint, it is compatible with almost all desktop and laptop computers.
This type of tool is bound to show up in many more work places in the near future and definitely bears watching.

About the Author
Joe Freund is the CEO and co-owner of Idan Computers Ltd. He is also co-author of CARTA, the first commercial triangulation based contouring system as well as the author of OBLIVISION.

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