Landing Zone Analysis for Autonomous Medevac

Varied Decision Weights

There are usually many landing sites that are good enough for a safe landing.  In order to chose a landing area, the algorithm gives each potential site a score that is a linear combination of the following four metrics, weighted by a corresponding scaling weight wX:

  1. Overall terrain slope and roughness (wA)
  2. Clearance of 3-d helicopter model above terrain (wB)
  3. Distance to the casualty (wC)
  4. Distance to closest obstacle (wD)

The pictures that follow illustrate the effect of varying the parameters (wA..wD) to see thier effects on landing site selection.  We increase the weights enough that each example effectively only shows the influence of the metric in question.  Normally, the selection process incorporates a combination of all the factors simultaneously.

Click on the images for a more detailed picture.


Example 1: Emphasized Terrain Slope and Roughness

In this example the effect of terrain slope roughness are weighed much higher in the final score (wA * 1000) than all the other factors.  This results in the flattest and most level spot being chosen, regardless of its distance to nearby obstacls or the distance to the casualty.


Example 2: Emphasized Clearance of Helicopter Above Terrain

The second metric measures the cumulative clearance of a three-dimensional model of the helicopter above the terrain at a given landing spot.   This metric ensures that obstacles such as shrubs or low structures do not collide with the rotor or tail, even if the landing gear themselves are clear.

In this example, we increase the weight of this clearance metric 1000 times (1000*wB).  In this particular case, the field is already relatively clear of rising obstructions, so there is little change in the chosen landing spot.


Example 3: Minimize the Distance to Casualty

In this example, the wieght for the penalty for distance to the casualty is increased (100*wC).  The algorithm therefore pics a safe landing spot that is as close to the casualty as possible without violating the minimum safety distance, even if there are better general landing sites in other areas.


Example 4: Deemphasis of Distance to Closest Obstacle

The final "distance to the closest obstacle" metric ensures that the selected site is located towards the center of suitable terrain.  For example, in the image below this factor was reduced to (wD*1/1000).  Normally, the system would chose to land in the large field on the lower left because it can maximize its distance to the surrounding trees and steep terrain; however, in this example, the system choses to land as close as possible to the casualty because there is no pressure to land away from forbidden or obstacle-laden zones.