Monday, May 17, 2004

"Visualisation of Surveillance Coverage by Latency Mapping"

A paper by Patrick Chisan Hew in 2003 from the Defence Science and Technology Organisation in Australia.

Hew describes a technique for visualizing information about surveillance coverage by mobile sensor platforms.

There are three key concepts that explain the approach:

1. Swath - This a space region R covered by a mobile sensor over a time interval T. That is, the union of all regions covered by the sensor in the time interval T.

2. Scan History - The value {1,0} of a point or region over a history indicating the instantaneous coverage by a sensor. This reflects whether the given point or region is covered by a sensor and for how long during the history. 1 if the point or region is instantaneously covered and 0 otherwise.

3. Latency Mapping - A visualization method where the regions of space that have a short time since they were last covered give a strong color or intensity and regions with a long time since they were last covered give a weak color or intensity. In addition there is a gradient of color in between the extrema of durations.

The use of latency mapping and latency history gives one the operational ability to visualize the sensor coverage of one's network or resources. This allows the ability to make judgements or design decisions.

What is useful about this method is that the details of the sensor modality and environmental conditions are abstracted from visualization. However, this is also a drawback because the details are not made available of how difficult it is to monitor a target or how costly it is to employ a sensor. In addition, the sensors, environmental conditions, and the target characteristics need to be modeled to give good specifications for coverage capability of each sensor.


At 4:24 AM, Anonymous Patrick Hew said...

Wow. Someone actually read this.

An updated version Analysis and Visualisation of Surveillance Coverage by Scan Mapping was published in Military Operations Research, Vol 10 Num 4, 2005. This paper fills out and expands upon the mathematical constructs, and in doing so the kinds of problems that scan mapping was intended to tackle.

The Scan Mapping procedure could be upgraded to capture the cost of sensor employment, by tagging the Scan History with sensors employed, and then doing weighted accumulation. This could actually be rather interesting -- for instance, in comparing costs of surveilling a region by aircraft or by satellite, the per area coverage by satellite could be very low ... until responsive revisits are factored in.

Difficulties in monitoring a target are actually an input to scan mapping, in doing the target modelling.

Thanks for your interest!


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