Ukleja S. Thermo and night vision system - its performance as a way to improve effectiveness of search and rescue action at sea.

THERMO AND NIGHT VISION SYSTEM - ITS

PERFORMANCE AS A WAY TO IMPROVE

EFFECTIVENESS OF SEARCH AND RESCUE

ACTION AT SEA

Ukleja S.

Gdynia Maritime University, Gdynia, Poland

Abstract: This paper presents research efforts on thermo vision system, which has been recently

done in Gdynia Maritime University. In addition there are included some aspects of search theory. The definition of sweep width and its importance for search and rescue action at sea is described.

1. Introduction

Despite of modern technique and cutting-edge design in maritime field there are many disasters at sea and tragic loss of lives . The nature can still be very dangerous and sea is bitterly hostile environment for human being. Surprisingly, many seamen don’t drown in shipping accidents, but die as result of hypothermia. People lose their lives because of rapid loss of body heat. With the course of time the body temperature goes down and survivor lose consciousness. The colder the sea the faster temperature decrease.

Therefore the most important aspect of Search and Rescue action at sea is to find survivors as fast as it can be done. However at least two problems can be addressed. First question is: “Where to search?” and second “How to search? This problem can be described with more scientific language as follows: “How to use the available resources to maximize the probability of finding survivors alive?” In other words, rescue unit has to carry out a search in appropriate region and using appropriate senor.

2. Background

In Gdynia Maritime University there is currently conducted a research on the Thermo and Night Vision System for detection of survivors at sea 3,7. The purpose of that research is to develop a brand new detector, which may improve the chances of finding survivors

alive. The main concept is to use thermo vision camera as a sensor which will enable to conduct search during night time. In addition it may help to reduce effect of searches’ fatigue.

The main component of described system are :

 Sensors: thermo vision and night vision camera with stroboscope laser illuminator  Computer system for analyzing images

The system is already done and after a field tests on research ship owned by Gdynia Maritime University. The next stage is to determine necessary characteristics of this device, which enable to use it effectively during real search action.

Fig. 1a. Thermo vision image with boat and a man – distance 0,3 nautical mile (approximately 0,5 km)

Fig. 1b. Thermo vision image with boat and a man in water – distance 0,3 nautical mile (approximately 0,5 km)

3. Measure of search performance

The person responsible for search planning is a SAR mission coordinator. She or he must know characteristic of available resources (search units with their sensors) in order to make best use of them. Therefore it shall be determined a measure of effectiveness, namely a measure of detectability. There is such a measure, which is called sweep width, which is simply a measure of the average detection potential of a single specific search unit 4 .

Sweep width (W) is the most important measure of search performance when comparing different sensors or sensor platforms searching for a particular target under the same environmental conditions 11.

The most common way to search an given area is to employ parallel straight-line search tracks. A distance between two adjacent search track is called a track spacing. Provided that search coordinator knows sweep width of resources available he or she can determine the track spacing. Figure 2 illustrates that situation.

If the track spacing is to big, it will be possible to miss search object. If it is to small, it will take to long time to find search object and the resulting death of survivors may happen. For this reason sweep width is so important.

To sum up, sweep width is the primary performance measure used by SAR mission coordinators to plan searches 9.

4. Search theory

The methodology used nowadays is based in large measure on the work of Koopman and originate from Second World War 5,12. Koopman defined sweep width as follows: If a searcher passes through a swarm of identical stationary objects uniformly distributed over a large area, then the effective sweep width (W) is defined by the equation 4:

W

_

_{ }

_



(1)

In order to compute sweep width it must be derived experimentally another measure – lateral range curve, because sweep width is an area under that curve.

Such a curve plots probability of detection (POD) versus lateral range. Lateral range describes the perpendicular distance from the search track to the target. In most cases it is the same as the closest point of approach (CPA) [4, 5, 11].

In order to compute this curve, a particular sensor must be moved through a field of widely spaced and randomly placed targets. This movement must have a form of parallel straight-line search tracks 11. After that some statistically computation need to be done and as result it will be obtained lateral range curve. Each point on it represents the probability that a target will be detected as the searcher approach the object at particular distance.

As mentioned earlier sweep width is an area under lateral range curve. Thus [5, 9, 11]: 

 

x - lateral range (i.e., CPA) to targets of opportunity, POD(x) - target detection probability at lateral range x.

However, lateral ranges beyond some maximum value are associated with zero POD and do not contribute to the sweep width value 9. An example of lateral range curve presents figure 4.

Fig. 4. An example of lateral range curve. Horizontal axis – lateral range; vertical axis – probability of detection 9.

5. Further work and conclusions

Author is preparing additional field tests in order to determine lateral range curve and sweep width for system designed in Gdynia Maritime University. The objective of such tests is to compute special tables, which may assist the search planner during preparing search and rescue action so that survivors may be found faster and more lives may be saved.

References

1. Burciu Z.: Modelowanie obszarów poszukiwania w aspekcie bezpieczeństwa transportu ludzi na morzu. Politechnika Warszawska, Prace Naukowe, Transport, z. 50, 2002.

2. Burciu Z., Smolarek L., Soliwoda J., Szklarski A.: Nadmiarowość w systemie SAR w aspekcie poprawy niezawodności akcji poszukiwania. XXXII Zimowa Szkoła Niezawodności, Szczyrk, 2004.

3. Burciu Z., et al : System optycznego poszukiwania rozbitków na morzu. Opracowanie wewnętrzne w ramach projektu celowego dofinansowanego prze Ministerstwo Nauki i Informatyzacji: Nr 6T12 083 2001C/5686, Gdynia, 2001.

4. Frost J. R.: Principles of Search Theory. Wydawnictwo SOZA, 1999.

5. Koopman B.O.: Search and Screening. General Principles with Historical Applications. Military Operations Research Society, Alexandria, Virgina USA, 1999. 6. Soliwoda J.: Efektywność systemu ratownictwa ze szczególnym uwzględnieniem

detekcji termowizyjnej w akcjach ratowniczych na morzu. Praca doktorska. Instytut Techniczny Wojsk Lotniczych, Warszawa, 2004.

7. Ukleja S., et.al.: Detection of survivors using "thermo & night vision" system. Technologies for Search, Assistance and Rescue, Brest, 2004.

8. Ukleja S.: Metody wyznaczania obszarów poszukiwania na morzu. Praca magisterska, AM, Gdynia, 2003.

9. Evaluation of night vision goggles (NVG) for maritime search and rescue: HH-65A sweep width verification and laser illuminator evaluation. Final field test results. U.S. Coast Guard Research and Development Center, Final report, October 1999. 10. International Aeronautical and Maritime Search and Rescue Manual, Volume II:

Mission Coordination, IMO/ICAO London/Montreal, 1999 (amended).

11. NSMRL See/Rescue® Project Target detectability testing, modeling, and analysis. U.S. Coast Guard Research and Development Center, Final report, January 2006. 12. Review Of Search Theory: Advances And Applications To Search And Rescue

Decision Support. U.S. Coast Guard Research and Development Center, Final report, September 2001.