**5. System experimental performance**

#### **5.1 Experiment design**

In our experiment, the *Yangtze River* estuary (Changjiangkou) precautionary (30°48′N ~ 31°20′N, 122°10′E ~ 122°47′E) is selected as the experimental working zone (Fig. 8). This region includes the inward and outward fairway of the *Yangtze River* estuary and the 1# and 2# anchorages. The *Yangtze River* estuary is a tide-coordinated region, and the tide rise and fall twice per day. The tidal range is up to 4 meters. And the flow is rapid. Both anchored ships and underway ships are aggregated at this place. Casualties happen often, and it is a key region for the monitoring of maritime search and rescue. Therefore, this place is an excellent experimental region.

Fig. 8. The experimental working zone in the nautical chart

#### **5.2 Experiment data**

From 2008.09.30 to 2008.10.19, we took four times of experiments. EnviSat-1 ASAR data is used in this experiment. Data acquisition is implemented considering the three tidal conditions: rise, fall and still. And the data includes: VTS maritime Radar, AIS, weather information, tide and flow, etc. The details are listed in Table 4. Here we present the experiment on 2008.10.19 as an example.



Table 4. The hydrological information in the experiment

#### **5.2.1 The remote sensing data**

398 Remote Sensing – Applications

The integrated processing module is mainly used for follow up processes of the detection result and search and rescue assisting forecast. It has two main functions. Firstly, search and rescue range estimation. According to the current location, navigation direction and the wave direction, estimate the potential searching areas of the distressed ship under the settled speed of the ship and velocity of flow. Secondly, ship location correction. Combine the satellite parameter to revise the error caused by slant-range projection imaging of the SAR images. The analysis data obtained by way of integrated processing module can be saved as \*.dat or \*.mat form and transmitted to marine department and the rescue spot,

In our experiment, the *Yangtze River* estuary (Changjiangkou) precautionary (30°48′N ~ 31°20′N, 122°10′E ~ 122°47′E) is selected as the experimental working zone (Fig. 8). This region includes the inward and outward fairway of the *Yangtze River* estuary and the 1# and 2# anchorages. The *Yangtze River* estuary is a tide-coordinated region, and the tide rise and fall twice per day. The tidal range is up to 4 meters. And the flow is rapid. Both anchored ships and underway ships are aggregated at this place. Casualties happen often, and it is a key region for the monitoring of maritime search and rescue. Therefore, this place is an

From 2008.09.30 to 2008.10.19, we took four times of experiments. EnviSat-1 ASAR data is used in this experiment. Data acquisition is implemented considering the three tidal conditions: rise, fall and still. And the data includes: VTS maritime Radar, AIS, weather information, tide and flow, etc. The details are listed in Table 4. Here we present the

**4.4 Integrated processing module** 

supplying assistant for the rescue areas determination.

Fig. 8. The experimental working zone in the nautical chart



**5. System experimental performance** 

**5.1 Experiment design** 

excellent experimental region.

**5.2 Experiment data** 

experiment on 2008.10.19 as an example.

Data: ASA\_APP\_1PNBEI20081019\_135613\_000000202073\_00082\_34705\_4038.N1 Polarization Mode: HH/HV

The detail information is listed in Table 5.


Table 5. The detail information of the remote sensing data

#### **5.2.2 The VTS reference data**

The radar data and AIS data are received from the VTS center of Shanghai port. Fig. 9 is the VTS shore-based radar detection picture simultaneously at the acquisition time of the remote sensing data. The VTS report shows the name and position of all the vessels equipped with AIS in the Yangtze River estuary. The Radar data and AIS data provide a reference for the performance analysis of the system experiment.

Fig. 9. The VTS report at the passing time of the satellite (2008-10-19, 13:56:17 UTC)

Remote Sensing Application in the Maritime Search and Rescue 401

Fig. 11. The working interface of the Remote Sensing Monitoring System for Maritime

Fig. 12. The original SAR image (2008-10-19, Changjiangkou precautionary, Envisat-1 ASAR

Search & Rescue (RS-MSR)

HH)

#### **5.2.3 The weather information**

The weather information includes the JMH weather chart, wave height, flow rate, and the tidal data. Fig. 10 shows the track of the No.15 typhoon (30 September, 2008).

Fig. 10. The track of the No.15 typhoon (30 September,2008)

#### **5.3 System experiment**

Here we set detecting zone as follow:


Fig. 11 presents the working interface of the Remote Sensing Monitoring System for Maritime Search & Rescue (RS-MSR). And Fig. 12 shows the original SAR image.

#### **5.3.1 Vessel detection**

Vessel detection includes: ship position detection, type identification, length estimation and heading estimation. The detection results are shown in Fig. 13(middle) and Table 6. The ship type classified into four categories: small, middle, large, and extra-large. The ship heading direction is the angle between the ship heading and the real north in clockwise.

In Fig. 13(right), the red circle represents small ship (point target) and the green arrow indicates the estimated heading direction of big ship (distributed corners).

The weather information includes the JMH weather chart, wave height, flow rate, and the

Fig. 11 presents the working interface of the Remote Sensing Monitoring System for

Vessel detection includes: ship position detection, type identification, length estimation and heading estimation. The detection results are shown in Fig. 13(middle) and Table 6. The ship type classified into four categories: small, middle, large, and extra-large. The ship heading

In Fig. 13(right), the red circle represents small ship (point target) and the green arrow

Maritime Search & Rescue (RS-MSR). And Fig. 12 shows the original SAR image.

direction is the angle between the ship heading and the real north in clockwise.

indicates the estimated heading direction of big ship (distributed corners).

tidal data. Fig. 10 shows the track of the No.15 typhoon (30 September, 2008).

Fig. 10. The track of the No.15 typhoon (30 September,2008)

**5.3 System experiment** 

**5.3.1 Vessel detection** 

Here we set detecting zone as follow: - UpperLeft longitude: 122.338E - UpperLeft latitude: 30.9261N - Range in longitude: 9.8276 nmile - Range in latitude: 8.96046 nmile

**5.2.3 The weather information** 

Fig. 11. The working interface of the Remote Sensing Monitoring System for Maritime Search & Rescue (RS-MSR)

Fig. 12. The original SAR image (2008-10-19, Changjiangkou precautionary, Envisat-1 ASAR HH)

Remote Sensing Application in the Maritime Search and Rescue 403

Incident Angle

The complete maritime search and rescue system supplies the function of ship detection, identification and location algorithm. It can be also used to inquire the satellite transit time and its orbit data. The precision of ship size estimation reached over 80% and the position

In this chapter, a remote sensing monitoring system for maritime search and rescue (RS-MSR) is presented. Some related algorithms are introduced. The satellite remote sensing imageries of large scale water area are acquired to detect and locate distress ships for guiding the search operation. Some important data such as current and sea state are retrieved to assist decisionmaking of the operation. System experiment design and test are presented, and the performance shows that this system can effectively improve the searching speed and accuracy,

The research work in this paper is partially sponsored by the Shanghai Leading Academic Discipline Project (grant number: S30602), and the Natural Science Foundation of China (grant number: 40801174), and the Program of Shanghai Subject Chief Scientist (grant

Estimated Direction

JMH Wave Analysis

**5.3.3 Sea state estimation** 

Acquisition Time (UTC)

The wave direction estimation result is shown in Table 7.

20081019 13:56 HH/HV 44.0092 104.8161

estimate the position detecting error is within 0.5 nautical miles.

and is of significance in promoting rescue success rate and efficiency.

Polarization Mode

Table 7. The wave direction estimation result

**5.3.4 Ship position prediction** 


**5.4 The system performance** 

**6. Conclusion** 

**7. Acknowledgment** 

number: 10QA1403100).


 Northwest: 123.1202E, 36.7825N; Southeast: 124.5202E, 35.3825N.



Fig. 13. (left) The selected detecting zone (original image), (middle) The vessel detection results (the red cross), (right) Ship size identification and the heading direction estimation result


Note: There are totally 44 vessels are detected, and only 10 are listed here.

Table 6. The vessel detection results

#### **5.3.2 Performance analysis**


Among the detection, six small vessels and one middle sized vessel were missed. The performance is better in the detection of big and extra big vessels.

#### **5.3.3 Sea state estimation**

402 Remote Sensing – Applications

Fig. 13. (left) The selected detecting zone (original image), (middle) The vessel detection results (the red cross), (right) Ship size identification and the heading direction estimation

No. Position Type Length(m) Heading angle (degree)

1 123.5118E 38.4035N M 99.3905 124.2916

2 123.8202E 36.0825N M 80.3638 176.8479

3 124.2371E 31.8074N M 98.8651 0.4757

4 124.2207E 38.8641N M 92.0447 173.3593

5 124.441E 32.1691N M 108.5735 89.9972

6 129.429E 35.3644N M 95.7427 233.4018

7 129.5839E 33.1727N L 140.0645 10.0805

8 129.8325E 36.7182N L 116.6667 179.5634

9 130.0705E 35.3129N XL 219.6904 0.0432

10 129.9275E 38.2278N M 73.48 7.3131

Among the detection, six small vessels and one middle sized vessel were missed. The

Note: There are totally 44 vessels are detected, and only 10 are listed here.

performance is better in the detection of big and extra big vessels.

Table 6. The vessel detection results

**5.3.2 Performance analysis**  - VTS vessel report: 51 - Detected vessel: 44 - Detecting rate: 86% - Position error: 0.06 nmile

result


The wave direction estimation result is shown in Table 7.

Table 7. The wave direction estimation result

#### **5.3.4 Ship position prediction**

	- Northwest: 123.1202E, 36.7825N;
	- Southeast: 124.5202E, 35.3825N.

#### **5.4 The system performance**

The complete maritime search and rescue system supplies the function of ship detection, identification and location algorithm. It can be also used to inquire the satellite transit time and its orbit data. The precision of ship size estimation reached over 80% and the position estimate the position detecting error is within 0.5 nautical miles.
