Nav 6 power point presentation

Group 4

Presented by: Genobiagon, Jayson J.

• Explain the capability & Limitations of ARPA

• What are the advantages of using ARPA?

• What does ARPA provide that are not on other devices?

• What are the disadvantages of using ARPA ?

A marine radar with automatic radar plotting aid (ARPA) capability can create tracks using radar contacts. The system can calculate the tracked object's course, speed and closest point of approach (CPA), thereby knowing if there is a danger of collision with the other ship or landmass.

Development of ARPA started after the accident when the Italian liner SS Andrea Doria collided in dense fog and sank off the east coast of the United States. ARPA radars started to emerge in the 1960s and, with the development of microelectronics. The first commercially available ARPA was delivered to the cargo liner MV Taimyr in 1969[1] and was manufactured byNorcontrol, now a part of Kongsberg Maritime. ARPA-enabled radars are now available even for small yachts.

1 INTRODUCTION

1.1 Automatic radar plotting aids (ARPAs) should, in order to improve the standard of collision avoidance at sea:

.1 reduce the workload of observers by enabling them automatically to obtain information about plotted targets, so that they can perform as well with several separate targets as they can by manually plotting a single target; and

.2 provide continuous, accurate and rapid situation evaluation.

1.2 The radar facilities provided by an ARPA display should comply with the performance standards for radar equipment (resolution A.477(XII)) appropriate to its mode of use.

1.3 In addition to the general requirements contained in resolution A.694(17), ARPA should comply with the following minimum performance standards.

Explain the capability & Limitations of ARPA

COMPARISON BETWEEN ARPA RADAR AND AISCHARACTERISTICS FOR VESSEL TRAFFICSERVICES

ARPA RADAR FUNCTIONALITY

Basically ARPA radar is the equipment by means

of a computer system operating in conjunction with

radar. Radar transmitter generates very short pulses of

radio waves. When the waves of one of these pulses

encounter any obstacle, such as a ship or shore line, part

of the radiated energy is reflected and received by the

original radar. The reflected pulse constitutes a radio

echo. The time between radiating the pulse and receiving

the echo can be accurately measured. Therefore the

distance between the radar and the ship is calculated.

The direction of the ship is the direction of the pulsetransmitted [12].

All radar installations should comply with IMO

minimum requirements. The variable range marker

should enable the range of an object to be measured with

an error not exceeding 1.5 per cent of the maximum

range of the scale in use, or 70 meters, whichever is the

greater. The means provided for bearings should enable

the bearing of a target whose echo appears at the edge of

the display to be measured with an accuracy of plus or

minus 1 degree or better [6].

Traditionally when finding a target echo showing

on radar screen, a ship officer plotted the relative motion

of the echo in order to get target’s course, speed, the

closest point of approach (CPA) and the time to CPA

(TCPA) by hands. Usually that took much time to

complete the plotting task. Owing to the error of

remarking the echo’s bearing and distance, results of

measurement were not very accurate. Sometimes a

large mistake in the radar plotting might lead the office

to take an incorrect judgment of target ship movements

and cause navigational faults. The situation has been

improved after ARPA radar fitted onboard. All data are

calculated by computer and clearly showed on the ARPA

display. The benefit is not only reduction of plotting

time in less than 2 minutes for the whole process but

also accuracy of the data. Furthermore, ARPA radar can

provide navigational warning, when a ship is approaching

a defined dangerous area or the CPA to another ship

is less than the limited CPA.

Although it is apparent that ARPA radar is a veryeffective aid to navigation, especially for anti-collision,the limitation of radar function still exists when pulsesof radio wave are transmitting. The first is that themaximum distance of an object detected is affected bythe height of antenna and the height of object due to thecurvature of the earth. Secondarily, some objects, suchas small wooden fishing boat, may not be detected untila short distance due to the reflecting power of the pulsesaffected by the surface and material of the objects.Thirdly, the accuracy of object’s bearing is affected bythe horizontal beam width of the pulses. In modernmarine radar the bearing discrimination is from 0.6 to 2degrees [10]. Fourthly a more obvious effect is blindareas and shower areas. For radar radiation a mountainousisland will cause a blind area, and objects behind theisland will not be detected on radar screen. A big shipat close range may cause a shadow, and small objectswill not always appear on the screen, especially in ashort distance because of the reduction of the echoenergy. The shadow effect will reduce the range of asmall object detected from 4 miles to 0.5 miles [10].

The loss of tracking will result in the need to reacquire

and re-identify. Heavy rain or snow sometimes also

affects the effectiveness of radar tracking. With modernARPA radar, traffic routes, fairways

and other marks of importance can be delineated on the

display. No matter the above limitations, ARPA radar

currently has become required equipment forsurveillance

of ship movements in VTS. To achieve the

operational purpose the ARPA radar should be able to

detect all moving or stationary targets which satisfy the

detection criteria within VTS coverage area during all

specified operating circumstances. Any target should

be acquired and maintain tracking in at least 5 out of

every 10 scans average over a period of 2 minutes [9].

Navigation data of target ship should be displayed either

on the VTS display using synthetic symbols near

the ship or in tabular form in an un-used part of the VTS

display. A failure to reacquire a target automatically in

a limited time should be brought to the attention of the

VTS operator. AIS FUNCTIONALITY

Functions of the AIS should satisfy the following

requirements: in a ship-to-ship mode for collision

avoidance, as a means for littoral States to obtaininformation

about a ship and its cargo, as a VTS tool, i.e.

ship-to-shore (traffic management) [8]. The AIS is a

shipboard broadcast system operating in the VHF radio

maritime frequencies: 161.975 MHz (channel 87B) and

162.025 MHz (channel 88B). The universal VTS using

self-organized time division multiple access (SOTDMA)

technology was adopted by IMO in 1998 for highbroadcast

rate and reliable operation. The system is characterized

by a transmission schedule. The transmission

time in the radio channel is divided into time slots of a

constant length. The spacing of the time slots for a

particular ship depends on its speed and maneuvering

status [3]. AIS is to be capable of handling over 2,000

time slots per minute per channel and updates as often

as very two seconds [5].

The AIS should automatically provide to appropriatelyother ships and shore stations equipped staticinformation, dynamic information and voyage relatedinformation. Static information, such as ship call sign,name and Maritime Mobile Service Identity (MMSI) ispermanently stored in the AIS. Dynamic information,such as ship’s position, course and speed, is collectedfrom ship equipment, such as GPS, gyro compass andspeed log. Voyage related information, such as ship’sdraught and hazardous cargo, is input by ship officers inmanually each voyage. It should also receive automaticallysuch information from similarly fitted ship.The information is autonomously sent at differentupdate rates depending on the type of message. Thereporting interval of dynamic information is dependenton speed and course alteration. When a high speed shipis changing course, the information update interval is 2seconds, but it is 3 minutes for the ship at anchor. Theinterval of static and voyage related information isevery 6 minutes or on request [5]. Dynamic informationmust be apparently sent at a shorter interval than others.The status of ship movement is changing faster theinterval of update rate is shorter. Other ship can find

thechange early. Therefore AIS can provide ship officerswith sufficient additional information of the ship encounteringthat is potentially extremely valuable fortaking action to avoid collision.Every message containing the ship identity is agreat value to VTS. Most of ship identifications trackedby VTS rely on approaching ships reporting their nameand location through VHF call, and the VTS operatorthen correlating this information with an unassignedARPA track. After VTS is fitted with AIS, as the nameimplies, ship identity can be automatically and immediatelyprovided that help overcome time consuming procedureand misunderstanding messages, inherent in theVHF communications due to the problems of differentlanguages and accents [13]. Another great benefit forVTS is ship tracking improved. VTS receiving AISmessages from a ship at the maximum range of the VHFcommunications usually in excess of detecting range ofconventional radar. As a consequence, VTS can extenddetection range and the detection is contained in AISmessages.

The multiple functions of AIS on navigation safetyhave had a major impact on maritime industry. Althoughthere are many advantages of using AIS receivingship information: accurate ship position, automaticand prompt update, good quality during adverse weather,reliable ship tracking without shadow effect, etc., thereare also some disadvantages in use of AIS. When a shipshuts off the AIS, or does not fit the AIS, such as fishingboats, the VTS operator can see the ship in sight but noinformation on AIS display. Under this situation, accuratelymonitoring ship movement could not achievewith AIS, has to use other equipment. If the operationstill concentrates on the AIS display and neglects existenceof the ship, it will be a seriously critical time.Another problem is that ship equipment in conjunctionwith AIS, such as GPS or gyro compass, has trouble sothat the information delivering to VTS and other shipsis incorrect or inaccurate. EXPERIMENTAL OBSERVATIONFor surveillance requirements VTS must realizeship movements within the severed area. In VTS center,maneuvering information of ships can be detected activelyby ARPA radar without the need of transmissionby other equipments from target ships, and receivedpassively by AIS because required data have to rely on

AIS transmitting from target ships. But the latter canprovide ships identity and voyage data automatically.As a VTS operator, facing the two sets of informationobtaining from ARPA radar and AIS what should beread first needs a careful consideration. It is necessaryto compare which of these two sets of data is moreimportant, useful and accurate for VTS.Although the effectiveness of receiving data isrelated to VTS location and ship pattern within the area,it is impossible to use the equipment in VTS for thecomparison, which must operate uninterrupted for navigationsafety. Therefore it was decide to complementthis study by means of experimental observation forobtaining a comprehensive understanding of the effectivenessof data from ARPA radars and AIS fitted in thebuilding of Merchant Marine Department (MMD), NationalTaiwan Ocean University (NTOU). In theobservation, two ARPA radars of JRC maker and twoAIS of Nauticast maker were used. The building facingocean is one mile east off Keelung VTS center. Shipsmoving within Keelung approaches can be scanned bythe ARPA radar and identified by the AIS fitted in thebuilding. Use of the equipments at NTOU provided aunique opportunity to compare present VTS operationsin Keelung harbor.

Wave lengths of the two ARPA radars were 3 cm

(X-band) and 10 cm (S-band) respectively. Therefore

during the period of the observation, screens of the two

radars were controlled in 6 miles and 24 miles

respectively. The maximum number of ship targets

detected by the ARPA radars was 6 in manual acquire,

and information including bearing, distance, course and

speed of three targets could be displayed each time. The

information was photographed at 6 minute internal by a

digital camera, and then keyed and stored in a computer.

Latitude and longitude of target position had to be

calculated according to its bearing and distance from

the known position of MMD building, as shown in Table

1.

One of the two AIS equipments was fixed in the

building, and another one was a portable. Both AIS

were connected with a computer. All received information

automatically transferred and stored in the computers

with ACCESS data base format, as shown in Table

2. Because the information of any target ship was received

every 2 seconds, the stored information was a

large quantity. There were many repeated information

or the information with small change for the same

target. Therefore the original files of the information in

data base had to be sorted out in accordance with the

MMSI of target ships. For the comparison with ARPA

radar information, each hour was divided into 10 time

points so that the information was read in 6 minute

Table 1. Example of ARPA radar information in the observation

Obs. no Time Latitude Longitude Bearing Dist. Course Speed

R0128001 2005/1/28 09:06:00 26.45001231 118.5283896 326 3.5 199 8.9

R0128002 2005/1/28 09:06:00 22.59564993 124.9850697 342 4.1 154 0

R0128003 2005/1/28 09:06:00 22.04544107 124.6067301 028 4.2 300 9.3

R0128004 2005/1/28 09:06:00 29.10156108 122.871236 051 4.1 118 2

R0128005 2005/1/28 09:06:00 30.18180072 120.946747 038 5.1 145 0.3

Table 2. Example of original AIS information in the observation

Index Time MMSI Navigational Position Longitude Latitude SOG COG True

status accuracy heading

1 2005/1/28 08:42:21 351056000 Default Low 121.752 25.148 0 150 241

2 2005/1/28 08:42:22 352388000 Under way Low 121.752 25.145 0 248 511

using engine

3 2005/1/28 08:42:23 416337000 Under way High 121.75 25.143 0 103 234

sailing

4 2005/128 08:42:23 538090053 Not under Low 121.73 25.334 0 229 96

command

5 2005/1/28 08:42:25 416207000 Under way Low 121.751 25.154 0 47 279

sailing

Table 3. Example of sorted AIS information in the observation

Index Time MSSI Lat. Long. Speed Course Heading Distance

2125 2005/01/28 09:00:00 1130504 121.778 25.149 0 0 511 0.549295003

2124 2005/01/28 09:00:00 215300000 121.724 252.0 12 51 130 3.9665911.6

2128 2005/01/28 09:00:00 309764000 121.617 25.368 16 269 227 15.86499307

2126 2005/01/28 09:00:00 351056000 121.752 25.148 0 178 241 1.063393154

2127 2005/01/28 09:00:00 352388000 121.752 25.145 0 284 274 1.116407184

3.1 Detection

Where a separate facility is provided for detection of targets, other than by the radar observer, it should have a performance not inferior to that which could be obtained by the use of the radar display.

3.2 Acquisition

3.2.1 Target acquisition may be manual or automatic for relative speeds up to 100 knots. However, there should always be a facility to provide for manual acquisition and cancellation: ARPA with automatic acquisition should have a facility to suppress acquisition in certain areas. On any range scale where acquisition is suppressed over a certain area, the area of acquisition should be defined and indicated on the display.

3.2.2 Automatic or manual acquisition should have a performance not inferior to that which could be obtained by the user of the radar display.

3.3 Tracking

3.3.1 The ARPA should be able automatically to track, process, simultaneously display and continuously update information on at least 20 targets, whether automatically or manually acquired.

3.3.2 If automatic acquisition is provided, description of the criteria of selection of targets for tracking should be provided to the user. If the ARPA does not track all targets visible on the display, targets which are being tracked should be clearly indicated with the relevant symbol* on the display. The reliability of tracking should not be less than that obtainable using manual recordings of successive target positions obtained from the radar display.

* Refer to IEC 872M : Marine Automatic Radar Plotting Aids (ARPAs)

3.3.3 The ARPA should continue to track an acquired target which is clearly distinguishable on the display for 5 out of 10 consecutive scans, provided the target is not subject to target swop.

3.3.4 The possibility of tracking errors, including target swop, should be minimized by ARPA design. A qualitative description of the effects of error sources on the automatic tracking and corresponding errors should be provided to the user, including the effects of low signal-to-noise and low signal-to-clutter ratios caused by sea returns, rain, snow, low clouds and non-synchronous emissions.

3.3.5 The ARPA should be able to display on request with relevant symbol* at least four equally time-spaced past positions of any targets being tracked over a period appropriate to the range scale in use. The time-scale of the past position plot should be indicated. The operating manual should contain an explanation of what the past position plots represent.


3.4 Display

3.4.1 The display may be a separate or integral part of the ship's radar. However, the ARPA display should include all the data required to be provided by a radar display in accordance with the performance standards for navigational radar equipment.

3.4.2 The design should be such that any malfunction of ARPA parts producing data additional to information to be produced bythe radar as required by the performance standards for navigational equipment should not affect the integrity of the basic radarpresentation.

3.4.3 The ARPA facilities should be available on at least 3, 6 and 12 nautical mile range scales, and there should be a positiveindication of the range scale in use.

3.4.4 ARPA facilities may also be provided on other range scales permitted by resolution A.477(XII) and, if provided, should comply with these standards.

3.4.5 The ARPA should be capable of operating with a relative motion display with "north-up" and "course-up" azimuth stabilization. In addition, the ARPA may also provide for a true motion display. If true motion is provided, the operator shouldbe able to select for the display either true or relative motion. There should be a positive indication of the display mode and orientation in use.

3.4.6 The course and speed information generated by the ARPA for acquired targets should be displayed in a vector or graphic form which clearly indicates the target's predicted motion with relevant symbols*. In this regard:


.1 an ARPA presenting predicted information in vector form only should have the option of both true and relative vectors. There should be an indication of the vector mode selected and, if true vector mode is selected, the display should show whether it is sea or ground stabilized;

.2 an ARPA which is capable of presenting target course and speed information in graphic form should also, on request, provide the target's true and/or relative vector;

.3 vectors displayed should be time-adjustable;

.4 a positive indication of the time-scale of the vector in use should be given; and

.5 if stationary targets are being used for ground referencing, this fact should be indicated by the relevant symbol*. In this mode, relative vectors including those of the targets used for ground referencing should be displayed when requested.


3.4.7 The ARPA information should not obscure the visibility of radar targets. The display of ARPA data should be under the control of the radar observer. It should be possible to cancel the display of unwanted ARPA data within 3 s.

3.4.8 Means should be provided to adjust independently the brilliance of the ARPA data and radar data, including complete extinction of the ARPA data.

3.4.9 The method of presentation should ensure that the ARPA data are clearly visible in general to more than one observer in the conditions of light normally experienced on the bridge of a ship by day and by night. Screening may be provided to shade the display from sunlight but not to the extent that it will impair the observer's ability to maintain a proper look-out. Facilities to adjust the brightness should be provided.

3.4.10 Provisions should be made to obtain quickly the range and bearing of any object which appears on the ARPA display.

3.4.11 When a target appears on the radar display and, in the case of automatic acquisition, enters within the acquisition area chosen by the observer or, in the case of manual acquisition, has been acquired by the observer, the ARPA should present in a period of not more than 1 min an indication of the target's motion trend, and display within 3 min the target's predicted motion in accordance with 3.4.6, 3.6, 3.8.2 and 3.8.3.

3.4.12 After changing range scales on which the ARPA facilities are available or resetting the display, full plotting information should be displayed within a period of time not exceeding one scan.

3.5 Operational warnings

3.5.1 The ARPA should have the capability to warn the observer with a visual and audible signal of any distinguishable target which closes to a range or transits a zone chosen by the observer. The target causing the warning should be clearly indicated with relevant symbols* on the display.

* Refer to IEC 872 : Marine Automatic Radar Plotting Aids (ARPAs)

3.5.2 The ARPA should have the capability to warn the observer with a visual and audible signal of any tracked target which is predicted to close within a minimum range and time chosen by the observer. The target causing the warning should be clearly indicated with relevant symbols* on the display.


3.5.3 The ARPA should clearly indicate if a tracked target is lost, other than out of range, and the target's last tracked position should be clearly indicated on the display.

3.5.4 It should be possible for the observer to activate or de-activate the audible warning signal.

3.6 Data requirements

3.6.1 The observer should be able to select any tracked target to obtain data. Targets selected should be marked with the relevant symbol* on the radar display. If data is required for more than one target at the same time each symbol should be separately identified, for example with a number adjacent to the symbol*.


3.6.2 The following data for each selected target should be clearly and unambiguously identified and displayed immediately and simultaneously in alpha-numeric form outside the radar area:

.1 present range of the target;

.2 present bearing of the target;

.3 predicted target range at the closest point of approach (CPA);

.4 predicted time to CPA (TCPA);

.5 calculated true course of the target; and

.6 calculated true speed of the target.

3.6.3 The display of the data in 3.6.2.5 and 3.6.2.6 should include an identification of whether the data provided is referenced to sea or ground stabilization.

3.6.4 When data for several targets is displayed, no fewer than two items listed in 3.6.2 should be displayed simultaneously for each target selected. If the items of data are displayed in pairs for each target, the groupings should be 3.6.2.1 with 3.6.2.2, 3.6.2.3 with 3.6.2.4, and 3.6.2.5 with 3.6.2.6.

3.7 Trial maneuver

3.7.1 The ARPA should be capable of simulating the effect on all tracked targets of an own ship manoeuvre with or without time delay before manoeuvre without interrupting the updating of target tracking and display of actual target alpha-numeric data. The simulation should be indicated with the relevant symbol* on the display.


3.7.2 The operating manual should contain an explanation of the principles underlying the trial manoeuvre technique adopted including, if provided, the simulation of own ship's manoeuvringcharacteristics.

3.7.3 It should be possible to cancel a trial manoeuvre at any time.

3.8 Accuracy

3.8.1 The ARPA should provide accuracies not less than those given in 3.8.2 and 3.8.3 for the four scenarios defined in appendix 2. With the sensor errors specified in appendix 3, the values given relate to the best possible manual plotting performance under environmental conditions of ± 10 ° of roll.

3.8.2 An ARPA should present within one minute of steady state tracking the relative motion trend of a target with the following accuracy values (95% probability values).

3.9 Connections with other equipment

3.9.1 The ARPA should not degrade the performance of any equipment providing sensor inputs, and the connection of the ARPA to any other equipment should not degrade the performance of that equipment. This requirement should be met whether the ARPA is operating or not. Additionally, the ARPA should be designed to comply with this requirement under fault conditions as far as is practicable.

3.9.2 The ARPA should provide an indication when any input from an external sensor is absent. The ARPA should also repeat any alarm or status messages concerning the quality of the input data from its external sensors which may influence its operation.

3.10 Performance tests and warnings

The ARPA should provide suitable warnings of ARPA malfunction to enable the observer to monitor the proper operation of the system. Additionally, test programmes should be available so that the overall performance of ARPA can be assessed periodically against a known solution. When a test programme is being executed, the relevant test symbols* should be displayed.


3.11 Sea and ground stabilization

3.11.1 The ARPA should be capable of sea and ground stabilization.

3.11.2 Log and speed indicators providing inputs to ARPA equipment should be capable of providing the ship's speed through the water in the fore and aft direction.

3.11.3 The ground stabilized input may be provided from the log, from an electronic position-fixing system, if the speed measurement accuracy is in accordance with the requirements of resolution A.824(19), or from tracked stationary targets.

3.11.4 The type of input and stabilization in use should be displayed.

Automatic Radar Plotting Aid

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