RTCM Paper 036-2014-SC119-174

Radio Technical Commission for Maritime Services

1611 N. Kent St., Suite 605

Arlington, Virginia 22209-2109

www.rtcm.org

Telephone: +1-703-527-2000 Telefax: +1-703-351-9932

February 19, 2014

SUMMARY RECORD

Meeting of RTCM Special Committee 119

Maritime Survivor Locator Devices (MSLDs)

Times: 9:30 a.m. – 11:00 a.m. and then 1:30 p.m. – 3:30 p.m.

Date: Thursday, December 12, 2013

Location: RTCM Headquarters, Arlington, VA

1  Call to order, introduction of attendees, and approval of agenda

Kerry Greer was not available to chair the meeting, so Chris Hoffman took on the role of acting chairman. He called the meeting to order and those present and on the teleconference introduced themselves. The agenda (paper 236-2013-SC119-168) was amended to add consideration of the MRT submissions (new agenda item 5). However, Neil Jordan requested that a paper they submitted to SC110 on testing with lifejackets also be considered under Other Business if there is time (paper 248-2013-SC119-172)

The Chairman then asked if anyone participating in the meeting had knowledge of their own or other organizations’ patents, including published pending patents, the use of which may be required to practice or implement the standard(s) being considered. There were no affirmative responses, noting that several were already identified in the standard, and in particular, no one knew about any patents involving AIS-MOB devices.

Those participating in the meeting are listed below:

Chris Hoffman,
Acting chairman / ACR Electronics, Inc. / +44 (0)1489 880326

Eric Hiner
(by teleconference) / Astronics / DME Corporation / +1 954 975-2258

Joseph Landa
(by teleconference) / Briar Tek Inc. / 703 548-7892 ex 202

Doug Ritter / Equipped to Survive Foundation / +1 480-598-1501

Glenn Dunstan
(by teleconference) / MRT Beacons / +61 408018291

Neil Jordan / Orolia Ltd. / +44 2392 623934

Joel Faul / Orolia Ltd. / +1 858-458-8110

Bob Markle
/ RTCM / 703 527-2000

Marty Jackson / USCG (CG-ENG-4) / +1 202 372-1391

Edwin Thiedeman / USCG (CG-SAR) / +1 202 372-2083

LCDR Aaron Ortenzio / USCG (CG-SAR-2) / +1 202 372-2089

2  Note – there are no minutes from previous meetings to review / approve

3  Overview of key differences between the Draft ETSI AIS MOB standard ETSI EN 303 098-1 V1.1.0 and the current RTCM 11901.1.

.1  Report on outcome of ETSI AIS MOB Comment Resolution Meeting, paper 232-2013-SC119-164

The paper was reviewed, but it was noted that a lot of it had been overtaken by events.

The leap second issue was briefly discussed with no conclusion.

.2  RTCM request for clarification of issues from IEC TC80 WG15 and response from WG15, paper 233-2013-SC119-165

IEC TC80 WG 15 believes that test transmissions should only take place when a GPS position has been determined, however live transmissions should continue even if GPS signals are lost with the last known position. The former of these recommendations is currently in conflict with the RTCM AIS MOB standard, which might be a change that we need to make to bring it into line.

The leap second issue was discussed by WG15 also. They observe that if the device does not have the correct leap second correction, the transmission might be off by one-half an AIS slot boundary until the GPS ephemeris data is obtained – potentially 12.5 minutes worst case assuming GPS ephemeris data is successfully received.

.3  ETSI Liaison Statement to ITU WP5B, paper 234-2013-SC119-166

(See next paragraph)

.4  Response from ITU WP5B, paper 244-2013-SC119-169

This liaison statement from ITU is in response to the request from ETSI (see paragraph .3 immediately above) it states that unsynchronized MOB device transmissions should be acceptable, in contrast to the ETSI position, due to the small coverage area and resulting minimal impact on the VDL. It also states that TEST transmissions should only occur when synchronized but ACTIVE transmissions should continue, even if synchronization is subsequently lost. This position is aligned with that of IEC TC80 WG15 as presented in paragraph 3.2 above.

4  Status of ITU Draft New Report, “Maritime survivor locating systems and devices (man overboard systems) – An overview of systems and their mode of operation”, paper 235-2013-SC119-167.

The paper can appear to be inconsistent, but it is an amalgam of inputs from various sources. It is a report on the current state of affairs, it is not a Recommendation or Standard at this time and is unlikely to become one in its current form. It has been sent to Study Group 5, which is expected to approve and publish it as a Report for information purposes. It is currently unclear if WP5B will continue to work on this subject and attempt to develop an MOB Recommendation and if so what types of MOB technology this would address.

5  MRT proposed changes to 11901.1 (papers 253-2013-SC119-170 and 254-2013-SC119-171)

Mr. Dunstan gave a summary of the first of these papers which discusses some of the differences between the ETSI and RTCM MOB standards and some of the points that came out of the IEC and ITU liaisons, he concluded by saying that the paper then goes on to support justification of the proposed changes in the second paper. Mr. Dunstan then introduced the second paper which proposes changes to the DSC Annex in RTCM 11901.1. He explained that the current version of the MSLD standard initially provides the alert to “own ship” (closed loop), then after a period of time, it switches to “open loop”. MRT now proposes that the device operates in “open loop” mode from the start as they understand that the U.S. Coast Guard no longer objects to this type of operation. The original concern was due to possible high rates of false alerts, but since the DSC transmission is clearly identified and of somewhat limited range, that concern is reduced, while open loop operation enables other vessels nearby to assist from the start. In addition removing the closed loop operation phase simplifies moving Alerting Units (AU) between vessels because reprogramming is not required.

There was a discussion on how an acknowledgement (ACK) cancels an alert. Mr. Landa said that one ACK may not be sufficient because of the low position and shielding of the antenna of an AU. Mr. Dunstan agreed that one ACK might not shut the AU down, but it is just a matter of sending additional ACKs to do this.

There was also a discussion on operating temperature range. Although salt water freezes at -2°C, the AU might be used well out of water (e.g. on a lifejacket exposed to lower air temperatures), so the committee felt that the -20°C criterion currently in the specification was appropriate. A question was asked as to why the operating lifetime was twelve hours rather than six to which it was stated that this was so that there would be a higher probability that the device would be operating in daylight at some point to aid SAR services.

6  Having reviewed the above discussion on whether RTCM needs to make any changes to its MSLD standard 11901.1

AIS issues – Appendix E:

The differences between the current version of the draft ETSI AIS MOB standard and the RTCM Appendix E were discussed. It was agreed that the RTCM 30 second time to transmit requirement did not need to be changed. The ETSI requirement is currently to transmit within one minute, so there is no conflict.

The allowance in E.3.8.1.1 to begin transmission unsynchronized was discussed. It is highly likely that an AU will not have a GPS position and time right away, so unsynchronized transmissions must be allowed at first, thus currently it was agreed that no changes were needed here. However it was suggested that we could add a footnote to the standard to help understanding along the following lines “Note that synchronization with UTC may be off by one second due to GPS leap seconds if the GNSS receiver has not downloaded an almanac from the satellites since insertion of a leap second.” Nevertheless, we need to understand this process better and what ETSI plan to do at their next meeting before making any changes.

As the provision in E.3.8.1.2 allowing test messages after 5 minutes even if COG, SOG and time have not been obtained, would now appear to be in conflict with IEC and ITU advice, it was considered prudent for RTCM to consider changes here to bring this feature into agreement with the latest advice from ITU.

Finally the RTCM standard currently does not make any reference to leap seconds, especially in section E.4.5.1.6, again it was considered prudent for RTCM to consider changes here to highlight this issue and possible ways to overcome it.

DSC issues – Appendix A:

The committee reviewed the proposed changes in paper 254-2013-SC119-171 to allow just “open loop” operation and remove “closed loop” as we understand that the U.S. Coast Guard now supports this mode. This results in the removal of the “closed loop” text in section A.3.7, a number of revisions to Table A.1 and the deletion of section A.3.8. The committee reviewed the proposed changes and made a number of minor amendments to Table A.1, the remaining changes were agreed as proposed.

Mr. Landa stated that he would like to have more time to consider the changes and better understand the effects of ACKs received or not received. He questioned how we expect people to react in these situations and how well the theory that the ACK will turn the device off actually works in practice? Mr. Landa stated that he felt this was a significant issue that needed further careful consideration. Mr. Dustan responded that all we are doing is moving forward the time that open loop operation begins, the operation at that point remains the same.

It was decided to send out the revisions in a Committee Draft for comment, rather than voting. In parallel we would ask MRT to see if there has been any real-world or trials experience with this mode of operation.

7  Action items

Participants are asked to investigate downloading of leap second information in the GPS almanac with respect to how long it takes and to report back.

Chris Hoffman to determine when IEC 61162-1 GPS sentences are transmitted what happens to the UTC time if you don’t have the UTC time.

Glenn Dunstan to determine if there is any MRT or Australian real-world or test experience with the open loop operation and acknowledgements.

Neil Jordan to draft a liaison statement to ETSI regarding antenna testing on lifejackets. (See paragraph 8 below)

Chris Hoffman and Bob Markle to develop and circulate Committee Draft for comment.

8  Other business

The committee looked at paper 248-2013-SC119-172 which considers performance of antennas mounted on lifejackets. Orolia suggested that the test methods currently proposed by ETSI would introduce errors that are not representative of this application (i.e. an MOB device on an inflated lifejacket at sea). Neil Jordan suggested that we provide a liaison statement to ETSI on this matter, explaining the limitations of their test “salty man” method. We should point out how we are working on improving the RTCM test methods.

9  Date and venue for next meeting (if required)

Tuesday March 4, 2014, from 09-30 to 11-00 AM at the RTCM offices in Arlington, VA.

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