Shipspotters all over the world => Site related news, functions and modules => Topic started by: davidships on August 03, 2018, 11:13:32 pm

Title: LR/IMO numbers on older vessels
Post by: davidships on August 03, 2018, 11:13:32 pm
On a member's photo a discussion has arisen about LR/IMO numbers for vessels whose existence ended 1963-1998, and therefore had a unique LR number, but with only 6 digits.  It is more appropriate to discuss this here where it can attract wider viewing and contributions, so I am moving it from
Bjørn Knudsen on Aug 01, 2018 15:46 added ship info, including "LR/IMO No: 5373335"
Phil English on Aug 01, 2018 15:56     
5373335 is not a valid IMO number. It might be a Miramar ID number, or something else. The vessel was scrapped at around the time the 7-digit LR number was introduced, so probably never had an IMO number.  I'm sorry, but can we please stop putting IMO numbers in comments unless they are properly checked?
davidships on Aug 01, 2018 19:22    
5373335 is a compliant 7-digit LR number (as correctly noted by Miramar). Added
simonwp on Aug 02, 2018 08:46    
The IMO# is correct. When the IMO#'s were introduced, vessels already in service adopted their LR# as their IMO#. Which is what happened with this vessel. Maybe it's comments that need to be checked before they are posted!!!!!!!!!!!
Bob Scott on Aug 02, 2018 09:27   
This ship of course never had an IMO number but it did carry the six-digit Lloyd's Register number 537333. If it had survived long enough to have a seventh digit added, it would have been a 5. That would have eventually become IMO number 5373335
Phil English on Aug 02, 2018 09:40    
I knew I was right, Bob. I don't wish to prevent people being helpful, but ships either have a 7-digit IMO number or they do not. If wishes to issue guidance (maybe it has?) on how to treat vessels which never had an IMO number, but had a 6-digit LR number, then I will gladly shut up!
and my conclusion:
Well, let's all draw breath.  This one is a little odd.

There is no doubt that the 6-digit unique LR number was 537333.

Also it is apparently also true that the ship does not appear in the 1969-70 LR, because LR knew she had been scrapped (of course there were many ships that no longer existed in 1969 that got 7-digit LR numbers because LR did not know they had gone - but this is not one of those).

Miramar's practice is to adopt 7-digit LR/IMO numbers as their internal ID where they exist, and create their own internal 7-digit numbers where they don't.  In practice, for vessels with only unique 6-digit LR numbers (issued 1963-1998) Miramar created their own 7-digit numbers by simply adding "5" at the beginning.  These numbers are not consistent with IMO numbers (though approximately one in 10 will produce an apparently correct check digit).

Left to their own devices, Miramar would have given this ship the ID 5537333, but they do think that 5373335 is actually a LR number (and specifically say so on their site).  Their source, perhaps indirectly, is likely to be from the preparatory work under way by LR during 1968.  So we are in a grey area here.

That's the immediate background to this discussion and now preserved here rather than on one photo contribution (and the "IMO number" left there for the time being).  

Title: Re: LR/IMO numbers on older vessels
Post by: davidships on August 03, 2018, 11:14:43 pm
We do not need to dwell further on the particulars of the case above/below, but can address the broader question about ships that did get unique LR numbers, but only six digits because they did not survive to 1969.  This has been discussed before, perhaps on this forum, but certainly in the Admin Forum in 2015, though I cannot recall the outcome.  At present I cannot access any forum threads before some time in 2017 due to the still-unresolved problem of Tizermedias diversions, but for Admin colleagues' reference it is at,14400.0.html (,14400.0.html).  

Strictly speaking 7-digit unique "IMO numbers" only came into existence on 1/1/1996, but as IMO adopted the existing Lloyd's Register numbering system, this covers all vessels that have appeared in LR from 1969.  In my view all those numbers can be considered as LR/IMO numbers, and that has been our practice for some time.  I am not aware of any objection to that.

The question at hand concerns that ships that had unique 6-digit LR numbers allocated to all existing ships in 1963, and to those added prior to 1969, when the seventh so-called check digit was added at the end.  Those numbers are in principle part of the same series as the later numbers, but LR did not see any point in adding the extra digit as the Register only covered vessels then current.  Prior to 1963 there was no global unique (ie, cradle-to-grave) numbering system in LR or, so far as I know, elsewhere.

Apart from being factual staments, we use IMO numbers for the important practical tank of linking all the images of specific ships regardless of what name they are carrying at the time, or the category that the images are in.  This facility is much valued and works well, but it is limited to those ships that have such numbers (excluding therefore virtually all warships and smaller fishing boats, work-boats, tugs etc and a large proportion of motor yachts as well as all vessels out of service by 1969.

So (with apologies for going on at such length), views are welcome on that.

Title: Re: LR/IMO numbers on older vessels
Post by: pieter melissen on August 04, 2018, 06:45:45 am
David, for this site, as you state correctly, having a unique number is essential for a number of functions. To me it is of less importance whether that is a "correct" IMO number or anything else. As long as it is really unique, there can be no confusion about which ship we are talking about. Therefore, while covering an interesting point in the history of the LR/IMO numbers the first post in this thread has only academic value as far as the site is concerned. I think in respect we cannot praise MIRAMAR enough for the work they did to get their files organised, and I have absolutely no problem with using their number as a proxy IMO number if needed. It helps us, it helps the site and the site community, even though some of us know that it might be technically incorrect.

In short, be practical, make use of the options and live with the incorrectness.

Perhaps there are people brave enough and with enough free time to sest up a numbering systeem (7-digits?) for the ships that can now not be covered in the site retrieval systems, but as these comprise categories in which I have very little interest, I am not volunteering.

Title: Re: LR/IMO numbers on older vessels
Post by: Bob Scott on August 05, 2018, 08:10:38 am
The seventh or “check” digit in an LR/IMO number is computed by an algorithm from the sequential first six digits such as were used in the original LR unique numbering system.
The formula is as follows, using LR no. 537333 as an example
Multiply the first digit (5) x 7 = 35; the second digit (3) x 6 =18; the third (7) x 5 = 35; the fourth (3) x 4 = 12; the fifth (3) x 3 = 9; and the sixth (3) x 2 = 6.
Then add together the units in each result (5 + 8 + 5 + 2 + 9 + 6) = 35. The unit from that result (5) is the check digit, making the final, seven digit number 5373335.
Any LR/IMO number can be checked in this way or the algorithm can be used to add the would-have-been seventh digit to old LR numbers.

Title: Re: LR/IMO numbers on older vessels
Post by: pieter melissen on August 05, 2018, 09:23:05 am
Bob, thank you for the explanation, it is beyond me why it had to be so complicated, but the issue was rather why we cannot use numbers that "look" like IMO numbers, but will fail the test. (as Miramar obviously does). As long as they are unique, I am fine with that. Lloyds Register is not the Bible, although they sometimes disaggree with that.

Title: Re: LR/IMO numbers on older vessels
Post by: Bob Scott on August 05, 2018, 10:04:50 am
Pieter, I know you have a less than enthusiastic view of Lloyd's Register but, in the absence of anything else that is better and widely accessible, LR will have to be the nearest thing to "the Bible" for our situation

Title: Re: LR/IMO numbers on older vessels
Post by: davidships on August 05, 2018, 11:47:03 am
Just for info at this point:

There would be a couple issues with using Miramar serial numbers:
1) some IMO numbers being issued (eg yachts in the 1------ series) have already been used by Miramar for other vessels - though I have a hunch that Miramar is changing those existing numbers as those come to light - which raises a question in itself about reliability
2) about one tenth of Miramar's internal numbers are compliant with the IMO number formula, including the 55----- numbers converted from 6-digit LR numbers) and could well be issued as IMO numbers in the future.

The Miramar number set may be subject to copyright, and in any case permission would be required to use it (not that I would expect any resistance from Rodger Haworth).

On the subject immediately to hand, we could stretch our own definition of "LR/IMO number" to include the 1963-1968 unique numbers - there are not very many of them and they could be constructed as and when required. I understand that these numbers will not in future be issued to new ships.

If we are talking more broadly, applying unique numbers to vessels which currently do not have 7-digit LR/IMO numbers nor appear in the Miramar database, would be a mammoth task.    They would have to be called something other than "IMO number". And members would not be able do anything beyond copying numbers already used for the same vessel - there would be no external database to refer to.

I think that it is unlikely that any development that involved software changes to the site could be achieved in the short term.

Title: Re: LR/IMO numbers on older vessels
Post by: OceanCraft on August 05, 2018, 06:21:18 pm
At OceanCraft we have constructed our own database to remove the confusion over IMO numbers.  We always work with the six-digit number as the key field in the database regardless of whether it is an LR number or an IMO number.  This is a problem with the Miramar database in that they chose to use the seven-digit IMO as a key field and then were stuck when they came to the six-digit numbers.  They chose to add a 5 at the beginning of the number as the 55xxxx series of numbers was not used.  This then causes problems within the ShipSpotting website as some posters choose to use the Miramar version and other use the six digit (IMOised) with a check digit at the end which is not strictly correct (and which is the point raised by Phil English).

From the OceanCraft database, the six-digit series appears to be in two primary groups, 50xxxx series and 54xxxx series.

The 50xxxx series (six-digit IMO) introduced in 1963 was applied to the list of ships in Lloyds in alphabetical order of the ship's name it carried in 1963.  This series ranged from 500001 to 539965, so this covers almost 40000 ships.

The second series of 54xxxx was used and this appears to be for ships built in 1963 after the application of the 50xxxx series and ships which experienced a name change in 1963.  This runs from 540001 to around 542950, so about 2950 ships and is applied in five alphabetical A-Z groups.  The only explanation we have for this is that the 50xxxx series was implemented in, say, July 1963 and the 54xxxx series was applied at the end of each month remaining in 1963 to those ships which either entered service or changed name within that month.  From 1964 the 64xxxx series was used.

Every number of both series was used and covers all ships extant in 1963.

There is evidence of 56xxxx, 57xxxx, 60xxxx series, (and possibly 61xxxx series, but this could be another Miramar 'invention') but we are still collating and evaluating these.

We hope the above info will be of some use but we do not know what the solutions is for the ShipSpotting website.  It is looks as if ShipSpotting is a gallery of photos trying to have some structure without a database, where it really needs to be a database with structure linking to a gallery of photos.  Discuss.

OceanCraft Models (

Title: Re: LR/IMO numbers on older vessels
Post by: simonwp on August 05, 2018, 07:12:23 pm
My personal preference would be to forge some sort of link with Miramar, and use Miramar not only for IMO / Unique vessel#'s, and also for classifying vessels. It won't be 100% perfect, but it's probably the best option available. If the site rules direct members to Miramar as their source of information, then at least there will be an element of consistency, even in the cases where it is not 100% correct. It would also eliminate the problem of different admins using different sources of information for both IMO#'s and vessel classification, and sometimes making incorrect changes. However, as we know, Miramar is a subscription service, which may be a problem for some, and make it difficult to have a formal tie in.

Title: Re: LR/IMO numbers on older vessels
Post by: Bjørn Knudsen on August 05, 2018, 09:02:10 pm
Here is a link where you can try it out yorself about IMO numbers.

Title: Re: LR/IMO numbers on older vessels
Post by: pieter melissen on August 06, 2018, 06:20:28 am
Quote of Oceanquest "It (is) looks as if ShipSpotting is a gallery of photos trying to have some structure without a database, where it really needs to be a database with structure linking to a gallery of photos. "

There used to be a connection with a database, Gross Tonnage, but they ceased to operate a couple of years ago. The data supplied below each picture on SS are still from them. As they stated themselves before their demise, they were focussing on "interesting ships", and they declared older ships as "not interesting", hence the sometimes rudimentary information on ships that ceased to exist a long time ago. Unfortunately it has not been possible to find a replacement database for Gross Tonnage, which more and more results in data om new ships being incomplete. This is another problem than the IMO number, but also here the way to go could be Miramar. In my ideal world Shipsspotting would be something like an illustrated Miramar, and if that would imply using their numerical systems, let it be that way, as long it it helps Shipspotting to have easy access to all photo's of one unique ship, irrespective under which name the pictures were posted.

The category system on Shipspotting is much more advanced than that on Miramar, so that either would have to be sacrificed, or being maintained manually with the first input coming from the poster with correctors to check that.   

Title: Re: LR/IMO numbers on older vessels
Post by: simonwp on August 06, 2018, 01:13:55 pm
Pieter, I've said this before, but I think the category system on Shipspotting is TOO advanced. It is too complicated and needs to be simplified, so going down the Miramar route might solve two problems at once.

Title: Re: LR/IMO numbers on older vessels
Post by: Pilot Frans on August 08, 2018, 10:41:42 am
Intresting to know I how the IMO/LR was put in force and how to calculate the check digit.

But I think the main purpose of the numbers is that you can trace back the vessel, during her/it's lifetime.
By putting in the IMO-field number multiple pictures are linked. This gave me (and others) a good view of the lifetime and namechanges through the years.

So in my opion it doesn't matter which number is used as long as it is an unique number.

I'm not familiar with Miramar, but if they have such unique number, that's fine to deal with. So it's easier to find picture of a unique ship


Title: Re: LR/IMO numbers on older vessels
Post by: davidships on November 29, 2018, 12:43:58 pm
This discussion rather faded without leading to any definite conclusion, but was revived in photocomments yesterday with following:
adenanthos on Nov 28, 2018 21:42    
Who cares about the fact that 5607782 is not an official valid IMO number, we only use this Miramar number in order to group all the photo's together, not everyone will now be aware that there are several nice other pictures of this vessel on the site.
This same discussion was made some time ago on this forum and it was then agreed to allow it this way only for reasons of getting the same photo's of a certain vessel together.
After all "Shipspotting" is not an official Government or Maritime institution.
May be we should add "Miramar" to the IMO/LR entry
pieter melissen on Nov 29, 2018 10:12    
Adenanthos, agreed...

Views from more members are welcome.  I am also asking Admin colleagues for their views on the technical aspects.

Title: Re: LR/IMO numbers on older vessels
Post by: Pier Master on November 29, 2018, 02:34:59 pm
I like this part, "we only use this Miramar number in order to group all the photo's together", makes perfect sense to have some sort of central reference point. The IMO/LR or whatever else you want to call it does exactly that.

Perhaps we could get the same from the ENI number...

Regards, Brian.

Title: Re: LR/IMO numbers on older vessels
Post by: Bob Scott on January 16, 2019, 11:06:20 am
With so may Miramar/Non-IMO numbers appearing on the site nowadays, is't it time for Admins to clarify the site rules on the subject? 
Do we use Miramar ID or not and wouldn't there be a copyright problem if we did?

Title: Re: LR/IMO numbers on older vessels
Post by: davidships on January 16, 2019, 11:35:06 am
I am in touch with Rodger Haworth about this.


Title: Re: LR/IMO numbers on older vessels
Post by: Tom Walker on January 16, 2019, 01:37:31 pm

I know this has been discussed fairly exhaustively in the past, but I would prefer to use the LR/IMO option as this is in wide spread use for current shipping.  I have an interest in researching my Father's photographs, many taken in the 50s and 60s, and some even older so am well aware of the historic limitations of IMOs.  I feel that making the Mirimar Number the standard only signifies a preference to 'look backwards' and may not attract the younger element.  This is my personal view and not intended to complicate the discussion.

Thanks you - best regards


Title: Re: LR/IMO numbers on older vessels
Post by: 3SX on January 18, 2019, 05:08:31 am
Need take a note that a lot of ships scrapped at 70-s/80-s and some even at the end on 60-s which of cause never had an official IMO number are in ship's data bases under LR number as most data bases constructed on LR's data.

So, exempting the IMO/LR number to a separate log on the site will be shown as the Miramar number etc. it will loose ship details for many ships with a number beginning by 9, while keeping data base for both logs will collapse the idea, and that looks unworkable.

Another point, that's  impossible to define is it LR number or just the Miramar for numbers beginning by 9 unless compared with LR's data but that's unworkable for a simple site user.

Still the Miramar alternative could be used for CARGO ships beginning with numbers other than 9 including those with 3-4 digit numbers only.

Also, it could be a solution to have a link or a note on the site explaining IMO number and its use, for example: " IMO number is valid for ships existed after the year 1987, otherwise is the LR number" , also to rename IMO log to a LR/IMO log will be correct in fact.

Regarding to split IMO/LR numbers is more unrealistic idea as will need to process sub million photos to revise i.e. all ships deleted before the year 1987 at least  :)