lustyd
Well-known member
Yes I get that. Safety backups take many forms, you know that. A three point fix being a specific requirement is borderline arbitrary. Is GPS mandatory?
UKHO backs down on paper chart withdrawal
- Thread starter dunedin
- Start date
capnsensible
Well-known member
Careful that you don't mix up equipment necessary to be carried with what's done with it! Don't think anyone has said a three point fix is a specific requirement. But the necessary tools are available should it be required.
ylop
Well-known member
or an appropriate paper chart -UKHO were/are not the only provider.
No need to have a supply issue if everyone switches to Imray, simply show the sales stats and you will have been right all along.
I remain convinced that a “print on demand” service is viable (certainly by post but probably in chandleries) using the digital data that UKHO were planning to still have for electronic plotters.
NormanS
Well-known member
It's people like us who don't buy new charts, who are causing the problem.
Yes, the detail and the art work on some of these old charts is fantastic. I think of a beautiful little sketch of the Falls of Lora, at the entrance to Loch Etive. These charts are literally "works of art".
capnsensible
Well-known member
MGN 280 (M) 18.3.2 answers you question. Yes for vessels operating more than 20 nm from land.
Required under a different list of equipment to be provided on traing vessels operated by Recognised Training Centres.
Required under a different list of equipment to be provided on traing vessels operated by Recognised Training Centres.
st599
Well-known member
"The ship's position shall be derived from a continuous positioning system of an accuracy consistent with the requirements of safe navigation."
"Provision shall be made for the connection of two or more position fixing devices from which the ship's position can be independently and continuously derived."
"It shall be possible to display an adequate number of points, free movable electronic bearing lines, variable and fixed range markers and other symbols as may be required for navigation purposes and specified in APPENDIX 3"
And that's not touching on the self test, self backup and power requirements.
For coding you either have paper charts from an MCA recognised agency in all required scales or you have an ECDIS (designed for the bridge of a merchant ship) or if under 24m a mini ECDIS (designed for the bridge of a trawler and published by the UK Sea Fishing organisation). There's no real option for yachts which don't run engines all the time.
Last edited:
st599
Well-known member
But for many areas, only UKHO provided charts, Imray don't.
Not an MCA recognised chart agency - so no good for coded vessels
john_morris_uk
Well-known member
Remember them! I’ve still got some. In fact one or two of the folios that I have for our current Caribbean sailing adventures still have a couple of fathoms charts in them!
zoidberg
Well-known member
I believe it used to be part of an RN midshipman's training. The 'wooden wall' ships of the line spent a lot of time in fleet anchorages e.g. Malta, Naples.... and a boy sailor would get up to mischief if not busy and occupied. He'd be encouraged, then coached, to sketch the scenes accurately, with a developing eye for the details a mariner would need to see when approaching said anchorage under sail. That also encouraged thinking in 3 dimensions, in cable-lengths ( 600' ), and ranges of guns.
That would be valuable when, later, he'd take a pulling-cutter into an unknown bight to take soundings on transits and prepare a pilotage chartlet to help identify a safe approach and anchorage.... complete with shoals, rocks awash, and so on.
That's exactly what Lt/Col Ewen Southby-Tailyour did when commanding a detachment of 'Royals' some time before the Argentinian invasion. His pilotage notes became the 'Falkland Islands Shores' and made a major contribution to the success of the Task Force landing and the insertion of Special Forces.
That would be valuable when, later, he'd take a pulling-cutter into an unknown bight to take soundings on transits and prepare a pilotage chartlet to help identify a safe approach and anchorage.... complete with shoals, rocks awash, and so on.
That's exactly what Lt/Col Ewen Southby-Tailyour did when commanding a detachment of 'Royals' some time before the Argentinian invasion. His pilotage notes became the 'Falkland Islands Shores' and made a major contribution to the success of the Task Force landing and the insertion of Special Forces.
AntarcticPilot
Well-known member
Sadly, maps of the Falkland Islands that were current when I was last there (2010) are not really up to modern standards; I think they were based on 1950s and 60s surveys. My former employer has offered to do survey work but unfortunately, up until 2011 (when I retired) the Falkland Islands Government had not been able to find the necessary (substantial) funding. I think that they have done some local surveys since then, but no comprehensive mapping to modern standards. The existing maps are not bad, but lack detail, and are referenced to a local survey datum rather than to a global one, as far as I recall. But I am out of touch with the current status.
In any area like that, the sheer cost of mapping is a problem. To survey an area the size of the Falklands requires the following:
- An aerial survey taking vertical air photos at a suitable scale and overlap.
- At least some ground control points, though these are less essential than they were, as the photocentres are fixed using high precision differential GPS in the aircraft. But at least a few are still required to produce the best results with the highest confidence.
- Analysis of the air photos to:
- Align the aerial photos (this is a complex, 3 dimensional problem - if anyone is interested, look up bundle adjustment). Usually a semi-automatic task, but still requires human input.
- Extract features of interest - generally a manual task.
- Extract surface elevation data - mostly automatic, but does require human checking.
- Carry out cartographic work to use the data from 3 to construct maps that are useful and carry the required information.
2 is probably the cheapest bit, but you need ground control points at locations that may be difficult to access, so it may be surveyor-days of effort to obtain a few control points in suitable locations. Identifying suitable locations is a non-trivial task; they need to be clearly identifiable and precisely locatable from the air. Old surveys tend to be unusable because they concentrated on peaks for intervisibility; peaks have very poor visibility in aerial photos. Things like abrupt changes in shorelines, small isolated islands, etc. are more useful.
3) Many person-hours of highly skilled labour are required here.
4) Ditto!
Finally, there is opportunity cost - time spent by an organization doing survey work in the Falklands is time NOT spent doing survey elsewhere.
Producing modern maps of a place like the Falklands would cost 7 figure sums, even if done by a non-commercial organization.
AntarcticPilot
Well-known member
As far as I know - and I may be out of date - the problem arises because of the sheet-centred nature of the data. Many charts are the subject of international agreements to share data, and these agreements work on a sheet by sheet basis. There are also issues to do with Chart Datum; managing things on a sheet-by-sheet basis means that a sheet can apply the same chart datum across the whole sheet, but an adjacent sheet may have a different datum. As the datum is usually LAT, it does differ from place to place. There are even a few charts (the River Thames comes to mind) where I understand the datum changes within a sheet, but that's exceptional. There are also issues to do with the scale of the data - you have very detailed and frequently updated data in (say) the vicinity of major ports and shipping lanes, and much less detailed data in areas like (for example) the Southwestern Approaches. Handling data of widely differing scales in a single database is non-trivial (I've had to do it for Antarctica) and requires very careful rules about what to do when more detailed data impinges on less-detailed data.
Later addition - another scale-related issue is depth contours. Less detailed charts will not have such detailed contours as more detailed ones (obviously!) But what do you do where the two types of chart meet? The contours are highly unlikely to join, and it generally takes human intervention to make them do so. Unfortunately, that is a very error-prone process - I was still finding errors of that nature in the Antarctic Database I managed, 20 years after its original creation! Also, contours may not be at the same interval on more or less detailed charts.
On shore, the OS use a single vertical datum for the whole country, and a generally uniform scale of base mapping (it differs between rural and urban areas, but only by a factor of two). This makes producing custom maps around a specific point both possible and relatively easy.
Last edited:
Sandy
Well-known member
True, but as a percentage of leisure craft the number of coded boats is tiny. For everybody else NV is an option.
dunedin
Well-known member
Only if you only sail the Englush Channel, for UK based boats
Sandy
Well-known member
I'm currently based on the La Manche, but enjoy heading
zoidberg
Well-known member
Part of my day job nearly 5 decades ago and before GPS, involved me being hands-on in doing all 4 of the above. The purpose being to generate 'photo-strip maps' using product from #1 which it made it practicable to fly low-level ( below radar ) strike missions against targets in otherwise ill-mapped terrain. One such was over 300nm long.
The 'photo-strip maps' thus produced were very crude - but they were sufficiently valid for the intended purpose.
The other mapping source was 1:500,000 Topographical sheets from the US - essentially useless.
AntarcticPilot
Well-known member
To be fair, USGS mapping in Antarctica is some of the best. But for the USA it doesn't even come close to the quality of OS mapping. I think - vague recollection - that the USGS did initiate a country wide aerial photo campaign, but I've no idea whether it actually happened.Part of my day job nearly 5 decades ago and before GPS, involved me being hands-on in doing all 4 of the above. The purpose being to generate 'photo-strip maps' using product from #1 which it made it practicable to fly low-level ( below radar ) strike missions against targets in otherwise ill-mapped terrain. One such was over 300nm long.
The 'photo-strip maps' thus produced were very crude - but they were sufficiently valid for the intended purpose.
The other mapping source was 1:500,000 Topographical sheets from the US - essentially useless.
For those who ask, "Can't you just use satellite imagery", the answer is yes and no. You can use it for feature mapping, and you can extract elevation data from it. But in the latter case, the accuracy is low. Also, high resolution (metre scale) satellite images are expensive, though cheaper than aerial photography.
MADRIGAL
Active member
Seven Spades
Well-known member
Th only charts I now use are those for passage planing and offshore passages.
dunedin
Well-known member
The “digital data” that the UKHO holds is all in vector format, per the international standards for IHO chart data. It needs both computer and skilled human intervention to convert into the raster images that can be Printed on Demand as paper charts.
As the UKHO has already largely outsourced physical printing to third parties, it is presumably the cost of creating the raster chart images that UKHO was trying to save in their original announcement (which was all about cost saving).
Though not mentioned in the original announcements, I believe the UKHO intention is/was to discontinue the electronic raster charts as well, hence it was the Print on Demand paper chart service that was proposed to be discontinued by 2026 (now 2030).