Reply
 
Thread Tools Search this Thread
 
Old 06 April 2012, 23:47   #11
Member
 
Country: UK - England
Town: London, Kent and Brittany
Boat name: Cameo
Make: Redbay Stormforce
Length: 6m +
Engine: 200hp Suzuki
MMSI: 235067011
Join Date: Aug 2005
Posts: 101
So back in the day we used to do a lot of GIS work, and although Raster Maps were great, they took up LOADS of room compared to the vector equivelant.

I'd also go with both, do your planning on the charts and then wack it into the GPS / Homeport. I'm sure as time goes on the vector maps will get there (and there nearly there now). But theres nowt like pouring over a chart!
__________________

__________________
horacebat is offline   Reply With Quote
Old 07 April 2012, 07:13   #12
RIBnet supporter
 
Pikey Dave's Avatar
 
Country: UK - England
Town: South Yorks
Boat name: Black Pig
Make: Ribcraft
Length: 5m +
Engine: DF140a
MMSI: 235111389
Join Date: Feb 2008
Posts: 7,590
RIBase
Quote:
Originally Posted by horacebat View Post
. But theres nowt like pouring over a chart!
Aye, don't you just hate it when that happens
__________________
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: See rule#5
Pikey Dave is offline   Reply With Quote
Old 14 April 2012, 12:35   #13
RIBnet supporter
 
Copinsay's Avatar
 
Country: UK - Scotland
Town: Orkney
Boat name: Skylark
Make: Bombard 500
Length: 5m +
Engine: 60hp Yamaha outboard
MMSI: 235091893
Join Date: Jan 2012
Posts: 416
Hello All

Thanks for all this.

Good to know this isn't just an issue with Garmin maps for a start, as otherwise I'm very pleased with the unit.

Secondly, good to know I'm not overlooking something here about the missing data.

While of course one should not just rely on one data source (and I love paper charts anyway), and features like the sand/rock areas can change, I still find it disappointing that this data is not digitised and thus not available on the maps supplied.

Clearly the Admiralty see it as valuable to plot these data on their charts, and if - say - in an emergency etc, I feel it would be helpful to have these data on the Garmin G2 charts to tell you, eg, at the time of survey this bit of coast was sandy and this bit was rocky. By them merging those two areas when digitising the charts, it denies the helm the opportunity to make such judgements.

I hope this thread helps others though, as this is one of the things that you don't find out until you actually buy. Certainly I feel users can be forgiven for expecting the sand/rock data to be shown, especially when the maps are promoted as:

"Features include shading between depth contours, spot soundings, navaids, port plans, wrecks, obstructions, intertidal zones, fishing charts, restricted areas and more... these charts also remove navigation information from the map to reduce clutter and give clearer definition to the sea floor, ideal for fishing." and more at Garmin | United Kingdom | Maps - BlueChart

Hopefully it also helps those people who may not appreciate how data quality or usefulness can be compromised in the vector maps, depending on the application. Certainly there's a very similar analogy with the Ordnance Survey Explorer maps and the corresponding digitised data. Horses for courses :o)

Off now to produce my own waterproof chartlets as backup anyway, thanks to the really helpful folk at: Free charts and pilotage

Once again, many thanks to you all for your input on this

Best wishes

Steve
__________________
Copinsay is offline   Reply With Quote
Old 15 May 2012, 00:10   #14
Member
 
tonto's Avatar
 
Country: UK - England
Town: Zummerset
Boat name: irven arlyss
Make: Humber Oceanpro
Length: 6m +
Engine: evinrude 135hp
Join Date: May 2012
Posts: 394
Just a quick note on the charts and Digital charts from a commercial, large vessel navigator.

The advent of ECDIS (Electronic chart display and information systems) has required the Admiralty, (plus many othe National hydrographic offices) to be working flat out over the last 15 to 20 years to digitise all the information on all of the charts they publish worldwide.

Raster charts are NOT reccomended for navigation when scaling up as they are basically digitally scanned copies of the paper charts, and significant scaling errors may be encountered when zooming in to show details.

Vector charts on the other hand have to have each individual piece of data assigned a Lat/Long, so that when sclaing in the position/relationship to other information does not change, and the information stored can be interrogated.

Obviously if you see the amount of data points on each chart, and then see the work that goes into digitising this, multiply that by the admiralty worlwide folio of more than 3,000 charts, this becomes a massive undertaking.

Commercial ships are required to start carrying ECDIS from this year, and we must use IMO compliant vector charts, which must be oproduced by a national hydrogaphic office, or get the information from one, and make the charts to a recognised IMO standard. I would suggest that the Garmin charts are not IMO compliant, which is why they are cheaper than the Admiralty charts.

Currently we pay over 30 pounds for each admiralty chart, and a full folio of charts is an extremely expensive set of charts, equally as is the full vector folio worldwide, and these still do not have the same level as detail as the paper chart, simply because the commercial side of shipping does not need that level of detail.

I still am old school, and love the paper charts, even though the writing is on the wall for them, but as far as I am concerned paper charts do not stop working when the sattelites fall out of the sky! all electronic ones can and are affected by interference/jamming and are subject to the whims of a country who owns the system who can turn off the civilian side of the signals!

I still believe google earth, and sattelite pictures are fantastic for determining coast, and close inshore topography, as long as the area is covered that is!

Rant over!
__________________
tonto is offline   Reply With Quote
Old 15 May 2012, 04:12   #15
Member
 
boristhebold's Avatar
 
Country: UK - England
Length: 7m +
Join Date: Aug 2009
Posts: 1,293
Charts are always going to have more detail it seems. Best use chart for planning purposes and then electronic chart plotter for ease of use. As my Garmin unit is now too old to be able to have newer maps put on I have recently done some research looking at newer types of elctronic charts and got some feedback from various sources, it looks to me like the Navionics charts are the way to go som im getting a RayMarine e7 with the gold chart package.
__________________
boristhebold is offline   Reply With Quote
Old 15 May 2012, 04:41   #16
Member
 
Country: UK - England
Town: Chesterfield
Boat name: Sea Quell
Make: Picton Cobra
Length: 5m +
Engine: Mercury 150 4 Stroke
MMSI: 235038298
Join Date: Sep 2003
Posts: 859
Navionics

I have just got the Navionics Gold UKI&Holland for my Lowrance HDS-5. The 'free' updates of NM's etc for a year is really good - but you will miss Mapsource for viewing, planning and waypoint management on your PC with Garmin.
The Navionics free version is very poor (IMHO)
Jeff
__________________
Jeff is offline   Reply With Quote
Old 01 August 2012, 09:44   #17
RIBnet supporter
 
Copinsay's Avatar
 
Country: UK - Scotland
Town: Orkney
Boat name: Skylark
Make: Bombard 500
Length: 5m +
Engine: 60hp Yamaha outboard
MMSI: 235091893
Join Date: Jan 2012
Posts: 416
Hello All

Many thanks for this.

While I agree about the enlarging of raster maps, what I like about viewing raster maps (I use them in other non-marine applications for work) is that you know the accuracy and limitations of the data, and it's very apparent when you zoom in too much.

What concerns me is that we seem not to know the digitising accuracy of the vector maps derived from paper/raster maps.

I've seen many cases where people believe the in the infinite accuracy of vector maps (as the screen lines don't get thicker when you zoom in) when it truth they are no better, and may well be worse, than the raster maps.

I'm sure as the commercial, full price digitised charts are produced, the accuracy will be there, but I've so far not been able to get any data on the accuracy of the Garmin maps.

And of course, we have to press the button to agree to "not for navigation" each time we power up (at least on my Garmin chartplotter), so that's there get out I guess. But Garmin must know the reality of how people use their chartplotter and data.

But personally, I'd like a choice of charts with known accuracy, and maybe a choice to pay more for those with a more transparent provenance / greater accuracy.

Thanks for the contributions and good to have the debate, as I'm sure some people do not realise the potential errors that digitising can in theory introduce at the budget end of the market.

Best wishes for now

Steve
__________________
Copinsay is offline   Reply With Quote
Old 01 August 2012, 13:51   #18
RIBnet supporter
 
Erin's Avatar
 
Country: UK - Channel Islands
Town: A large rock
Boat name: La Frette
Make: Osprey Vipermax
Length: 6m +
Engine: 200 Suzzy
Join Date: May 2004
Posts: 2,830
Unless the digital chart producers go and re-chart all the seas then we will never have totally accurate detail on our charts. Most of the data comes from soundings and charting taken in the 1800's round our way with one or two areas slightly more up to date having been done in the 1960's! Not only that, but some charts have been scanned slightly out of sync. This is something I identified on an early Garmin chart of Alderney. They acknowledged and agreed there was an error when I told them and I think it has now been rectified.
Erin is offline   Reply With Quote
Old 01 August 2012, 15:18   #19
RIBnet supporter
 
Copinsay's Avatar
 
Country: UK - Scotland
Town: Orkney
Boat name: Skylark
Make: Bombard 500
Length: 5m +
Engine: 60hp Yamaha outboard
MMSI: 235091893
Join Date: Jan 2012
Posts: 416
Hello Erin

Thanks for this - I quite agree re coverage... Indeed up here we still have areas that have never been surveyed and so are basically blank on the Admiralty paper charts (apart from the word "unsurveyed) or as they put it on the Garmin chart "inadequately surveyed area". Indeed, there's the pretty accurate saying that any map or chart is out of date as soon as it's printed.

The issue of concern to me though was that of the accuracy of digitisation. Or in other terms:

1 Any chart or map is an interpretation of the real word based on certain rules on what to show and how.

2 For the paper charts were are used to (and love) those rules are pretty well known and documented

3 When people then (eg like Garmin and everyone else) produce digitalised maps from the latter data, they too are further interpreting the existing map/chart according to their chosen rules of interpretation and accuracy.

4 The drawback I've found with the Garmin charts is that one does not know the limitations imposed in the interpretation, until you start to compare with the paper charts... Eg Garmin have chosen to not differentiate between rocky and sandy areas, and where there's lots of rocks/obstructions in a small area (as shown in detail on Admiralty charts), Garmin just put a general notation over the whole area as "Danger area".

5 So basically Garmin (and all the other firms I'm sure) are adding an additional degree of interpretation of the "real world" and potential for additional inaccuracies creeping in. When letting digitising contracts, such details are specified so you know what you are getting, whereas as a consumer of Garmin charts, I've not been able to find out what spec they work to... But if anyone knows, that would be helpful.

Hopefully that explains the issue a little better....? (though it is a bit of a techie issue :o) ) Basically about data interpreation than coverage

Best wishes

Steve
__________________
Copinsay is offline   Reply With Quote
Old 01 August 2012, 16:05   #20
RIBnet supporter
 
Erin's Avatar
 
Country: UK - Channel Islands
Town: A large rock
Boat name: La Frette
Make: Osprey Vipermax
Length: 6m +
Engine: 200 Suzzy
Join Date: May 2004
Posts: 2,830
I'm not sure who currently digitises Garmin charts, but it was I believe Transas whom I were told are Russian based. I agree with what you say about interpretation, although I would clarify that to some extent and say that it is as much to do with their choice of symbols and abbreviations as it is their interpretation and generalsiation. As you say, they group or cluster rocks and features and just give a generic hatching or splodge of colour rather than keep the detail that a paper chart would show. I als find that some of the symbols are not very clear or are too general and I quite often find the text is the wrong scale or badly positioned. It even moves around as you zoom in which makes identifying certain features or places rather tricky.
Erin is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 20:02.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.