Vloggers hit an uncharted rock/reef in the Kimberleys

[RaymondR]

By Australian standards the Kimberly coast is reasonable well charted with a full set of 800 series charts.

That being said if you actually inspect an 800 series chart you will find a chart reliability diagram which graphically sets out the manner in which the survey for the chart was carried out.

In some areas a lot of closely spaced survey runs were made and in others far less.

If one is looking for a spot in which to encounter unmarked hazards wandering about in an area only covered by widely spaced survey lines is your home territory. If you are a nervous soul staying in the high reliability areas might be less stressful.

When I came across the top in 2002 the only chart available between Darwin and Gove was one with a notation which said it was based upon a survey carried out by Mathew Flinders in about 1820. Since then it has been resurveyed and 800 series charts are now available for the area. I found that in some places the locations of islands were misrepresented and were a couple of miles from their GPS locations.

I have transited the Kimberly coast four times in total since the original in 2002 and my experience is that it is best to stay well offshore if one is going to do night passages.

[Seaslug Caravan]

Originally Posted by RaymondR

By Australian standards the Kimberly coast is reasonable well charted with a full set of 800 series charts.


........

When I came across the top in 2002 the only chart available between Darwin and Gove was one with a notation which said it was based upon a survey carried out by Mathew Flinders in about 1820.
..........

WELL CHARTED? very interesting

Do Tell us where the "Mathew Flinders" Notation appears on the Chart.

I take it you are referring to the old AUS 442? This chart was used with corrections for quite a period starting in the 1950's. I have one in my chart collection.

Love to know what AUS charts this 800 series of which you speak is derived from. Certainly not a number associated with the paper series.

The Kimberly is covered by the 300 series 1:300,000 and the 700 series 1:150,000

[Dave_S]

I'm a candidate for computer assisted grounding.

If I go to The Kimberly and find I'm in or want to go in an uncharted area. What are the procedures for going on these areas?

Clearly not at night.

I will have radar and depth sounder (on one hull) and Navionics.

I was thinking of getting the mobile sounder that can go on a tinny and map it but I'd have to find an anchorage first and that might not be so easy always.

[Pelagic]

Originally Posted by Dave_S

...If I go to The Kimberly and find I'm in or want to go in an uncharted area. What are the procedures for going on these areas?

I have been exploring uncharted or poorly charted areas for years in the pacific region(well before GPS) and the tactics are the same as was done in the 1800's by explorers, which relied on eyeball navigation.

Approach slow and easy on a flooding tide no earlier than 10am when the Sun starts to help.

Wait for stable weather before prospecting unknown bays, calm winds but with a touch of ground swell is ideal for reading the conditions

Read the water, watching for back eddies and current guides to deeper water

If unsure, be prepared to anchor in an uncomfortable spot while you prospect by tender.

Obviously have good lookout up the mast and get a tough steel boat with a full keel and protected prop and rudder, for when you eventual touch in a remote area.

High tech, prospecting by drone will become more popular

[Seaslug Caravan]

Originally Posted by Dave_S

If I go to The Kimberly and find I'm in or want to go in an uncharted area. What are the procedures for going on these areas?

Good, question.

Mr Pelagic has some good tips.

The water colour varies from the appearance and consistency of chocolate milk through to reasonably clear with 6+Meter vis.

Most of it is a lovely azzure blue colour caused by the suspended sediments. (not good for watermaking) or for eyeball nav to judge depth from colour changes. A drone will be of little use.

Therefore telltale signs on the water, like tide/flotsam/scum lines and the shape of any wind chop tidal slop are the main telltales.

One technique we use a lot is find a spot (beach) to park the boat on and then check out the area at low tide either by dingy or a scramble to a good vantage point.

The rocky bars in the river and creek systems are the most testing to locate and a lot of kimberly waterways have them.

[Dave_S]

Thanks guys

I was thinking of a drone or a camera up the mast. I bought a $30 drone to see it I could learn to fly it. Ha, I must have crashed it 500 times for 3 minutes of uncontrolled flight. I see they have some drones for dummies now that take off automatically and follow you so there is hope.

The Kimberley Cruising Club has some really good information but I won't always be there.

[Simi 60]

Good dinghy with plotter/sounder is what we use if going into suspect areas.
Then bring big boat in.

Next thing to play with is transferring track/route from our dinghy SD card to opencpn on big boat PC.
https://opencpn.org/wiki/dokuwiki/do...e_mark_manager

[daletournier]

SAS planet, Google earth or ovitalmap, off line satalite navigation helps alot. I'm surprised more don't use it.

[CatNewBee]

I wonder if forward sonar would be of any use.. I guess, you will run into a submerged rock faster than even get alarmed by the sonar.

The Dingi / Depth-sounder solution is good if you are already aware of a danger and need to go short distances safely. It would not help on a passage or far away from the coast, where you do not expect shallow waters.

[CatNewBee]

Originally Posted by daletournier

SAS planet, Google earth or ovitalmap, off line satalite navigation helps alot. I'm surprised more don't use it.

Well it requires online connectivity and most google earth pictures are low-res or cloudy in those areas. Usually there is no affordable broadband Internet in remote atolls.

[Simi 60]

Originally Posted by CatNewBee

Well it requires online connectivity and most google earth pictures are low-res or cloudy in those areas. Usually there is no affordable broadband Internet in remote atolls.

Obvious answer to that is planning and get the kaps before you go when internet access is easy.

[Palarran]

I use Google Earth all the time to research harbors. I just copy the image and save them to folders. If there are clouds, use the date slider to change to one where it's clear. Love it and also don't understand why people don't use it more.

[Dave_S]

Originally Posted by Palarran

I use Google Earth all the time to research harbors. I just copy the image and save them to folders. If there are clouds, use the date slider to change to one where it's clear. Love it and also don't understand why people don't use it more.

Is it possible for a computer dummy to save them and overlay them on Navionics as a moving image as you go ?

[Simi 60]

Originally Posted by Dave_S

Is it possible for a computer dummy to save them and overlay them on Navionics as a moving image as you go ?

Probably not but easy with opencpn.

I have navionics on a $100 tablet, there is a button that does Google earth or map overlays as part of navionics.
You do need a data connection when in use.

[daletournier]

Originally Posted by CatNewBee

Well it requires online connectivity and most google earth pictures are low-res or cloudy in those areas. Usually there is no affordable broadband Internet in remote atolls.

That's the whole point it doesn't. Ive downloaded over 60gig of satalite imagery which enabled accurate satalite navigation in places like raja ampat where the charts are hugely out and no Internet reception for 100nm.

Before setting of on a passage I download everything in advance while I have good Internet. Before leaving Australia this year I had the entire east coast of Australia, Ashmore reef, Indonesia, cocos keeling, Christmas island, Chagos, Mauritius, Rodriguez, seychelles, Madagascar etc etc etc.
I can swap from open cpn to SAS planet instantly or have them both on the screen at the same time, no Internet reception needed.
Its free, it's easy and it works.