Wreck Locations

6 months 2 weeks ago - 3 months 5 days ago #303453 by packo
packo replied the topic: Wreck Locations
Update 1 week later:-
After a few back and forth emails with Peter Harvey from Heritage Vic I think the key to my dilemma may have been found. Peter mentioned that way-back (but post 1980s sketch) a scallop dredge had run across the site. It dragged the original plinth out of position and damaged it. That is why a second plinth was later installed.

So, just maybe just this 60 degree clockwise rotation of the original sketch, plus moving its plinth to a new position makes some sense. It leaves the bow NW as Heritage Vic and Stan Bugg both assert, and both plinths on the east side as I observed. My mystery heavy separated ironwork is the remains of the stern, and the odd "sandy patch" that separates stern from the rest could be the "wiped clean" path of the scallop dredge.

Although I could see the puzzling inconsistency, I was too closed minded to think that large concrete blocks might "go walkies".
Glad the scallop boats got kicked out of the Bay, but not so sure about the pro fishers. Those rec fishers sure have clout.

Here is a proposed solution to solve the inconsistency I struggled with before. Sorry about some miserable font sizes:-


cheers,
packo
Last Edit: 3 months 5 days ago by packo. Reason: colour adjust

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1 week 2 days ago #303700 by lloyd_borrett
lloyd_borrett replied the topic: Wreck Locations
G'day,

Over recent weeks I've been making a lot of changes to the Melbourne Dive Sites pages on The Scuba Doctor website. Some new dive sites have been added, and a lot of information has been added or updated about dive sites.

There is now a long description for most of the dive sites being stored in the database, which makes this information a lot easier to maintain. Plus the same long description can now be easily displayed everywhere the full details for a dive site is shown.

More importantly the full information for most dive sites is being displayed at least once somewhere, whereas before only the GPS marks were shown for all dive sites. (I'm still working on making sure the full information for every dive site is displayed somewhere.)

There are now pages for:
Melbourne Shore Dives
Melbourne Wreck Dives
Victoria Wreck Dives
Melbourne Boat Dives
Melbourne Bommie Dives
Melbourne Drift Dives
Melbourne Pier Dives
Melbourne Reef Dives
Melbourne Wall Dives
Melbourne Other Dives

I wrote some PHP code so that I can see the nearest neighbour to each dive site, the distance between them, and the bearing from the first site to its closest neighbour. This enabled me to find a number of 'duplicate' sites. That is, sites with different names but the same, or very close locations. I've managed to clean up most of those problems.

The code to do the nearest neighbour calculations for all dive sites uses a brute force approach. Thus it has a reasonable impact on the performance of the web site when it runs, so I wont be making that page available to the public. In time I might add the nearest neighbour as fixed information for each dive site, rather than it being calculated every time. Maybe even come up with a way to automate the creation or updating of that information in the database.

I still don't have the GPS marks for some of the dive sites frequented by the dive charter operators. Or at least I think I don't. In some cases it will probably turn out that some of these dive sites are at the same location for an exiting dive site in the database, but just with a different name. For example, Awesome Bommie and Al's Bommie. Today I realised that Plateau and The Plateau were just 130 metres from each other and removed one.

I also don't have the GPS marks for some significant wrecks, e.g. TSS Kanowna and SS Queensland. Anyone?

It would be great to add the orientation of each wreck to the long description. But I would mostly have to reply on others to provide me with the information.

I'd be happy to add the equivalent of Packo's GPS plotting sheets to the long description, where available. But I really think these need to be done with North being up, and as I understand it, currently they're not like that.

There will always be more that can be done. For example, adding more links to suitable videos, and showing some images for each dive site. But there is only so much one person can do.

Best regards, Lloyd Borrett.

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1 week 2 days ago - 1 week 1 day ago #303701 by packo
packo replied the topic: Wreck Locations
Hello Lloyd,

I send you a sincere and generous appreciation of your tireless work on this most comprehensive collection of info on VIC dive sites. It is creating a great and extensive resource that will aid many divers and scuba doctor customers.

There are however a few (but faint) brickbats! This is a contrast to my usual scubadoctor posts, where the brickbats come thick and fast with the praise being rather faint. Let's leave that issue aside for the moment.

I am pleased you are at least thinking of the idea of marked up GPS plotting sheets for some sites as I believe these are really helpful in all sorts of ways. Sorry the "packo plotting sheet" examples given earlier in this thread made you think north wasn't "up". It is - with latitude increasing down the page. Perhaps it was the sideways digits, or that the Coogee was drawn pointy at both ends that caused the confusion.

Maybe you might think up a better standardised format plotting sheet that we could all use and then submit. (Better still use your code cutting skills to automatically generate a sensible looking image of a plotting sheet when the appropriate GPS "corner point" coordinates are entered.)

Anyway you are doing a great piece of long hard work with this part of your website. Now for the brickbats!

What you are working on is so comprehensive and complex that there needs to be consideration of how to stop avoidable errors creeping in. Of a few quick checks I did of the mapping page, I noticed a problem with the "Lonsdale Wall" site. Actually there are two problems, but I'll deal with them separately. (Sorry this example should appear in a "wreck post" but it really morphed a bit sideways into a "GPS coord trustworthiness" thread.)

The "Sites Map" page on the Scuba Doctor website shows the Wall icon sitting in about the right place, but clicking on it gives the wrong coordinates. The user might not notice the difference between the google map position and the given coords, but in this case the given longitude is a little bit WEST of the Pt Lonsdale lighthouse!

"Copy & paste" errors are notorious in many GPS POI lists - and you have so many POIs! I think code is needed to scan the webpage html code to pick up on errors like this one. Divers looking at the "Divesite List" page will see the incorrectly translated numbers, as well as the original, so might pick up there is a problem and investigate. However the "Map browsers" will not usually spot such errors and may go to the wrong location.

Here is the a snippet of the page code with the error, and an idea on how to prevent this sort of thing:

The second point is that as I have mentioned to Lloyd some time ago, the intended google format coords are way out over deep water and around 100m from the Lonsdale Wall. Their source is described as "Unknown" and in my view are of little value.

To get more realistic numbers you might consider the image of a PoMC multi-beam echosounder survey of the area, onto which I have overlaid a WGS84 GPS grid. They use pretty high end gear in their survey work and I find it very trustworthy. (Forget the "packo's dropoff" indicator as I'm not really sure how accurate it is. It is a remnant of me trying to translate the sextant angles I used when I began diving here in the mid 1970s, into today's GPS numbers.):


The final issue is one that was raised several times earlier in this thread but seemed to have fallen on deaf ears at the scubadoctor. The site listed as a "Rye Scallop Drift", seems to have a coordinate problem too. Its over 8km northeast of Rye and in a pretty dangerous "no diving/prohibited anchorage" a bit further past Hovell Pile Light.

Maybe you have some special knowledge that the area does give up fat juicy scallops, but there are plenty of other legal scalloping areas, and I don't think these coordinates should remain on the scubadoctor list.

Translating the coords into "MGA speak" we have an Easting = 316,775 and a Northing of 5,757,896. This PoMC map shows why drifting for scallops here is both dangerous and irritating to the port authorities:


(speaking of dangerous scalloping adventures, I hope the scubadoctor folks read this account of a recent "missing diver" incident:
Missing Diver Rescued
As best I can gather the intended dive time was 2pm to 3pm (about 3hrs after Rip slack), a time that I claim is max Ebb flow in all areas, whereas some other "very delayed slack folk" claim would be close to slack water for the waters offshore from Rye.)


Enough of the negative, this post is supposed to be a generous and positive recognition of some jolly good hard work. Lloyd has created a great body of work that will be a wonderful help to many (including me!) aiming to explore what Victoria has to offer scuba divers.

The large size of this project just means that there will be a few errors that we need to be on the lookout for and quickly bring to Lloyd's attention. However these minor glitches will be quickly forgotten in the generous wealth of information that has been collected together in this significant site.

Well done Lloyd,
packo
Last Edit: 1 week 1 day ago by packo.

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1 week 1 day ago #303702 by packo
packo replied the topic: Wreck Locations
Thanks Lloyd for these fast fixes, but please take a bit more time to ensure accurate re-edits. The map was supposed to make this step (and checks of other nearby sites) easier, but the Lonney Wall latitude has now slipped down to 17.153 minutes?

This is well inside the Bay up near Boarfish Reef. Might you have meant 17.453 minutes instead of 17.153? The source is listed as "GPS" but not sure if you mean off someone's GPS unit at sea or from the map I provided. As always care is needed at all steps in sharing GPS info.

I don't know how these bad numbers come about but maybe a help to avoid errors might be an administrator editable "tag" that would mean a tagged site would show up on your map in a different colour (and overlaid on top of other site icons). That way you would have a good visual check on what you are doing to the tagged site's location when you re-edit its coordinates. Don't despair, sh#@ happens and it is a complex job you are doing.

cheers,
packo

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1 week 1 day ago #303703 by lloyd_borrett
lloyd_borrett replied the topic: Wreck Locations
G'day,

I've updated the Lonsdale Wall location with a mark from a better source. (It's what was the Lonsdale Wall Shallow mark.) Not sure how that other location got in there.

Rye Scallop Drift has been updated with a mark from a better source. Packo, I know you raised concerns about the previous location numerous times. But without a better option, I ain't changing it. And no-one provided me with a better option.

The code I wrote to find the nearest neighbour, distance and bearing, for each location helped me to identify and fix a few problem. Later this week I hope to have an automated process to save that information in the database. Then I'll be able to display it as appropriate.

Where a wreck site has a page on the MAAV website, I've provided links to that page in the long description.

The Melbourne Dive Site GPS Marks page delivers a list of the GPS marks for the dive sites we know about. Now the listing for each dive site also has a link to the page with more information about the dive site, if we have some.

I wrote code to check that the GPS marks stored in the database as d.dddddd matched the entries in d m.mmm given in the short description. I've updated the descriptions so that they now all do.

Packo, as to your remarks about the recent diving incident. In my opinion, anyone who dives from an unattended boat deserves an outcome that qualifies them for a Darwin Award. To do this in a current prone area suggests the person is trying to set a new standard for stupidity. To do so without a DSMB and any other signalling device suggests this idiot is trying to maximise their chances of receiving a Darwin Award. This clown ignored every basic fundamental of boat diving safety. If you think a moron like this would consult any source of information anywhere about slack water time, then I think you're dreaming.

Best regards, Lloyd Borrett.

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1 week 1 day ago #303704 by lloyd_borrett
lloyd_borrett replied the topic: Wreck Locations
The mark for Lonsdale Wall, -38 17.153, 144 37.839, is what is/was used by the dive charter operators.

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1 week 1 day ago - 1 week 12 hours ago #303705 by packo
packo replied the topic: Wreck Locations
Hello again Lloyd,

You need to get more sleep! Doing all this stuff in the wee hours of the morning maybe is what is creating a mindset that seems to lead to silly stuff. It seems we are back to a slanging match again.

"I've updated the Lonsdale Wall location with a mark from a better source. (It's what was the Lonsdale Wall Shallow mark.) Not sure how that other location got in there."

A better source than a PoMC survey? You now have one of Victoria's most popular dives sites missing from your site list! (and are misleading divers trying to find it!)

I gave it to you on a plate, and yet you still refuse to absorb anything I say as factual. I'm actually trying to help your business get everything right but get a slap in the face each time. Didn't the map mean anything?

The mark you still have is for some far northern section of the "Wall", well beyond where the real wall turns east-west. It is not the "Lonsdale Wall" that everybody knows and loves.

I wonder if the problem is that you are working in decimal degrees rather than d mm.mmm? While decimal degrees might make life easier in the google mapping world, it deprives you of any sense of the "southness" or "eastness" relativity between dive sites. That can help pick up silly problems like this one.

For example the Lat for the "North Wall Corner" is 17.407 minutes, about 0.250 mins (or 460m) further south of what you are now claiming is the main part of the Lonsdale wall. If you work in decimal fractions of a degree you can't so easily apply these simple "does it make sense?" tests.

"Rye Scallop Drift has been updated with a mark from a better source. Packo, I know you raised concerns about the previous location numerous times. But without a better option, I ain't changing it. And no-one provided me with a better option."

Did you ask anybody? I couldn't suggest a good scallop area at the time cos I don't collect them. However I don't think it is a state secret and many would have responded if you had asked around widely enough.

I worry that you publish some incorrect info, and then when a customer complains it is potentially dangerous, you leave it in place ("I ain't changing it") without any sort of active investigation - wait, doesn't that have a familiar ring to it?

"I wrote code to check that the GPS marks stored in the database as d.dddddd matched the entries in d m.mmm given in the short description. I've updated the descriptions so that they now all do."

Good! In such a big project such computerised consistency checks are important. I hope you didn't find many others. It will be comforting to your website readers to know those computerised checks are now being done.

"Packo, as to your remarks about the recent diving incident. In my opinion, anyone who dives from an unattended boat deserves an outcome that qualifies them for a Darwin Award. To do this in a current prone area suggests the person is trying to set a new standard for stupidity. To do so without a DSMB and any other signalling device suggests this idiot is trying to maximise their chances of receiving a Darwin Award. This clown ignored every basic fundamental of boat diving safety. If you think a moron like this would consult any source of information anywhere about slack water time, then I think you're dreaming."

( note the underlining of the insults is my own work and not part of Lloyd's original quote. )

What is it about some people that they can't see the forrest for the trees! This is all about "shooting the messenger" (again!).

Whatever motivated this guy to do what he did, and when he did it, is still unclear. I've tried to get more info from the cops and his rescuer's but it is rather hard going. We may never get to know his side of the story.

Forget all about his personal attributes, or lack of them, and see him as a humble messenger with this message:-

1) "For whatever reason, I chose to dive a Rye site at a time that by pure chance matched the time the Rye Dive Shop claims would be near slack water." [Although others, including Packo, the Port authorities, and the Ship Pilots (plus many others) claim it would be near maximum ebb tide flow with currents for that general area of between 0.6 and 2.0 knots].

2) "I was rescued alive 4 hours later, exhausted and very cold, and over 10 km away from my entry point. I was so lucky to be found in time."

(end of message)

"If you think a moron like this would consult any source of information anywhere about slack water time, then I think you're dreaming."

Only for a brief moment did I dream he may have consulted your advice on when to dive off Rye to avoid currents. However while wide awake I know that many, many, other divers do. Your article on it is so high up there in the google rankings!

Other readers, be they: stupid, idiots, clowns, morons, or even quite ordinary folk who also might take the advice given will also create a chance their lives could be put in danger and the search & rescue helicopters be needed again. (To the great embarrassment of the diving community.)

Lloyd it is way past time for you to stop ducking and weaving on this issue - for heaven's sake get out from behind your keyboard and go and take a cold hard open-minded look at (and a simple test of) the Scuba Doctor's advice on slack water times in areas 5km - 20km inside the Heads.

packo - over and out!
Last Edit: 1 week 12 hours ago by packo.

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1 week 1 day ago - 1 week 1 day ago #303706 by lloyd_borrett
lloyd_borrett replied the topic: Wreck Locations
G'day,

So I wrote code to output a KML file of the marks for use with Google Maps.

It looks fine. Google Maps imports it.

But Google Maps gets 90 for every latitude, plus puts in the latitude as the longitude. Stuffed if I can work out why.

I thought I'd be able to attach the file here for people to try it, but no. (The forum software Webby is using would have to be one of the most awkward and klunky systems to use I've ever come across.)

So I'll try a link to the file
https://www.scubadoctor.com.au/downloads/divemaps-2018-01-08.kml

Maybe someone can see something I can't.

Best regards, Lloyd Borrett.


UPDATE: Guess which muppet had the coordinates as lat lon when a KML file needs them as lon lat? The file is now fixed and working.

And here's an example of how errors creep in via format conversions.

When imported into Google Maps we get...

Osprey
-38 32.100 (-38.535000), 143 58.700 (143.978333)
-38.53499, 143.97833

The first line is the data I provided. The second is what Google Maps is showing. Note how Google Maps is showing that the lat has changed from -38.535000 to -38.53499.

Urhhhh!
Last Edit: 1 week 1 day ago by lloyd_borrett.

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1 week 1 day ago #303707 by lloyd_borrett
lloyd_borrett replied the topic: Wreck Locations
G'day,

To give you an example of what I have to deal with when trying to get the GPS mark for a dive site.

Here is the mark I'm using for The Pinnacles off Phillip Island, as supplied by someone who has told me they regularly dive it.

The Pinnacles - Phillip Island
Latitude: 38° 34.683' S (38.57805° S / 38° 34' 40.98? S)
Longitude: 145° 20.216' E (145.336933° E / 145° 20' 12.96? E)

Here are other marks I have, some from charter boat operators, others from people who say they regularly dive it:

37° 59'.958S, 145° 01'.771E PINAC2
38° 34'.086S, 145° 21'.579E PINNEW

38° 17'.847S, 144° 35'.699E PINNACLES DEEP DV (PINDEP)
38° 17'.706S, 144° 35'.741E THE PINNACLES DV (THEPINNDV)

38° 32'.252S, 145° 12'.094E THE PINNACLES PI DV (THEPINNPI)

-38.572633, 145.337300 DK PINACL
-38 34.358, 145 20.238

They are all over the place. So which is correct?

Best regards, Lloyd Borrett.

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1 week 1 day ago #303708 by lloyd_borrett
lloyd_borrett replied the topic: Wreck Locations
G'day,

packo wrote: A better source than a PoMC survey?

The survey map is NOT a mark. I'm now using a mark used by charter boat operators. The previous mark was supplied by someone who said they regularly dived the location, but was wrong. If someone provides me with a verified mark for a better location on Lonsdale Wall, then I'll change to it.

packo wrote: I wonder if the problem is that you are working in decimal degrees rather than d mm.mmm?

I'm working in both. I need decimal degrees for mapping and doing calculations. I need degrees and decimal minutes to show the mark in a format used by marine GPS units. I'm well aware that converting back and forth between the two formats is problematic. The errors introduced drive me crazy.

packo wrote: Did you ask anybody?

Yes. Plus I already had plenty of unverified marks to choose from. And none of them are in the area I would go, but I don't have a mark for that area.

packo wrote: I worry that you publish some incorrect info, and then when a customer complains it is potentially dangerous, you leave it in place.

On every dive site related page of the website I ask for people to provide more information. But simply saying something is wrong, when I have other sources saying it isn't, ain't very helpful. An alternative verified mark is helpful.

packo wrote: It will be comforting to your website readers to know those computerised checks are now being done.

Maybe. The process of 'fixing' them is yet another potential source of mistakes.

packo wrote: the Scuba Doctor's advice on slack water times.

It's not The Scuba Doctor's advice. It's the advice published in books and widely held by many highly respected and experienced commercial and private divers. It's provided as a resource on the website for others to make of what they will, along with alternative advice.

Best regards, Lloyd Borrett.

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1 week 17 hours ago #303709 by lloyd_borrett
lloyd_borrett replied the topic: Wreck Locations
G'day,

Scuba Doctor Dive Map KML File

In the true spirit of making it easy to obtain, utilise and share the information, you can now download/view the Scuba Doctor Dive Map GPS Marks in the Keyhole Markup Language (KML) file format used to display geographic data in an Earth browser such as Google Earth and Google Maps.

Some marine GPS units can import the information from a KML file. For others you can use use a file translate program (e.g. GPSBabel) to convert the KML file into an import file format (e.g. GPX) supported by your GPS unit.

There is a link to the KML file in the disclaimer information at the bottom of all of the dive site pages, e.g. https://www.scubadoctor.com.au/melbourne-dive-site-gps-marks.htm .

Best regards, Lloyd Borrett.

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6 days 11 hours ago #303710 by lloyd_borrett
lloyd_borrett replied the topic: Wreck Locations
G'day,

Now we're also now showing the nearest neighbour, distance in metres and bearing to the neighbour for each dive site.

See https://www.scubadoctor.com.au/melbourne-dive-site-gps-marks.htm

Best regards, Lloyd Borrett.

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3 days 10 hours ago #303712 by packo
packo replied the topic: Wreck Locations
Hello,

Lloyd I tried so hard for a few days to let you have the last word in our "discussion", but in the end couldn't bring myself to do it. There were a few too many loose ends to attend to. Sorry about that!

On the positive side thanks for implementing the "nearest neighbour" feature. At first I did think "wank feature", but I was quite wrong. It is helpful in lots of ways and will help everybody "fit it all together" a lot better. I found it particularly useful for sites I hadn't even heard about before. Now you can easily imagine where they fit into the picture as a whole.

I was a little worried that the "nearest neighbours" code was being used to "detect and eliminate duplicate sites" with a criterion of 130m or less separation.

Underwater 130m is quite a long way! It is perfectly possible for two boats to be diving different sites that far apart and each group of divers enjoy their dive without ever seeing anyone from the other group.

For example the popular "Castle Rock" dive site has a rather shy "little brother" at about that distance away. Each is a valid dive site in its own rite with different charms. In these cases it would be sad to see the coordinates of one sibling "put to the sword" and be lost. Perhaps a "duplicates threshold" distance of down around 30m might be more appropriate?

Lloyd wrote:

"So I wrote code to output a KML file of the marks for use with Google Maps.
It looks fine. Google Maps imports it.
But Google Maps gets 90 for every latitude, plus puts in the latitude as the longitude. Stuffed if I can work out why."


Would have been an interesting map - all Melbourne dive sites clustered around the North Pole. The warm water NSW & QLD crowd might have considered that would seem about right!

I see you figured out your "muppet moment" that with Lat/Long presented in the wrong order the Long values would be truncated to max allowed 90 degree Lat values, and the Lat values of -38 degrees used as valid Longs. Marine traffic.com also once had a "reverse format" going for a while in some of their API output files.

"The first line is the data I provided. The second is what Google Maps is showing. Note how Google Maps is showing that the lat has changed from -38.535000 to -38.53499.
Urhhhh!"


An error of one unit in the 5th decimal place corresponds to distance error of around +/- 1m which is adequate for the task. Google would be simply trying to save time in using 16-bit precision maths for the fractional part. Don't sweat over it.

"Here is the mark I'm using for The Pinnacles off Phillip Island, as supplied by someone who has told me they regularly dive it.
The Pinnacles - Phillip Island
#1) Latitude: 38° 34.683' S (38.57805° S / 38° 34' 40.98? S)
Longitude: 145° 20.216' E (145.336933° E / 145° 20' 12.96? E)
Here are other marks I have, some from charter boat operators, others from people who say they regularly dive it:
#2) 37° 59'.958S, 145° 01'.771E PINAC2
#3) 38° 34'.086S, 145° 21'.579E PINNEW
#4) 38° 17'.847S, 144° 35'.699E PINNACLES DEEP DV (PINDEP)
#5) 38° 17'.706S, 144° 35'.741E THE PINNACLES DV (THEPINNDV)
#6) 38° 32'.252S, 145° 12'.094E THE PINNACLES PI DV (THEPINNPI)
#7)-38.572633, 145.337300 DK PINACL = -38 34.358'S, 145 20.238'E

They are all over the place. So which is correct?"


I don't think the one you have chosen (#1) is the correct one. There must be dozens of "pinnacle sites" in oz. This common name really needs a leading qualifier like "Cape Woolamai Pinnacle". Sorting it all out runs like this:-

#2 is somewhere off Beaumaris Bay and so can be be eliminated.

#3 is near Cape Woolamai on Phillip Island - but a little too near! Seems to be in the bay below the light and might be the bommie in that bay that breaks the surface. ( As a stupid teenager I shore-dived that site from the surf club. The distance damn near killed me! Ah the invincibility of the young.)

#4 & #5 refer to a site "Deep Pinnacles / Pinnacles Deep" off the Pt Lonsdale coast. Running your nearest neighbour code on these would have picked that up.

#6 is a Phillip Is site (hence the PI), but it is about 1km SW of Pyramid Rk. In my shore diving days I did strike some nice bommies SW of the rock but I would not have thought that far out. Maybe there is a nice sharp one out there!

#7 at 38 34.358'S, 145 20.238'E I think this one might be the go. Site #1 seems a little too far offshore from memory.

I found some other coordinates that might corroborate this:-
a) 38 34.364 145 20.232  (from a 2005 getunder dive club list) 
b) 38 34.353 145 20.250  (latrobe valley scuba club guy in old dive-oz post)
c) 38 34.340 145 20.257  (as above, different guy)
So #7 plus a, b and c seem to form a 40m x 40m "cluster". Perhaps a little further apart than one would like to see for a "pinnacle" shaped site. Maybe some people "mark it" after the boat lays back on its anchor line?

*Note also that with a bit of dyslexia between two latitude digits, Mark #1 that Lloyd has opted for could transform into: 38 34.368 145 20.216 which is not really that far from the cluster of the others. (Do I remember the pinnacles has two "lobes"?)

So Lloyd I would rethink your choice here, or at least ask around for someone to confirm whether the more offshore mark (#1), or the more inshore marks (#7, a, b, c) are closer to this great site.

Alternatively for sites you are unsure about you could either:-
a) Leave them of the list! (Most divers using the website might be more concerned with the quality of the information rather than the quantity of it.)

b) Place a note like "needs verification". This would do two things. Firstly it warns viewers to seek confirmation elsewhere before using the mark. Secondly it would send a signal to anyone who knows the marks are good, to then pass you a note to that effect.

The original poster (Peter6956) did bring up the good point that some means of indicating the "quality" of the marks would be valuable. Not sure how this could be implemented but in the meantime a simple "needs verification" note might be easier. So at this time it looks like both the "Pinnacles" (Cape Woolamai) and "Lonsdale Wall" entries could be noted in that way.


"packo wrote: A better source than a PoMC survey?

The survey map is NOT a mark."


No a survey map is not a mark - it is so much better! It is many thousands of closely spaced "marks" (soundings), each with a colour coded depth band. It is laid out in a 2-D array that represents the same scaled down geography as the seafloor itself.

Sure each individual point doesn't have its coordinates listed anywhere, but that is not necessary. Virtually any muppet who spots an interesting feature can reverse engineer its coordinates from the given grid, and then go visit that feature!

Accuracy might be around +/- 5m if you either measure it carefully on the screen, or can get the pixel X,Y ordinates and do some maths. This is more than adequate, and possibly be better than marks from some guy's GPS who couldn't quite be sure they were exactly overhead anyway. Even an "eyeball" assessment will give WSG84 numbers that will get you pretty damn close.

Maybe AB could chip in here with some actual Wall numbers, (or at least the first decimal minutes digits!) to get things back on track. I think this is his boat (the smaller one!) on the Lonsdale Wall:-


The pic is taken from Pt Nepean. Note the Pt Lonsdale houses in the background. The 34.153'S 37.839'E mark Lloyd wants to stick with for the time being would have a background somewhere between the Pt Lonsdale footy oval and the caravan park - not the background scene we see here.

If you plot up the 34.153'S 37.839'E mark, it also seems to fall just outside the boundary of the marine park, so Parks Vic must also consider this is not the best that Lonny Wall has to offer. Maybe the charter boat used that mark because it would then be legal (just) to take crays?

I see Lloyd has shifted discussion on the Scuba Doctor dive maps to another topic, so those interested in further developments should switch to that thread.

I'll also switch further posts on the bad slack times issue to a more appropriate thread instead of blasting away here!

cheers,
packo

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3 days 1 hour ago #303714 by AB
AB replied the topic: Wreck Locations
That is my boat, but I can't tell what site I'm on! (jeez, you just never know who's watching you!) If there are marine Park boundary buoys nearby it would be a site we call Cave wall (Charters might call it North Wall Corner) as it has caves 38 17.407. 144 38.020 or it could be Paradise Wall (an old DE site) at 38 17.447 144 37.899. At either site we often move along a bit if there is another dive boat near the site, coz, let's face it, it's hard to go wrong on Lonnie Wall! Actually, I rarely use gps on my wall sites as I am in the old habits of using land transits so I can concentrate on the sounder as we like to accurately locate out shot on the lip of the wall as I demand my divers come back up the shot.

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2 days 23 hours ago #303717 by lloyd_borrett
lloyd_borrett replied the topic: Wreck Locations

AB wrote: it could be Paradise Wall (an old DE site) at 38 17.447 144 37.899.


Please excuse my ignorance, but what is DE short for AB?

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2 days 23 hours ago - 2 hours 56 minutes ago #303718 by AB
AB replied the topic: Wreck Locations
Dive Experience, from the old Calypso and Corsair days! It's the shallowest part of the wall with the dropoff starting in 10 or 12 metres, starting with a couple of steps then dropping fairly steeply. Line the big pine up with the notch in the treeline behind Lonsdale.


Alan
Last Edit: 2 hours 56 minutes ago by AB. Reason: Stoopid autocorrect

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7 hours 28 minutes ago - 7 hours 27 minutes ago #303737 by peter6956
peter6956 replied the topic: Wreck Locations
Are all the positions listed above on the datum WGS84 ???
Last Edit: 7 hours 27 minutes ago by peter6956. Reason: correction

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