Comparing Dive Site Maps

Keep up-to-date about what's happening with the Scuba Doctor's Melbourne and Victorian dive maps and dive site information.
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packo
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Comparing Dive Site Maps

Postby packo » Fri, 11 May 2018 12:12 pm

I'm getting a little frustrated that only one of a list of six GPS coordinate corrections to the Scuba Doctor Dive Sites Database that I put in a long while back has been processed so far. Recently a VSAG crew failed to find the Pioneer Wreck because the stated coordinates were slightly off. These were corrected within a week! I felt "queue jumped".

If corrections only get made when someone physically uses the numbers and then reports "the numbers are bad", it is going to be a much longer process to get the database into tip-top shape.

I know Lloyd is not particularly fond of "armchair corrections" but it avoids the messy business of divers having to "waste dives" and then report bad numbers (been there, done that!). Well researched corrections with references to maps, charts, surveys, and clusters of alternate coordinates from other divers should be sufficient to generate a correction or at least some investigation.

If the dive shop is temporarily too busy to process these things within a reasonable time after they are submitted, then perhaps the simple solution is to insert a quick cautionary warning that the coordinates of that particular site(s) are currently under review. At least that warns readers to be cautious and perhaps seek alternative advice before relying entirely on the marks given.

One danger of being very slow to act is that bad numbers are more likely to spread far and wide across the internet the longer they are left uncorrected. Another is that frustrated users failing to find sites, or being directed to the wrong site, may also become disaffected with the Scuba Doctor database and so be less likely offer up contributions of new sites. That would be a very sad outcome. There have been some hints that this may already be occurring.


***** So Packo, what exactly is your problem? *****

The initial complaint (way back!) about the Lonsdale Wall dive site was simply that its "Google format" coords were too far off the wall for safety, and should be moved from very deep water by about 90m to the wall lip.

At the same time I also pointed out that the minutes and decimal minutes of Longitude in the "short form" site description were wrong, putting the site roughly somewhere in the middle of the main street of Point Lonsdale.

There were also some other needed corrections. The most important of which was the Cape Woolamai Pinnacles Site. (NOW FIXED!)


***** Onward and upwards! *****

My complaint triggered a whole sequence of actions from Lloyd over the summer. Most of these were exceedingly good, with fully computerised format conversions and only one central source of coordinates (in decimal degrees :( ). Lloyd also added code so coords could be entered in any chosen format with later automatic conversions to minutes and decimal minutes as needed by the various display options. These were all excellent steps towards reducing the likelihood of coordinate mix-ups and other types of errors.

Lloyd also then added a lot of other good functionality like "nearest neighbour distance", and the *.kml files which he has made freely available to users. These text files can be examined and processed by end users to do useful things with like further site filtering and uploading site coordinates into GPS units and chart plotters.

All this work involved a lot of hard yakka for which all end users should be very grateful. I know I am. It's very comprehensive (and building) range of sites has something for everyone. Even shore divers and snorkelers, who can access GPS via their smartphones, are catered for. In terms of its functionality and large range of sites it is hands down the best site for info about dive sites in range of divers in the wider Melbourne region.


***** BUT! *****

While all the improvements were good up to this point, then some sort of minor meltdown occurred in sites around Point Lonsdale. The Lonsdale Wall site coordinates were shifted away 0.5km northwards (instead of 90m towards the wall lip), and the Lonsdale Arches and the Lonsdale Bommies sites (as defined by the old Dive Vic operation) were left uncorrected. Frustratingly I have had no success so far getting this muck up sorted out (as well as a small number of other corrections).

This will be my last "nag" on this issue and I will accept whatever does, or does not, come of it. There will of course be disappointment if the changes are not made, but as they say "there is no use flogging a dead horse". Anyway for this last attempt I have decided to use pictures rather than words to underline the current problem as I see it. Hopefully this makes the tangle easier to see and sort.


***** THE LAST PUSH - Using some pictures! *****

As far as naming dive sites goes, the old "Dive Vic" charter operation had the most influence because they took more divers to these sites than anybody else. During their financial troubles and liquidation sales their website and "Dive Sites Map" were taken down. However I had gathered enough material to recreate a facsimile of that map, but restricted to just a handful of sites whose names and positions include my current issue. The map looks like this:-
Image
Note that Dive Vic seems to have slightly disguised the real positions to protect that info.

Around the time of the Channel Deepening Project 2005 - 2009, the Port of Melbourne Corporation tried to show they cared about the impact of the dredging by "sucking up" to some segments of the industry by helping with dive site maps of their own making with input from the charter industry. One map of theirs looked like this:-
Image
I've used red dots to highlight the sites I am talking about. You can see these names and positions are in good accord with the previous map. They also plotted many dive sites onto an old nautical chart (but then later got the depth contours within their deepened channel suppressed from all new charts - grrr!). That map looked like this:-
Image
Although the names are not readable at this scale, they are in accord with all previous maps as are the positions of the red dots. Unfortunately the "Lonsdale Bommies" site somehow fell off this map.

I'll chip in next with a map showing the "red dot sites" marked on a bathymetric map of reefs and water depths around Point Lonsdale. It looks like this:-
Image

***** The case so far *****

Ok so there has developed over the years a semi-official agreed set of names and locations at least for the major sites.

***** What about The Scuba Doctor Dive Sites Map? *****

This is by far the most comprehensive dive site database and the map can get a little cluttered around the Rip area. I think some additional filtering options should be built as your screen can easily be filled by a sea of overlapping orange icons at low to medium magnifications.

However if you could remove most of the clutter of numerous Rip sites and just restrict the mapping to the six "red dot sites", you would see something similar to this:-
Image
Three of the six sites are in reasonable agreement with all previous maps. Three are not! "Lonsdale Wall" has hightailed it north well into Victory Bight and the "Lonsdale Arches" and "Lonsdale Bommie" sites have swapped sides around the "Twin Bommies". So some things got broken during Lloyd's re-build of the dive site database and have yet to be fixed.

Things do get broken easily when data and data structures are being tinkered around with at the same time as the underlying code that makes it all work is being modified. The key for repairing it all is firstly to make sure you can see exactly what got broken. Not sure Lloyd is at that point yet and this is the reason for this picture show.


***** Some old ghosts! *****

In an effort to find how and possibly why things got broken I delved around into some stuff I collected at various times when the VSAG and BSAC websites also used to display dive site maps.

These were the simpler forerunners to the current Scuba Doctor dive info/maps pages. Copies of the old lists showed a number of mismatched GPS values were rattling around in the system back then. They would come to haunt the present day.

I think in those days there might have been some fairly tedious manual "syncing" of the different position formats. I think Lloyd has now computerised all those interconversions so there should be no problems now when sites are added or edited. That is provided everybody submits good quality data!

Although the VSAG sites map is no longer available, and the VSAG website itself seems now to be a pale shadow of its former glory (despite some attempt to breath life into again last summer). Neglected and forgotten as it was, I was in for a big surprise!

There must be sufficient intact bits and pieces lurking in the dark dusty corridors of the site, that my attempts to run an old copy (2009) of the "sites map" webpage code saw it mostly come back to life from the local copy!

I was quite astonished to see google's map of the Heads pop-up and be populated by those elegant "inverted teardrop" place markers. I grabbed a couple of screenshots to show that back in the day the site names and google positions were mainly ok. However there were a number of coordinate problems in the "pop up" information. It was one of these at least 9 year old bad coordinates that triggered both the big improvements seen this year and also the unfortunate site mix-up.

I don't wish to embarrass the Scuba Doctor crew by putting up this decade old bad screen shot but I have to go in hard because this will be my last attempt at getting across my point. If it fails I won't revisit this, having already spent way too much time and effort trying for a fix. As extra incentive if all the corrections in my previous post under the Scuba Doctor Dive Maps Database topic get done, then most of this post will come down.

The old style VSAG dive site map looked like this:-
Image


***** Comparing old and the new (post Jan2018) dive site maps *****

The main points of comparing the old and new maps are:-
1) For ten or so years Lloyd's old VSAG, BSAC and pre 2018 ScubaDoc maps had two "Lonsdale Wall" sites. These were on the "shallow" and "deep" sides of the drop-off but too far away from it! (IMHO - about 40m & 80m respectively.)
Image
2) When the unedited copy & paste longitudes were corrected earlier this year the higher longitude number by pure fluke turned out to be very close to the longitude of another site 500m or so due north that was only present in Lloyd's personal website locations database. He had dived it twice before and it was also called, wait for it, "Lonsdale Wall Shallow".

This was up near Boarfish Reef and featured only a limited drop from around 13m to 22m.

3) In the confusion between the now three separate sites, two with identical names, and two with near identical longitudes, Lloyd had a mild brain snap and:-
a) Deleted both the old VSAG "Lonsdale Wall" sites.
b) Transferred the "Lonsdale Wall" name to the far northern site with the limited height drop.

4) To complete the fun and games:-
a) The original "Lonsdale Arches" site was replaced by a new but very nearby mark from Peter Fear. It was given the name "Lonsdale Bommies".
b) Somehow the displaced "Lonsdale Arches" name was then given a new set of GPS numbers that came from an old (but slightly off) mark for the "Twin Bommies" site.

***** The result *****

So that Scuba Doctor folk is how the SD dive site map fell out of step with all previous maps. In the process the marks for the "real Lonsdale Bommies" and "real Lonsdale Wall" fell out of the ScubaDoc database and I think the "new" Lonsdale Arches site is largely "nothingness", being about 80m SW of the "Twin Bommies" and in uniformly deeper water.

***** The fix *****

a) The "Lonsdale Wall Shallow" site could be left as is but the "read more" text, videos, and info amended.

b) A "Lonsdale Wall" reinstated with coords near the wall lip plucked off the previous PoMC survey map, and perhaps inheriting the "read more" link from the current "Shallow" site.

c) Talk with Peter Fear and consider whether the two 37.74x & 37.73x sites are really one in the same (only 20m apart) and consider restoring the "Lonsdale Arches" name to keep in step with the other maps.

d) Revive the old "Lonsdale Bommies" site. What coords to give it maybe an issue. Not sure exactly where Dive Vic spot was but there seem to be at least 3 possible choices:-

i) Packo's mark 38 17.965 144 36.497 - a bommie rising to 11m with a large split, a few more to the S and SW. One at 38 17.975 144 36.488 has a swim through.

ii) Bommie around approximately 38 17.948'S 144 36.464'E. Haven't dived this yet.

iii) A double bommie in shallower surrounds around approximately 38 17.810'S 144 36.374'E. Haven't dived this either!

Anyone else with a good spot in the general area they would like to put up as a "Lonsdale Bommies" candidate?

Anyone else who has dived all of i), ii) & iii) who would like to give a "best recommendation", and the exact coords?

THE END (on this topic!). I'll keep fingers crossed but will accept any action, or no action.


***** Something completely different *****

This forum needs more content! It can't always be the moderators banging on. There are about 55 new members since the forum was revived. So far only "Watsea" has chipped in and he's not a even a native! How did your trip down south go Watsea? Note sure of the exact time frame of your visit but our Autumn weather ranged from wonderful to woeful.

The "tell us about your club" post was a lead balloon as well. A wider variety of back and for discussions are needed. We have seen before that diving forums can be a "use it or lose it" situation. I know "Clubdiver" is a fountain of good info but someone needs to ask a question before the good oil can begin to flow.

For my part I would like to know about scuba diving off a plastic kayak. I would like to give it a go to do some quick underwater jobs near my local shoreline. However I don't want to capsize and make a complete goose of myself. Also getting less nimble with age and I am a little afraid of successfully getting all gear on and off. Did think of leaving the tank strapped in the kayak and putting in 20m of air hose between the first and second stages of the regulator to make a sort of "engineless hookah" setup.

Was going to fit a small stabilising side-pontoon but am not sure if that is really necessary. Can anyone offer "kayak diving" advice please?

cheers,
packo
Last edited by packo on Tue, 04 Aug 2020 1:46 pm, edited 4 times in total.



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lloyd_borrett
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Re: Comparing Dive Site Maps

Postby lloyd_borrett » Sat, 12 May 2018 10:33 am

G'day,

packo wrote:a) The "Lonsdale Wall Shallow" site could be left as is but the "read more" text, videos, and info amended.


Info amended to what?

packo wrote:b) A "Lonsdale Wall" reinstated with coords near the wall lip plucked off the previous PoMC survey map, and perhaps inheriting the "read more" link from the current "Shallow" site.


What verified coordinates do you have?

packo wrote:c) Talk with Peter Fear and consider whether the two 37.74x & 37.73x sites are really one in the same (only 20m apart) and consider restoring the "Lonsdale Arches" name to keep in step with the other maps.


I'd like someone like Alan Beckhurst, Ian Sholely, or Peter Beaumont, to provide me with a verified set of GPS marks before making such a change. There is no point in just picking one and hoping it's right. I want to stop this sort of thing as it's bad practice.

packo wrote:d) Revive the old "Lonsdale Bommies" site. What coords to give it maybe an issue. Not sure exactly where Dive Vic spot was but there seem to be at least 3 possible choices:-

i) Packo's mark 38 17.965 144 36.497 - a bommie rising to 11m with a large split, a few more to the S and SW. One at 38 17.975 144 36.488 has a swim through.

ii) Bommie around approximately 38 17.948'S 144 36.464'E. Haven't dived this yet.

iii) A double bommie in shallower surrounds around approximately 38 17.810'S 144 36.374'E. Haven't dived this either!

Anyone else with a good spot in the general area they would like to put up as a "Lonsdale Bommies" candidate?

Anyone else who has dived all of i), ii) & iii) who would like to give a "best recommendation", and the exact coords?


And once again we have a clear example of why I haven't made a change. I don't want to pick from just one of three marks randomly. It might well be that this is best handled by having all three marks as dive sites. But then what to call them, and what should the descriptions be?

Packo, I truly respect the time and effort you put into posts like the above, and the detailed research you conduct. They are valuable contributions. But unless it can be distilled down to verified GPS marks, site names and descriptions, I'm no longer prepared to make changes. We'd end up like a dog chasing its tail.

I've made recent changes only when I've been given verified GPS marks from trusted sources, including yourself. Thankfully they have usually been with additional information about the dive site, and I've added that as well.

Today I've reached out to Luke English from Redboats.com.au to see if he would be prepared to share the verified marks they use for our problem dive sites. If Luke helps us all out by proving the information, I'll change the source attribution accordingly.

Who knows, Luke might even be prepared to provide us with the his verified marks for dive sites we already have listed. If they match what we have I'll change the attribution to Redboats. If they're different, then I'll have to decide if to go with Luke's marks, or get a third party to verify them before making changes.

And if Luke generously provides us with the marks for additional dive site, bonus!

Best regards, Lloyd Borrett.




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