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Author Topic: Lagoon Map Project  (Read 23666 times)

Ric Gillespie

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Lagoon Map Project
« on: December 26, 2016, 08:12:07 AM »

I’ve started a project that I think will help us understand the lagoon and plan a more effective search.  The 1939 U.S. Navy survey of the island by USS Bushnell personnel included extensive soundings in the lagoon.  This was presumably accomplished by men in a whaleboat dropping a weighted line and recording the depth on a map in fathoms and feet.  A fathom is six feet so, for example, a notation of 3 fathoms 2 feet is a depth of 20 feet.  There are hundreds of such notations on the map that was the end-product of the 1939 survey. 
The map is a great resource.  Depths in the lagoon are probably not significantly different today than they were in 1939.  However, a forest of tiny numbers does not provide a meaningful visual image of how depths vary throughout the lagoon.  If we have a good portrayal of where it’s deep and where it’s shallow we may be able to see logical flow patterns that could influence where debris entering through the main passage would go.  To create a more useful lagoon map I have assigned colors to the various depth values recorded in 1939 - darker blue for the deep depths gradually lightening as the depth gets shallower. I’m then overlying swatches of those colors on the depth notations.  It’s a tedious process but I think the result will be worth the effort.  I’ve attached an image of the project so far.  I'll post the finished map when it's done.
« Last Edit: December 26, 2016, 08:14:56 AM by Ric Gillespie »
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Arthur Rypinski

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Re: Lagoon Map Project
« Reply #1 on: December 26, 2016, 10:21:22 AM »

Ric-
You might consider:

1) geo-referencing your digital image of the Bushnell survey, by identifying points on the image with known latitude and longitude, and saving as a GeoTiff file.
2) creating a georeferenced blank grid covering the area of the lagoon, using GIS software.
3) copy the values of the Bushnell survey soundings, with the shoreline values =>0 into the appropriate cells on the blank grid.
4) Use the software to interpolate values for the empty cells.

The product will be a geo-referenced digital elevation model (DEM) of lagoon, from which you can then use the software to generate contour maps, as well as better appreciate any subtle features that the Bushnell survey may have detected.  Additional information can be incorporated into the DEM from later surveys or field work.  Further, both the Bushnell survey and the DEM can be overlaid on satellite imagery or charts, which may be helpful in matching visible features, including water color, to the soundings.

adr


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Ric Gillespie

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Re: Lagoon Map Project
« Reply #2 on: December 26, 2016, 10:43:58 AM »

Sounds like a great idea but beyond my pay-grade.  I'm a paint-by-numbers guy. We have a TIGHAR member who is a GIS professional - Jim Thompson.  I can ask him if he be interested in working on this - unless you lose your head and volunteer.
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Arthur Rypinski

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Re: Lagoon Map Project
« Reply #3 on: December 27, 2016, 07:39:16 AM »

Jim can probably do a much more competent job, with less effort.  However, if you send me an digital version of the chart with sufficient resolution to read the soundings, I can probably make some progress.

adr
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Ric Gillespie

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Re: Lagoon Map Project
« Reply #4 on: December 27, 2016, 07:44:09 AM »

Jim can probably do a much more competent job, with less effort.  However, if you send me an digital version of the chart with sufficient resolution to read the soundings, I can probably make some progress.

I've asked Jim for his thoughts about your suggestion.  Meanwhile, I'll send you a hi-res digital copy of the map.
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Jerry Germann

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Re: Lagoon Map Project
« Reply #5 on: January 09, 2017, 10:28:33 AM »

What type equipment will be used in the lagoon search? And could instruments such as this; http://www.quantrosensing.com/ be of use to cover a larger area? I believe the focus is on trying to determine where any artifacts may have settled , via currents and depressions on the lagoon floor, and spend most time exploring those.....but would this tool help search more area? I am not familiar with this technology,....My experience is only using land model metal detectors ....White's by the way, one of our sponsors.
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Ric Gillespie

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Re: Lagoon Map Project
« Reply #6 on: January 09, 2017, 10:46:25 AM »

What type equipment will be used in the lagoon search?
The current plan calls for side-scan sonar as the primary search tool. We'd also like to have some kind of towed metal detection equipment but it would need to be able to detect aluminum.  All of the products by the Quantro company  seem to be magnetometers.  Magnetometers respond only to ferrous metal.  The question then is whether there is a reasonable expectation that steel components ended up in the lagoon.
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Jerry Germann

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Re: Lagoon Map Project
« Reply #7 on: January 09, 2017, 12:03:13 PM »

http://www.metaldetector.com/learn/buying-guide-articles/marine-salvage-search-recovery/best-metal-detectors-for-underwater-search-recovery

This site has a few boat towed, that will detect both ferrous and non-ferrous ....JW Fishers Pulse 10 or 12 may be worth checking out, if funds can be raised to include it on the trip.
« Last Edit: January 09, 2017, 12:25:27 PM by Jerry Germann »
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Ric Gillespie

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Re: Lagoon Map Project
« Reply #8 on: January 09, 2017, 12:34:47 PM »

Thanks jerry.  The JW Fisher Pulse 12 looks like just the ticket, but the price is $10K.  It's worth asking them if they might want to donate the use of a unit for the publicity.
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Jeff Lange

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Re: Lagoon Map Project
« Reply #9 on: January 09, 2017, 02:18:44 PM »

Ric,
With the focus now on a lagoon search, rather than the underwater submersible search, can you refresh our collective memories of what previous searches, if any, have been done in the lagoon, when, and what the results were? I seem to recall some searching of the lagoon, but I can't put my hands on the info. (Marty will insert "search" link for site here!  ::))

Happy New Year!
Jeff Lange

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Martin X. Moleski, SJ

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Re: Lagoon Map Project
« Reply #10 on: January 09, 2017, 02:44:34 PM »

(Marty will insert "search" link for site here!  ::) )

Yes!

You can find it on every page of the Forum

It's up there now.  ^^^^^^^

It's a tab labeled "search."

The tab leads to a page with a Google box in the middle of it.

Putting the two words, "lagoon", and "search", into the Google box yields a bunch of relevant pages on the website.

 ;D
LTM,

           Marty
           TIGHAR #2359A
 
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Jerry Germann

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Re: Lagoon Map Project
« Reply #11 on: January 09, 2017, 03:07:15 PM »

Thanks jerry.  The JW Fisher Pulse 12 looks like just the ticket, but the price is $10K.  It's worth asking them if they might want to donate the use of a unit for the publicity.

Looking at the product overview; they state that it locates items such as cannons, cannon balls, anchors, Propellers, LOST AIRPLANES, sunk cars, and ship wrecks.
This may be a great chance to demonstrate it's working abilities....think of the publicity if one of their detectors helped in finding another smoking gun clue.
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Steve Lyle Gunderson

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Re: Lagoon Map Project
« Reply #12 on: January 09, 2017, 09:55:45 PM »

The Department of Fish and Game uses dye markers to track water flow and migration in lakes and streams. Would dye markers be of any use in determining the tidal flow into and around the lagoon? The dye could be tracked via drone or using the old camera on a kite trick.
Steve G
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Ric Gillespie

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Re: Lagoon Map Project
« Reply #13 on: January 10, 2017, 07:32:35 AM »

The Department of Fish and Game uses dye markers to track water flow and migration in lakes and streams. Would dye markers be of any use in determining the tidal flow into and around the lagoon?

It's worth considering, but the real question is what happens when storm events push a surge of water into the lagoon.  Does that just intensify the power of normal flow patterns?  How much motive power are we talking about? How far would it push non-buoyant objects?  Where would buoyant objects go?  Tough questions.
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Ric Gillespie

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Re: Lagoon Map Project
« Reply #14 on: January 10, 2017, 07:36:14 AM »

With the focus now on a lagoon search, rather than the underwater submersible search, can you refresh our collective memories of what previous searches, if any, have been done in the lagoon, when, and what the results were? I seem to recall some searching of the lagoon, but I can't put my hands on the info. (Marty will insert "search" link for site here!  ::))

Excellent question.  Yes, we've done some searching in several parts of the lagoon at various times with various technologies.  An annotated map of those areas is needed.  I'm working on that and will post it when it's done.
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