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[Matt Revington]

I know that in the past TIGHAR has got lower res satellite imagery of Niku but has any consideration been given to hi-res satellite data being taken of Niku, this page ;

http://www.landinfo.com/satellite-imagery-pricing.html

has 50 cm ( or a little less) resolution imaging available for for $24 USD /km^2 although there may be additional fees for a place as far off the beaten path as Niku ( that price seems so low that I may not understand their pricing).  They also produce images from multiple parts of the spectrum which might make it easier to observe abnormalities in the vegetation where something unusual is buried.  I'm not sure of the resolution of the current google maps image which was updated recently but this might be a bit better and provide an ideal image to map any data from the lagoon search on. 

[Ric Gillespie]

We have a great relationship with Digital Globe and get half-meter and better resolution imagery for free.  We just recently got fantastic geo-refrerenced imagery taken on November 15, 2016 which we plan to use to create a poster-size (36"x24") print on heavy paper annotated with all kinds of information about points of interest on the island.

[Jerry Germann]

  They also produce images from multiple parts of the spectrum which might make it easier to observe abnormalities in the vegetation where something unusual is buried.  I'm not sure of the resolution of the current google maps image which was updated recently but this might be a bit better and provide an ideal image to map any data from the lagoon search on. 

By Air By Land and By Sea....I know this is probably getting way out there, ...but if those images could help identify a possible target, one that is very difficult to get too, ..maybe something like this; http://accuratelocators.com/quadcopter-metal-detector.html is a way to go.....coverage of ground where humans find it hard going.
As far as the lagoon search....what objects do you feel may have found there way there? One item I would like to see found , would be that wheel.....https://tighar.org/Projects/Earhart/Archives/Research/Bulletins/41_WheelofFortune/41_Wheel.html
hoping it is still in there.

[Ric Gillespie]

As far as the lagoon search....what objects do you feel may have found there way there?

Good question.  We'll know more when we have a feel for how much force is delivered into the lagoon during storm events.  Bob Brandenburg is working on that.  I think a lot would depend on whether the object is buoyant or not.  Stuff that floats will go the farthest.  Imagine the Electra, largely intact, but submerged in, say, 20 feet of water under the surf line.  It can stay there, invisible, for years until a big storm comes along and tears it up. The fuselage rips open and buoyant stuff like fuel tanks and plywood flooring (along with anything fastened to the flooring) bobs to the surface and gets washed into the lagoon.

Another thought:  Where did the Bevington Object go?  If the wreckage of the landing gear assembly is at all buoyant due to the inflated tire, it could go into the lagoon.

[Greg Daspit]

As far as the lagoon search....what objects do you feel may have found there way there?

Another thought:  Where did the Bevington Object go?  If the wreckage of the landing gear assembly is at all buoyant due to the inflated tire, it could go into the lagoon.

This question is exactly why I am trying to get done with the shadow study.  I'm not finished (I may never be) but I believe enough is done to determine the tire was not inflated. I can post the applicable exhibits in the thread I just started.   

[Ric Gillespie]

This question is exactly why I am trying to get done with the shadow study.  I'm not finished (I may never be) but I believe enough is done to determine the tire was not inflated. I can post the applicable exhibits in the post I just started.

When the landing gear failed and separated in the Luke Field accident the tire was definitely torn open.

[Jon Romig]

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.

I'm finally employed again, and my dues are paid up. Glad to be back!

Musings:

Storm waves and surges coming through the Tatiman Passage will slow as they enter the lagoon and normally will drop any carried metal artifacts just inside the passage. Absent the turbulence caused by the wave compression in the Passage, drop-out at the entry to the lagoon is almost assured, unless the waves are huge. If there is sand at that location (current maps seem to show a reef there?) then artifacts may sink deeper into the sand, as successive waves and storms roil the sand. Aluminum has a specific gravity of 2.7; regular sand (which is mostly quartz) has a specific gravity of about 1.6 and coral sand is likely even lighter. Water of course has a specific gravity of 1.0. Given the relative numbers, aluminum will sink quickly unless transported by a lot of turbulence, or unless the objects has a very large surface/volume ratio, which aircraft skin material will have.

My intuition is that artifacts dropped by surges/waves in the lagoon would be as likely to sink into the sand over time as to be transported deeper into the lagoon by successive action. It would be very interesting if Tighar could plant detectable sample artifacts at various points just inside the Tatiman Passage on the lagoon bed, that Tighar could locate during subsequent expedition(s) to determine dispersal patterns.

Alternately, metal artifacts that fall into the reef just inside the lagoon could get caught and eventually become part of that reef.

A third option is that metal artifacts are transported (much?) deeper into the lagoon. This might require quite large storm waves, which may in fact occur at Niku (recall the overwash events).

I think it would be helpful to map/explore in greater detail the "fallout" area just inside the Tatiman Passage, that I believe is by far the most likely place to find anything. If we could get some information on what geology lies below the lagoon bottom in this area we might have a better idea of the VOLUME of material (rather than just the area) that might contain artifacts. With that information we will then be able to plan concurrent or future explorations of it.

Jon

[Ted G Campbell]

This logic makes a whole lot of sense!

Ted

[Ric Gillespie]

This logic makes a whole lot of sense!

Yes, it does.  Expanding on Jon's excellent observations:
I think we have to consider two types of aircraft debris that could travel across the reef flat, through the passage, and into the lagoon - buoyant and non-buoyant. If the aircraft remained relatively intact in shallow (40 feet?) of water off the edge of the reef flat and broke up over time due to deterioration and periodic storm events (as suggested by anecdotal accounts and island folklore), the transit of debris into the lagoon could happen at any time over the years.

 
• Examples of buoyant debris would be empty fuel tanks, oil tanks, inflated tires and attached landing gear components, and plywood flooring (with any lightweight non-buoyant structures attached to the flooring).  Once buoyant debris enters the lagoon, its distribution will be determined by flow and wind, and by how long it remains buoyant.

• Non-buoyant debris could be anything whose mass is less than the driving force of water entering the lagoon. Bob Brandenburg is trying to quantify that force.  Bob says, "Wave behavior on a coral reef has been well-researched by the oceanographic community, as well as the coastal engineering community.  A major insight for our present analysis is that we can't consider the reef flat -- where you can walk -- as the sole determinant in wave height at the lagoon entrance.  We also need to account for the slope of the reef just seaward of the walkable area.  That's because a wave of height approximating the depth of the submerged reef just seaward of the survey transect area will start breaking before it gets to the flat."  There are good data on reef seaward of the lagoon passage collected by the New England Aquarium.  When Bob has concluded his calculations we should have some idea of what sort of non-buoyant components could make it into the lagoon.

There is a large "delta" of fine sand at the mouth of the passage that extends well into the lagoon.  Aerial photos show that the delta has grown over the years.  Any non-buoyant debris that is buried deep in that delta is not accessible to us.  Non-buoyant debris that made it past the delta and sank onto the floor of the lagoon should not have moved much in subsequent years.  We've done some searching with metal detectors in that area with no results but it needs a more thorough inspection.  There is no reef in the lagoon.  There are coral heads ( you can see them in the satellite images) that grow to just below the surface of the water.  Whenever we're using the lagoon, for example, to travel back and forth to the Seven Site, we buoy the coral heads with empty plastic milk jugs.  Hitting a coral head in a skiff traveling at 20 knots will spoil your day.

[Jon Romig]

How do we intend to differentiate pieces of wreckage of the Norwich City from the Electra, using a metal detector? The Norwich City was ~1000 times the weight of the Electra, and we know for sure that it was spewing debris for seven+ decades from a wreck that was both longer-lasting and closer to the mouth of Tatiman Passage than the Electra's.

Odds would seem to be less than 1/1000 that any item detected is from the Electra.

My January post above suggests that there may be a natural rate at which aluminum (as opposed to other metals) will sink in the coral sand over time. Combining that with the fact that the sand delta has been growing into the lagoon, is it not possible that there is a stratum (horizontal, curved or sloped) in the sand delta where aluminum debris from the middle decades of the last century ended up? If the answer is a qualified yes, how should one go about determining the location of that strata?

Also, is there any hydrodynamic explanation for the Eastward growth of the sand delta? The causal mechanisms that I can imagine are: 1. a gross migration Eastward of the entire delta due to rising sea levels and bigger storms, and/or 2. deposition of additional sand due to erosion of ocean-facing beaches on Niku. Which mechanism is at work would substantially change where historic debris (from, say, the late 1930's) might be found today.

Under 1. for example, older wreckage might be jumbled together at (or just beneath) the West end of the sand delta. I may be off the mark but I am imagining that the morphology of the ocean-facing side of the delta is something like a sandy beach, with the typical beach face being analogous to the sloping West end of the sand delta (as drawn in the March 2017 edition of TIGHAR Tracks), and the typcical beach step being analogous to the adjacent flat area of the Passage, just to the West of the delta. As any beachcomber knows, most of the heavier stuff ends up on the beach step, which is typically exposed at low tide.
 
Jon

[Ric Gillespie]

How do we intend to differentiate pieces of wreckage of the Norwich City from the Electra, using a metal detector?

Our metal detectors do not differentiate between ferrous and non-ferrous metals so the only way to differentiate between NC wreckage and Electra wreckage is by examination - but at least the metal dectecor gives you something to examine.

The Norwich City was ~1000 times the weight of the Electra, and we know for sure that it was spewing debris for seven+ decades from a wreck that was both longer-lasting and closer to the mouth of Tatiman Passage than the Electra's.

Odds would seem to be less than 1/1000 that any item detected is from the Electra.

I'm not qualified to calculate the odds, but it seems to me that light-weight debris is easier to move than heavy debris.  We see no NC debris on the reef flat further than about 200m from the wreck, except for one large section along the shoreline at 400m which we can't explain unless it was originally buoyant.

My January post above suggests that there may be a natural rate at which aluminum (as opposed to other metals) will sink in the coral sand over time. Combining that with the fact that the sand delta has been growing into the lagoon, is it not possible that there is a stratum (horizontal, curved or sloped) in the sand delta where aluminum debris from the middle decades of the last century ended up? If the answer is a qualified yes, how should one go about determining the location of that strata?

I have no idea.  It's not possible to dig a hole in the sand delta.  It fills in as fast you dig.  In 1997 we considered dredging the delta and even bought a gas-powered dredge and hose but extreme sea conditions prevented us from taking it ashore.  In retrospect, dredging the delta could really screw-up the lagoon and today, with Niku being a World Heritage Site, there is no way we could ever get permission to do something so invasive (and dumb).

Also, is there any hydrodynamic explanation for the Eastward growth of the sand delta? The causal mechanisms that I can imagine are: 1. a gross migration of the delta due to rising sea levels and bigger storms, and/or 2. deposition of additional sand due to erosion of ocean-facing beaches on Niku. Which mechanism is at work would substantially change where historic debris (from, say, the late 1930's) might be found today. Under 1. for example, older wreckage might be jumbled together at or just beneath the West end of the sand delta.

Sand is nothing more than granulated coral.  Fish nibbling on the coral and wave action on the reef create sand which washes ashore and makes beaches.  Sand washing through the passage builds up into a delta that slowly expands eastward into the lagoon over time.  If there's a pile of old wreckage at the base of the West end of the delta that would be nice.

[Jon Romig]

Sand is nothing more than granulated coral.  Fish nibbling on the coral and wave action on the reef create sand which washes ashore and makes beaches.  Sand washing through the passage builds up into a delta that slowly expands eastward into the lagoon over time.  If there's a pile of old wreckage at the base of the West end of the delta that would be nice.

That's amazing that you brought a sand dredge in 1997! There is no such thing as a new idea, especially here.

Over time I would expect the size and location of the sand delta to stabilize. The fact that it is observably growing over a span of a few recent decades, suggests that this is a new process, otherwise the lagoon would be full of sand. The other possibility is that it has a long, multi-decadal period, as we are now finding is true for some other natural processes like ocean currents.

Jon

[Ric Gillespie]

That's amazing that you brought a sand dredge in 1997!

Hell, we also brought an ultra-light aircraft on floats strapped to the top deck, but when we got to Niku the sea was too rough to put it over the side.