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Author Topic: Sunrise Encounter  (Read 94604 times)

Robert J Schafish

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Sunrise Encounter
« on: May 31, 2011, 08:24:40 PM »

The  discussions in the Celestial Navigation forum have led down many informative paths on aspects of navigation that have kept me coming back to see what new topics have come up or what new insights have been uncovered.  So I have decided to plunge in at the risk of exposing my ignorance of navigation, celestial or otherwise.  The general topic is the line of position technique.  The concept appears to be clear;  when you observe the sunrise then you know you are somewhere along the line that sunrise  describes over the surface of the earth.  The forum discussion on the line of position included much speculation on whether this technique was used by Noonan on the route to Howland.  It set me to ask if it was possible to estimate the time and/or distance from Howland when the AE aircraft would/could have encountered sunrise on the approach to Howland.  Would the results be consistent with communications from AE? 

After reviewing the information in the Celestial Navigation forum it made sense to me to characterize the line of sunrise as moving along the earth’s surface at the velocity of the earth’s rotation.  Starting with that idea, and using the estimated flight path of the aircraft ( a line from Lae to Howland),  I plotted  the time of sunrise along the flight path but travelling from east to west,  opposite the direction of the aircraft.  The aircraft can be described as travelling along the same line from Lae to Howland  but in the opposite direction.  The intersection of the aircraft with sunrise on the morning of July 2, 1937  can be calculated from the two plots or by using the associated equations.

Sunrise at a given date and latitude and longitude was calculated using the National Oceanic and Atmospheric Administration’s (NOAA) sunrise/sunset calculator at http://www.srrb.noaa.gov/highlights/sunrise/sunrise.html  I used the  NOAA web site to calculate the time of sunrise at Howland and at intervals of 100 miles, 200 miles and 300 miles from Howland along the projected flight path of the AE aircraft from Lae to Howland.  Latitudes and longitudes of these points were obtained using Google Earth. 

I plotted the time and distance for sunrise along the Howland – Lae path using Excel which also produced an equation relating the time of sunrise west of Howland  (GMT)  = 0.00106 x +17.75 hours where x is the distance from Howland. 

                                                   Table 1
Sunrise GMT   Miles from               Lat         Long
                        Howland
17:45         0         0 47’ 57.84” N      176 37’ 14.75”W
17:52         100         0 30’ 25.62” N             178   2’ 50.09”W
17.58          200         0 11’ 15.02” N      179  28’ 21.67”W
18.04         300         0   5’ 51.73” S      179   7’  14.03”E

 I then used the time and location of the ship siting reported by AE (the Myrtlebank at 10:30 hours GMT) and  two radio transmissions by AE;   200 miles out  17:42, and 100 miles out at 18:12 hours and departure from Lae at 0:00 GMT  to plot the aircraft’s location along the projected flight path (Table 2)

                                                         Table 2
                                        Time      Miles from Howland
                                         18:12         100
                                         17:42         200
                                         10:30            1,121 (Myrtlebank siting)
                                           0:00            2,556 (Lae)

Again, I used Excel to plot the data and produce an equation; GMT = -0.0077 X + 19.091 where X is the distance from Howland. 

When the aircraft’s path and the sunrise line coincide then the time for both is the same. So at that time the two equations are equal;
 
0.00106 x +17.75 = -0.0077 X + 19.091. 

Solving for X, the result is 153 miles from Howland at GMT = 17:55.


So, does this pass the laugh test?  Is the basic analysis correct?  Does the result make sense and does it tell us anything new or interesting? Comments and constructive criticism are welcome! 
Cheers, Bob Schafish
   
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h.a.c. van asten

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Re: Sunrise Encounter
« Reply #1 on: May 31, 2011, 09:48:43 PM »

R.Schaf. I come back  one time for it : excellent analysis , separated from that your results confirm computations made by application of navigation technique of the era , see EJN-2008 & 2011.
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Martin X. Moleski, SJ

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Re: Sunrise Encounter
« Reply #2 on: May 31, 2011, 10:19:46 PM »


Solving for X, the result is 153 miles from Howland at GMT = 17:55.

So, does this pass the laugh test?  Is the basic analysis correct?  Does the result make sense and does it tell us anything new or interesting? Comments and constructive criticism are welcome!  


It sounds like it is in the ballpark, but you should think about how many assumptions you have made about air speed and course made good from Lae to the intersection.

Note the information from Bob Brandenburg and Gary LaPook about how high the sun has to rise before a useful observation can be made: six degrees above the horizon (about a half-hour).  That shifts the time and place when Noonan would have drawn his line of position on his chart later in the morning and further east from your intersection between the flight line and the terminator.

I can't count how many times Ric and Bob and others have cautioned against using the time of transmission as the time of the position fix.  We don't know how long before Earhart's regularly-scheduled broadcasts Fred calculated their position or whether he took into account the lag between his calculation and the time of the transmission.  "All of the flight data provided by Earhart, with the possible exception of "ship in sight ahead", can be fit with a variety of paths. In other words, there are no internal inconsistencies with Earhart's data that she provided. The 200 and 100 mile out position reports are compatible simply because those positions were not the positions at the time she broadcast her messages, but were positions made somewhat prior to those times" ("Monte Carlo Simulation of Flight").

You can tell from the timeline of the transmissions that the position reports are sketchy at best.  In the half-hour between the "200 miles out" message (1742 GMT) and the "100 miles out" message (1812 GMT), the aircraft almost certainly did not travel at 200 mph.  The second report seems more likely to be close to the time of the fix because it is after sunrise for the airplane.

What you have done is calculate one possible flight path and timeline.  Randy Jacobson talks about the defects of that approach:

"Another flaw in researcher's analysis is trying to reconstruct the flight using paper and pencil, as though there was only one solution that fit the data. There are literally millions of possible flight permutations that fit the available data, and it is only by using the computer and Monte Carlo simulations that any hope of determining the flight path can be considered. Monte Carlo methodology is a brute force means to obtain a solution to a set of equations or problem: literally thousands, if not millions, of possible solutions are examined. Some of these solutions are not valid, since they violate known data constraints; whereas others are assigned probabilities, based upon probabilistic estimates of input parameters. For example, let us consider that Earhart accounted for expected cross-winds, based upon forecasts, during her flight. She received a number of forecasts, and we must assign a probability to each forecast that she may have used. Similarly, we have to assign probabilities to actual wind aloft velocities and directions, extrapolated from surface measurements. Once all of these probabilities have been assigned, the Monte Carlo simulations are run, and what results is a probabilistic map of Earhart's position as a function of time. Even if there was a sharp peak in the distribution at any particular time, that does not mean Earhart was actually there, she could be anywhere where the probability is non-zero. The best use of Monte Carlo simulations is not only to determine the most likely flight, but where Earhart could not have gone"  ("Monte Carlo Simulation of Flight").
LTM,

           Marty
           TIGHAR #2359A
 
« Last Edit: May 31, 2011, 10:40:14 PM by Martin X. Moleski, SJ »
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Gary LaPook

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Re: Sunrise Encounter
« Reply #3 on: June 01, 2011, 04:32:00 AM »

The  discussions in the Celestial Navigation forum have led down many informative paths on aspects of navigation that have kept me coming back to see what new topics have come up or what new insights have been uncovered.  So I have decided to plunge in at the risk of exposing my ignorance of navigation, celestial or otherwise.  The general topic is the line of position technique.  The concept appears to be clear;  when you observe the sunrise then you know you are somewhere along the line that sunrise  describes over the surface of the earth.  The forum discussion on the line of position included much speculation on whether this technique was used by Noonan on the route to Howland.  It set me to ask if it was possible to estimate the time and/or distance from Howland when the AE aircraft would/could have encountered sunrise on the approach to Howland.  Would the results be consistent with communications from AE? 

After reviewing the information in the Celestial Navigation forum it made sense to me to characterize the line of sunrise as moving along the earth’s surface at the velocity of the earth’s rotation.  Starting with that idea, and using the estimated flight path of the aircraft ( a line from Lae to Howland),  I plotted  the time of sunrise along the flight path but travelling from east to west,  opposite the direction of the aircraft.  The aircraft can be described as travelling along the same line from Lae to Howland  but in the opposite direction.  The intersection of the aircraft with sunrise on the morning of July 2, 1937  can be calculated from the two plots or by using the associated equations.

Sunrise at a given date and latitude and longitude was calculated using the National Oceanic and Atmospheric Administration’s (NOAA) sunrise/sunset calculator at http://www.srrb.noaa.gov/highlights/sunrise/sunrise.html  I used the  NOAA web site to calculate the time of sunrise at Howland and at intervals of 100 miles, 200 miles and 300 miles from Howland along the projected flight path of the AE aircraft from Lae to Howland.  Latitudes and longitudes of these points were obtained using Google Earth. 

I plotted the time and distance for sunrise along the Howland – Lae path using Excel which also produced an equation relating the time of sunrise west of Howland  (GMT)  = 0.00106 x +17.75 hours where x is the distance from Howland. 

                                                   Table 1
Sunrise GMT   Miles from               Lat         Long
                        Howland
17:45         0         0 47’ 57.84” N      176 37’ 14.75”W
17:52         100         0 30’ 25.62” N             178   2’ 50.09”W
17.58          200         0 11’ 15.02” N      179  28’ 21.67”W
18.04         300         0   5’ 51.73” S      179   7’  14.03”E

 I then used the time and location of the ship siting reported by AE (the Myrtlebank at 10:30 hours GMT) and  two radio transmissions by AE;   200 miles out  17:42, and 100 miles out at 18:12 hours and departure from Lae at 0:00 GMT  to plot the aircraft’s location along the projected flight path (Table 2)

                                                         Table 2
                                        Time      Miles from Howland
                                         18:12         100
                                         17:42         200
                                         10:30            1,121 (Myrtlebank siting)
                                           0:00            2,556 (Lae)

Again, I used Excel to plot the data and produce an equation; GMT = -0.0077 X + 19.091 where X is the distance from Howland. 

When the aircraft’s path and the sunrise line coincide then the time for both is the same. So at that time the two equations are equal;
 
0.00106 x +17.75 = -0.0077 X + 19.091. 

Solving for X, the result is 153 miles from Howland at GMT = 17:55.


So, does this pass the laugh test?  Is the basic analysis correct?  Does the result make sense and does it tell us anything new or interesting? Comments and constructive criticism are welcome! 
Cheers, Bob Schafish
   

--------------------------------------------

Where did you get the assumption that they were (or should have been) at Howland at 19:05:28 Z (accurate to the nearest second) since this is where your 19.091 factor comes from?

How did you deal with the discrepancy in the required ground speeds from the 100 and 200 mile reports? Since you have them arriving at 19:05:28 Z the ground speed from the 100 mile report at 18:12 Z must have been 112 mph but from the 200 mile report it must have been 144 mph?

And you are assuming that they went straight in without flying an offset landfall approach which they might have been doing when they realized that the radio was not working . If they did fly a standard landfall approach then they would have had to travel more miles until they thought that they were at Howland. But regardless of the exact flight path we can be sure that they thought that they were at Howland by 1912 Z when Earhart reported "must be on you" but it is also quite likely that this report came some time after they thought they were at Howland, a delay of 5, 10  or even 15 minutes until making this transmission would not be unreasonable.

-----------------------------------------------------------------------------------------------

One thing I do have to laugh about is the level of precision that you (and others) use in stating your results. A calculator or computer is perfectly happy working to a precision of 10 or more  decimal places, 10 or more significant figures, but this is an example GIGO. As I have pointed out to others before, you cannot state your result to the nearest second when your original data was accurate only to the nearest minute (and maybe not even that accurate.) For example, the coordinates you used for Howland of 00° 45' 57.84" N and 176° 37' 14.75" W that you input into the sunrise calculator website (thank you for that link) you state to the nearest one-hundredth of a second of arc, how did you get the coordinates to that level of precision? One second of latitude (and longitude at the the position of Howland) is only 101.2685914 feet (let's just call it a hundred feet) so by stating the coordinates to a one-hundredth of a second you are claiming a precision of one foot! Even GPS only claims 10 meter accuracy which is more than 30 feet. The same with the other coordinates that you state, all accurate to within one foot? Your computer is perfectly happy coming up with numbers like this but they don't have any meaning in the real world.  The report of "100 miles" also has some margin of error. Even if it Noonan's estimate was perfect, the way it was stated, "100 miles", means that there is still a one mile ambiguity from 99.5 to 100.5 miles, 5280 feet,  which is 52 seconds of latitude or longitude at the position of Howland so it is kinda silly stating those position to the nearest one hundredth of a second, to the nearest foot.

The same problem with your times of sunrise. You put your coordinates into the sunrise website and just took out the results. But there is a one minute ambiguity, +/- 30 seconds, resulting in an ambiguity of 15 minutes of longitude (15 NM) ambiguity for the location and times of sunrise using this website, just like when using the Nautical Almanac sunrise table. Go back and enter any longitude from 176° 24' 28" W through 176° 39'  27" W for Howland and you will get the same 1745 Z time of sunrise. For the 100 mile out position you can enter any longitude from 178° 01' 59" W through 178° 16' 58" W and you will get the same time of 1752 Z.

One more way to look at this, you state the longitudes to one-hundredth of a second of arc. The terminator (the line separating day from night, the sunrise line) moves towards the west at a rate of 15° per hour so it takes 4 minutes to go one degree of longitude. A minute of arc is one-sixtieth of a degree so it takes 4 seconds to go 1' of longitude. A second of arc is also one-sixtieth of a minute so it takes only 1/15th of a second to move one second of longitude. At the precision that you are stating your longitudes, 0.01" or 1 foot, the terminator moves this far in 0.00067 seconds so I think it is interesting that you think you can predict sunrise to a  precision of 1/1500 of a second! Especially since the website gives the data to a level of 60 seconds, so you manage to calculate to a precision 90,000 times better than the original data!

Anyway, you should give some thought to what the numbers you computer spits out really mean.

Gary LaPook
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Ric Gillespie

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Re: Sunrise Encounter
« Reply #4 on: June 01, 2011, 07:10:02 AM »

One thing I do have to laugh about is the level of precision that you (and others) use in stating your results.

TIGHAR board member, expedition veteran, retired USAF pilot/airline captain/NASA consultant and all-around great guy "Skeet" Gifford like to say, "Measure with micrometer, mark with chalk, cut with an axe."

In truth there can be no precision at all in reconstructing what happened during the failed Lae/Howland flight. All of the various analyses are full of confident statements about what Noonan would have done and wouldn't have done. It's all speculation.  To determine what actually happened requires evidence. The available evidence consists of reported radio transmissions from the aircraft both before and after it vanished, reported search results, photographs of apparent wreckage, and recovered artifacts. All of the available evidence suggests that the flight ended at Gardner Island. That it could have gotten there is undeniable. How it might have gotten there is unknown and ultimately unknowable.
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Bill Lloyd

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Re: Sunrise Encounter
« Reply #5 on: June 01, 2011, 10:05:42 AM »

All of the available evidence suggests that the flight ended at Gardner Island. That it could have gotten there is undeniable. How it might have gotten there is unknown and ultimately unknowable.

Gary LaPook goes to great links to argue against the TIGHAR theory.  He writes what amounts to a treatise on why it was not possible to follow the 157° LOP to Niku.

Mr. LaPook is very adamant that there was no way for Noonan to navigate the 157° LOP since, among other reasons, it relocated after the first hour.   
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Gary LaPook

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Re: Sunrise Encounter
« Reply #6 on: June 01, 2011, 01:31:51 PM »

All of the available evidence suggests that the flight ended at Gardner Island. That it could have gotten there is undeniable. How it might have gotten there is unknown and ultimately unknowable.

Gary LaPook goes to great links to argue against the TIGHAR theory.  He writes what amounts to a treatise on why it was not possible to follow the 157° LOP to Niku.

Mr. LaPook is very adamant that there was no way for Noonan to navigate the 157° LOP since, among other reasons, it relocated after the first hour.   

-----------------------------------------------------------------

That should come as no surprise to anyone since I have been saying the same thing since I started posting to TIGHAR in 2002. Look at my March 18, 2002 post available in the archives at:

http://tighar.org/Projects/Earhart/Archives/Forum/Forum_Archives/200203.txt

Gary LaPook
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Chris Owens

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Re: Sunrise Encounter
« Reply #7 on: June 01, 2011, 02:10:32 PM »

I have read, but don't understand  Gary LaPook's argument as to why it is impossible to fly the 157/357 LOP.  What happens if you:

  • Take a sight at some time shortly after sunrise, giving you a LOP
  • Continue flying for, say, an hour.  Advance the LOP by your best dead reckoning estimate of your course and speed over the ground.
  • Hang a right and fly, by DR, a course as close to 157 as you can.
Admittedly this does not guarantee that you're flying any particular LOP, but it's pretty damn close.
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Gary LaPook

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Re: Sunrise Encounter
« Reply #8 on: June 01, 2011, 03:31:50 PM »

I have read, but don't understand  Gary LaPook's argument as to why it is impossible to fly the 157/357 LOP.  What happens if you:

  • Take a sight at some time shortly after sunrise, giving you a LOP
  • Continue flying for, say, an hour.  Advance the LOP by your best dead reckoning estimate of your course and speed over the ground.
  • Hang a right and fly, by DR, a course as close to 157 as you can.
Admittedly this does not guarantee that you're flying any particular LOP, but it's pretty damn close.


--------------------------------------------------------------
In short, it's not "pretty damn close."

Sure you can fly a heading of 157° but there is no guarantee of staying on the line that leads to Nikumaroro, or even near that line. Since we know that there was a wind out of the easterly direction, a heading of 157° would guarantee that they did NOT stay on the LOP since the crosswind would have blown them off to the west. A wind out of the east at 20 knots would have caused the plane to drift to the right by 9° so their track would have been 166°, not even close to their 157° heading. If the wind speed was 30 knots then the drift would have been 13° to the right making their track 170°. Based on a visibility of 20 miles, it would take an error of only 3° to cause them to pass so for to the west of Nikumororo that they wouldn't  have been able to see it. And Nikumroro is the furthest to the west of the Phoenix islands so missing it to the west would also guarantee that they would never see any of the other islands either.

The reason the difference between following an LOP versus just flying a heading is important is that if the LOP had been available then Noonan could have taken additional sights and corrected back onto the LOP if he got blown off course and there is no such corrective mechanism when just flying a heading. It is the difference between driving down a street that has curbs on both sides versus just driving off cross-country across an empty desert. Even on a long trip of 350 miles, if you stay on the road you are guaranteed of getting to your destination. Driving cross-country across 350 miles of featureless desert only guarantees you that you will end up somewhere in the desert.

Gary LaPook
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Ric Gillespie

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Re: Sunrise Encounter
« Reply #9 on: June 01, 2011, 07:26:07 PM »

Gary LaPook is correct that you can't fly down (or up) an LOP.  All you can do is DR the course described by an LOP - in Earhart's case an 157 -337 line that passes through Howland.  Yes, the wind will blow you off course if you don't correct for it but correcting for drift is pretty basic to DR and Noonan should have had plenty of opportunity to get a handle on what the wind was doing that morning.   

As I said above, we're never going to know for sure how the plane got to Gardner but I don't think you can "debunk" the entire body of evidence that suggests that it did by speculating that Fred Noonan couldn't Dead Reckon that airplane along a 157° True course for a couple hours without wandering way off the line.
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Chris Owens

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Re: Sunrise Encounter
« Reply #10 on: June 01, 2011, 08:09:11 PM »

I have read, but don't understand  Gary LaPook's argument as to why it is impossible to fly the 157/357 LOP.  What happens if you:

  • Take a sight at some time shortly after sunrise, giving you a LOP
  • Continue flying for, say, an hour.  Advance the LOP by your best dead reckoning estimate of your course and speed over the ground.
  • Hang a right and fly, by DR, a course as close to 157 as you can.
Admittedly this does not guarantee that you're flying any particular LOP, but it's pretty damn close.


--------------------------------------------------------------
In short, it's not "pretty damn close."

Sure you can fly a heading of 157° but there is no guarantee of staying on the line that leads to Nikumaroro, or even near that line. Since we know that there was a wind out of the easterly direction, a heading of 157° would guarantee that they did NOT stay on the LOP since the crosswind would have blown them off to the west. A wind out of the east at 20 knots would have caused the plane to drift to the right by 9° so their track would have been 166°, not even close to their 157° heading.


I was not talking about flying a heading of 157, I was talking about flying a  course of 157.  I would think that with an estimate of the winds, drift sights, and other tricks of the DR trade a navigator could get pretty close.  I don't know the state of the art in 1937, but would guess that hitting within 3 degrees of a desired course wouldn't be a miraculous feat.
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Gary LaPook

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Re: Sunrise Encounter
« Reply #11 on: June 01, 2011, 10:36:49 PM »



I was not talking about flying a heading of 157, I was talking about flying a  course of 157.  I would think that with an estimate of the winds, drift sights, and other tricks of the DR trade a navigator could get pretty close.  I don't know the state of the art in 1937, but would guess that hitting within 3 degrees of a desired course wouldn't be a miraculous feat.
[/quote]

----------------------------------------------------------------------

I think the most accepted value for the uncertainty in a DR position is 10% of the distance covered although Weems is overly optimistic and uses an estimate of 5%. The U.S. Navy Air Navigation Manual, H.O. 216, is much less optimistic. See:

https://sites.google.com/site/fredienoonan/topics/accuracy-of-dead-reckoning

So flying 350 miles to Nikumaroro would  lead to an uncertainty in the DR position of 35 miles (enough to miss Niku) even with a good DR. So if they knew they were right over Howland and purposefully decided to DR to Niku, they couldn't be certain of finding it. And, since they didn't know where they were (if they had known, they would have landed on Howland) there would be no way that they could DR to Niku. You cannot DR to a destination without knowing where you are starting from. The error or uncertainty in the starting position is carried forward into all subsequent DR positions to which there it the additional loss of accuracy due to the distance traveled.  The way you do DR is you put a dot on your chart representing your starting location, draw a line from that starting position in the direction you are going to fly, and then measure down that line the distance you think you have traveled. If you put the starting dot in the wrong place then everything on the course line that you drew are also wrong. Noonan's problem was that he wouldn't have known where to place that starting dot! If he had known where he was he would have drawn a line from that dot to Howland and would have DRed to Howland. You cannot start a DR plot without a starting location.

An example of how this works might make it clearer. If they were 60 miles west of Howland when they started DRing down the 157° course, even  with absolutely  perfect DRing and no additional loss of accuracy, at the end of 350 miles of flying, they would still be exactly 60 miles west of the course line. With a loss of accuracy of 35 miles, based on the accepted 10% estimate, you would draw a circle of 35 mile radius around the new DR position and estimate that your are somewhere within that circle. This means that you would be from 25 miles to to 95 miles west of the course line.

Gary LaPook
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Gary LaPook

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Re: Sunrise Encounter
« Reply #12 on: June 01, 2011, 10:47:02 PM »

All of the available evidence suggests that the flight ended at Gardner Island. That it could have gotten there is undeniable. How it might have gotten there is unknown and ultimately unknowable.

Gary LaPook goes to great links to argue against the TIGHAR theory.  He writes what amounts to a treatise on why it was not possible to follow the 157° LOP to Niku.

Mr. LaPook is very adamant that there was no way for Noonan to navigate the 157° LOP since, among other reasons, it relocated after the first hour.   

---------------------------------------------------

You should also note that I don't think too much of the various Japanese capture theories either which all depend upon Earhart being on some sort of a spy mission. See:

https://sites.google.com/site/fredienoonan/discussions/flight-planning-aspects-relating-to-a-possible-earhart-s-spy-flight

https://sites.google.com/site/fredienoonan/discussions/was-earhart-a-spy

Gary LaPook
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Gary LaPook

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Re: Sunrise Encounter
« Reply #13 on: June 01, 2011, 10:59:06 PM »




----------------------------------------------------------------------

I think the most accepted value for the uncertainty in a DR position is 10% of the distance covered although Weems is overly optimistic and uses an estimate of 5%. The U.S. Navy Air Navigation Manual, H.O. 216, is much less optimistic. See:

https://sites.google.com/site/fredienoonan/topics/accuracy-of-dead-reckoning

------------------------------------------------------------------------------------

10% accuracy is the same as a 6° course accuracy.

-------------------------------------------------------------

Put yourself in Noonan's position. Even if in the past, on some occasions you achieved better than 10% accuracy, now that you are looking for a small island in the Pacific would you use that optimistic estimate or a more conservative estimate when making plans for what might be the rest of your life.

Gary LaPook
« Last Edit: August 10, 2011, 02:43:08 PM by Gary LaPook »
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John Joseph Barrett

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Re: Sunrise Encounter
« Reply #14 on: June 02, 2011, 05:23:43 AM »

I don't think anyone has suggested that, upon not finding Howland, a decision was made to fly to Gardner. From what I gather, when Howland couldn't be located it just made sense to head for an area where there were known to be several islands. This would at least give them a chance to find something other than ocean to land on. Finding and landing on Gardner would have been more of a fortunate happening than a planned destination. Viewed from that perspective, if you know you are in one area, you should be able to navigate to another area with some degree of accuracy, not necessarily to a specific point, but at least to the general area. Get there, spot an island, land your plane, radio for help, and wait. I agree, to navigate to a specific place you do need to know where you are to begin with, not so much to go area to area.     -LTM-  John
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