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Author Topic: Navigating the LOP with the offset method.  (Read 198612 times)

h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #180 on: June 12, 2011, 07:47:50 PM »

... he has his own idea
of what “sunset” is that doesn’t comport with anybody else’s understanding of that word! ...

On your remark abt. E.Long : remarkably and fully independent of each other , supposed that mr.Long could not have read my contribution on fuel supplies & management of 1996 in the magazine of R.Neth.A.F. museum , Soesterberg , we register the 1845 GMT fuel reserves @ 45 US . In his book published after 1996 , Long gives just the figure ,no calculation .
In the course of 2008 mr.D.Jourdan handed over to mr.Long a copy of my EJN-2008 article . On receiving it he replied that , after thirty years research on the subject , he could no more afford the time and energy for studying other vistas .

I hate to admit that Elgin Long is smarter than I am but he was smart enough to ignore Mr. van Austen and his weird theories and did not waste a lot of his time, as I have, in responding to Mr. van Austen.

gl

Mr. Long´s reply was not to me , he replied to mr. Jourdan , who later said to me that it was mr.Long´s getting on in years , that kept him from studying the 2008 article .
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #181 on: June 12, 2011, 08:02:31 PM »

Chichester , and a variety of ocean pilots used marine sextants to establish A/c´s position w.r.t. lines of position in the One Line Approach operation , they all were succesful in finding their destiination this way , there is no record of any miscarriage by using the method. Hegenburger/Maitland (on a completely precomputed navigation plan to Hawaii) even carried a single telescope to be able observing objects of which elevation was of no importance , p.e. for sunset/sunrise not any instrument besides the unarmed eye and facultatively a green filter is needed , since only the point of time @ U.L. appearance is of importance , to match it with the running list figures for latitude/longitude. If p.e. mr. Noonan used the mariner´s sextant (for it´s green filter) or not , that has zero influence on the error he possibly/probably committed by not using the bubble sextant like @ sunset . The only second condition for observing sunrise from an A/c is : fly low to avoid seeing the sun earlier than @ sea level which is the lower reference for elevation of heavenly bodies. It is for these reasons of no use to bring yes or no marine sextants in the field of discussion , for any navtable or navformula if computed elevation is zero .

Mr. van Asten,

It would be an error to use the marine sextant only if he had computed data for use with a bubble sextant and then only if he were using the "van Asten sunset/sunrise" method which you have never produced any proof whatsoever that it was ever used by anybody, and this includes you, since you have never used it either.

gl

mr.Noonan actually computed data for using the bubble sextant , namely for the sunset fix . Later @ sunrise he accidentally maintained them , but did not continue the use of the b-sextant , replacing it for observation by unarmed eye , telescope , marine sextant , or whatever it may have been . In EJN 2008 I suggested the marine sextant having been used because of it´s green filter against dazzle .
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #182 on: June 12, 2011, 08:20:28 PM »

... If they used the bubble sextant to
measure the dip then there would have been no need to determine dip at all since they would just
use the bubble sextant for taking the observations.  ...

Does the Pioneer bubble sextant obviate the need to know one's altitude when drawing a LOP based on an observation?

Or does the potential error introduced by not being able to calibrate their altimeter to a local barometric reference affect both kinds of instruments equally?





Altitude is of no importance for any artificial horizon sextant since the bubble is in line with the celestial horizon which is parallel with the observer´s "equator" , both pointing to infinity.

Altimeter and b-sextant have no interconnection in the given sense . If no QNH is available and the altimeter off scale , the possibility to assess low altitude remains by consulting the table for dip in H.O.208 , giving 00-31´ for 1,000 ft. If you turn up a mariner´s sextant to 31´ and you see the optical horizon in the reference line , you are @ 1,000 ft altitude.
--------------------------------------------------

It only works if you already know your altitude accurately. If you set your marine sextant to 31' and you are not actually at 1,000 feet then the sextant will define a false horizontal and all of your reading will be wrong. You have come up with a circular argument. If you measured the angle between the visible horizon and the "optical horizon" (that's a new term that you just came up with, I take it you meant the true horizontal) and the measurement was 31' you're right, you would be at 1,000. The problem is there is no reference out in the air somewhere showing where the true horizontal is so there is no way to make this measurement.

See the dip table at: https://sites.google.com/site/fredienoonan/resources/air-almanc-1982/AirAlmanac1982%2Cdiptable.jpg?attredirects=0

and you will see that if your true altitude is just 33 feet different from 1,000 feet then your horizontal will be off by 1'. If off by 500 feet then your horizontal will be off by 8'.

gl



Optical (= ´by vision´)  horizon is another word for visible horizon , therefore ,  taking into account the horizon dip of 00-31´ for 1,000 ft from table in H.O.no.208 will assure you to be @ 1,000 ft altitude if you use a mariner´s sextant . A few days ago you mentioned  , by comment  , to consider this a method of interest in case of an off-scale altimeter.
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #183 on: June 12, 2011, 08:30:22 PM »

... The only second condition for observing sunrise from an A/c is : fly low to avoid seeing the sun earlier than @ sea level which is the lower reference for elevation of heavenly bodies.

The only way to fly low enough to "to avoid seeing the sun earlier than @ sea level" is to be in a submarine, since you would have to be below sea level.

gl

Plse explain , I do not follow this.
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #184 on: June 12, 2011, 08:38:51 PM »

G.Lapk . btw , @ 1912 GMT A/c was  reported to be @ 1,000 ft altitude , very good that you do not believe me , but why don´t you believe the pilot herself ?
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Gary LaPook

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Re: Navigating the LOP with the offset method.
« Reply #185 on: June 12, 2011, 11:20:43 PM »

Chichester , and a variety of ocean pilots used marine sextants to establish A/c´s position w.r.t. lines of position in the One Line Approach operation , they all were succesful in finding their destiination this way , there is no record of any miscarriage by using the method. Hegenburger/Maitland (on a completely precomputed navigation plan to Hawaii) even carried a single telescope to be able observing objects of which elevation was of no importance , p.e. for sunset/sunrise not any instrument besides the unarmed eye and facultatively a green filter is needed , since only the point of time @ U.L. appearance is of importance , to match it with the running list figures for latitude/longitude. If p.e. mr. Noonan used the mariner´s sextant (for it´s green filter) or not , that has zero influence on the error he possibly/probably committed by not using the bubble sextant like @ sunset . The only second condition for observing sunrise from an A/c is : fly low to avoid seeing the sun earlier than @ sea level which is the lower reference for elevation of heavenly bodies. It is for these reasons of no use to bring yes or no marine sextants in the field of discussion , for any navtable or navformula if computed elevation is zero .

Mr. van Asten,

It would be an error to use the marine sextant only if he had computed data for use with a bubble sextant and then only if he were using the "van Asten sunset/sunrise" method which you have never produced any proof whatsoever that it was ever used by anybody, and this includes you, since you have never used it either.

gl

mr.Noonan actually computed data for using the bubble sextant , namely for the sunset fix . Later @ sunrise he accidentally maintained them , but did not continue the use of the b-sextant , replacing it for observation by unarmed eye , telescope , marine sextant , or whatever it may have been . In EJN 2008 I suggested the marine sextant having been used because of it´s green filter against dazzle .

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

Mr. van Asten,

Now you are changing your story and talking about a normal sunrise LOP which can be taken with the naked eye by simply observing the upper limb of the sun appear above the visible horizon which, as viewed from an airplane, the sun's altitude is actually below zero. The problem with this is that Noonan did not have a refraction table that showed the refraction correction for altitudes less than 6 degrees above horizontal so would not have been able to make the necessary corrections so as to derive an accurate LOP. The lowest altitude of 6 degrees in his refraction table shows a correction of 8' but for a zero altitude we know that it is 34.5' (you claim 37') He would have been aware of this problem so would not have attempted this. See the refraction correction table in the 1937 edition of H.O. 208 that Noonan was using here:
  https://sites.google.com/site/fredienoonan/resources/navigation-tables-for-mariners-and-aviators-h-o-208-dreisonstok-1937/HO208%281937%29.pdf?attredirects=0

It is because you realized that Noonan's refraction table did not allow a "sunrise" observation that you invented the "van Asten" sunrise" concept since you thought it could be computed with the Nautical Almanac's sunrise table which already incorporated refraction in the computation of the times of sunrise and sunset. Now that you have admitted that you couldn't use the sunrise table to compute an accurate time of sunrise, you are back to trying to have Noonan guess at a refraction correction without a table showing corrections for low altitudes.

You wrote in you 2008 paper:

"The Observation Error Translates to a Virtual
Time Error
Figure 3 represents the situation for 1754:53 GMT
when Noonan, coming from the Nukumanu-Nikunau
night flight, observes sunrise, U.L.H., with the
marine sextant preset (+25'.2 arcmin for 1,000 ft
altitude, green filter) for dip and dazzle."

You have the marine sextant set to allow for dip, which is in "van Asten sunrise/sunset" method through which to observe the sun. You did not say that Noonan simply watched the sun appear above the visible horizon.

You can't wiggle out of it now because you have posted way too many times that the problem was caused by Noonan taking the sunrise observation with the marine sextant.

You posted on May 8th on the "Dateline" thread:

"we follow H.O.208 the marine sextant setting for a sunrise observation @ 1,000 ft should be :   I. set the index screw to (+) 31´ by which II. the horizon will show up ahead with the instrument held horizontally"

and there are a plethora of other examples where you clearly wrote that he observed the sunrise with the marine sextant preset to 31'.

Another reason that you can't change your story now is that your computations would have shown Noonan more than 28 nautical miles further to the west if he had actually just observed a real sunrise at the time you stated because the sun rises sooner to an observer at altitude. The time you give, 17:54:53 GMT, is the time an observer at 0° 09' north, 178° 47' west at sea level would have observed the upper limb of the sun appear above the visible sea horizon. An observer one thousand feet directly above this spot on earth would have observed the sun appear above the visible sea horizon 1 minute and 52 seconds earlier at 17:53:01 GMT. If you had been claiming that Noonan actually observed the sun rise above the visible sea horizon without using a sextant, just his naked eyeballs, then you would have told us his longitude was 178° 19' west, 28 nautical miles further west than you have constantly claimed in all of your posts and in your 2008 article. The only way to make an observer flying at 1,000 feet note the time of sunrise as being the same time as the observer at sea level directly below him notes the time of sunrise is to use the "van Asten sunrise/sunset" method with the flying observer using a marine sextant set to 31'.

Nice try.

gl


« Last Edit: June 12, 2011, 11:45:00 PM by Gary LaPook »
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Gary LaPook

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Re: Navigating the LOP with the offset method.
« Reply #186 on: June 12, 2011, 11:34:26 PM »

... The only second condition for observing sunrise from an A/c is : fly low to avoid seeing the sun earlier than @ sea level which is the lower reference for elevation of heavenly bodies.

The only way to fly low enough to "to avoid seeing the sun earlier than @ sea level" is to be in a submarine, since you would have to be below sea level.

gl



Plse explain , I do not follow this.

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

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

OK. An observer above sea level, either on a cliff or in an airplane, will see the sun rise earlier than an observer directly below him at sea level. At the location and time that you claim, an observer at 1,000 feet above sea level will see the upper limb of the sun appear above the visible sea horizon one minute and fifty two seconds before the observer directly below him at sea level will see the sun appear.  The only way to see the sun rise after the observer at sea level sees the sun rise is to be at a lower altitude than sea level, hence the need for a submarine.

gl
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Gary LaPook

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Re: Navigating the LOP with the offset method.
« Reply #187 on: June 13, 2011, 12:25:40 AM »

G.Lapk . btw , @ 1912 GMT A/c was  reported to be @ 1,000 ft altitude , very good that you do not believe me , but why don´t you believe the pilot herself ?

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

I  answered this question in a prior post.

 “She did not report being at 1000 feet until 1912 Z, 78 minutes after you believed that they were
observing sunrise at 1000 feet as part of their “must be on you” transmission when they believed
that they were already at Howland. They would have traveled approximately 170 nm in that time
interval. There is no reason to assume that they descended from their cruising altitude as soon as
you believe. Flying higher provided better fuel economy and better opportunities for celestial
observations. Clouds are often in layers at different altitudes. So, for example, if there was a
scattered layer at 15,000 feet and a broken layer at 8,000 feet then flying at 10,000 feet would
provide very good observation conditions with only a small part of the heavens obstructed.
Flying below 8,000 feet would produce possibly complete obstructions to observations as the two
layers (each having large openings) could overlap.”

Mr. van Asten wrote back:

“2. Besides mentions in biographies , why would Noonan have the plane going down to 1,000 ft ,
an unfavorable altitude for seeing a small island , if it was not necessary to have the horizon
sharply within visual range ?”

-To which I responded:

“Most people believe that they were down at 1000 feet when they thought they were near the
island and at that point (and not before) they had been compelled to descend below a low cloud
layer in order to search for Howland. “

gl
« Last Edit: June 13, 2011, 12:31:17 AM by Gary LaPook »
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Gary LaPook

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Re: Navigating the LOP with the offset method.
« Reply #188 on: June 13, 2011, 12:49:03 AM »

Mr.Lapook ,



The possibly only direct irrelevancy of the navigation model is that on the error-offset lane the sun´s altitude (16 deg) @ the erroneous turn-off-point differed considerably from the elevation (21 deg) @ the correct t-o-point , normally Noonan would have seen this . I can evade the complication (1) since when steering on the offset course the sun was below elevation (04--21) for reliable corrected sextant altitude , up to about halfway and (2) by estimating the 102 mls offset having been flown on D.R. , this last by preference . But it remains the more or less a flaw on the step of internal inconsistency . With the correct offset initial point the elevation difference was negligible (04-26 vs 04-21) for low sun given.



_________________________________
Mr. van Asten,

Your diagram in your article shows that they reached the turnoff point at 1859 GMT at which point the sun's altitude was 16° 04.5' (not the 21 ° that you stated) for an observer at Howland and anywhere else on the correct LOP through Howland. This was plenty high enough for accurate sextant sights.

Anytime after 1815 GMT the sun's altitude was above the six degree minimum needed by Noonan's refraction correction table so he would have been taking sights of the sun for 44 minutes prior to the interception and would not have relied on dead reckoning for 102 miles which would have introduced an uncertainty of 10 miles in the turn off point onto the LOP.  You apparently do not understand the basic idea behind the landfall procedure, that you take sights as you approach the LOP so that it is an accurate interception and then you take additional sights to ensure staying on the LOP to the destination. You do not DR for a long leg to the interception. If you were going to DR for 102 miles then there would be no reason to do the landfall procedure.

Try reading the flight manuals that explain this procedure that I have posted here:

https://sites.google.com/site/fredienoonan/topics/landfall-procedure

gl
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #189 on: June 13, 2011, 03:00:08 AM »

Chichester , and a variety of ocean pilots used marine sextants to establish A/c´s position w.r.t. lines of position in the One Line Approach operation , they all were succesful in finding their destiination this way , there is no record of any miscarriage by using the method. Hegenburger/Maitland (on a completely precomputed navigation plan to Hawaii) even carried a single telescope to be able observing objects of which elevation was of no importance , p.e. for sunset/sunrise not any instrument besides the unarmed eye and facultatively a green filter is needed , since only the point of time @ U.L. appearance is of importance , to match it with the running list figures for latitude/longitude. If p.e. mr. Noonan used the mariner´s sextant (for it´s green filter) or not , that has zero influence on the error he possibly/probably committed by not using the bubble sextant like @ sunset . The only second condition for observing sunrise from an A/c is : fly low to avoid seeing the sun earlier than @ sea level which is the lower reference for elevation of heavenly bodies. It is for these reasons of no use to bring yes or no marine sextants in the field of discussion , for any navtable or navformula if computed elevation is zero .

Mr. van Asten,

It would be an error to use the marine sextant only if he had computed data for use with a bubble sextant and then only if he were using the "van Asten sunset/sunrise" method which you have never produced any proof whatsoever that it was ever used by anybody, and this includes you, since you have never used it either.

gl

mr.Noonan actually computed data for using the bubble sextant , namely for the sunset fix . Later @ sunrise he accidentally maintained them , but did not continue the use of the b-sextant , replacing it for observation by unarmed eye , telescope , marine sextant , or whatever it may have been . In EJN 2008 I suggested the marine sextant having been used because of it´s green filter against dazzle .

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

Mr. van Asten,

Now you are changing your story and talking about a normal sunrise LOP which can be taken with the naked eye by simply observing the upper limb of the sun appear above the visible horizon which, as viewed from an airplane, the sun's altitude is actually below zero. The problem with this is that Noonan did not have a refraction table that showed the refraction correction for altitudes less than 6 degrees above horizontal so would not have been able to make the necessary corrections so as to derive an accurate LOP. The lowest altitude of 6 degrees in his refraction table shows a correction of 8' but for a zero altitude we know that it is 34.5' (you claim 37') He would have been aware of this problem so would not have attempted this. See the refraction correction table in the 1937 edition of H.O. 208 that Noonan was using here:
  https://sites.google.com/site/fredienoonan/resources/navigation-tables-for-mariners-and-aviators-h-o-208-dreisonstok-1937/HO208%281937%29.pdf?attredirects=0

It is because you realized that Noonan's refraction table did not allow a "sunrise" observation that you invented the "van Asten" sunrise" concept since you thought it could be computed with the Nautical Almanac's sunrise table which already incorporated refraction in the computation of the times of sunrise and sunset. Now that you have admitted that you couldn't use the sunrise table to compute an accurate time of sunrise, you are back to trying to have Noonan guess at a refraction correction without a table showing corrections for low altitudes.

You wrote in you 2008 paper:

"The Observation Error Translates to a Virtual
Time Error
Figure 3 represents the situation for 1754:53 GMT
when Noonan, coming from the Nukumanu-Nikunau
night flight, observes sunrise, U.L.H., with the
marine sextant preset (+25'.2 arcmin for 1,000 ft
altitude, green filter) for dip and dazzle."

You have the marine sextant set to allow for dip, which is in "van Asten sunrise/sunset" method through which to observe the sun. You did not say that Noonan simply watched the sun appear above the visible horizon.

You can't wiggle out of it now because you have posted way too many times that the problem was caused by Noonan taking the sunrise observation with the marine sextant.

You posted on May 8th on the "Dateline" thread:

"we follow H.O.208 the marine sextant setting for a sunrise observation @ 1,000 ft should be :   I. set the index screw to (+) 31´ by which II. the horizon will show up ahead with the instrument held horizontally"

and there are a plethora of other examples where you clearly wrote that he observed the sunrise with the marine sextant preset to 31'.

Another reason that you can't change your story now is that your computations would have shown Noonan more than 28 nautical miles further to the west if he had actually just observed a real sunrise at the time you stated because the sun rises sooner to an observer at altitude. The time you give, 17:54:53 GMT, is the time an observer at 0° 09' north, 178° 47' west at sea level would have observed the upper limb of the sun appear above the visible sea horizon. An observer one thousand feet directly above this spot on earth would have observed the sun appear above the visible sea horizon 1 minute and 52 seconds earlier at 17:53:01 GMT. If you had been claiming that Noonan actually observed the sun rise above the visible sea horizon without using a sextant, just his naked eyeballs, then you would have told us his longitude was 178° 19' west, 28 nautical miles further west than you have constantly claimed in all of your posts and in your 2008 article. The only way to make an observer flying at 1,000 feet note the time of sunrise as being the same time as the observer at sea level directly below him notes the time of sunrise is to use the "van Asten sunrise/sunset" method with the flying observer using a marine sextant set to 31'.

Nice try.

gl





@ 1,000 ft , 305 m altitude the horiron dips 00-31´ whereas the sun rises @ 13´.8 per time minute . Sun will appear 31´/13´.8 = 2m15s earlier (yours 1m50s) @ 1,000 ft than @ zero ft. Subtract from 175453 GMT and find 175238 GMTthe instant mr.Noonan saw sunrise . By addition of 2m15s he knew to be 150 mls off Howland . Sea navigators were much more familiar with calculation of angles etc. since they had not from the beginning of their career the "short methods" to their disposal . You p.e. have mentioned that the paragraph on sunrise fix for aircraft has been deleted from ´Dutton´ since 1934 . For that year Noonan was 41 with a 20 years seaman´s career behind . Within that era , sea liners captains ordered
two , sometimes three navigators on deck to separately shoot sun , moon or stars , after which , below deck , they computed for 20 minutes to establish position of ship . It is in short , reasonable that mr. Noonan exactly knew what he was doing.
I consequently jump to your critics on the 0720 GMT announced position near Nukumanu . Your statement about the time point having been 0718 GMT (before GMT sunrise 071930) does not hold . The figure is from a citation of the "Chater´s report" document and concerns tranmissions Lae to Earhart for weather updates @ 18 minutes past the hour. The figure is repeated (0418 , 0519 , 0718) through the report . The figure , not from radio logbook (there was none) , does not at all represent an agreement with the Earhart crew themselves. 

Third : there have been comments stating that the departure time from Lae , 0000 GMT , concerned an @ random decision etc. etc. It was not : @ 6 a.m. 7/1 Earhart to Black radiogram reads in part "PLAN LEAVE BY TEN THIS MORNING NEW GUINEA TIME" . Later @ 7/01 followed , in part : "BLACK ITASCA DUE LOCAL CONDITIONS TAKE OFF DELAYED UNTIL 2130 GMT JULY SECOND" . Eventually , 7/2 : "URGENT BLACK ITASCA AMELIA EARHART LEFT LAE TEN AM LOCAL TIME JULY 2ND DUE HOWLAND ISLAND 18 HOURS TIME" . it is at least a reasonable supposition that the crew tuned departure time to mr.Noonan´s precomputed flight data .
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #190 on: June 13, 2011, 03:38:05 AM »

Mr.Lapook ,



The possibly only direct irrelevancy of the navigation model is that on the error-offset lane the sun´s altitude (16 deg) @ the erroneous turn-off-point differed considerably from the elevation (21 deg) @ the correct t-o-point , normally Noonan would have seen this . I can evade the complication (1) since when steering on the offset course the sun was below elevation (04--21) for reliable corrected sextant altitude , up to about halfway and (2) by estimating the 102 mls offset having been flown on D.R. , this last by preference . But it remains the more or less a flaw on the step of internal inconsistency . With the correct offset initial point the elevation difference was negligible (04-26 vs 04-21) for low sun given.



_________________________________
Mr. van Asten,

Your diagram in your article shows that they reached the turnoff point at 1859 GMT at which point the sun's altitude was 16° 04.5' (not the 21 ° that you stated) for an observer at Howland and anywhere else on the correct LOP through Howland. This was plenty high enough for accurate sextant sights.

Anytime after 1815 GMT the sun's altitude was above the six degree minimum needed by Noonan's refraction correction table so he would have been taking sights of the sun for 44 minutes prior to the interception and would not have relied on dead reckoning for 102 miles which would have introduced an uncertainty of 10 miles in the turn off point onto the LOP.  You apparently do not understand the basic idea behind the landfall procedure, that you take sights as you approach the LOP so that it is an accurate interception and then you take additional sights to ensure staying on the LOP to the destination. You do not DR for a long leg to the interception. If you were going to DR for 102 miles then there would be no reason to do the landfall procedure.

Try reading the flight manuals that explain this procedure that I have posted here:

https://sites.google.com/site/fredienoonan/topics/landfall-procedure

gl

You may safely assume that in the course of 23 years I have consulted all representative flght manuals . When commencing the 055 T offset @ 1815 for the correct longitude sun´s altitude  was 04-26 , at the end @ 1859 it was 21-00 . On the erroneous offset the respective elevations were 04-21 and 16-00 , all figures rounded to arcmin. I already mentioned by comment that the 16-00 / 21-00 difference may be a weakness of determination , also since textbooks prescriptions ask for repeated observation like you say . Because for the article I had to do the work alone (no old style navigators available , no readers) , and against deadlines , combined with the menace of  making the treatise unreadable due to too many details , I decided for the text & diagrams as published . I have worked for 20 years in the sciences during my professional career , there is not any reason for which I would venture  to " wiggle out" (as you call it) from a problem . There is namely , a possibility (not yet computed) that the offset entire track was longer than 132 mls because instead of having made good 348 mls @ 175453 GMT , only 337 mls had been made good , this has influence on the ETA time-position groups .
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #191 on: June 13, 2011, 06:30:47 AM »

G.Lapk . btw , @ 1912 GMT A/c was  reported to be @ 1,000 ft altitude , very good that you do not believe me , but why don´t you believe the pilot herself ?

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

I  answered this question in a prior post.

 “She did not report being at 1000 feet until 1912 Z, 78 minutes after you believed that they were
observing sunrise at 1000 feet as part of their “must be on you” transmission when they believed
that they were already at Howland. They would have traveled approximately 170 nm in that time
interval. There is no reason to assume that they descended from their cruising altitude as soon as
you believe. Flying higher provided better fuel economy and better opportunities for celestial
observations. Clouds are often in layers at different altitudes. So, for example, if there was a
scattered layer at 15,000 feet and a broken layer at 8,000 feet then flying at 10,000 feet would
provide very good observation conditions with only a small part of the heavens obstructed.
Flying below 8,000 feet would produce possibly complete obstructions to observations as the two
layers (each having large openings) could overlap.”

Mr. van Asten wrote back:

“2. Besides mentions in biographies , why would Noonan have the plane going down to 1,000 ft ,
an unfavorable altitude for seeing a small island , if it was not necessary to have the horizon
sharply within visual range ?”

-To which I responded:

“Most people believe that they were down at 1000 feet when they thought they were near the
island and at that point (and not before) they had been compelled to descend below a low cloud
layer in order to search for Howland. “

gl

The "low cloud cover" appears in every unquantified story , as well as the 200 mph fiction , the one for flying low , the other to make up for lost time etc. etc. Both phenomena did not exist and about the first : there was no cloud cover in the Howland region that day.
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #192 on: June 13, 2011, 06:43:44 AM »

... The only second condition for observing sunrise from an A/c is : fly low to avoid seeing the sun earlier than @ sea level which is the lower reference for elevation of heavenly bodies.

The only way to fly low enough to "to avoid seeing the sun earlier than @ sea level" is to be in a submarine, since you would have to be below sea level.

gl



Plse explain , I do not follow this.

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OK. An observer above sea level, either on a cliff or in an airplane, will see the sun rise earlier than an observer directly below him at sea level. At the location and time that you claim, an observer at 1,000 feet above sea level will see the upper limb of the sun appear above the visible sea horizon one minute and fifty two seconds before the observer directly below him at sea level will see the sun appear.  The only way to see the sun rise after the observer at sea level sees the sun rise is to be at a lower altitude than sea level, hence the need for a submarine.

gl

Nice joke .  Only : from the higher position one sees the sun come up earlier due to the horizon dip , for which aviators can as well compensate as seamen from the deck , either by directlly applying the dip from table , or by applying a time difference from simple computation like shown earlier . As a general result , all comments up to now have not injured consistency , and not displaced the erroneous position line for one inch .
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #193 on: June 13, 2011, 06:59:46 AM »

Mr.Lapook ,

You write " We will start with his idea that Noonan measured the point of "van Asten sunrise" with a marine sextant .."  mr.Noonan´s  assumed observation error did not occur due to using the mariner´s sextant , but on the contrary : it occurred by not using the bubble sextant like @ sunset. At best the m-sextant delivered an easy means of establishing A/c´s exact altitude above ocean´s surface (via the dip table of H.O.no.208) , whereas also the dark green filter was a feature . Sunrise point of time could be established by observing with the unarmed eye (but : see filter) , with a telescope , binoculars , etc. since sunrise time is not a measurement , it is an observation only to match time with the preomputed running fix graph , or time-position group listing . Also the short period between  071930 GMT sunset & the 0720 position report delivers proof that a running fix table , or graph , had been precomputed.

The possibly only direct irrelevancy of the navigation model is that on the error-offset lane the sun´s altitude (16 deg) @ the erroneous turn-off-point differed considerably from the elevation (21 deg) @ the correct t-o-point , normally Noonan would have seen this . I can evade the complication (1) since when steering on the offset course the sun was below elevation (04--21) for reliable corrected sextant altitude , up to about halfway and (2) by estimating the 102 mls offset having been flown on D.R. , this last by preference . But it remains the more or less a flaw on the step of internal inconsistency . With the correct offset initial point the elevation difference was negligible (04-26 vs 04-21) for low sun given.



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

Yep, that is a pretty amazing performance by Noonan and Earhart. Since he took the sextant reading (according to van Austen) at 07:19:30 GMT and the message was received at Lae at 07:20:00 GMT. This means that in only 30 seconds Noonan read the sextant, compared his reading with his precomputed table, wrote the position on a piece of paper, stuck that paper on the end of a fishing pole, slid the pole across the fuel tanks to the cockpit, Earhart removed the note from the fishing pole, read the message, picked up the microphone and sent that message! I wonder how many times they had to practice those maneuvers in order to get their time down to only 30 seconds. But wait, in keeping with Mr. van Austen's level of precision in his computations, we must allow for the time it took for the radio signals to travel all the way to Lae. From that position is was 1,384,820 meters to Lae and radio waves travel only at the speed of light, 299,792,458 meters per second so it took 0.00461962 seconds for the message to get to Lae, so Earhart must have started transmitting at 7:19:59.995380738 GMT. This means that all these action had to have been completed in less than 30 seconds, in only 29.995380738 seconds. I am really impressed now.

Of course, what makes this performance even more amazing is that the message was received in Lae at 0718 GMT, a minute and half before Noonan took the sextant reading (according to Mr. van Austens's theory) so the radio signals must have traveled faster than the speed of light and traveled back in time by one and a half minutes. See the Chatter report.

Basically, this proves that Mr. van Austen was wrong about his "sunset running fix" in his published paper and his theory relies on this "sunset running  fix" for proof that Noonan was attempting a "sunrise fix" the next morning. He also relies on the distance traveled from this earlier "sunset running fix" as a basis for the "sunrise fix". Neither of these fixes were precomputed or measured by Noonan.

gl

What , properly , was Noonan doing o/b of that aircraft  , play at cards ?
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h.a.c. van asten

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Re: Navigating the LOP with the offset method.
« Reply #194 on: June 13, 2011, 07:03:56 AM »

Mr. Lapook ,

Mr. van Asten also doesn’t allow for the uncertainty in the readings from a marine sextant.
Various statistical studies have been made using data from thousands of observations by
hundreds of observers and the standard deviation is about 1.6' so the uncertainty is twice this,
3.2'. This would be added to the uncertainty in determining the dip setting to be used so the total
uncertainty, if Noonan wanted to use a marine sextant to determine “van Asten sunrise”, would
be 10' or 11' which is worse than just using the bubble sextant alone.



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I forgot to say that the accuracy of marine sextant sights was determined for observations taken on shipboard where the height of eye above sea level was measured so there was no uncertainty in the dip correction to be use. There is no reason to believe that an in-flight marine sextant observation would be  more accurate than a shipboard observation and would probably be less accurate but there are no statistics on that BECAUSE NO ONE USES A MARINE SEXTANT IN FLIGHT!

gl

Chichester , and a variety of ocean pilots used marine sextants to establish A/c´s position w.r.t. lines of position in the One Line Approach operation , they all were succesful in finding their destiination this way , there is no record of any miscarriage by using the method. Hegenburger/Maitland (on a completely precomputed navigation plan to Hawaii) even carried a single telescope to be able observing objects of which elevation was of no importance , p.e. for sunset/sunrise not any instrument besides the unarmed eye and facultatively a green filter is needed , since only the point of time @ U.L. appearance is of importance , to match it with the running list figures for latitude/longitude. If p.e. mr. Noonan used the mariner´s sextant (for it´s green filter) or not , that has zero influence on the error he possibly/probably committed by not using the bubble sextant like @ sunset . The only second condition for observing sunrise from an A/c is : fly low to avoid seeing the sun earlier than @ sea level which is the lower reference for elevation of heavenly bodies. It is for these reasons of no use to bring yes or no marine sextants in the field of discussion , for any navtable or navformula if computed elevation is zero .
 .
  


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Chichester, Coutinho and several other early pioneering aviators did use marine sextant but this was only because bubble sextants had not yet been perfected. During the 1910's and 1920' rapid progress was made in improving and perfecting bubble sextants, with many false paths until it all came together, the right lenses and, most importantly, the right curvature to the top of the bubble chamber.

You can read about these developments here: http://www.fer3.com/arc/imgx/Bubble-sextants-Precision-Astrolabe.pdf

By the early 1930's the bubble sextant had been perfected so no one used a marine sextant after that to take observations from airplanes.

I sent this to him before:

"It is interesting that you list some early aviators implying that they used your sunrise method, do
you have any sources for this claim? Ellsworth used a bubble sextant, Lindbergh used a Pioneer
bubble sextant (there is a photo of his navigation equipment in Weems, 1938). They all used the standard Line Of Position computation, not your "van Asten sunrise" method.  I have analyzed
Chichester’s navigation extensively and he used a marine sextant to take five sextant
observations on the New Zealand to Norfolk Island flight in 1931, all were in the range of 23° 12' to 50°
50'. On the next leg to Lord Howe Island he also took five observations, all in the range of 23° 48'
to 53° 42'.  So contrary to your claim, none of his observations were anywhere near a zero altitude
or a sunrise sight. "


Coutinho in 1922 took 40 observations with a mariner's sextant but the lowest altitude he measured was 16° 15', nowhere near the "van Asten horizon."

Mr van Asten also mentioned that these early aviators precomputed their sights and although that may be true what they precomputed were the normal "computed altitudes" used for the normal Line Of Position navigation method, not for the "van Austen sunset/sunrise" method. It appears that Mr. van Austen doesn't understand how these precomputations were done. Here is link to many flight navigation manuals that explain this procedure and he might get some value from reading them.

https://sites.google.com/site/fredienoonan/topics/precomputed-altitude-curves

I have asked Mr. van Austen repeatedly to produce any proof that he might have that anybody ever used his method and he has never produced a thing.

gl

[/quote

Never produced a thing ?  Read EJN-2011 for mr.Noonan´s own sunset fix with same fashion as for sunrise.
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