# TIGHAR

## Amelia Earhart Search Forum => Celestial choir => Topic started by: Chris Johnson on August 18, 2011, 05:44:01 AM

Title: LOP-Possible stupid question
Post by: Chris Johnson on August 18, 2011, 05:44:01 AM
I hold my hands up and admit that I am no navigator but have a question regarding the LOP that I hope doesn’t become another theory battle between our esteemed navigational colleagues.

I may have asked something similar before so be patient.

FN and AE miss Howland Island but FN’s observations and calculations say he has reached the LOP 157 – 337.  How wide/broad is this line for them to fly up/down?  Could AE not just watch a compass to stay on the LOP with FN then taking shots to adjust for wind etc?
In this way could they then not reach the ‘catchers mitt’ of the Phoenix island?
Title: Re: LOP-Possible stupid question
Post by: Martin X. Moleski, SJ on August 18, 2011, 07:25:41 AM
FN and AE miss Howland Island but FN’s observations and calculations say he has reached the LOP 157 – 337.  How wide/broad is this line for them to fly up/down?

A line, considered as a mathematical abstraction, has no width.

A line of position, considered as "the amount of territory visible from the aircraft" has a width that is variable, depending on weather, altitude, and the field of view from the aircraft.

Did you miss the discussion of how to visualize the LOP? (http://tighar.org/smf/index.php/topic,206.msg1549.html#msg1549)

Quote
Could AE not just watch a compass to stay on the LOP with FN then taking shots to adjust for wind etc?
In this way could they then not reach the ‘catchers mitt’ of the Phoenix island?

Gary LaPook has given several links to his website (https://sites.google.com/site/fredienoonan/home) where he argues that a navigator would have to continually revise position estimates in order to end up in the vicinity of Nikumaroro.

All that we know about what Fred did or did not do ends with the final received transmission (http://tighar.org/wiki/Last_transmission): "We are on the line 157 337.  Will repeat the message.  We will repeat this on 6210 kcs.  Wait.  We are running [on] line [north and south]."

We do not know how long they stayed on that line.

We do not know how far east or west of Howland that line was, in fact.

We may surmise that Fred thoughtthat that line ran through Howland (there was no other reason for them to have identified that line or to have turned on it unless this was the case).

We can see that that line points down toward the vicinity of Niku.

We don't know what other position information Fred might have derived from later observations.

We don't know what other headings he might have told Amelia to fly.

If Earhart and Noonan ended up on Niku, we don't know exactly how they got there--on purpose or by accident.  In 1937, the Navy thought it was worthwhile to search there.  In 1988, a couple of seasoned military navigators, Tom Gannon (http://tighar.org/wiki/Tom_Gannon) and Tom Willi (http://tighar.org/wiki/Tom_Willi) (the "two Toms"), persuaded TIGHAR that Niku was worth exploring.  Stuff happened, and here we are today, still wondering whether the Niku hypothesis (http://tighar.org/Projects/Earhart/Overview/AEhypothesis.html) is correct.

Finding the aircraft in Gary LaPook's search area would disprove the Niku hypothesis.  Finding the aircraft on or near Niku would disprove Gary's hypothesis that they splashed and sank near Howland.
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 18, 2011, 07:53:41 AM
Thanks Marty

Missed the 'visualise' discussion, might just answer my questions.

Its Reading Mr LaPooks site that makes me ask these questions to try and understand the whole argument.
Title: Re: LOP-Possible stupid question
Post by: Harry Howe, Jr. on August 18, 2011, 11:39:45 AM

Chris
I don't think there are any "stupid" questions, except the question not asked.

I have one of my own.  If I am not mistaken the plane was equipped with a Sperry AutoGyro Autopilot.  Anyone have any info on its capabilities??  Surely, it would have been used to maintain course on the long journey.

It also had a drift indicator which, I assume, would give info relative to wind drift and allow corrections to be made.  Then, how in the world did they miss Howland?  Maybe Howland was mislocated on the chart FN used for his course planning?
Title: Re: LOP-Possible stupid question
Post by: h.a.c. van asten on August 18, 2011, 12:04:19 PM
First and evidently the recorded aircraft progression line did not by far cover the sun line as advanced over Howland´s true coordinates , secondly an on board compass pointing flight in any direction including north gives no resolution of the coordinates you are over .
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 18, 2011, 12:34:04 PM
First and evidently the recorded aircraft progression line did not by far cover the sun line as advanced over Howland´s true coordinates , secondly an on board compass pointing flight in any direction including north gives no resolution of the coordinates you are over .

I'll use an example from compass navigation on land.  In poor visability and using a map where I have some idea (like FN said with his LOP) I can follow a bearing that gets me to my destination or there abouts!

If the LOP was correct then why not just fly along the line?

Good question about the auto pilot, nether thought of that.
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 18, 2011, 02:08:53 PM
First and evidently the recorded aircraft progression line did not by far cover the sun line as advanced over Howland´s true coordinates , secondly an on board compass pointing flight in any direction including north gives no resolution of the coordinates you are over .

I'll use an example from compass navigation on land.  In poor visability and using a map where I have some idea (like FN said with his LOP) I can follow a bearing that gets me to my destination or there abouts!

If the LOP was correct then why not just fly along the line?

Good question about the auto pilot, nether thought of that.

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

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

You cannot determine if you are staying on the course line that would take you to Niku because the azimuth of the line changes as the sun moves (the LOP  pivots on Howland island) and doesn't go anywhere near Niku later in the day.

gl
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 18, 2011, 02:37:01 PM
Ok simplistic idea here!

You think you are on the LOP and will either fly over the Howland area or the Phoenix area.  You fly North South in the hope its Howland, Baker, Jervis but its not its Gardner er al.  Possible? I don't know but could it have been?
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 18, 2011, 07:05:50 PM
I hold my hands up and admit that I am no navigator but have a question regarding the LOP that I hope doesn’t become another theory battle between our esteemed navigational colleagues.

I may have asked something similar before so be patient.

FN and AE miss Howland Island but FN’s observations and calculations say he has reached the LOP 157 – 337.  How wide/broad is this line for them to fly up/down?  Could AE not just watch a compass to stay on the LOP with FN then taking shots to adjust for wind etc?
In this way could they then not reach the ‘catchers mitt’ of the Phoenix island?

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

You have to allow for the possibility of up to a 7 NM uncertainty in an LOP derived from a sextant observation.  This means you may be up to 7 NM to the right or to the left of the LOP that you believe should take you to Howland so the possible error band in 14 NM wide. However, you are much more likely to be closer to the center of the error band than to either edge but you must allow for that maximum possible error in planning your approach. If they did perfect navigation then following the LOP should have taken Noonan directly over Howland. If, at the moment they were passing Howland, the error was at maximum then they might have passed up to 7 NM east or west of the island, so Howland would have been easily visible with 20 NM visibility.

There is the possibility that Noonan was using coordinates for a point about 5 NM west- north west of he island and this would have produced an LOP that was offset from the proper LOP by 4 NM. Following this erroneous LOP would cause the plane to fly by Howland within a 14 NM error band centered 4 NM to the west of the island. So looking at the worst case, flying the 4 NM offset LOP and being at the furthest error to the west, another 7 NM, then the plane could have been passing the island offset by, at most, 11 NM, again well within visibility range.

gl
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 18, 2011, 07:23:40 PM
Ok simplistic idea here!

You think you are on the LOP and will either fly over the Howland area or the Phoenix area.  You fly North South in the hope its Howland, Baker, Jervis but its not its Gardner er al.  Possible? I don't know but could it have been?

gl
Title: Re: LOP-Possible stupid question
Post by: h.a.c. van asten on August 19, 2011, 12:36:13 AM
From alt. 1,000 ft @ distance 11 nm the optical angle covering the west-east width of Howland is 2 arcminutes ; 1 arcmin is the minimum for resolution of an image by the eye , so island was for theory within visual range , but marginally for practice . That destination was GMT 1912 far on the port bow in lieu of head on as expected was a first reason to announce  A/c being over the latitude , but nevertheless not in sight . The 1 arcmin limit for observation lies @ 14 miles off for alt. 1,000 ft . Koepke in 1967 o/b the Pellegreno flight with Polhelmus navigator , saw Howland when 10-12 mls away after continued looking out by the entire crew .
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 19, 2011, 01:45:59 AM
Ok simplistic idea here!

You think you are on the LOP and will either fly over the Howland area or the Phoenix area.  You fly North South in the hope its Howland, Baker, Jervis but its not its Gardner er al.  Possible? I don't know but could it have been?

gl

I read it before I posted my question, your Starbucks analogy is quite simple to understand in the context of you know exactly where you are starting from and going with plenty of land marks.  Makes sense then that you can’t use a LOP to hit your target dead on.
Wasn’t the purpose of FN’s LOP to get as close to Howland as possible then use RDF to lock onto the Itasca and thus Howland?
So for whatever reason they miss Howland or at least can’t see it but by FN’s calculations are on his stated LOP.  FN’s LOP isn’t as simple as your finding a Starbucks on a named street.  His LOP says islands somewhere within a radius, lets fly northward for X miles/time, if no landfall fly southward for Y miles/time, should find Howland, Baker or Jarvis.  What FN doesn’t know is he is off line (?) and thus more likely to hit the Phoenix Islands.
Title: Re: LOP-Possible stupid question
Post by: Harry Howe, Jr. on August 19, 2011, 10:42:52 AM

Chris
Expand a bit on what you mean by FN being "off-line" (?)
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 19, 2011, 12:57:33 PM

Chris
Expand a bit on what you mean by FN being "off-line" (?)

Thinking he was online with Howland but actualy off line and online with the Phoenix group if thats possible
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 20, 2011, 04:22:39 AM
Ok simplistic idea here!

You think you are on the LOP and will either fly over the Howland area or the Phoenix area.  You fly North South in the hope its Howland, Baker, Jervis but its not its Gardner er al.  Possible? I don't know but could it have been?

gl

I read it before I posted my question, your Starbucks analogy is quite simple to understand in the context of you know exactly where you are starting from and going with plenty of land marks.  Makes sense then that you can’t use a LOP to hit your target dead on.
Wasn’t the purpose of FN’s LOP to get as close to Howland as possible then use RDF to lock onto the Itasca and thus Howland?
So for whatever reason they miss Howland or at least can’t see it but by FN’s calculations are on his stated LOP. FN’s LOP isn’t as simple as your finding a Starbucks on a named street.  His LOP says islands somewhere within a radius, lets fly northward for X miles/time, if no landfall fly southward for Y miles/time, should find Howland, Baker or Jarvis.  What FN doesn’t know is he is off line (?) and thus more likely to hit the Phoenix Islands.

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

Since you liked the Simi Valley example I will expand upon that one.

See first diagram:

In that example your friend told you to meet him at the Starbucks located on Cochran Street, east of First Avenue. Since you know that your destination is located on Cochran street you know that if you intercept Cochran street at First Avenue and follow Cochran to the east that you are assured of finding the Starbucks. Cochran Street in an LOP and the center line of the pavement and the curbs and the street signs allow you to check and make sure you are staying on course.

Let's change the scenario slightly. This time your friend just tells you that the Starbucks is located straight east from the intersection of Cochran and First. You know that there is also a Starbucks located in the town of Gardner that is also straight east of the intersection of Cochran and First in Simi Valley. You backup plan is that if you can't hook up with your buddy at that Starbucks then you will go to the one in Gardner and get a Latte.

So you start out as before and drive to the intersection of Cochran and First and then drive east on Cochran looking for the Starbucks. For some reason you fail to spot it and you then notice that Cochran is curving to the left and is no longer going straight east. You decide that you have missed the meeting place and you decide to go to your backup Starbucks in Gardner so you drive over the curb and head off across the trackless desert, still heading east. You have no guidance except your compass because the LOP you had been following (Cochran Street) has changed directions and no longer goes towards Gardner. You drive across the desert for half a mile and then, suddenly, you hit yourself on your forehead. "This is stupid" you say to yourself, "there is not a chance in the world that I will be able to maintain my course accurately enough, with just a compass, driving across this desert, having to go around rabbit holes, cactus, rocks and what not, for me to find Gardner. And, duh, I don't have much gas left, I could run out and end up dying in this desert with the vultures pecking my eyes out. I better turn around and go back and look thoroughly for that Starbucks that I missed, and besides, that's where my friend is waiting for me!"

"This is the situation at Howland after 2013 Z.

See attached revised Simi Valley diagram.

I have also attached two photos of the ONC chart for the area which is at 1,000,000 to 1 scale, one inch equals 14 NM. I have drawn in the Sun line LOP running 157° True that existed from 1745 Z to 1845 Z. I have also drawn in the LOP for 2013 Z by which time it had changed to 153°. The LOP continues to rotate counter-clockwise, pivoting on Howland and by 2240 Z (the approximate time that the plane would be arriving at Gardner) it has changed all the way to 126°.The second photo shows an aeronautical plotter laid on the chart with the beginning of the scale at Gardner and you can see by how many miles the plane would have missed Gardner while staying on the LOP. This would be just like staying on Cochran Street after it curved to the left which would also cause you to miss Gardner.

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

For Noonan, following his LOP to his destination IS as simple as following the street to Starbucks. There is no radius involved, he knows he is on that line plus or minus (at most, very unlikely to be more) 7 NM both sides of the line, following the line should bring him close enough to find Howland just like driving down Cochran should get you close enough to spot that Starbucks in the back of the shopping center parking lot.

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

For the rest of you question see my prior post at:

https://tighar.org/smf/index.php/topic,383.msg5120.html#msg5120

gl
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 22, 2011, 06:37:08 AM
Thanks Gary! Think I may still flunk this class but at least i'm trying.

I see how a LOP works and understand that without reference points then yes you would more than likely struggle to stay on the line.  It wouldn't stop you from getting there with some good fortune and luck though.

In simple terms why do the lines change from 157 to 153, 148 and finaly 126? re read again and had a light bulb moment.

Can you not navigate a LOP and take into account the counter clockwise rotate centred on Howland? Thus keeping along the LOP. Otherwise by the looks of it TIGHAR should be looking on Kanton not Niku  ;)
Title: Re: LOP-Possible stupid question
Post by: Martin X. Moleski, SJ on August 22, 2011, 11:24:14 AM
... Otherwise by the looks of it TIGHAR should be looking on Kanton not Niku  ;)

Canton was thoroughly occupied by both the British and Americans in 1937; they called the arrangement a "condominium."  I suppose you could write a new conspiracy theory beginning with the premise that AE and FN landed there ...
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 22, 2011, 12:13:08 PM
... Otherwise by the looks of it TIGHAR should be looking on Kanton not Niku  ;)

Canton was thoroughly occupied by both the British and Americans in 1937; they called the arrangement a "condominium."  I suppose you could write a new conspiracy theory beginning with the premise that AE and FN landed there ...

Thats OK i'm persuing one about a cross dressing coastguard at the moment ;)
Title: Re: LOP-Possible stupid question
Post by: Harry Howe, Jr. on August 22, 2011, 01:02:11 PM

cHRIS, gARY
Do not forget that the Lockheed was equipped with an autopilot (George).  When they , AE/FN passed over where they thought Howland was (at 0843 Howland time) and set a course for Gardner (337 to 157) they would have set George for that course (wind corrected of course) and monitored their progress by time and speed.  That would have got them to a point where they could spot Gardner (3 times as long, 2 times as wide, 6 times the area when compared with Howland ) with a distinctively colored lagoon.  George would have got them there, just like George got them to the "Charted Position" which, unfortunately was 5 nm west of where Howland "Truly" was.

Moral of this story,  Never trust your life to a chart provided by some governmental body!  Be damned sure that your information is correct and verified before taking off on a long voyage completely over water and be damned sure you know your DF is operating properly and you know how to use it.
Title: Re: LOP-Possible stupid question
Post by: h.a.c. van asten on August 22, 2011, 01:26:56 PM
Autopilot maintains (compass) course after it has been set . From an unknown departure position you cannot set any course to any place . In the other event it would have been best to program George (auto pilot but not auto navigator) for Howland ...
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 22, 2011, 02:09:28 PM
Autopilot maintains (compass) course after it has been set . From an unknown departure position you cannot set any course to any place . In the other event it would have been best to program George (auto pilot but not auto navigator) for Howland ...

I thought that if FN thought he was on the LOP then yes set the autopilot for points North the South in search of land?
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 22, 2011, 02:21:56 PM
Thanks Gary! Think I may still flunk this class but at least i'm trying.

I see how a LOP works and understand that without reference points then yes you would more than likely struggle to stay on the line.  It wouldn't stop you from getting there with some good fortune and luck though.

In simple terms why do the lines change from 157 to 153, 148 and finaly 126? re read again and had a light bulb moment.

Can you not navigate a LOP and take into account the counter clockwise rotate centred on Howland? Thus keeping along the LOP. Otherwise by the looks of it TIGHAR should be looking on Kanton not Niku  ;)

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

On January 15, 2003 I posted this challenge to the navigation experts on the TIGHAR forum:

=========================================================================
Date:         Wed, 15 Jan 2003 13:39:33 EST
From:         Gary LaPook
Subject:      Re: Marshall Islands and LOP

You are right Alan, the line on his chart would not move.

However the only value of a LOP is that it represents a line on the surface of the earth. We both agree that there was no LOP painted on the water that Noonan could see and follow. It was not a terrestrial line of position like a railroad track, road, river or shore line that a pilot can follow to an airport located next to such LOPs.

The celestial LOP is useful for finding an island if the line on the chart passes through the island and so representing a line on the earth's surface that also passes through the island. Then, if you can determine that you are staying on the line on your chart you will also be determining that you are staying on the  line on the surface of the earth that goes to the island. You make this determination by taking additional observations of the sun and comparing the altitude that you measure  to the altitude you would  have measured (which you compute) if you were on the LOP. If they are the same you are on the LOP, if not you can determine how far off you are and which way to turn to regain the line.

>He would check
>his position periodically in relation to the line he had drawn on
>his chart. A line that never moved.

I don't know how he does this after the sun's azimuth has changed, perhaps you can explain it to me. Use this example to check his position in relation to the line he had drawn on the chart:

It is now 2240 Z on July 2,1937, about two and a half hours after the last transmission, and the airplane has been maintaining a true heading of 157 degrees and an airspeed of 120 knots and so should be getting close to Gardner. Noonan uses his bubble sextant and measures the altitude of the center of the sun. After making corrections for refraction and index error his observed altitude (Ho) is 59 degrees 15 minutes.

Where is he in relation to the line he had drawn on the chart?

Is the plane still on the LOP drawn on the chart?

If the plane is not on the line on the chart then how far off the LOP is the airplane?

Is the plane still on course for Gardner?

If it is not on the line to Gardner then which way should he turn to get to Gardner?

Please explain how you reach you conclusions and include the math.

If you have a scanner available I would appreciate it if you could scan in the chart work you do to figure out this example and email it to me at : glapook@pacbell.net since I would like to see how you accomplish this.

gl
===================================================

It's been 8 years and 7 months and still no serious response.

So, to answer your question, no you can't just make some compensation for the change in the azimuth of the LOP and then use it to find Gardner.

gl
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 22, 2011, 02:32:43 PM
Woohhh big home work for a year 7 student (uk education 11 year old).  Need to go and think about it!
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 22, 2011, 02:45:47 PM

cHRIS, gARY
Do not forget that the Lockheed was equipped with an autopilot (George). When they , AE/FN passed over where they thought Howland was (at 0843 Howland time) and set a course for Gardner (337 to 157) they would have set George for that course (wind corrected of course) and monitored their progress by time and speed.  That would have got them to a point where they could spot Gardner (3 times as long, 2 times as wide, 6 times the area when compared with Howland ) with a distinctively colored lagoon.  George would have got them there, just like George got them to the "Charted Position" which, unfortunately was 5 nm west of where Howland "Truly" was.

Moral of this story,  Never trust your life to a chart provided by some governmental body!  Be damned sure that your information is correct and verified before taking off on a long voyage completely over water and be damned sure you know your DF is operating properly and you know how to use it.

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

But since they were not over Howland at the start, setting a course of 157° (actually it is 159°) to Gardner would not take them to Gardner. If I want to fly to Chicago and I think I am over New York I would set my autopilot to maintain a heading of 270°. But, if I were actually over New Orleans that 270° heading would take me to Texas, not even close to Chicago. A basic premise in navigation is that you can not dead reckon to a destination starting from an unknown spot. Your DR can never be more accurate than the accuracy of your starting position and then it degrades further as you proceed.

Having flown behind many autopilots for many years I know that they would not be accurate enough to keep the plane on heading for 350 NM. Remember, "George" was not coupled to any VOR or GPS signal so could not keep the plane on "course" it was simply on "heading hold" which means it could only maintain a fixed heading as determined by the directional gyro (DG). Since directional gyros drift over time, "George" would be able to maintain a heading only if Earhart constantly compared her compass with the DG and kept resetting the DG to agree with the compass. The directional gyro was not "slaved" to the compass. I am sure that a 1937 autopilot did not do a better job than much more modern autopilots.

In fact, I am not even sure that "George" even had a "heading hold" mode, it might have been the much simpler "wing leveler" which just holds the wings level, more or less, and gets no input about the actual heading of the aircraft. With this type of simple autopilot any time the plane wanders off course due to turbulence or due to the "wing leveler" gyro not being perfect, the autopilot then just maintains the new position with no tendency to return to any particular heading. With a wing leveler the plane can end up going around in circles and the autopilot is perfectly happy about it. Wing levelers were common in planes even 50 years after the Earhart flight so it would not be surprising if her's was just a wing leveler. (Does anybody know the answer to this question?)

gl
Title: Re: LOP-Possible stupid question
Post by: Harry Howe, Jr. on August 22, 2011, 03:05:26 PM

Gary
Geez, you mean a good pilot would have to be told that the Gyroscopic Directional Indicator might "drift" periodically and thus affect the autopilot that is slaved to it, and therefore must periodically be compared with the compass and adjisted periodically, as necessary?

When I learned to fly, that was standard practice and noone had to tell me.  But I guess we have to make allowances for AE.  She wasn't anywhere near a good pilot, just a famed aviatrix, whatever that might have been.
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 22, 2011, 03:14:15 PM
ok confussed question but I read that they were setting a course for Gardner? but wern't they looking for Howland in the first instance?
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 22, 2011, 04:28:45 PM
ok confussed question but I read that they were setting a course for Gardner? but wern't they looking for Howland in the first instance?

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

You're right, they were looking for Howland. When they didn't arrive, some people jumped to the conclusion that they could just fly down the extended LOP to Gardner, if they had done the math they would have known it was not possible. See: https://sites.google.com/site/fredienoonan/discussions/navigation-to-howland-island

gl
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 22, 2011, 04:40:38 PM

Gary
Geez, you mean a good pilot would have to be told that the Gyroscopic Directional Indicator might "drift" periodically and thus affect the autopilot that is slaved to it, and therefore must periodically be compared with the compass and adjisted periodically, as necessary?

When I learned to fly, that was standard practice and noone had to tell me.  But I guess we have to make allowances for AE.  She wasn't anywhere near a good pilot, just a famed aviatrix, whatever that might have been.

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

Certainly not a slam against Amelia, all pilots understand about resetting the DG, including Amelia. But most of the people reading these posts are not pilots and your post could give the mis-impression that "George" was perfect and could easily fly to Gardner even if Amelia couldn't, which couldn't be further from the facts.

gl
Title: Re: LOP-Possible stupid question
Post by: Harry Howe, Jr. on August 22, 2011, 05:40:12 PM

Facts??  What facts??  Do you mean the last radio transmission heard on the Itasca from AE where she was running on the line North and South 157/337? but didn't give anyone a clue about her heading or intentions?  Those facts?  Not a very good pilot.
I remember learning early on as a flight student that radio transmissions needed to contain  PHACTI  (Position, Heading, Altitude, Communication and Time and most important  Intentions!  Perhaps AE should have spent more time becoming a pilot and less time trying to break records.
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 22, 2011, 07:10:22 PM

Facts??  What facts??  Do you mean the last radio transmission heard on the Itasca from AE where she was running on the line North and South 157/337? but didn't give anyone a clue about her heading or intentions?  Those facts?  Not a very good pilot.
I remember learning early on as a flight student that radio transmissions needed to contain  PHACTI  (Position, Heading, Altitude, Communication and Time and most important  Intentions!  Perhaps AE should have spent more time becoming a pilot and less time trying to break records.

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

"mis-impression that "George" was perfect and could easily fly to Gardner even if Amelia couldn't, which couldn't be further from the facts."

You misinterpreted what I wrote and took my reference to "facts" as applying to Amelia when I was actually referring to what I had written about the imperfection of "George."

gl
Title: Re: LOP-Possible stupid question
Post by: Harry Howe, Jr. on August 22, 2011, 09:10:46 PM

I didn't mean to imply that George was Perfect and could have flown from Howland to Gardner gy himself, certainly not,  but, with proper flying AE and Ceorge could easily have flown the distance and spotted Gardner.  I believe that is what they did, landing at Gardner at about 2400 (GCT) Noon Howland time.  Too bad that AE didn't let the Itasca in on her intentions.  If she had then Cmdr Thompson would have known which quadrant to steam off to, the SE,  which heading to take, 157 degrees, and would have arrived at Gardner in 20 hours or so to find AE and  FN standing next to their plane waving vigorously.  Alas, that/s not what she did.  Saying "Running north and south on 157/337" is meaningless.  "Running north to south on 337 to 157"would have passed on critical info.  To have said "diverting to Cardner Island" would also have been helpful.
Title: Re: LOP-Possible stupid question
Post by: John Kada on August 22, 2011, 10:22:26 PM
As long as we're asking possibly stupid questions,  I'm curious whether variations in magnetic declination might have played a role in the failure of AE and FN to find Howland. Just as there was incorrect information circulating about the exact coordinates of Howland, is it possible that the correct information about magnetic declination in the vicinity of Howland was not provided to AE and FN?

If my crude understanding of their navigation procedure is correct, after the last position determination by celestial navigation was made they would have had to rely on compass readings to stay on course and then to stay on the LOP for the last part of the flight. If the correction for magnetic declination was in error, this would have led to a systematic navigational error; whether this could have been a significant systematic error I leave for the likes of the estimable Mr. LaPook to shed light on.

If a magnetic declination correction error could conceivably have been a significant source of error on the flight, then I wonder if a record exists somewhere of the information that FN and AE had when they left Lae.

By the way, NOAA has an online magnetic declination calculator, which gives a magnetic declination of 5 degrees 26 minutes East for Lae and 9 degrees 29 minutes East at Howland in 1937...

Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 23, 2011, 02:11:23 AM
As long as we're asking possibly stupid questions,  I'm curious whether variations in magnetic declination might have played a role in the failure of AE and FN to find Howland. Just as there was incorrect information circulating about the exact coordinates of Howland, is it possible that the correct information about magnetic declination in the vicinity of Howland was not provided to AE and FN?

If my crude understanding of their navigation procedure is correct, after the last position determination by celestial navigation was made they would have had to rely on compass readings to stay on course and then to stay on the LOP for the last part of the flight. If the correction for magnetic declination was in error, this would have led to a systematic navigational error; whether this could have been a significant systematic error I leave for the likes of the estimable Mr. LaPook to shed light on.

If a magnetic declination correction error could conceivably have been a significant source of error on the flight, then I wonder if a record exists somewhere of the information that FN and AE had when they left Lae.

By the way, NOAA has an online magnetic declination calculator, which gives a magnetic declination of 5 degrees 26 minutes East for Lae and 9 degrees 29 minutes East at Howland in 1937...

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

Surveyors call it "declination" while navigators call it "variation." The NOAA computer modeling of the Earth's magnetic field computes the variation at Howland in July 1937 as 9° 29' east, nine and a half degrees east. This means the magnetic field of the Earth at that location was shifted 9.5° east of true north so if you turned to "magnetic north" using a perfect compass you would actually be heading 009.5° true. Williams (and presumably Noonan) used the value of 9° east, one half a degree different than the NOAA value, and this assumes that the NOAA prediction is correct. Williams listed 6° east for Lae, again a half degree difference. In a perfect world this half a degree difference could make a half NM error after flying 60 NM, not enough to make them miss Howland while flying the LOP but would grow to about 3 NM on a flight to Gardner, but nobody can maintain a heading to a one degree accuracy anyway. Noonan would have made the normal correction for this easterly variation by subtracting 9° from the 157° true course, determining the magnetic course to be 148°. Since the compass installed in the plane was also affected by the magnetic fields of components in the plane itself an additional correction needed to be made for this "deviation." I have attached a photo of the "compass correction card" showing the deviation on various headings. The deviation on a course of 150° is 2° "west" so Earhart would have added this 2° to the magnetic course of 148° to arrive at the compass course of 150°. Remember the mnenomic for making these corrections: "True Virgins Make Dull Companions." To this Noonan would have added or subtracted the wind correction angle to determine the heading to keep them on the LOP.

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

Errors can creep in at many places in this process and these accumulate to cause the cross track uncertainty in the dead reckoning, so the dead reckoning must be corrected from time to time by taking addition sights of the sun. In computing the compass heading needed to maintain the true course of 157°, Noonan had to add three numbers that had been rounded to one degree accuracy even though they were not exactly at an even degree. For example, 9.5° variation was rounded to 9° even. The azimuth of the Sun was rounded to 067° T while the actual azimuth varied from 66.9° at 1745 Z to 66.5° at 1845 Z and 62.8° at 2013 Z. The compass correction card showed a correction for a heading of 120° of + 1° and for 150° of + 2° so the correction for the magnetic heading of 148° is somewhere in between. (And the correction card itself was not perfect since it was derived by swinging the compass and that is not a perfect process.) Adding three quantities, each of which were rounded to one degree precision, introduces a 3° uncertainty in the result.

Then, to this, Noonan had to allow a wind correction angle to counteract the cross-wind. The WCA is also rounded to one degree so the uncertainty in the calculation increases to 4° . The WCA itself has an even greater uncertainty since it was derived by calculating the wind from drift observations or by "wind between fixes" and each of these procedures have their own levels of uncertainty.

So, the half a degree discrepancy between the Williams variation value and the NOAA variation is the least of the problems. These uncertainties add up and this is the reason that you have to allow for a 10% uncertainty in dead reckoning. If Noonan knew that he was over Howland (and the one thing he knew for sure was that he was NOT over Howland) and he wanted to go to Gardner, then he would have to take into consideration that his DR position, after flying 350 NM to Gardner, could be as much as 35 NM in error and he could miss that island by passing 35 NM east or 35 NM west. With 20 NM visibility his chance of finding Gardner was 40/70, or only 57%, the odds were only 4 to 3, barely better than even money. Would you bet your life at these odds?

Or, since their lives were on the line, in making their to abandon the search for Howland and to attempt to find Gardner, Noonan and Earhart might have used something more conservative like the estimate of DR accuracy contained in the U.S. Navy Flight Navigation Manual, H.O. 216, of 20 NM per hour plus 1% of the distance. Using this formulation you find the uncertainty to be 63 NM meaning that they could have passed up to 63 NM east or west of Gardner, a total of 126 NM. Since they would only be able to see the island for 20 NM from either side, a total detection diameter of 40 NM, the probability of seeing Gardner was only 40/126, 32%, making the odds 40 to 86, or more that 2 to 1 against saving their lives. Would you make that bet? And Noonan had to know that he was at least 20 NM from Howland, since he did not see that island, and he had no way to determine exactly where so he would have known that his actual odds were much worse.

and:

gl
Title: Re: LOP-Possible stupid question
Post by: Harry Howe, Jr. on August 23, 2011, 11:46:08 AM

I was wondering how long it would take for someone to ask about variations in the compass headings relative to true north.
There were two pilots aboard, AE and FN, one of whom was an expert navigator as well who we can assume knew about corrections necessary on trips that span large east/west directions.  Presumably the necessary declination "lines" were marked on their chart and corrections made to  the compass as the trip progressed, but we really don't know what information they had prior to takeoff and during flight.

I can only  say by experience as a pilot that, on every cross-country flight without fail,  I made it a practice to adjust my magnetic compass for declination as marked on my chart and for variatioins due to plane components from the planes card prior to takeoff and periodically during the flight.  That practice got me in the habit of doing it regularly and to check it as I flew the course.  It is essential to develope good habits early on in one's flying experience so that these things become "second nature".  Whether AE and FN had developed such habits is not known.  I have a personnel opinion.
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 23, 2011, 03:26:25 PM

I was wondering how long it would take for someone to ask about variations in the compass headings relative to true north.
There were two pilots aboard, AE and FN, one of whom was an expert navigator as well who we can assume knew about corrections necessary on trips that span large east/west directions.  Presumably the necessary declination "lines" were marked on their chart and corrections made to  the compass as the trip progressed, but we really don't know what information they had prior to takeoff and during flight.

I can only  say by experience as a pilot that, on every cross-country flight without fail,  I made it a practice to adjust my magnetic compass for declination as marked on my chart and for variatioins due to plane components from the planes card prior to takeoff and periodically during the flight.  That practice got me in the habit of doing it regularly and to check it as I flew the course.  It is essential to develope good habits early on in one's flying experience so that these things become "second nature".  Whether AE and FN had developed such habits is not known.  I have a personnel opinion.

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

It has been posted on the TIGHAR forum that the several islands of the Phoenix Island group provided a "catcher's mitt" ensuring that Noonan would be certain to stumble onto at least one of these islands, that they were impossible to miss. This also is not true as these islands are spread very far apart from each other and the plane could fly through the entire island group without being close enough to any of the islands to be certain of seeing land. See chart ONC M-17, (each square on this chart is 60 nautical miles on a side, 69 statute miles.)

The Phoenix islands consist of McKean island which is 50 NM to the left of the course to
Gardner, Hull is 140 NM, Sydney is 180 NM, Birnie is 190 NM, Canton is 200, Enderbery is
230 and Phoenix island is 250 NM. There are no islands to the right of the course. Most
are at greater distances from Howland than Gardner and there is a lot of water in between.
It is not a sure thing like turning till the compass says "E for Europe" like Lindbergh did.

Here is an analogy to help make this clear.

You are walking down a street. A black limousine pulls up next to you. Two big guys jump out, rough you up and throw you into the trunk. After a long drive the car finally stops and you are pulled out of the trunk. It is now dark. You look around and you realize you are standing in Yankee Stadium.

Vito Corleone walks up to you and says. "I've got a little proposition for you."
"What kind of a proposition, " you ask nervously.
"See the outfielders out there, right, center and left field?"
"Yes" you say.
"Here is my proposition" says the Godfather. "I will have my pitcher pitch one ball to you. You hit it, and if it is caught on the fly by any of the outfielders, I will give you a hundred thousand dollars."
"And if they don't catch it, what do I have to pay you?" you reply.
"Oh, nothing" say the Godfather, "My boys will just shoot you in the head and dump your body in the river where you can sleep with the fishes. Oh, I forgot to mention, the outfielders are not allowed to move."
"Gee, do I have any other options?" you ask.
"Tell you what" the Godfather goes on, "since I am such a nice guy I will make you another proposition but you will have to choose between just these two. I will have the pitcher pitch you three balls and you hit them back to the pitcher or to the shortstop and if either the pitcher or the shortstop catches one of the balls on the fly I will give you a million dollars."
"And if they don't catch one of the balls..." your voice trails off.
"Same deal, my boys shoot you in the head."

So which proposition do you choose?

This is the true "catcher's mitt" situation.

If you take the first proposition you have only one chance to hit the ball and the non-moving outfielders present very small targets to hit that are far away. Even if the ball is caught you only get one hundred thousand bucks. If the ball is not caught you sleep with the fishes.

If you take the second proposition you get three chances to hit the ball and the pitcher and shortstop have three chances to catch the ball and they are much closer and make much bigger targets to hit at this close range. If one of them catches the ball you get a million dollars, ten times more than the first proposition. If they don't catch the ball you are no worse off than with the first proposition, you still end up sleeping with the fishes.

So would Noonan and Earhart have decided to fly 350 nautical miles across the sea, hoping to find several small island which are spread so far apart that even with 20 mile visibility they could fly between them without seeing any of them, knowing that they would have only one chance since they would burn up all of their fuel on the way leaving nothing left to fly a search pattern with? And even if they are successful in finding one of the islands, there they are, barely alive, with no water or food, the airplane destroyed, no round the world flight, AE and Putnam bankrupt. If not successful they sleep with the fishes.

Or would they turn around and fly a standard search pattern with three hours of fuel on board to allow a long search, with Howland and Baker, with twenty mile visibility, presenting a target 80 miles wide and only 50 to a hundred miles away, a target hard to miss. And if successful they win the big prize, the airplane is refueled and the round the world flight is completed, accolades and money roll in and AE and Putnam have fame and wealth. If not successful they are no worse off than if missing the Phoenix islands, they still sleep with the fishes.

What choice would you make?

gl
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 23, 2011, 04:20:41 PM
Thanks Gary! Think I may still flunk this class but at least i'm trying.

I see how a LOP works and understand that without reference points then yes you would more than likely struggle to stay on the line.  It wouldn't stop you from getting there with some good fortune and luck though.

In simple terms why do the lines change from 157 to 153, 148 and finaly 126? re read again and had a light bulb moment.

Can you not navigate a LOP and take into account the counter clockwise rotate centred on Howland? Thus keeping along the LOP. Otherwise by the looks of it TIGHAR should be looking on Kanton not Niku  ;)

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

The LOP is plotted at right angles to the azimuth of the Sun. From 1745 Z to 1845 Z the azimuth of the Sun was 067° plus 90° makes 157°. As the earth turns the sun moves across the sky and the azimuth changes during the day. But the LOP didn't stop at 126° since the sun kept moving.  At noon the azimuth of the sun at Howland was straight north so an LOP taken at that time would have run 090/270°. The azimuth was changing in a counter-clockwise direction which may be confusing you since you are probably used to seeing the direction of the sun changing in a clockwise direction. But from a position south of the sun, the sun moves in the opposite direction and noon occurs with the sun to the north while for the U.S. and Europe the sun is south at noon.

gl
Title: Re: LOP-Possible stupid question
Post by: Harry Howe, Jr. on August 23, 2011, 05:45:40 PM

AE/FN probably knew exactly where Gardner was relative to Howland before they took off and had it in mind as a possible alternative forced landing  place.

That is my belief.

They also probably had places to the NW in the Marshalls for the same purpose but also knew that they were close to twice as far away as Gardner. .  They also would have known that the Japanese were in control of the Marshalls.  Their choice would have been to the SSE  to Baker, McKean, and Gardner, Common Sense.
Title: Re: LOP-Possible stupid question
Post by: John Kada on August 23, 2011, 09:33:26 PM
Gary,

I assume that Williams is the standard navigational reference that FN would have used, and apparently the value for the magnetic variation at Gardner given in Williams matches the NOAA value for all practical purposes, so we have no reason to think that a magnetic variation correction error was a factor in the loss of the flight.
Title: Re: LOP-Possible stupid question
Post by: Harry Howe, Jr. on August 24, 2011, 11:41:39 AM

The magnetic declination and variation of the compass probably did not play a part in the failure of the flight from Lae to Howland, however we really don't know what went on in that cockpit.  Only AE and FN knew and they aren't with us.

Whether they adjusted their compass for magnetic declination and variation at takeoff and periodically during the long west to east flight, I do not know.  Their failure to find Howland and/or to be rescued at Gardner was a result of many errors, the moist egregious of which was to take off without knowing that their RDF (Radio Direction Finder) was working properly and that they knew and understood the limitations of the RDFs at Howland and on the Itasca.
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 24, 2011, 06:16:43 PM
Gary,

I assume that Williams is the standard navigational reference that FN would have used, and apparently the value for the magnetic variation at Gardner given in Williams matches the NOAA value for all practical purposes, so we have no reason to think that a magnetic variation correction error was a factor in the loss of the flight.

------------------------
Williams had the variation for Lae, Howland and some places in between but not Gardner.

gl
Title: Re: LOP-Possible stupid question
Post by: John Kada on August 24, 2011, 06:31:53 PM
Oops--I meant to say Howland, not Gardner/Nikumaroro...
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 25, 2011, 12:15:21 PM
OK slight thread drift (should have called the thread Chris's dumb questions on navigation) but can anyone explain this to me?

Quote
Recent research has indicated that on July 2, 1937, Earhart´s aircraft was not (contrary to current literature) flown over the great circle New Guinea-to-Howland.
From Wikipedia (http://en.wikipedia.org/wiki/Fred_Noonan) sourced from
Quote
European Journal of Navigation, Vol. 9, no. 1, 2011.
Title: Re: LOP-Possible stupid question
Post by: Edgard Engelman on August 25, 2011, 02:07:12 PM
It was written by H.A.C.van Asten. It would be interesting to have Gary LaPook's opinion on this paper.
Title: Re: LOP-Possible stupid question
Post by: Chris Johnson on August 25, 2011, 02:21:55 PM
It was written by H.A.C.van Asten. It would be interesting to have Gary LaPook's opinion on this paper.

Thanks :)
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 25, 2011, 02:32:21 PM
OK slight thread drift (should have called the thread Chris's dumb questions on navigation) but can anyone explain this to me?

Quote
Recent research has indicated that on July 2, 1937, Earhart´s aircraft was not (contrary to current literature) flown over the great circle New Guinea-to-Howland.
From Wikipedia (http://en.wikipedia.org/wiki/Fred_Noonan) sourced from
Quote
European Journal of Navigation, Vol. 9, no. 1, 2011.

---------------------
There is nothing magic about the great circle course. Compared to the rhumb line course a great circle course may be significantly shorter depending mainly on the latitude of the departure and the destination. Near the equator there is virtually no difference between them, the rhumb line from Lae to Howland is less than 0.2 SM longer than the great circle, the course is just 1.4 degrees different at the start and it is never more than 10 SM offset to the side of the great circle. Prior to GPS it would not have been possible for any navigator to determine whether he was flying the rhumb line or flying the great circle on this flight.

On a long flight even large deviations to the side do not appreciably lengthen the flight. On the fight from Lae to Howland he plane could have been off course 100 SM at the midpoint and this would add only 8 SM to the total distance.

gl

gl
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 25, 2011, 02:47:31 PM
It was written by H.A.C.van Asten. It would be interesting to have Gary LaPook's opinion on this paper.
------------------------

Don't waste your time trying to work your way through the gibberish in Mr. van Asten's two published papers.

We have thoroughly discussed Mr. van Asten's theories on the  "Navigating the LOP with the offset method" topic, see:

https://tighar.org/smf/index.php/topic,169.120.html

and subsequent posts, especially reply 203 pointing out his 300 NM error in his computation of this "10 mile" error line and his admission of this error in reply 204.

https://tighar.org/smf/index.php/topic,169.203.html

We have also dicussed Mr van Asten's theories on the "Noonan navigation error" thread starting at reply 47 and continuing through reply 80.

https://tighar.org/smf/index.php/topic,383.45.html

The short answer, I can't believe he got his articles published because they are so full of errors. He wrote that he had a surface navigator review his papers prior to publication and I told him his problem was that he didn't have the papers reviewed by  a flight navigator, the procedures are quite different.

Here are links to better articles.

http://www.oceannavigator.com/content/celestial-air

http://www.avweb.com/news/avtraining/IFR_bySunAndStars_200781-1.html

gl
Title: Re: LOP-Possible stupid question
Post by: h.a.c. van asten on August 26, 2011, 12:13:54 AM
Mr.gl says that he has "debunked" , always with many words and few arguments ,  the contents of two articles but in fact he has debunked nothing , neither the consistency nor the relevancy for probability , and without presenting any alternative from himself .
Title: Re: LOP-Possible stupid question
Post by: h.a.c. van asten on August 26, 2011, 03:07:03 PM
Navigator could not determine about great circle and rhumb line distance in the equatorial region , but the principles are different : by great circle the true course is altered from one chord to another and a circle outline is flown ,  by loxodrome a constant true course is maintained throughout the flight length and an elipsoid outline is followed .
Title: Re: LOP-Possible stupid question
Post by: Jeff Scott on August 26, 2011, 10:43:55 PM
Mr.gl says that he has "debunked" , always with many words and few arguments ,  the contents of two articles but in fact he has debunked nothing , neither the consistency nor the relevancy for probability , and without presenting any alternative from himself .

Mr. LaPook has methodically and systematically dismantled your entire argument, pointing out numerous flaws, faulty assumptions, mathematical errors, misconceptions, half-truths, and outright lies in your statements.  He's also written an entire site documenting his alternative, a site that is far better supported, documented, justified, and infinitely more readable than anything you've provided.  While I find some of your arguments mentally stimulating, they are usually written in such a confusing manner as to make them nearly indecipherable.  A course on technical writing would serve you well.
Title: Re: LOP-Possible stupid question
Post by: Gary LaPook on August 27, 2011, 10:12:23 AM
Mr.gl says that he has "debunked" , always with many words and few arguments ,  the contents of two articles but in fact he has debunked nothing , neither the consistency nor the relevancy for probability , and without presenting any alternative from himself .

Mr. LaPook has methodically and systematically dismantled your entire argument, pointing out numerous flaws, faulty assumptions, mathematical errors, misconceptions, half-truths, and outright lies in your statements.  He's also written an entire site documenting his alternative, a site that is far better supported, documented, justified, and infinitely more readable than anything you've provided.  While I find some of your arguments mentally stimulating, they are usually written in such a confusing manner as to make them nearly indecipherable.  A course on technical writing would serve you well.

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

Wow, thanks.

gl
Title: Re: LOP-Possible stupid question
Post by: Martin X. Moleski, SJ on August 28, 2011, 05:37:20 AM
I have locked this topic.

The question about what a Line of Position is has been answered.

I have removed and/or edited a number of posts because they strayed into ad hominem (http://tighar.org/smf/index.php/topic,377.0.html) remarks.

This is a moderated forum.  You may report any post and any poster to the moderators.  Please do not enter into contests of manhood and honor, no matter how much you may feel yourself to have been provoked.  If you find that you cannot tolerate the posts from a participant in the Forum, you may place that person on your ignore list. (http://tighar.org/smf/index.php/topic,398.0.html)