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Author Topic: international time  (Read 8902 times)

Craig Romig

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international time
« on: August 05, 2011, 08:57:38 AM »

while thinking about the post loss messages. i considered a couple of things.  what time would it have been on Nicu? at the times the message were recieved by dana on the fourth? and then when betty heard the other message.
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Martin X. Moleski, SJ

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Re: international time
« Reply #1 on: August 05, 2011, 10:44:34 AM »

while thinking about the post loss messages. i considered a couple of things.  what time would it have been on Nicu? at the times the message were recieved by dana on the fourth? and then when betty heard the other message.

Here is a table of post loss messages and estimated tides on Niku in GMT.

Randy Jacobson's explanation of how he calculated GMT for his radio reception database.  He says, "Prior to WWII, many parts of the world had time zones of 0.5 hours different than Greenwich Mean Time. For example, Hawaii's standard time was +10.5. To determine how to get back to GMT time from a local time, always add that number to get GMT time. To get from GMT time to local time, subtract the value if positive (west of Greenwich) to get local time; add the absolute value if the value is negative (east of Greenwich), or simply
subtract the value."

Howland seems to have been on Honolulu Standard Time (HST; +10.5).  Niku is east of Howland and west of Hawaii, so I suppose that it would also have been on HST. 

So it sounds as though you subtract 10.5 from GMT to find Niku time in 1937, more or less. 
LTM,

           Marty
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Craig Romig

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Re: international time
« Reply #2 on: August 05, 2011, 10:54:29 AM »

so if we take bettys time of 3 pm in fla. that would be about 9 am  the next day on gardner island.  assuming that is correct. what time does the tide come in at gardner island?
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Martin X. Moleski, SJ

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Re: international time
« Reply #3 on: August 05, 2011, 10:15:44 PM »

so if we take bettys time of 3 pm in fla. that would be about 9 am  the next day on gardner island.  assuming that is correct. what time does the tide come in at gardner island?

We don't have a complete tide table for Niku on the web site (that I know of).

The post loss messages and estimated tides on Niku in GMT give you some idea of the estimated heights of the tide at times that coincide with post-loss radio messages.
LTM,

           Marty
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Craig Romig

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Re: international time
« Reply #4 on: August 06, 2011, 12:54:37 AM »

i did finally blow up the chart on that page. and i saw tide heights of up to 4 feet.  so they still would be able to send the messages with that height of tide water.

another report of  a message i read someplace said something about they had landed half on land and half on water. so could we assume or guess from that reading. that the plane may have been very close to the edge of the reef. and possibly was dragged off the reef by the time the search plane came over. after the messages had stopped? that may be why only part of the plane was seen by the others who may have seen it there. even thought the tides dont seem to be quite high enough to hide a whole plane under it.
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h.a.c. van asten

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Re: international time
« Reply #5 on: August 21, 2011, 01:54:06 AM »

while thinking about the post loss messages. i considered a couple of things.  what time would it have been on Nicu? at the times the message were recieved by dana on the fourth? and then when betty heard the other message.

Here is a table of post loss messages and estimated tides on Niku in GMT.

Uninhabited places have no time indications from themselves , as soon as the first member of mankind arrives , with GMT 1000 by his watch hands , it is 1000 GMT there . US Navy ships accounted for 1/2 hr time zones and so did Itasca staff @ Howland .

Randy Jacobson's explanation of how he calculated GMT for his radio reception database.  He says, "Prior to WWII, many parts of the world had time zones of 0.5 hours different than Greenwich Mean Time. For example, Hawaii's standard time was +10.5. To determine how to get back to GMT time from a local time, always add that number to get GMT time. To get from GMT time to local time, subtract the value if positive (west of Greenwich) to get local time; add the absolute value if the value is negative (east of Greenwich), or simply
subtract the value."

Howland seems to have been on Honolulu Standard Time (HST; +10.5).  Niku is east of Howland and west of Hawaii, so I suppose that it would also have been on HST. 

So it sounds as though you subtract 10.5 from GMT to find Niku time in 1937, more or less.
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Gary LaPook

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Re: international time
« Reply #6 on: August 29, 2011, 02:55:30 PM »

while thinking about the post loss messages. i considered a couple of things.  what time would it have been on Nicu? at the times the message were recieved by dana on the fourth? and then when betty heard the other message.
---------------------------------------------

That's kind of a nonsensical question. "Time" is a human construct so has no meaning on an uninhabited island since the land crabs do not wear watches. People choose whatever "time" is convenient for them. In the olden days every town kept its own time with towns further east seeing the sun rise before towns further west so their clocks were ahead and displayed a later time. With the arrival of railroads it became necessary to coordinate schedules across distances east and west so the concept of "zone time" was invented. Standard time zones are 15 ° wide because the sun travels 15° west every hour so this makes the "zone times" differ by exact hours. They extend 7.5 degrees (7° 30') each way from the standard meridians (which are spaced every 15° starting with the Greenwich Meridian) for that zone. This is the system used at sea but is often modified on land for convenience by not using the exact dividing lines between zones so that entire political units, such as states , can be on the same time and also some countries change their time to "daylight savings time" in the summer. So, for example, the standard meridian for the time in California is 120° west longitude and the zone extends from 112.5° (112° 30') to 127.5° (127° 30') west. To make it easy to convert from a zone time to GMT ("Z" time, or Zulu time) the zones are given numbers (called "Zone Descriptions, Z.D.) that you add to the zone time to find GMT. For California time it is + 8 so you add eight hours to California clocks to find Zulu time. (It changes for daylight savings time to + 7, but only in the U.S. It remains + 8 at sea.)

There is an exception in that there are two zones, each only 7.5° wide (7° 30'), abutting the 180th meridian. To the east the Z.D. is + 12 while to the west it is - 12 to account for the clocks saying the same time in each of these zones but the date being different. An example will make this clear. If you are at 175° east longitude (west of the 180th, Z.D. - 12) on July 3rd and your clock says 2100 you subtract 12 hours and the GMT is 0900 on July 3rd. If you are at 175° west longitude (east of the 180th, Z.D. + 12) your clock also says 2100 but your calender says July 2nd. You add 12 hours and and find the same answer, 0900 the next day, July 3rd.

The clocks are set for convenience which is why the people on Howland kept their clocks set with a Z.D. of + 10:30 so as to keep the same time as that being kept in Hawaii for convenience of radio schedules. Hawaii was an exception and kept time with a Z.D. of + 10:30 because Hawaii is near the dividing line between two time zones and keeping time using either of those standard zones would cause their clocks to always be in disagreement with the sun, noon would never happen at 12:00 o'clock. Note, there was no such thing as "half-hour time zones," ships at sea at the same longitude of Hawaii kept their clocks set to the standard zone time with a Z.D. of + 10. (Hawaii now uses the standard time zone with  Z.D. of + 10.)

U.S. Navy Regulation, Article 1031 issued in 1920 required Navy vessels to keep time based on the standard time zones. Paragraphs 6e and 8 however gave the commander the authority to set his clocks in a non-standard way (but he must note in the logbook the exact "hours, minutes and seconds" needed to convert ship's time to GMT as the Z.D.) when near a shore that kept non-standard time or under circumstances that "may render desirable a departure from the regular method." Itasca used this authority and kept time thirty minutes fast from the standard time zone for its location (+ 12), but Itasca was not keeping  time in conformance non-existent "half hour time zones". A half hour zone would be 3.75 degrees (3° 45') wide so in such a system the + 12 hour zone would extend from 176.25° (176° 15') west longitude to the 180th meridian. If they had been using "half hour time zones" then both Howland and the Itasca would have been in the +12 "half hour zone" since they were at 176.6° (176° 38') west longitude, only 3.4° east of the 180th meridian. Itasca kept their clocks set to Z.D. + 11:30 for their own convenience (probably to keep their time exactly one hour different than Hawaii's to avoid confusion with radio schedules too.)

So what time was it on Gardner? Its longitude is 174.5° (174° 32') west so the Z.D. there is + 12 for that standard time zone and Earhart did not know that Itasca was using a Z.D. of + 11:30 so she would have had no reason to use that Z.D. But there is no reason to believe anybody on Gardner kept either of these zone times. If Earhart landed on Gardner then her time, the time on the cockpit clock, would be the same as Lae time, Z.D. -10, since her practice was to leave her clock set to the time at the departure airport. If Noonan looked at his chronometers then the time was GMT since his were set to GMT for navigational purposes.

gl
« Last Edit: September 05, 2011, 12:12:25 PM by Gary LaPook »
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