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

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

Sunrise at a given date and latitude and longitude was calculated using the National Oceanic and Atmospheric Administration’s (NOAA) sunrise/sunset calculator at

http://www.srrb.noaa.gov/highlights/sunrise/sunrise.html I used the NOAA web site to calculate the time of sunrise at Howland and at intervals of 100 miles, 200 miles and 300 miles from Howland along the projected flight path of the AE aircraft from Lae to Howland. Latitudes and longitudes of these points were obtained using Google Earth.

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

Table 1

Sunrise GMT Miles from Lat Long

Howland

17:45 0 0 47’ 57.84” N 176 37’ 14.75”W

17:52 100 0 30’ 25.62” N 178 2’ 50.09”W

17.58 200 0 11’ 15.02” N 179 28’ 21.67”W

18.04 300 0 5’ 51.73” S 179 7’ 14.03”E

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

Table 2

Time Miles from Howland

18:12 100

17:42 200

10:30 1,121 (Myrtlebank siting)

0:00 2,556 (Lae)

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

When the aircraft’s path and the sunrise line coincide then the time for both is the same. So at that time the two equations are equal;

0.00106 x +17.75 = -0.0077 X + 19.091.

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

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

Cheers, Bob Schafish