NavList:

It was interesting to think about the correction for change in heading during the observation again. The US Airforce calls this "wander." So I pulled out my Mears slide and did a computation using the numbers in the example of a 0.8 degree change per minute at 480 knots. The example comes up with a 19 minutes, or nautical miles, correction for this. Drawing a line on the .8 line on the E6-B at 480 knots and then rotating the disk ninety degrees up gives the correction as 20'.

Doing the same computation on the Polhemus computer produces a correction of 19.6. The ground speed is set for 480 knots and the wander scale shows a correction of 12.' for a one degree heading change in two minutes. But the heading change was only 0.8 so we multiply by 0.8 (the actual heading change)  and determine that the correction would have been 9.6 IF the heading change had taken two minutes. But it actually took only one minute so we have to double that value and find the actual correction to be 19.6.'

Looking at the wander correction table in US AFPAM 216 shows the correction to be 20.2' by interpolating between the 475 knot and 500 knot values for ground speed and then doubling for the one-minute observation period.

According to HO 216, "Air Navigation," (1967)

The formula for the "wander" correction is 5.25  V  TR

V is in hundred of knots

TR is track change in degrees per minute. 

So, for the example,  5.25 x 4.8 x 0.8 =20.16'. 

So, not surprisingly, all the methods are in close agreement.

gl

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