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406pilot
15th Apr 2004, 18:14
hi guys,..
just found my hands on a really old magazine(mind u im not that old) and the authour claims of a poor mans dme..a dangleometer,anybody else heard of this device?...
CONCEPT:is to get the angle in degrees between the object and the actual aircraft position,thn by using trigonometry calculate the distance of the object..its quite possible given the angle..
now i know its not prcticle in the days of gps and fms and god knows wht else is coming our way in terms of navigation,but im just a bit curious..


ps:just wondering how many new generation pilots have actually heard of this device.

no more 406pilot

Empty Cruise
15th Apr 2004, 18:36
Dangleometer? Never heard - but it sounds very much like a sextant. In maritime navigation, the sextant is mostly used to measure the height of a heavenly body (no, not mine :D ) above the horizon. When used for this purpose, it is held vertically, but it may also be used for lateral measurements, in which case it is held horizontally.

I have - on a holiday trip to France in a SuperCub - used a bubble sextant for naviagtion. But I must admit - it was not the primary navaid :} . When all the calcs for 4 stars had been done, I was able to get the lines to intersect with approx 8 NM accuracy. OK perfomance, but the point is - it took 10 min. from the first measurement before the pos. was plotted. This hardly qualifies for P-RNAV departures :rolleyes:

Brgds,
Empty

oxford blue
16th Apr 2004, 18:39
Until about 10 years ago, the sextant was used in aviation as well. The RAF continued to use them until the wide availability of GPS made them obselete.

The aviation periscopic sextant was a precision instrument and could be used to measure depression angles as well. There was a formula to calculate your range from the depression angle and your height relative to a ground object. As it also had an azimuth ring which was accurate to about a degree or so, you could get an accurate range and bearing fix from a ground feature with a single observation.

406pilot
17th Apr 2004, 18:07
thanks guys yeah i have heard about the sextant,the dangleometer could in some ways resemble it only that this is a home made thing(its more like a protractor with a piece of string hanging to measure the azimuth of the object) that guys used,could even be the mother of the sextant as we know it today...i never seen it just read in a really old magazine like i said..

406pilot

Empty Cruise
17th Apr 2004, 18:21
Yes, have heard of it as a survival tool. But - as far as heavenly bodies go - unless you should happen to be flying around with a copy of the Admiraltys H.O.249, you would be limited to measuring bodies that you know stuff about. The north star is usefull for finding your lattitude. Having a watch running UTC, your lattitude and a sunrise/sunset table, you would be able to locate your approximate longtitude by timing local sunrise (assuming you had already determined your lattitude).

Brgds
Empty