measuring 10 km with 1m accuracy
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From: Frank Buss on 15 Feb 2010 10:32 Vladimir Vassilevsky wrote: > Use a long enough measuring tape. I guess it would be difficult to get 1 m accuracy with a 10 km measuring tape (non-planar ground, tape stretching etc.). -- Frank Buss, fb(a)frank-buss.de http://www.frank-buss.de, http://www.it4-systems.de
From: invalid on 15 Feb 2010 10:43 "Surinder Singh" <gogreenmiles(a)gmail.com> wrote in message news:630d8cc3-abb4-49ae-9d98-730e2f257e32(a)a17g2000pre.googlegroups.com... > What would be best technology (GPS,IR,Radio/freq,ultrasonic etc) for > doing distance measurements upto 10km with accuracy of 1 meter? > GPS could be good for greater distance but accuracy seems coarse. The original baseline of the Ordnance Survey was measured with glass tubes laid end to end. Mind you, they had a team of squaddies to do it for them, a much better activity than coming off second best against an army of 3rd World peasants in Afghanistan.
From: Rich Webb on 15 Feb 2010 11:45 On Mon, 15 Feb 2010 16:32:51 +0100, Frank Buss <fb(a)frank-buss.de> wrote: >Vladimir Vassilevsky wrote: > >> Use a long enough measuring tape. > >I guess it would be difficult to get 1 m accuracy with a 10 km measuring >tape (non-planar ground, tape stretching etc.). It also depends on what one considers distance to be. Is it the straight cord between the points? Or the great circle distance? Or the measured ground distance? Or something else? There are statutory definitions for civil survey work but those aren't appropriate in all cases. Actually, I would have guessed that the difference between the arc length and chord would have been greater but imagination isn't always a good guide at these scales. Turns out that it's only about 1 mm over a 10 km arc, so probably not too significant in the OP's 1 m requirement. -- Rich Webb Norfolk, VA
From: Tauno Voipio on 15 Feb 2010 12:29 Vladimir Vassilevsky wrote: > > > Tauno Voipio wrote: > > >> If you are not in a hurry, GPS using the geodetic methods will >> give accuracies well under a meter with static relative measurement. >> The needed measurement time will be about an hour, simultaneously >> at both ends of the measurement distance. >> >> With top-end geodetic receivers and sufficient measurement time, >> an accuracy of a centimeter or less is attainable. The position >> is the phase centerpoint of the antenna. > > While ago I did a plot of a common GPS module readings taken at every > second. The distribution was clearly not Gaussian; it was asymmetrical > and skewed. I am not sure if it would be possible to improve the > accuracy by averaging and how much of averaging it would take. > > Vladimir Vassilevsky > DSP and Mixed Signal Design Consultant > http://www.abvolt.com That's why I said 'static relative measurement'. It means that the skew will be about the same at both ends. To get geodetic quality measurements, the raw data has to be adjusted so that the points will be taken at the same time (and plenty of them). -- Tauno Voipio tauno voipio (at) iki fi
From: linnix on 15 Feb 2010 12:43
On Feb 15, 9:29 am, Tauno Voipio <tauno.voi...(a)notused.fi.invalid> wrote: > Vladimir Vassilevsky wrote: > > > Tauno Voipio wrote: > > >> If you are not in a hurry, GPS using the geodetic methods will > >> give accuracies well under a meter with static relative measurement. > >> The needed measurement time will be about an hour, simultaneously > >> at both ends of the measurement distance. > > >> With top-end geodetic receivers and sufficient measurement time, > >> an accuracy of a centimeter or less is attainable. The position > >> is the phase centerpoint of the antenna. > > > While ago I did a plot of a common I.e. cheap and low resolution GPS. > > GPS module readings taken at every > > second. The distribution was clearly not Gaussian; but identical at both end. > > it was asymmetrical > > and skewed. I am not sure if it would be possible say that to the military. > > to improve the > > accuracy not by averaging, but other means. > > by averaging and how much of averaging it would take. > > > Vladimir Vassilevsky > > DSP and Mixed Signal Design Consultant > >http://www.abvolt.com > > That's why I said 'static relative measurement'. or Differential GPS. > It means that the > skew will be about the same at both ends. To get geodetic quality > measurements, the raw data has to be adjusted so that the points > will be taken at the same time (and plenty of them). > > -- > > Tauno Voipio > tauno voipio (at) iki fi |