It's going to be hard to use LORAN C, if the system is shut down. -John ================= > Stanley Reynolds wrote: >> Yes, found this patent : >> >> http://www.freepatentsonline.com/y2008/0186232.html >> >> "A method and radio navigation system compass apparatus for determining >> true north or azimuth or orientation of a vehicle or the like by the use >> of integrated Loran and satellite radio navigation receivers employing >> crossed-loop H-field antennas for the Loran reception, or the use of at >> least three Loran type transmitter, or two Loran type transmitter and a >> synchronized clock for determining both position and azimuth. " >> >> >> synergy, the whole is greater than the sum of the individual parts > > Traditional Directional Finding techniquest combined with positional > information from the Loran-C is a good mix. Question is if the invention > is that big that a good patent would hold. [snip]

Hi Antonio: That's an interesting question. It turns out that one of the key military applications of GPS, in addition to position and time, is to find North to high accuracy. This is needed to be known to better that one grad (1/6400 of a circle). In that past it was done using a theodolite integrated with a gyroscope (AG8 (Kern DKM1) North Finding System). This system was heavy, cost the government about $250k and was very easy to break. http://www.prc68.com/I/Alidade.shtml#AG8 I think starting with the PLGR96 and now the DAGR there are two or more methods of accurately finding North. http://www.prc68.com/I/PLGR.shtml http://www.prc68.com/I/DAGR.shtml#GLS http://www.prc68.com/I/DAGR.shtml#AzD In one method you place the receiver on stake #1, go to stake #2 (while not obstructing the antenna to allow carrier phase tracking sats) then at stake #2 press enter and the GPS gives you the bearing and distance between the stakes. In another method two GPS receivers are used. One at stake #1 and the other first is synchronized to the one at stake #1 then moved to stake #2, press enter, and go back to stake #1 and reconnect the two units. Again you get bearing and distance between the stakes based on carrier phase processing inside the GPS unit. Have Fun, Brooke Clarke http://www.prc68.com iovane@inwind.it wrote: > Does a stationary (not in motion) GPS receiver know where the North is? > > As far > as I can understand, it doesn't, isn't it? > > Antonio I8IOV > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

Hi Bruce: Do you know where I might find connection information on the MD-1 star tracker used in the B-52? See: http://www.prc68.com/I/MD1.shtml The system was good to 1 arc minute (including temperature, pressure, etc.) and I've heard that the sensor was far better than that (into the arc second range). Have Fun, Brooke Clarke http://www.prc68.com Bruce Griffiths wrote: > When a star tracker is used as a stellar compass in effect takes > simultaneous fixes on several stars and the better ones are capable of > an rms error of a few arc seconds, largely limited by atmospheric > instability. > These are usually used for determining space vehicle attitude, in which > case the instability due to seeing is much smaller than when immersed in > the atmosphere. > They have been used as relatively inexpensive position encoders for > pointing a telescope to within a few arc seconds. > Pattern recognition techniques are used to identify stars in a > relatively wide field (a few degrees) slightly defocused image (improves > centroiding accuracy). > > Star tracker for Clementine mission: > http://www.osti.gov/bridge/servlets/purl/86977-ULkJcR/webviewable/86977.pdf > > A more accurate version: > http://www.newworldt.com/download/DTU/microASC%20Summary.pdf > > telescope pointing application: > http://www.ifa.hawaii.edu/faculty/pickles/AJP/spie3351.07.pdf > http://www.ifa.hawaii.edu/users/pickles/AJP/AMOS2003_v4.pdf > > Measuring the position (altitude + azimuth) of one star at a time using > a theodolite is not the most efficient method of determining the > direction of the meridian. > Its far better to measure the position of several stars at once as in > the stellar compass, however a longer focal length camera lens than > usually used in a star tracker is desrable for increased accuracy. > > Bruce > > J. Forster wrote: >> Not so. I'm very familiar with laying in accurate North lines for gyro >> testing. To get anything close to accurate (1 arc second or better) takes >> many hours of stellar observation with a Wild T-3 class instrument. >> >> -John >> >> =============== >> >> >> >>> Neville Michie wrote: >>>> When you think of time specifications from GPS, the GPS system is a >>>> poor way to find north. >>>> Even with a base line of 1000 metres you only have a fraction of a >>>> degree. >>>> The GPS system may be useful to get accurate time to simplify a star >>>> observation, from a known (GPS) >>>> position on this planet, but finding north is still a problem because >>>> of the accuracy of a small >>>> number of observations from a star fix. >>>> Gyrocompasses take some time to get a measurement >>>> ( one hour) but even their estimate of North cannot match the >>>> precision that the GPS system can get us with time. >>>> cheers, Neville Michie >>> If you are taking star shots a stellar compass can easily provide a >>> boresight pointing accuracy of a few arcsec. >>> >>> Bruce >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

Brooke No idea about MD1 connections source. I can well believe that the photocell plus telescope is capable of arc second accuracy sensitivity. Zeiss used to offer a sun tracker as well as photomultiplier based tridant star sensor/trackers with sub arc second sensitiviy. Bruce Brooke Clarke wrote: > Hi Bruce: > > Do you know where I might find connection information on the MD-1 star > tracker used in the B-52? See: > http://www.prc68.com/I/MD1.shtml > > The system was good to 1 arc minute (including temperature, pressure, > etc.) and I've heard that the sensor was far better than that (into > the arc second range). > > Have Fun, > > Brooke Clarke > http://www.prc68.com > > Bruce Griffiths wrote: