Re: [time-nuts] Bulletin Board / Forum
On Wed, Aug 25, 2010 at 16:47, J. Forster j...@quik.com wrote: Hi Jim, Yes, it would be a lot of work to write Wiki style articles on all list topics. The point of wikis is that people write what they know, if they have the will to write about it, and when they have the time. Another option would be an archive of all Group posts, searchable via Google. There is apparently a Google app that does that. I've seen options on web pages where there is a Google search button, that has options of: ( ) Search the site ( ) Search the web No app needed! This is done using the site: keyword to google searchs, for example, this query will report only results on febo.com: http://www.google.it/search?q=unobtanium+site%3Afebo.com or put manually in the google form: unobtanium site:febo.com (I think this is my first post here, so greetings to all) Cheers P. ___ 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.
Re: [time-nuts] Slightly OT - GPS-Based Accurate Direction Finding
[VOR vs DF] doh,, of course... Brains are weird. They often get stuck in the wrong mode. Optical illusions are a good example. When I first saw this thread, my reaction was Try a sundial. When I started typing in a response, I got flipped to the other mode and couldn't figure out how that could possibly work if you didn't already know which way was north. Fortunately, before I poked SEND, my brain got flipped back to the right mode and I fixed up the text I had typed in. -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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.
Re: [time-nuts] Slightly OT - GPS-Based Accurate Direction Finding
All the fire towers I've been in have a plumb line in the centre of the room and circular graduated ring above window height. When the spotter sees something of interest, all (s)he has to do is stand behind the string and make a report. ian ___ 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.
Re: [time-nuts] Slightly OT - GPS-Based Accurate Direction Finding
I never found a better method than observing a circumpolar star at night with a theodolite and an almanac to find South or North. You then find a distant object known as the referred object, and find its azimuth. From then on at that station you can use the RO to set your azimuth. At home I have a street light 4 km distant that I use as a RO, either by day or night. It seems strange, with all those satellites, whose position is known with such accuracy, that we can not get an accurate azimuth, but then we do not have a sighting device to observe a referred object or satellites. cheers, Neville Michie ___ 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.
Re: [time-nuts] Slightly OT - GPS-Based Accurate Direction Finding
Hi I suspect that the term fire tower was being used in the generic sense. More or less any tower with a deck on a hill top is a fire tower. Bob On Aug 27, 2010, at 8:50 AM, gonzo . cadbl...@hotmail.com wrote: All the fire towers I've been in have a plumb line in the centre of the room and circular graduated ring above window height. When the spotter sees something of interest, all (s)he has to do is stand behind the string and make a report. ian ___ 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.
Re: [time-nuts] Slightly OT - GPS-Based Accurate Direction Finding
Thomas A. Frank wrote: I would suggest you buy an old surveying transit. This is what largely they were intended for. ANd with a transit, you can easily see Polaris in the day time. Here's an article discussing how to do it http://www.cadastral.com/cad-polr.htm skip down to the section on Observation Procedure It's a bit trickier than it says... -- you won't be able to do this the first time small field of view on the telescope means you have to be pointed pretty close to find it. What I wound up doing is marking the place where I'd set the theodlite up, going out at night and finding Polaris, and finding a suitable object on the horizon to reference to. Then the next day, I set up the tripod and used that object to get the azimuth approximate, tipped up to the right elevation, and, et voila, there it was in the scope. The comment about focus is right on though. ___ 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.
Re: [time-nuts] Slightly OT - GPS-Based Accurate Direction Finding
- Original Message From: Neville Michie namic...@gmail.com snip It seems strange, with all those satellites, whose position is known with such accuracy, that we can not get an accurate azimuth, but then we do not have a sighting device to observe a referred object or satellites. cheers, Neville Michie If you have some experience installing DDS and FTA small TV dishes then it maybe possible to get within a degree using them as a reference. The Ku band 1 meter dish would be better than the small .5 meter / 18 dish. Has the advantage of working on cloudy day when landmarks are not visible. Stanley ___ 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.
Re: [time-nuts] Slightly OT - GPS-Based Accurate Direction Finding
Back in the early 1980's when attending college I worked on a single axis multi-mode fiber optic rate gyro project that used GRIN fiber. Back then a military three axis unit based on single mode fiber was alleged to be a little larger than a one inch cube and cost slightly less than a million dollars. We used a three inch spool for the fiber and put everything in a six inch cube for a housing. The NASA contract was part of the NASP program. The company that we worked with wanted to produce a product for the commercial private pilot aviation market. I will have to ask what happened... I think the patent issue may have had something to do with it since the company had a relationship with Litton. Jim Cotton n8qoh b...@lysator.liu.se wrote: Does anyone know how laser gyroscopes are developing? Laser gyroscopes - as in Ring Laser Gyroscopes or as in Fiber Optic Gyroscopes? RLGs are a standard commercial product. Several years back I was walking through the Honeywell plant in St Paul, MN, and they had a display case of at least a dozen RLGs that they've made over the past few decades. Commercial? US RLGs are all ITAR. All types of gyros usable in the systems in Item 1, with a rated drift rate stability of less than 0.5 degree (1 sigma or rms) per hour http://www.fas.org/spp/starwars/offdocs/itar/p121.htm Honeywell has about 2 different RLGs. Only one (gg1320) of which you can make a north sensing out of. Litton (now NGC) used to do RLGs (their zero lock gyros) but I think they were on the loosing side of a patent war with Honeywell. French Sagem do some for high end military systems. Have I missed a RLG manufacturer? Almost as few vendors as in the Cesium oscillator market... No new RLG sensors has been announced during the last decade or two. -- Björn ___ 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] Better GPS
Hi I've been digging around at acc.igs.org. They seem to think that their clock models are good to below 0.05 ns. They compare that to a 2 ns number for the as broadcast models. 2 ns is a pretty familiar number if you look at a lot of TBolt plots. All of their data is online and available for download at some point in time past live. The longer you wait the better the data. They really like the idea of L1/L2 receivers and fancy post processing. They also are after a lot more than just time. I still have not noticed any complete L1/L2 receivers for $100, so I can't do their full solution approach. Ionospheric correction seems to be one big thing you loose by going single freq. There's a pretty good summary of all that at http://acc.igs.org/UsingIGSProductsVer21.pdf Since the TBolt sort but not quite of does carrier phase you might be able to use their data to improve things. I doubt that you would get to 50 ps, but even a 2 or 3X improvement would be worthwhile. Even getting it some of the time (midnight?) would still be useful. It would be a log lots of data and compare thing - not that unusual. Has anybody else dug into any of this? Is there a secret stash of cheap L1/L2 fixed location receivers out there that I haven't stumbled across? Can you really win the lottery by picking up the winning ticket off the sidewalk? Lots of questions Bob ___ 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.
Re: [time-nuts] Better GPS
Hi Bob: The ultimate is a carrier phase GPS Timing receiver. The early work was done using Ashtech Z12 models that have a provision for an external 10 MHz oscillator. I have a feeling that the units you're talking about are a refinement of this approach. The new L5 frequency of GPS, intended for FAA use, will allow for civilian two frequency ionosphere corrections in a more straight forward way than the existing methods (squaring, Ashtech) of using L2 without knowing the P(Y) crypto keys. http://www.prc68.com/I/DAGR.shtml#GPSs Have Fun, Brooke Clarke http://www.PRC68.com Bob Camp wrote: Hi I've been digging around at acc.igs.org. They seem to think that their clock models are good to below 0.05 ns. They compare that to a 2 ns number for the as broadcast models. 2 ns is a pretty familiar number if you look at a lot of TBolt plots. All of their data is online and available for download at some point in time past live. The longer you wait the better the data. They really like the idea of L1/L2 receivers and fancy post processing. They also are after a lot more than just time. I still have not noticed any complete L1/L2 receivers for $100, so I can't do their full solution approach. Ionospheric correction seems to be one big thing you loose by going single freq. There's a pretty good summary of all that at http://acc.igs.org/UsingIGSProductsVer21.pdf Since the TBolt sort but not quite of does carrier phase you might be able to use their data to improve things. I doubt that you would get to 50 ps, but even a 2 or 3X improvement would be worthwhile. Even getting it some of the time (midnight?) would still be useful. It would be a log lots of data and compare thing - not that unusual. Has anybody else dug into any of this? Is there a secret stash of cheap L1/L2 fixed location receivers out there that I haven't stumbled across? Can you really win the lottery by picking up the winning ticket off the sidewalk? Lots of questions Bob ___ 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. -- Have Fun, Brooke Clarke http://www.PRC68.com ___ 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.
Re: [time-nuts] Better GPS
Hi Bob: Here's an interesting sidebar: Precision Modeling for Orbit Determination http://www.aero.org/publications/crosslink/summer2002/02_sidebar2.html from the web page: Orbit Determination and Satellite Navigation http://www.aero.org/publications/crosslink/summer2002/04.html I didn't know the Moon tides can change the elevation of LA by 40 cm! Have Fun, Brooke Clarke http://www.PRC68.com Bob Camp wrote: Hi I've been digging around at acc.igs.org. They seem to think that their clock models are good to below 0.05 ns. They compare that to a 2 ns number for the as broadcast models. 2 ns is a pretty familiar number if you look at a lot of TBolt plots. All of their data is online and available for download at some point in time past live. The longer you wait the better the data. They really like the idea of L1/L2 receivers and fancy post processing. They also are after a lot more than just time. I still have not noticed any complete L1/L2 receivers for $100, so I can't do their full solution approach. Ionospheric correction seems to be one big thing you loose by going single freq. There's a pretty good summary of all that at http://acc.igs.org/UsingIGSProductsVer21.pdf Since the TBolt sort but not quite of does carrier phase you might be able to use their data to improve things. I doubt that you would get to 50 ps, but even a 2 or 3X improvement would be worthwhile. Even getting it some of the time (midnight?) would still be useful. It would be a log lots of data and compare thing - not that unusual. Has anybody else dug into any of this? Is there a secret stash of cheap L1/L2 fixed location receivers out there that I haven't stumbled across? Can you really win the lottery by picking up the winning ticket off the sidewalk? Lots of questions Bob ___ 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. -- Have Fun, Brooke Clarke http://www.PRC68.com ___ 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.
Re: [time-nuts] Better GPS
Thanks Bob, Interesting stuff. Has anybody else dug into any of this? I have no experience with using LI/L2, or how good it is, But as far as making Tbolt's better, No problem to make them 2 or 3X better all the time, by going to an external better optimized controller algorithm. Lady Heather has a simple external PID controller built in that shows proof of concept. Much better could be done with the Tbolt if there is a need, using a simple PIC micro and add that into something like the Tbolt monitor. ws ** Hi I've been digging around at acc.igs.org. They seem to think that their clock models are good to below 0.05 ns. They compare that to a 2 ns number for the as broadcast models. 2 ns is a pretty familiar number if you look at a lot of TBolt plots. All of their data is online and available for download at some point in time past live. The longer you wait the better the data. They really like the idea of L1/L2 receivers and fancy post processing. They also are after a lot more than just time. I still have not noticed any complete L1/L2 receivers for $100, so I can't do their full solution approach. Ionospheric correction seems to be one big thing you loose by going single freq. There's a pretty good summary of all that at http://acc.igs.org/UsingIGSProductsVer21.pdf Since the TBolt sort but not quite of does carrier phase you might be able to use their data to improve things. I doubt that you would get to 50 ps, but even a 2 or 3X improvement would be worthwhile. Even getting it some of the time (midnight?) would still be useful. It would be a log lots of data and compare thing - not that unusual. Has anybody else dug into any of this? Is there a secret stash of cheap L1/L2 fixed location receivers out there that I haven't stumbled across? Can you really win the lottery by picking up the winning ticket off the sidewalk? Lots of questions Bob ___ 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.
Re: [time-nuts] Better GPS
I didn't know the Moon tides can change the elevation of LA by 40 cm! Yup, tides in solid rock. I think it's been mentioned here before, probably more than once. There are two cases that I know about where it really matters: Radio Astronomy If you are doing VLBI, you need to know the position of the antennas accurate to a fraction of a wavelength. CERN They did an experiment that was very very sensitive to the diameter of the ring. The data was much noisier than they expected. Correcting for the phase of the moon cleaned things up. http://en.wikipedia.org/wiki/Earth_tide#Earth_tide_effects http://www.catb.org/~esr/jargon/html/P/phase-of-the-moon.html -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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.
Re: [time-nuts] Better GPS
Brooke Clarke wrote: Hi Bob: Here's an interesting sidebar: Precision Modeling for Orbit Determination http://www.aero.org/publications/crosslink/summer2002/02_sidebar2.html from the web page: Orbit Determination and Satellite Navigation http://www.aero.org/publications/crosslink/summer2002/04.html I didn't know the Moon tides can change the elevation of LA by 40 cm! oh yeah... all my GPS/geodetic friends at work say that once you get down into the sub-meter range for gps (or sub 3 ns..same thing) there's a whole raft of errors in that ballpark.. tidal displacement, ionosphere, multipath, atmospheric refraction, etc. They say it's sort of a whack-a-mole when you're trying to get better than that (for non-differential measurements) ___ 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.
Re: [time-nuts] Better GPS
You'd think that something at the edge of a continent that moved up and down that much every month would break off. Wait, it's rock all the way down. Bill Hawkins -Original Message- From: Brooke Clarke Sent: Friday, August 27, 2010 12:34 PM ---snip--- I didn't know the Moon tides can change the elevation of LA by 40 cm! ___ 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] Better GPS
Hi Some how I seem to be disconnected from the list. I suspect something is amiss with my local mail server The issue of how to really improve accuracy is indeed whack a mole sort of stuff. Averaging better data is always a good start, but only if it's better data. Since the data is not available real time, this is not a direct correction approach. It's more like a time transfer process. You can take data relative to your GPS and then correct it later to improve the accuracy. Not so useful for tuning a radio, but likely useful for checking out an atomic clock. Back to pounding on the mail server. Bob ___ 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] FTS 1000B
I've listed an FTS 1000B on eBay. Item # 320580887914 if anyones interested. Corby Top 2010 Online Colleges Grant Funding May Be Available to Those That Qualify. http://thirdpartyoffers.juno.com/TGL3141/4c78419771a07cdf84m04duc ___ 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.
Re: [time-nuts] Better GPS
On 08/27/2010 07:03 PM, Brooke Clarke wrote: Hi Bob: The ultimate is a carrier phase GPS Timing receiver. The early work was done using Ashtech Z12 models that have a provision for an external 10 MHz oscillator. I have a feeling that the units you're talking about are a refinement of this approach. The new L5 frequency of GPS, intended for FAA use, will allow for civilian two frequency ionosphere corrections in a more straight forward way than the existing methods (squaring, Ashtech) of using L2 without knowing the P(Y) crypto keys. http://www.prc68.com/I/DAGR.shtml#GPSs The L2C alongside L1 C/A and L5 would allow three-frequency observations. You would always benefit from doing P(Y) observations along-side. A modern receiver would be able to make at least 5 observations from the most modern birds, 4 from many and just 3 from the older birds. Modern receivers may also support GLONASS so an additional 3 observations may be done. Cheers, Magnus ___ 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.
