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Everything posted by Kerry.

  1. The GALILEO in the name is intriguing wonder what that is supposed to imply Cheers, Kerry.
  2. Just depends witch waas http://www.waasinfo.net/ Cheers, Kerry.
  3. The clock only tells/shows you the time, nothing more. Has no affect on the accuracy either horizontal or vertical. A unit that ignores time (as in time of day etc) from the nav message does have a problem though as it really should update the time on a reasonably regular basis but not being a mission critical value doesn't waste rescourses in doing this either. Some receiver clocks can be off by as much as few seconds anyway and actually 3m 42 seconds is quite interesting in some respects. Cheers, Kerry.
  4. Southern or northern hemisphere and far far north or south of the equator? Cheers, Kerry.
  5. Difference purely Format, nothing to do with Datum. Cheers, Kerry.
  6. 350 feet? I'd go along with around 85 feet. Cheers, Kerry.
  7. Maybe accuracy needs to be defined as to exactly what accuracy is. Cheers, Kerry.
  8. Viking, allowance for only 32 GPS satellites, above 32 they will be something else. There's allowance for 19 WAAS Geo's and even though some manufacturers use the next 19 slots as identifiers 33 thru 51 the WAAS geo's do have proper PRN numbers. The 2 WAAS geo's are PRN 122 & PRN 134, which Garmin ID as 35 & 47. WAAS has and requires physical ground stations just as dGPS requires ground stations but WAAS uses some of the GPS channels for reception whereas dGPS requires a beacon receiver (if not built-in). The satellites that the WAAS corrections are being transmitted through are simply communication satellites leased for the purpose and a WAAS geo may also be used in determining the position solution if activated as part of the navigation message. Cheers, Kerry.
  9. EraSeek, yeah basically that's what dual freq allows, determination of atmospheric issues in real-time rather than using a modelled type atmosphere as is applied if one is only using L1. L1 C/A (Course Acquisition code) is available to all users and has a very long wavelength (~300 metres), which a very short sequence (fraction of a second) and continues to repeat itself over and over again. The P (precise) code, which is carried on both L1 & L2 has a wavelength of only about 30 metres but the code sequence lasts something like nearly 300 days before it repeats itself. Until recently L1 C/A (the one we use) was required to resolve/initialize the P code but now they've apparently found a way to shutdown L1 and use L2 Pcode by itself. Basically we (the public) don't currently have full access to a compete second frequency but that is about to change. Survey type receivers achieve accuracy using differential positioning (requires more than 1 receiver) and squeezes millimetres into the measurements using carrier wave phase measurements. So with the new second civil frequency accuracy will improve and with that there is also some new additional military frequencies. Basically the above has little to do with WAAS as WAAS only uses L1 simply because it requires the remaining bandwidth to carry the integrity information/messages and doesn't have time (time being the critical factor in WAAS error messages) to also do things with phase measurements. For the purpose of WAAS the integrity/monitoring and timely transmission of error messages takes precendence over the accuracy, with accuracy basically not being the primary function. Cheers, Kerry.
  10. Yes one might say that's a very worried defense laywer. Very hard trying to argue all the data is off but how about the sentence is reduced to say 95% Cheers, Kerry.
  11. ghOzt, if you like "light" reading then try THIS just take into account the application and equipment compared to what's used for caching. Cheers, Kerry.
  12. EraSeek, dual frequency isn't really the same thing as Wide Area Differential GPS (WADGPS). For sure the second freq allows some of the errors to be resolved in real-time but one still needs some form of accurate reference mark to get a similar accurate position within some reasonable distance and the distance basically dictates the time required and/or accuracy achievable from real-time differential or static differential. Actually the commercial Satellite Based Wide Area systems, which do use dual frequency gets much better accuracy than say WAAS but at the cost of no integrity. WAAS uses a lot of bandwidth applying integrity and monitoring to the position, which basically then restricts remaining bandwidth to using L1 but at a cost. Really every thing is a compromise, cost, distance, accuracy, integrity, coverage, simplicity etc etc. Many in fact often wonder if the dollar cost per each additional metre from WAAS is actually good accounting. Many countries are implementing other augmentation type systems as simply the cost of WAAS/EGNOS type systems is extremely prohibitive. Give things a few years when enough Block IIR-M's and IIF's are in orbit a new handheld (of course) and around 1.5 metres will be the accuracy of the day, un-augmented, stand-alone. Cheers, Kerry.
  13. Nothing to do apart from re-initialize it. Same re-initialize process as if the reciever is re-located more than a few hundred mile. Mapping, now that's certainly going to be different. Connection to a laptop etc, several mapping systems can handle that. Stuff like Oziexplorer works fine and complete 1:250,000 mapping covering all of Oz is around the A$90 mark. If using Oziexplorer then all the map indexing for the 250 thou sheets (~500+ odd map sheets) is already done. Cheers, Kerry.
  14. Clouds never have any effect? As far as anybody has been able ascertain, attenuation due to thick fog, torrential rain, clouds etc is insignificant at GPS frequencies and one reason why specific freq's are used. Extreme concentrations of sand, dust etc might account for something around 2cm/km in signal delay through that part of the actual sand storm. There's certainly nothing to suggest clouds will block a GPS signal, there's simply nothing to substantiate any such claim and be assured many many people have an interest in this type of issue for critical applications. There are affects on systems used for critical precise applications but nothing that a recreational GPS receiver would ever be able to detect. Cheers, Kerry.
  15. Impacted by cloud cover, definately not. Being your first GPS probably reading the manual first will help a little as immediately straight out of the box they simply don't work until initialized. Leave it stationary with a clear view of the sky and let it sit for 10-15 minutes and if that don't work then look for another reason apart from cloud cover. Cheers, Kerry.
  16. .... I don't like to have to remember the declination for my area, so I let the GPS do that .... So what are we saying that the declination in all and every GPS is the same, I doubt that. UTM grid north is different but without confusing things it should be the grid bearing (from grid north) that UTM projections are based on. Magnetic north has no mention in anything to do with UTM projections what so ever. Even plane bearings are based from grid north but for long distance projections the I would be involving azimuth based from true north. Cheers, Kerry.
  17. Geo your attitude and senseless questions, mumbo gumbo about things you have absolutely no idea about are absolute rubbish. And if you want some links to some of your other senseless rubbish then I will gladly oblige. Here is you lifejacket, anyone else? have some manners, I'll take you task anytime and there's already plenty of links without wasting more time with your pathetic rubbish. Cheers, Kerry.
  18. Magnetic north is something that isn't absolute or fixed so why would anybody want to project on magnetic north anyway. Magnetic north wanders around quite considerably on any given day. So why would anybody want to project a coordinate based on something that is very variable. It's rather meaningless. Cheers, Kerry.
  19. Well some of us have been thru Geo's many claims before and really needs to actually understand some of the words being used and not just dropping in big sounding words as if they know what they're talking about. Some of it is absolute rubbish. Cheers, Kerry.
  20. Most units have internal magnetic tables (which do require updating from time to time) for auto mode and also allow specific user input. Coordinates, except for projecting another waypoint have no interest if things are set to true/mag etc. Projected waypoints certainly should not be projected using magnetic bearings etc. Cheers, Kerry.
  21. 18 channels, not simply with NAVSTAR GPS but there are 24 channel receivers designed for GPS/GLONASS. However right now 18 channel recreational GPS receivers are more a sales pitch. Cheers, Kerry.
  22. Averaging? (and especially auto-averaging) is really a feel good thing, if it feels good then do it but the chance of any improvement is 50/50, which means one can actually achieve coordinates that can be worse. Averaging isn't simply a one way factor and averaging certainly doesn't necessarily make a position better. The first factor in "knowing" that the cooridnates are the best possible on the day is to do the positioning at the best time(s) of the day. Cheers, Kerry.
  23. Based on that location if your seeing 2 WAAS Geo's then that's a little strange as POR PRN 134 (Garmin #47) is below the horizon. AOR-W PRN 122 (Garmin #35) should be high enough to be consistent at about 30-31 degrees. Cheers, Kerry.
  24. George, what's your approx Lat/long and lets see just what elevations the 2 WAAS Geo's are actually at. Cheers, Kerry.
  25. George, some Garmin models can/do average but it's not like the fixed auto-averaging that Magellan uses. The Yellow and Vista I don't think has averaging but this might depend on software upgrades as I am aware of some Garmins that in recent time have been burdened with Auto type averaging. Units like the GPS48 has a manual averaging function prior to saving. This "confidence" reading, just an estimate, simply can't be anything more than that. As for the "closeness" of the readings? you might find some differences (if one could call them that) if you were recording the output from each unit, which might havve better precision than what is displayed on the screen. However doing that is not really meeting the practical side of everyday use, is it. Cheers, Kerry.
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