Kerry.

Some USB implementations can't support NMEA output and with the GPS18 I understand it does not output NMEA but outputs data using the Garmin USB interface/protocol? So with the GPS18 if one wants NMEA support then it is either the GPS18 PC or GPS18 LVC versions but it appears all the 3 GPS18 version can be configured to output binary phase data. Cheers, Kerry.

Can he have 1meters accurancy ALWAYS, even below trees and so on? I claim that he can't and that EPE means calculated positioning? 1 metre always, No not even 1metre any of the time really as it might display silly figures like this some of the time but really means little and shouldn't be taken seriously at all. EPE is basically implemented differently by all manufacturers and shouldn't be taken as anything absolute at all. As a relative trend say if EPE improved then one might assume the accuracy is getting better but the actual accuracy would certainly not be indicated by the EPE value. Cheers, Kerry.

Not to sure where some people dig up these myths? SA was not turned back on after 9/11, SA has never been turned back on since it was discontinued in May 2000. Lets get something straight, SA is not actually turned off as such, it is simply set to zero but since the use of SA was discontinued in May 2000 it has not been re-activated (moved off zero) since, technically there is simply no need to use SA again. Cheers, Kerry.

Extra, no not much at all. Keep it for a few more years when there might be something new worth upgrading for. Until then and beyond your poor old E-Trex will still probably be doing what it's doing now. Cheers, Kerry.

Basically able to hook any recreational GPS up to a laptop etc for logging data using several different freely available software packages. Most recreational will record points based on time (distance) setings as tracks, which can also be downloaded to simple ascii files for coordinate/point extraction. With track recording one restriction is the available track points v time interval, the longer the time interval the longer the period that can be saved. There's also specific data loggers available for external logging much like a laptop can do but really all these devices are, are NMEA interfaces with memory capabilities that can be downloaded to a laptop. Also there is some specific recreational models that do output RINEX and can be post-processed. Cheers, Kerry.

wondering how thick clouds effect signal Basically they don't not in any context that affects what you are doing with a recreational handheld and certainly nothing you will ever be able to detect. Actually it takes some rather sophisticated gear to detect any anomolies at all and then it's more of interest in some specialised fields. Cheers, Kerry.

Again night time doesn't necessarily mean better accuracy. Cheers, Kerry.

No Cheers, Kerry.

However, more people visited last night, and they said the cache was actually 10 feet North-West of the coordinates I gave. Huh. I'd being say Huh too, like what is it will some who think they can actually determine 10 feet in any direction with any confidence/integrity anyway, tell em they are kidding themeselves. Cheers, Kerry.

Now that WAAS has been found not able to meet Category 1 performance at most US airports funding has been cut due to the now reduced expectations regarding WAAS performance. Based on the funding cutbacks maybe the future of WAAS might be a little suss? Cheers, Kerry.

With a 3D position solution (4 sats or more) the elevation is part of the solution so is relative. With a 2D solution (3 sats) the elevation has to be assumed or manually input and if assumed wrongly then it can equate to around 5 metres in position for 1 metre in height. About the only place where specific 2D solutions can be implemented with any reliability is on a boat but even then a 3D solution is generally going to be the preferred option. But as far as a "waypoint" is concerned, that is one previously stored with the height at the time then it has no affect on latter accuracy with respect that waypoint what so ever. Cheers, Kerry.

A little depends on the relationship of each satellite to each other as they are all moving and fairly quickly at that, around 4000m/sec. In an hour each atellite has basically tracked 30 degrees and with the number of sats in the current constellation it really doesn't take long for things to change. It is very dynamic and this type of situation can be predicted so as to be aware of, when and how long the condition might last. Cheers, Kerry.

Jamming? No. But GPS is a very Dynamic system and normally so is the (handheld) user. Simply turning around, moving the receiver to view something, turning the receiver, tilting the receiver could change things. One reason why GPS specifications are for Signal-In-Space (SIS) characterics as the operators have no control over how users apply the technology. Then again it could be the system itself, maybe an incident with rising/setting satellites where there's a flutter in signals on the horizon. Could in fact be many things but the description of the problem isn't jamming. Cheers, Kerry.

Common problem with some PC's/GPS and it normally thinks it's connected to one of those pointing (pen) devices. Go into Device Manager and under Mice and Other Pointing devices check for the rogue pointing device and uninstall it. Reboot the machine without the GPS connected. Cheers, Kerry.

No, not at all really correct as 20-30 feet is certainly not an indication of a datum issue. For sure check the datum but 20-30 feet doesn't highlight a datum issue one little bit. Cheers, Kerry.

No, not so and especially in the case of differential night time is actually the worst. In many respects things are more linked to geometry than simply day/night but if circumstances exist then it can be but it ain't necessarily so. Cheers, Kerry.

The first of the Block IIR-M's are now set for launch Feb 1, 2005 (IIR-14/M-1) and with IIR-16/M-3 on June 24, 2005 will make 3 but 3 is not enough and really until there is enough IIR-M's and at least some IIF's to make up the numbers there won't be that much improvement until some time after 2005/06. Based on current timetables maybe about 2008 will see 18-20 sats with L2C then it will be starting to be usefull on a world wide basis most of the time. 2008 is showing less than 10 sats (IIF's) with L5C (and L2C). So 2005 is just the start and there will require a few more years to become any where effective but it's the start and is a lot sooner than originally having to wait for the first IIF's which will also carry L2C and the first of the L5C signals. But even without the new L2C (which will require new hardware/firmware) every new Sat is that little bit better than the last one and certainly a lot better than some of the ones that have been in orbit (and still there) well past their design life. Also there will be some improvement in existing accuracy when the new ephemeris message comes on line. Also L2C and L5C will have forward error correction which the existing L1 can not do. L2C will have different signal characterics than the existing L1 and so will actually improve navigation capabilities both indoors and in forest areas. Cheers, Kerry.

"fine tuned the accuracy" that's interesting. Cheers, Kerry.

For sure almost like clockwork, one can forecast/predict what should occur, including taking into account planned outages (if known and available at the time) but barring unplanned satellite outages that occur from time to time. After the event then based on actual recorded data one can actually recall what did occur and the longer one wants to wait the better the actual data becomes. Precise Ephemeris is available after 14 days or so but to the use of this is generally only practical for high order results. But basically what the receiver is using at any time is predicted satellite positions (emphemeris), otherwise the whole system really wouldn't work in real-time if it didn't have/know the actual positions of the sats. Cheers, Kerry.

I don't believe this was an outage as recording ground stations in and around Connecticut were receiving data during that period so would more than likely be some sort of "local anomaly" and not anything that relates to the actual GPS signalsm proper, they appear to have been normal. Just out of interest what would be some rough coords? Cheers, Kerry.

What were you actually expecting? 20-30 feet, about what might be expected. On a good day if your less than 40 feet that's a bonus, bad day could be 120 feet. It's really not the accuracy figure that's important as much as the integrity of (knowing) the accuracy and how good the actual result is. Cheers, Kerry.

US$11.3M in GPS terms shouldn't be many pages at all Future funding for WAAS has been cut, LAAS has been cut back to R&D due to something called "lacking maturity" or as the FAA call it something about "misjudging technological maturity and unexpected cost growth". GPS performance probably fits into the 90/10 rule, where 90% of the $$'s will result in a 10% improvement. 11.3M probably won't achieve a great lot but at least there's some systems, which haven't meet expectations to gauge what might not be the best thing to do, especially cost effectiveness. Cheers, Kerry.

The future of WAAS appears to be starting to look a little grim and is facing budget cuts based on the revised expectation that WAAS will now not be able to provide Cat I performance at many airports. Not working to expectations then no funding and considering the huge amounts of $$'s already spent on WAAS maybe it's a case of not wasting more huge amounts of $$'s for no useful purpose. LAAS has also hit cuts in funding as this system is also not as mature as the FAA had expected and has gone back into a research and revelopment stage with completion dates now uncertain. Cheers, Kerry.

Two years? won't be much different. Feb 2005 will see the first of the modified IIR's (IIR-14/M-1) launched, with IIR-15/M-2 in April and IIR-16/M-3 in June/05. This will be the start of something new but even by June/06 one wouldn't expect enough IIR-M's or IIF's to be really usefull and certainly not anywhere cm accuracy. Five years? probably starting to achieve a useable civil L2 dual freq number of sats, around the 20 mark but still not complete. Maybe around 10 sats with the third civil L5. Ten years? probably still on the short side with L5 but one might expect a full constellation of L2 dual freq. cm accuracy in a single piece of gear? umm one day, maybe? but not any time soon and some rather large hurdles to jump first. Cheers, Kerry.

So what does everybody associate as the "nature" of GPS position solutions over some generic time frame, Plot 1 or 2? Cheers, Kerry.