Kerry.

quote:Originally posted by SecretSpy & LowlyWorm:... If you want to find caches in houses or underground buy a TRIMBLE. Your kidding Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by SecretSpy & LowlyWorm:... If you want to find caches in houses or underground buy a TRIMBLE. Your kidding Cheers, Kerry. I never get lost everybody keeps telling me where to go

The "performance" still has to meet the "specifications". The specifications are what they say they guarantee to provide, the performance is more actually happens or is supposed to happen. The measured performance (accuracy and other things) still has to fall under the specification otherwise the system isn't meeting its specifications. Also the specifications these days don't take into account things that the system can't predict such as atmospherics etc hence the specification are based on Signal-in-space characterics as there's no way anybody can control what a GPS user actually does. Yes, they can (and do) change things at times for specific purposes (and not just military related either) but they still have to meet minimum specifications world wide. Cheers, Kerry. I never get lost everybody keeps telling me where to go

The "performance" still has to meet the "specifications". The specifications are what they say they guarantee to provide, the performance is more actually happens or is supposed to happen. The measured performance (accuracy and other things) still has to fall under the specification otherwise the system isn't meeting its specifications. Also the specifications these days don't take into account things that the system can't predict such as atmospherics etc hence the specification are based on Signal-in-space characterics as there's no way anybody can control what a GPS user actually does. Yes, they can (and do) change things at times for specific purposes (and not just military related either) but they still have to meet minimum specifications world wide. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Alan, as I understand it DoD can basically localize an area under Selective Deniability but just what size that foot print can be is a bit of a mystery (to me anyway, sort of). However I do get the impression that it can be "very specific". There were hints of this in some regions of recent times but there's no certainity if it was SD or something else. If it was SD then it's fairly controllable based on the surrunding data available. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Alan, as I understand it DoD can basically localize an area under Selective Deniability but just what size that foot print can be is a bit of a mystery (to me anyway, sort of). However I do get the impression that it can be "very specific". There were hints of this in some regions of recent times but there's no certainity if it was SD or something else. If it was SD then it's fairly controllable based on the surrunding data available. Cheers, Kerry. I never get lost everybody keeps telling me where to go

That would make it True north. Cheers, Kerry. I never get lost everybody keeps telling me where to go

That would make it True north. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Alan2, SA certainly isn't (wasn't) simply a shift as SA was unique to each individual satellite. The overall effect was the less than 100 metres 95% of the time specification. It is believed that SA could throw a position by more than 2000m if fully wound up (of course nobody will officially confirm that one). Basically SA created an unpredictable (but not random as some believe) continuous shift in displayed navigation from the real world. SA was accomplished by the purposeful manipulation of the navigation message orbit data and/or the satellite timing. Military units have the advantage of a specific military frequency (still with SA), using coded/keyed encrypted receivers (which eliminate the effects of SA) and things like Anti-spoofing to guard against fake transmissions. The approval to discontinue SA was due to the DoD implementing other measures which suited their specific requirements. Selective Deniability is its name but just what type of functionality it has (coverage, accuracy degradation etc) I've not aware. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Alan2, SA certainly isn't (wasn't) simply a shift as SA was unique to each individual satellite. The overall effect was the less than 100 metres 95% of the time specification. It is believed that SA could throw a position by more than 2000m if fully wound up (of course nobody will officially confirm that one). Basically SA created an unpredictable (but not random as some believe) continuous shift in displayed navigation from the real world. SA was accomplished by the purposeful manipulation of the navigation message orbit data and/or the satellite timing. Military units have the advantage of a specific military frequency (still with SA), using coded/keyed encrypted receivers (which eliminate the effects of SA) and things like Anti-spoofing to guard against fake transmissions. The approval to discontinue SA was due to the DoD implementing other measures which suited their specific requirements. Selective Deniability is its name but just what type of functionality it has (coverage, accuracy degradation etc) I've not aware. Cheers, Kerry. I never get lost everybody keeps telling me where to go

An "Azimuth" is a horizontal angle measured from the spheroidal meridian clockwise from north through 360 deg. This then makes the forward Azimuth different from the reverse Azimuth by a varaible amount (Convergence). However unless one can actually measure this then for all intent and purposes it could generally be ignored especially for Azimuths given in whole degrees only and treated more as a Grid Bearing which is the angle between Grid North and the for want of a better reference the point. Again int he real world the reverse Grid bearing and forward Grid bearing are different by the line curvature so the difference is variable as well. Azimuth, Grid Bearing, Plane bearing are all related but in the real world but different. That's enough as this could become more confusing that it should Cheers, Kerry. I never get lost everybody keeps telling me where to go

An "Azimuth" is a horizontal angle measured from the spheroidal meridian clockwise from north through 360 deg. This then makes the forward Azimuth different from the reverse Azimuth by a varaible amount (Convergence). However unless one can actually measure this then for all intent and purposes it could generally be ignored especially for Azimuths given in whole degrees only and treated more as a Grid Bearing which is the angle between Grid North and the for want of a better reference the point. Again int he real world the reverse Grid bearing and forward Grid bearing are different by the line curvature so the difference is variable as well. Azimuth, Grid Bearing, Plane bearing are all related but in the real world but different. That's enough as this could become more confusing that it should Cheers, Kerry. I never get lost everybody keeps telling me where to go

Jamie, EPE is basically a "managed" value based on some propriety software code. When SA was terminated EPE's didn't change as much as the "actual" accuracy but change they did and one thing it really highlighted was that manufacturers were caught out a little in that the EPE routines reflected accuracy that didn't really exist anyway. Howevever change they did and since SA was terminated most manufacturers have "re-managed" the EPE routines to "best" reflect really what they want it to reflect (an estimate). NO, EPE's certainly didn't indicate a few feet with SA On and EPE's that consistently indicate a few feet now are also a worry. EPE is only an Estimate but is an estimate of the relative position(s) (plus some other "unknowns") and if that position is wandering around then so does the Estimated Position Error. And it tries to all this without actually knowing where it is anyway. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Jamie, EPE is basically a "managed" value based on some propriety software code. When SA was terminated EPE's didn't change as much as the "actual" accuracy but change they did and one thing it really highlighted was that manufacturers were caught out a little in that the EPE routines reflected accuracy that didn't really exist anyway. Howevever change they did and since SA was terminated most manufacturers have "re-managed" the EPE routines to "best" reflect really what they want it to reflect (an estimate). NO, EPE's certainly didn't indicate a few feet with SA On and EPE's that consistently indicate a few feet now are also a worry. EPE is only an Estimate but is an estimate of the relative position(s) (plus some other "unknowns") and if that position is wandering around then so does the Estimated Position Error. And it tries to all this without actually knowing where it is anyway. Cheers, Kerry. I never get lost everybody keeps telling me where to go

You don't mention what grade of GPS you are referring but I'm not sure I'd like to be relying on a consumer grade GPS if it was my job on the line. The line between if missing by an inch or missing by a mile one still misses. As an aid certianly but not totally dependent on what a common GPS will/does provide. Cheers, Kerry. I never get lost everybody keeps telling me where to go

You don't mention what grade of GPS you are referring but I'm not sure I'd like to be relying on a consumer grade GPS if it was my job on the line. The line between if missing by an inch or missing by a mile one still misses. As an aid certianly but not totally dependent on what a common GPS will/does provide. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Just to clarify a couple of things. If for "certain" reasons there was a need to cover specific installations the the EPE most likely wouldn't get "tighter" it would get worse, much worse to the point of nothing once jammers were used, which is easier to do for small specific areas. SA is technically not shutdown just set to zero (0) but Selective Deniability is something else. Be assured that if the signals are manipulated then your GPS will show that clearly especially in the EPE. I don't know where the source of this comment is coming from that somehow they can put SA back into to the signal and nobody will notice My word you'd know about it your position would go ape and so would your EPE to match. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Just to clarify a couple of things. If for "certain" reasons there was a need to cover specific installations the the EPE most likely wouldn't get "tighter" it would get worse, much worse to the point of nothing once jammers were used, which is easier to do for small specific areas. SA is technically not shutdown just set to zero (0) but Selective Deniability is something else. Be assured that if the signals are manipulated then your GPS will show that clearly especially in the EPE. I don't know where the source of this comment is coming from that somehow they can put SA back into to the signal and nobody will notice My word you'd know about it your position would go ape and so would your EPE to match. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by ApK:There's a sidebar in this month's Scientific American about the possibility of soon adding tiny atomic clocks to handheld gpsrs to correct errors. I'll have to think about that one as I'm not really sure what an atomic clock in the unit would really do as the timing is handled very cleverly (and cheaply) as it is. The biggest error to correct is atmospherics and dual frequency (next civil generation) will counter some of that but as with all the other error effects not 100%. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by ApK:There's a sidebar in this month's Scientific American about the possibility of soon adding tiny atomic clocks to handheld gpsrs to correct errors. I'll have to think about that one as I'm not really sure what an atomic clock in the unit would really do as the timing is handled very cleverly (and cheaply) as it is. The biggest error to correct is atmospherics and dual frequency (next civil generation) will counter some of that but as with all the other error effects not 100%. Cheers, Kerry. I never get lost everybody keeps telling me where to go

A bit like peeling peanuts with a sledge hammer, bit of an overkill for what people do here especially considering one is searching for marks positioned with much different receivers. Cheers, Kerry. I never get lost everybody keeps telling me where to go

A bit like peeling peanuts with a sledge hammer, bit of an overkill for what people do here especially considering one is searching for marks positioned with much different receivers. Cheers, Kerry. I never get lost everybody keeps telling me where to go

The next generation is coming (has been in progress for a little while) but these things do take time but in the meantime new models will certainly be released by just about everybody (new models based on an old theme). Next generation however doesn't equate to next model, they are totally different. Cheers, Kerry. I never get lost everybody keeps telling me where to go

The next generation is coming (has been in progress for a little while) but these things do take time but in the meantime new models will certainly be released by just about everybody (new models based on an old theme). Next generation however doesn't equate to next model, they are totally different. Cheers, Kerry. I never get lost everybody keeps telling me where to go

The next generation is coming (has been in progress for a little while) but these things do take time but in the meantime new models will certainly be released by just about everybody (new models based on an old theme). Next generation however doesn't equate to next model, they are totally different. Cheers, Kerry. I never get lost everybody keeps telling me where to go