Kerry.

Yes, WAAS totally useless. Averaging certainly has problems and by the sound of it if you are on a boat then I definately can't see the point in averaging (but then I can't see all that much general application for averaging at the best of times ) Heaps of 3rd party software but for the best results can depend on the specific GPS unit. If you're looking for position integrity (including accuracy) then there are augmentation systems available but they are subscription services (satellite based) and they do require specific hardware and they do cost. Just depends on how serious your accuracy and integrity concerns really are. Also going up a level or two away from the simple recreational receivers will/can gain a "little" more integrity in most instances but of course the $$'s go up as well. Again it all depends on how serious the accuracy requirements are Cheers, Kerry. I never get lost everybody keeps telling me where to go

Yes, WAAS totally useless. Averaging certainly has problems and by the sound of it if you are on a boat then I definately can't see the point in averaging (but then I can't see all that much general application for averaging at the best of times ) Heaps of 3rd party software but for the best results can depend on the specific GPS unit. If you're looking for position integrity (including accuracy) then there are augmentation systems available but they are subscription services (satellite based) and they do require specific hardware and they do cost. Just depends on how serious your accuracy and integrity concerns really are. Also going up a level or two away from the simple recreational receivers will/can gain a "little" more integrity in most instances but of course the $$'s go up as well. Again it all depends on how serious the accuracy requirements are Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Alan2:Kery: If we know the conversion factor when switching from Nad 27 quads to NAD84, why doesn't the USGS just produced printed mapes with the coordinate system lines updated to the latest Datum? Tks Alan Alan, in time I imagine that will be the ultimate goal but these things do take time and $$'s. Australia has been on this type of project since the early 90's and is still on going even though the original data was reasonably good compared to other countries. One of the problems in the U.S is some of the NAD27 data is spread over many many years of differing data quality and simply converting bad NAD27 data simply ends up with bad NAD83 data. That's one reason why some GPS receivers have something like 11 "different" conversions for NAD27. Really with the availability of modern navigation and positioning the oportunity is there to update maps with respect to the accuracy of the navigation systems currently available. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Alan2:Kery: If we know the conversion factor when switching from Nad 27 quads to NAD84, why doesn't the USGS just produced printed mapes with the coordinate system lines updated to the latest Datum? Tks Alan Alan, in time I imagine that will be the ultimate goal but these things do take time and $$'s. Australia has been on this type of project since the early 90's and is still on going even though the original data was reasonably good compared to other countries. One of the problems in the U.S is some of the NAD27 data is spread over many many years of differing data quality and simply converting bad NAD27 data simply ends up with bad NAD83 data. That's one reason why some GPS receivers have something like 11 "different" conversions for NAD27. Really with the availability of modern navigation and positioning the oportunity is there to update maps with respect to the accuracy of the navigation systems currently available. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Pneumatic:I think the primary reason for using the H DDD MM.MMM coordinate format and the WGS84 datum is becuase most GPSRs come configured for them out of the box. WGS84 is an earth centred datum, the same reference GPS is based on and hence to a GPS receiver is a zero transformation. All other datum's generally require some approximation and tend to make life awkard but back then things were based on the best information at the time. One day there might only be 1 datum, that will be a good day. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Pneumatic:I think the primary reason for using the H DDD MM.MMM coordinate format and the WGS84 datum is becuase most GPSRs come configured for them out of the box. WGS84 is an earth centred datum, the same reference GPS is based on and hence to a GPS receiver is a zero transformation. All other datum's generally require some approximation and tend to make life awkard but back then things were based on the best information at the time. One day there might only be 1 datum, that will be a good day. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Yes 28 but then we are a little spoilt as the system spec's are still based on a 24 (+3 spares) sat constellation so 4 could be shutdown tommorrow and still meet system spec. Which 4 well which ever ones that leaves 24 that still fits the system's requirements. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Yes 28 but then we are a little spoilt as the system spec's are still based on a 24 (+3 spares) sat constellation so 4 could be shutdown tommorrow and still meet system spec. Which 4 well which ever ones that leaves 24 that still fits the system's requirements. Cheers, Kerry. I never get lost everybody keeps telling me where to go

If GPS supports upload/download (most do) then to PC then to GPS and software would depend on what the GPS was. Cheers, Kerry. I never get lost everybody keeps telling me where to go

If GPS supports upload/download (most do) then to PC then to GPS and software would depend on what the GPS was. Cheers, Kerry. I never get lost everybody keeps telling me where to go

WAAS is as yet a $6 billion system that has yet to be completed, only services a small part of the world (compared to GPS as such) and really was never intended to be used in a handheld running around in the forest. Loosing 2 channels from most 12 channel recievers really doesn't make or break 2D or 3D navigation and besides the % of time 12 satellites (or more) are available is reasonably low compared to the designed average. Besides we are a little spoilt having 28 operational sats and system specs modelled around 24. Actually if antenna and/or software was designed to be the most effective there probably wouldn't be a need for 12 straight GPS channels at all. Put simply WAAS shouldn't be used outside the ground station network even though one can actually recieve the signal as this link shows http://www.cqnet.com.au/~user/aitken/a116_117.jpg Cheers, Kerry. I never get lost everybody keeps telling me where to go

WAAS is as yet a $6 billion system that has yet to be completed, only services a small part of the world (compared to GPS as such) and really was never intended to be used in a handheld running around in the forest. Loosing 2 channels from most 12 channel recievers really doesn't make or break 2D or 3D navigation and besides the % of time 12 satellites (or more) are available is reasonably low compared to the designed average. Besides we are a little spoilt having 28 operational sats and system specs modelled around 24. Actually if antenna and/or software was designed to be the most effective there probably wouldn't be a need for 12 straight GPS channels at all. Put simply WAAS shouldn't be used outside the ground station network even though one can actually recieve the signal as this link shows http://www.cqnet.com.au/~user/aitken/a116_117.jpg Cheers, Kerry. I never get lost everybody keeps telling me where to go

Then the GPS is set to NAD27. The same would occur (in the reverse direction) if you enetered NAD27 coordinates into a unit set to WGS84. The GPS datum setting must match the datum of the coordinates being entered. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Then the GPS is set to NAD27. The same would occur (in the reverse direction) if you enetered NAD27 coordinates into a unit set to WGS84. The GPS datum setting must match the datum of the coordinates being entered. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Can be for many reasons, sometimes system, sometimes user operation, which is one reason why system accuracy, availability etc is based on Signal-in-space (SIS) specifications as there are some things, circumstances which can't be totally controlled both on the system side and the user side. One reason why accuracy is quoted at the 95% level as there's that other 4% uncertainty and especially the last 1% which can be totally unknown and uncontrollable. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Can be for many reasons, sometimes system, sometimes user operation, which is one reason why system accuracy, availability etc is based on Signal-in-space (SIS) specifications as there are some things, circumstances which can't be totally controlled both on the system side and the user side. One reason why accuracy is quoted at the 95% level as there's that other 4% uncertainty and especially the last 1% which can be totally unknown and uncontrollable. Cheers, Kerry. I never get lost everybody keeps telling me where to go

GPS is not an absolute positioning (nothing is) and expecting to be within a few feet (and especially zero) is a little over ambitious. Under the circumstances sounds like things are as would be expected. Average worldwide accuracy specification is less than 13 metres (43 feet) 95% of the time and that's signal-in-space accuracy, which doesn't allow for things like trees, obstructions etc tec. Signal strength is not as important as the geometry of those signals (satellite positions) but unfortuneately that's something many recreational receiver manufacturers don't bother to display. Cheers, Kerry. I never get lost everybody keeps telling me where to go

GPS is not an absolute positioning (nothing is) and expecting to be within a few feet (and especially zero) is a little over ambitious. Under the circumstances sounds like things are as would be expected. Average worldwide accuracy specification is less than 13 metres (43 feet) 95% of the time and that's signal-in-space accuracy, which doesn't allow for things like trees, obstructions etc tec. Signal strength is not as important as the geometry of those signals (satellite positions) but unfortuneately that's something many recreational receiver manufacturers don't bother to display. Cheers, Kerry. I never get lost everybody keeps telling me where to go

If it's due to signal bounce then that's generally what's called Multipath, not a great lot that can be done about it except move. A short distance can make all the difference. Cheers, Kerry. I never get lost everybody keeps telling me where to go

If it's due to signal bounce then that's generally what's called Multipath, not a great lot that can be done about it except move. A short distance can make all the difference. Cheers, Kerry. I never get lost everybody keeps telling me where to go

That's an open ended question and depends on so many variables that antenna's really are only a minor issue. Something the system is absolutely not spec'd for at all. Cheers, Kerry. I never get lost everybody keeps telling me where to go

That's an open ended question and depends on so many variables that antenna's really are only a minor issue. Something the system is absolutely not spec'd for at all. Cheers, Kerry. I never get lost everybody keeps telling me where to go

the earth moves , yes that's a worry (for some of us) and at the present rate over this way when cival dual frequency becomes available it will probably have a greater accuracy capability then the actual distance this country will have moved since the new datum reference was adopted in 1994. Cheers, Kerry. I never get lost everybody keeps telling me where to go

the earth moves , yes that's a worry (for some of us) and at the present rate over this way when cival dual frequency becomes available it will probably have a greater accuracy capability then the actual distance this country will have moved since the new datum reference was adopted in 1994. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Probably going to depend on a few things including the constellation and your own orientation. Holding up a little higher probably clears the effect of the body as an obstruction as sat signals are line of sight and ones body is enough to stop them. That's the idea behind external antenna's as they generally get the recieved signals away from any obstructions. Possibly pick up that extra previously obstructed satellite (or 2 or more) and it might be enough to improve the constellation geometry (PDOP, HDOP etc) considerably and since accuracy is basically directed to DOP, improve your DOP you'll improve your basic accuarcy to a point. Generally for best reception with a handheld try to face the equator as there's no satellite orbits over either of the poles. As for external antenna's they also have a preferred horizontal orientation (try one upside down and see what happens) and any tilting can cause an artifical cut-off horizon. Cheers, Kerry. I never get lost everybody keeps telling me where to go