is WAAS (EGNOS) available yet ?
- Thread starter gasman
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PanEuropean
Registered user
The European Satellite Based Augmentation System (EGNOS) is currently running in test format. Sometimes you pick up an augmentation satellite, sometimes you don't. The testbed, which is referred to as ESTB (EGNOS System Test Bed) doesn't always send out fully up to date almanac information, which is why some GPSR's get it, and some don't.
When I attended the European Business Aviation Conference in Geneva this past spring, the folks from EuroControl (the air traffic control agency) said that they estimated that the EGNOS system would be fully operational - in other words, finished with the testing - in 2006.
Any form of augmentation system - whether it is satellite based (SBAS) such as the European EGNOS or American WAAS, or whether it is land based, such as some differential correction systems used for marine or land survey applications (DGPS, LAAS) is really useless as a third handle on a chamberpot to those of us who use the GPS navigation system for automotive or motorcycle use.
The average un-augmented accuracy of a contemporary 12 channel GPSR (such as the SP III, SP 26xx, Garmin 2x6 models, etc.) is about 30 feet. That's less than the width of an average small residential street. If you turn on an augmentation system - either satellite based or land based - you then have to dedicate some of your 12 channel reception capability for the exclusive use of the augmentation system. This means, in practice, that you now have a 10 channel GPSR, not a 12 channel one, so you can expect to see more "satellite reception lost" messages.
Even if you do manage to pick up 10 normal satellites and 2 augmentation signals (land or sky), what's the point? The automotive GPSR's snap the vehicle symbol to the roadway, to eliminate nuisance position indications caused by minor errors in the cartography. This will take precedence over any accuracy increase that comes from the augmentation system, which means your just wasting your time turning on WAAS, LAAS or DGPS on any automotive GPSR. In fact, worse than that, you're actually handicapping the performance of your automotive GPSR, because you are restricting it to using only 10 of the 'normal' GPS satellites that are in view overhead, in non-geosynchronous orbit.
Keep in mind that SBAS was designed for use by aircraft GPSRs, not ground based GPSRs. The augmentation satellites orbit around the equator, which means they are very low in the southern horizon for most users in the northern hemisphere. It's easy to pick up a SBAS signal in an aircraft that has a clear view of the whole sky, but less easy to do so when you are beside a tree or building that is blocking your view of an augmentation satellite that is only 5 degrees above the horizon.
The Garmin engineers wisely did not provide SBAS capability in any of the Garmin automotive GPSRs, until the folks at Magellan brought out an automotive GPSR that had SBAS capability. When that happened, the Garmin marketing department asked the automotive software engineers to add SBAS to the SP 26xx series, which they then did. It wasn't difficult, just a small software tweak. Keep this in mind - SBAS is available on the SP 26xx series as a marketing countermeasure, not because it's a useful feature that an automotive user needs.
I spent the last few weeks in Western Canada, flying around and using SBAS (the American WAAS) in my aircraft when testing the Garmin 296. To be honest, I couldn't really see the point of SBAS even for 95% of aviation use - what's the difference between 30 foot accuracy and 2 foot accuracy when the runway is 200 feet wide and 8,000 feet long?
Bottom line: For automotive use, Turn it off, and forget about it.
PanEuropean
When I attended the European Business Aviation Conference in Geneva this past spring, the folks from EuroControl (the air traffic control agency) said that they estimated that the EGNOS system would be fully operational - in other words, finished with the testing - in 2006.
Any form of augmentation system - whether it is satellite based (SBAS) such as the European EGNOS or American WAAS, or whether it is land based, such as some differential correction systems used for marine or land survey applications (DGPS, LAAS) is really useless as a third handle on a chamberpot to those of us who use the GPS navigation system for automotive or motorcycle use.
The average un-augmented accuracy of a contemporary 12 channel GPSR (such as the SP III, SP 26xx, Garmin 2x6 models, etc.) is about 30 feet. That's less than the width of an average small residential street. If you turn on an augmentation system - either satellite based or land based - you then have to dedicate some of your 12 channel reception capability for the exclusive use of the augmentation system. This means, in practice, that you now have a 10 channel GPSR, not a 12 channel one, so you can expect to see more "satellite reception lost" messages.
Even if you do manage to pick up 10 normal satellites and 2 augmentation signals (land or sky), what's the point? The automotive GPSR's snap the vehicle symbol to the roadway, to eliminate nuisance position indications caused by minor errors in the cartography. This will take precedence over any accuracy increase that comes from the augmentation system, which means your just wasting your time turning on WAAS, LAAS or DGPS on any automotive GPSR. In fact, worse than that, you're actually handicapping the performance of your automotive GPSR, because you are restricting it to using only 10 of the 'normal' GPS satellites that are in view overhead, in non-geosynchronous orbit.
Keep in mind that SBAS was designed for use by aircraft GPSRs, not ground based GPSRs. The augmentation satellites orbit around the equator, which means they are very low in the southern horizon for most users in the northern hemisphere. It's easy to pick up a SBAS signal in an aircraft that has a clear view of the whole sky, but less easy to do so when you are beside a tree or building that is blocking your view of an augmentation satellite that is only 5 degrees above the horizon.
The Garmin engineers wisely did not provide SBAS capability in any of the Garmin automotive GPSRs, until the folks at Magellan brought out an automotive GPSR that had SBAS capability. When that happened, the Garmin marketing department asked the automotive software engineers to add SBAS to the SP 26xx series, which they then did. It wasn't difficult, just a small software tweak. Keep this in mind - SBAS is available on the SP 26xx series as a marketing countermeasure, not because it's a useful feature that an automotive user needs.
I spent the last few weeks in Western Canada, flying around and using SBAS (the American WAAS) in my aircraft when testing the Garmin 296. To be honest, I couldn't really see the point of SBAS even for 95% of aviation use - what's the difference between 30 foot accuracy and 2 foot accuracy when the runway is 200 feet wide and 8,000 feet long?
Bottom line: For automotive use, Turn it off, and forget about it.
PanEuropean
GSPeP
Registered user
I'm thinking the same.PanEuropean said:
I tested it once with my GPS V and got an avarage accuracy of 2-3 meters instead of my usual 5-6 meters. I also got the impression that it slowed down the performance of the GPS. Recalculating a route took a lot longer than normal.
I switched it off.
shouldn't that be ESBAS ??
then - ESTB (EGNOS System Test Bed)
would be ESBASSTB ??
as for (DGPS, LAAS) ........
WALOB ( what a load of bollox )
TheJoker
Registered user
motomartin said:shouldn't that be ESBAS ??
then - ESTB (EGNOS System Test Bed)
would be ESBASSTB ??
as for (DGPS, LAAS) ........
WALOB ( what a load of bollox )
I thought you ozzies have some shrimps to barbeque and some VB to drink...?! Instead of WALOBing...
Or, let me guess, you've just had the shrimp, got to get some more sunscreen on and fetch another beer, and just happened to glance at the computer... ?!?
Well close.
I just got back from work .
glass o red wine
Its dark and a bit nippy.
just checkin my email - and OBVIOUSLY ukgser.
in the mood fer a bit o pisstakin'
ps - buyin a bbq tomorrow - already lined up - second hand - weber kettle - as new £30 - BARGAIN !!
soon be nice warm SUMMER - thats 30 deg
haven't got a bike yet tho
.......and pay attention at the back - I'm from UK
I just got back from work .
glass o red wine
Its dark and a bit nippy.
just checkin my email - and OBVIOUSLY ukgser.
in the mood fer a bit o pisstakin'
ps - buyin a bbq tomorrow - already lined up - second hand - weber kettle - as new £30 - BARGAIN !!
soon be nice warm SUMMER - thats 30 deg
haven't got a bike yet tho
.......and pay attention at the back - I'm from UK
PanEuropean
Registered user
Alphabet Soup
Yea, I know, all the acronyms are a PITA. Here's a quick decoder:
SBAS - Satellite Based Augmentation System. SBAS is the correct 'generic' term to use when describing all the different worldwide satellite augmentation services. These include:
WAAS - Wide Area Augmentation Service, the North American SBAS program, which is operated by the US FAA (Federal Aviation Administration).
EGNOS - European Geostationary Navigation Overlay Service, the European SBAS program, which is operated by the European Space Agency.
MSAT - The Japanese SBAS program.
DGPS - Differential Global Positioning System. This consists of the regular Global Positioning System (GPS) with an additional correction (differential) signal added. This correction signal improves the accuracy of the GPS and can be broadcast over any authorized communication channel. DGPS is commonly used for augmenting GPS signals used by mariners. Small portable DGPS systems can be purchased and set up in any location to provide additional precision as needed - for example, by land surveyors. GPSR's that accept DGPS input always expect to get that input supplied to them by a stand-alone DGPS receiving device. As far as I know, there is no GPSR in the world that has the DGPS correction signal receiving device built into it.
LAAS - Local Area Augmentation System. Another form of DGPS, in this case designed specifically for aircraft. it only works in a limited area, usually a 20 to 30 mile radius of an airport. LAAS is comprised of ground equipment and avionics (gizmos on the aircraft instrument panel). The ground equipment includes 4 reference receivers, a LAAS ground facility, and a VHF data broadcast transmitter.
All of these augmentation systems - satellite based and ground based - accomplish the same thing: They enhance the precision of the position noted by the GPSR by comparing the known (traditionally surveyed) position of a GPS ground reception station to what the standard satellite signals are suggesting the position of the ground station is. The ground station then notes the amount of position error that exists, and re-transmits this as an error correction value that is then applied by the end user's GPSR.
The best visual explanation of how all this works can be found here: LAAS - how it works. Although this explains how the LAAS system works, sending its correction messages to the end user aircraft GPSR by VHF transmission, the general idea is the same for SBAS. In the case of SBAS, the correction signal is processed on the ground, and beamed up to a SBAS satellite, which then sends the correction information out to everyone's GPSR more or less in the same manner that the GPSR gets the 'regular' satellite signals. That explains why, when you turn SBAS on, you lose 2 of your 12 satellite channels - these need to be dedicated to listening to the augmentation satellites, to get the correction signals.
Nuff' said?
PanEuropean
Yea, I know, all the acronyms are a PITA. Here's a quick decoder:
SBAS - Satellite Based Augmentation System. SBAS is the correct 'generic' term to use when describing all the different worldwide satellite augmentation services. These include:
WAAS - Wide Area Augmentation Service, the North American SBAS program, which is operated by the US FAA (Federal Aviation Administration).
EGNOS - European Geostationary Navigation Overlay Service, the European SBAS program, which is operated by the European Space Agency.
MSAT - The Japanese SBAS program.
DGPS - Differential Global Positioning System. This consists of the regular Global Positioning System (GPS) with an additional correction (differential) signal added. This correction signal improves the accuracy of the GPS and can be broadcast over any authorized communication channel. DGPS is commonly used for augmenting GPS signals used by mariners. Small portable DGPS systems can be purchased and set up in any location to provide additional precision as needed - for example, by land surveyors. GPSR's that accept DGPS input always expect to get that input supplied to them by a stand-alone DGPS receiving device. As far as I know, there is no GPSR in the world that has the DGPS correction signal receiving device built into it.
LAAS - Local Area Augmentation System. Another form of DGPS, in this case designed specifically for aircraft. it only works in a limited area, usually a 20 to 30 mile radius of an airport. LAAS is comprised of ground equipment and avionics (gizmos on the aircraft instrument panel). The ground equipment includes 4 reference receivers, a LAAS ground facility, and a VHF data broadcast transmitter.
All of these augmentation systems - satellite based and ground based - accomplish the same thing: They enhance the precision of the position noted by the GPSR by comparing the known (traditionally surveyed) position of a GPS ground reception station to what the standard satellite signals are suggesting the position of the ground station is. The ground station then notes the amount of position error that exists, and re-transmits this as an error correction value that is then applied by the end user's GPSR.
The best visual explanation of how all this works can be found here: LAAS - how it works. Although this explains how the LAAS system works, sending its correction messages to the end user aircraft GPSR by VHF transmission, the general idea is the same for SBAS. In the case of SBAS, the correction signal is processed on the ground, and beamed up to a SBAS satellite, which then sends the correction information out to everyone's GPSR more or less in the same manner that the GPSR gets the 'regular' satellite signals. That explains why, when you turn SBAS on, you lose 2 of your 12 satellite channels - these need to be dedicated to listening to the augmentation satellites, to get the correction signals.
Nuff' said?
PanEuropean
TheJoker
Registered user
Re: Alphabet Soup
With all these TLAs and FLAs you could be a consultant!!
PanEuropean said:
With all these TLAs and FLAs you could be a consultant!!
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