Air Force Gps Satellite Accuracy Improved

[+Muddler]

Has anyone else read this, it appeares to be a week old. This should make things up to 15% better?

 

Check THIS out!

[+Glenn]

Has anyone else read this, it appeares to be a week old. This should make things up to 15% better?

 

Check THIS out!

 

My guess would be that instead of reading 10EPE your GPSr would read 8.5EPE no manual conversion would be needed on your part, you GPSr will just be more accurate. Also the closer you are to one of the 14 new ground stations the better your accuracy will be. There is very little detail in the article but it sounds like these may be WAAS ground stations. So you would need WAAS enabled on your GPSr to take advantage of this improvement.

[+budd-rdc]

Interesting article. I've seen EPE of 7' recently, and have never seen better than 9' before. But then, people have mentioned 7' EPE on other threads, so who knows if this is related.

Edited February 9, 2006 by budd-rdc

[+Airmapper]

I've seen 6' on a Garmin, which was running next to a Lowrance saying 18-20'. The Lowrance was returning back to the same spot better than the Garmin. From what I've seen, the EPE is different from unit to unit, and not always as accurate as reported.

[+Lil Devil]

From what I've seen, the EPE is different from unit to unit, and not always as accurate as reported.

Duh. Considering it stands for Estimated Positional Error

 

Think about it. If the GPSr really knew how far off it is, it would just apply a correction and give you accurate data

[+budd-rdc]

I've seen 6' on a Garmin, which was running next to a Lowrance saying 18-20'. The Lowrance was returning back to the same spot better than the Garmin. From what I've seen, the EPE is different from unit to unit, and not always as accurate as reported.

Clarification: in my case, this is the EPE from the same unit, not from comparing different makes or models.

[+EraSeek]

Has anyone else read this, it appeares to be a week old. This should make things up to 15% better?

 

Check THIS out!

 

My guess would be that instead of reading 10EPE your GPSr would read 8.5EPE no manual conversion would be needed on your part, you GPSr will just be more accurate. Also the closer you are to one of the 14 new ground stations the better your accuracy will be. There is very little detail in the article but it sounds like these may be WAAS ground stations. So you would need WAAS enabled on your GPSr to take advantage of this improvement.

 

This has nothing to do with WAAS or nearness of stations. It has to do with the new generation of duel frequency sats, improved monitoring of them, and improved equipment and programing:

 

"In the current effort, known as the Legacy Accuracy Improvement Initiative, NGA is doubling the volume of observation data it provides from the agency's global network of unmanned ground monitoring stations.

 

The Air Force is combining the additional NGA data with data from its own network of ground stations to improve estimates of GPS satellite positions and velocities. For customers, these efforts will translate into more accurate GPS navigation signals. NGA's initiative will also improve the integrity of GPS signals: With the increase in monitoring, controllers will be able to respond more rapidly when a satellite experiences technical problems. "

 

Part of this is more powerful signals, better antennea, comparing the duel signals, but also increased accuracy of WGS84 by watching and adjusting for things like variations in the earths rotation, and tidal fluxes and stuff like that.

(As I understrand it)

[+Glenn]

Has anyone else read this, it appeares to be a week old. This should make things up to 15% better?

 

Check THIS out!

 

My guess would be that instead of reading 10EPE your GPSr would read 8.5EPE no manual conversion would be needed on your part, you GPSr will just be more accurate. Also the closer you are to one of the 14 new ground stations the better your accuracy will be. There is very little detail in the article but it sounds like these may be WAAS ground stations. So you would need WAAS enabled on your GPSr to take advantage of this improvement.

 

This has nothing to do with WAAS or nearness of stations. It has to do with the new generation of duel frequency sats, improved monitoring of them, and improved equipment and programing:

 

"In the current effort, known as the Legacy Accuracy Improvement Initiative, NGA is doubling the volume of observation data it provides from the agency's global network of unmanned ground monitoring stations.

 

The Air Force is combining the additional NGA data with data from its own network of ground stations to improve estimates of GPS satellite positions and velocities. For customers, these efforts will translate into more accurate GPS navigation signals. NGA's initiative will also improve the integrity of GPS signals: With the increase in monitoring, controllers will be able to respond more rapidly when a satellite experiences technical problems. "

 

Part of this is more powerful signals, better antennea, comparing the duel signals, but also increased accuracy of WGS84 by watching and adjusting for things like variations in the earths rotation, and tidal fluxes and stuff like that.

(As I understrand it)

 

I knew an expert would wonder in here sooner or later. So will this improve our current GPSrs or do we need to buy a new one to see the improvements?

[+fizzymagic]

So will this improve our current GPSrs or do we need to buy a new one to see the improvements?

 

It will improve your current GPS unit. The improvement will not appear in the EPE, though, as that number is a very crude approximation anyway.

 

Those 7-foot and 6-foot EPEs you are seeing are actually 2 meter EPEs. The precision of the EPE calculations are typically 1 meter. Have you ever noticed that you never see an 8-foot EPE? Magellans go from 7 to 10 feet (from 2 to 3 m) and Garmins convert the numbers slightly differently; IIRC, they go from 6 to 10 feet. But in either case you are only seeing a very crude guess about the actual accuracy of your unit.

 

Never, ever treat the reported EPE as anything but a crude relative guide to the satellite geometry. It's not good for anything else.

[+EraSeek]

Let me quote a post from Engadget readers:

"No, you won't need a new reciever, but a new dual band reciever could perform better. The new frequency is key to getting more acurate positions. If you have two frequencies you can compare the effect of the ionosphere on the signals and correct for it. The military (GPS P-Code) can already do this, hence their greater acuracy. Problem is adding another frequency is expensive and power consuming on the reciever end. Its also worth noting, this sat has higher power and better antenna's and thats gonna help even the oldest reciever. Also, this is only 1 of 24 sats needed for coverage. You are going to have to wait until 2011+ for full covarage with the new system."

 

Let me also add the the newer level of monitoring and programing will also help older recievers as well.

[+BigWhiteTruck]

Interesting article. I've seen EPE of 7' recently, and have never seen better than 9' before. But then, people have mentioned 7' EPE on other threads, so who knows if this is related.

 

I can second that. My GPS has the Sirf Star II chipset, which is supposed to be one of the most accurate available. I consistantly see HEPE above 20 feet reported, but I feel that it is less than that. I have been on cache hunts under trees, and stood at what I thought was ground zero, with the gps never wavering out of single digits for distance to the cache, and seen HEPE over 30 feet.

 

Example: I marked a waypoint for a relative's gravestone so we could find it easier again. I actually set the gps on the stone and let it average for about 30 seconds. A few months later we came back and the gps was showing between 2 and 4 feet, with the proper bearing the whole time we were standing next t the stone. I actually stepped back a few steps and watched the distance jump to 6 feet, and never wavered more than 5 and less than 7. The entire time this ws going on, and when i was marking the waypoint, the gps was reporting between 20 and 30 foot HEPE.

 

I guess different models are more or less optimistic about their EPE

[+Glenn]

Let me quote a post from Engadget readers:

"No, you won't need a new reciever, but a new dual band reciever could perform better. The new frequency is key to getting more acurate positions. If you have two frequencies you can compare the effect of the ionosphere on the signals and correct for it. The military (GPS P-Code) can already do this, hence their greater acuracy. Problem is adding another frequency is expensive and power consuming on the reciever end. Its also worth noting, this sat has higher power and better antenna's and thats gonna help even the oldest reciever. Also, this is only 1 of 24 sats needed for coverage. You are going to have to wait until 2011+ for full covarage with the new system."

 

Let me also add the the newer level of monitoring and programing will also help older recievers as well.

 

Are you saying that the software upgrade and 14 additional monitoring stations can only be use by the new satellites? Even if the current satellites arn't able to have their software upgraded, why wouldn't the additional monitoring stations have any affect? It make sense that more monitoring stations would help produce a more accurate atmospheric "map" resulting in a better EPE.

[+EraSeek]

 

Are you saying that the software upgrade and 14 additional monitoring stations can only be use by the new satellites? Even if the current satellites arn't able to have their software upgraded, why wouldn't the additional monitoring stations have any affect? It make sense that more monitoring stations would help produce a more accurate atmospheric "map" resulting in a better EPE.

 

No I am not saying that. As I understand it some of the improvements affect us immediately. But first of all the EPE is nothing but a programmed guestimate so don't focus on that. Secondly, it is not about atmospheric mapping, it is about tracking the sats better and creating a more accurate model of the earth (WGS84) with all its constant changing variation.

 

So what do you get with old sats and old recievers? Improved satellite monitoring, positions, and some better modeling of the earth.

 

What do you get with new sats ond old recievers? More powerful signals, improved sat postions, much better modeling of the earth and where your GPS is on it.

 

What do you get with new sats and new duel recievers? All of the above, plus the ablilty to compare 2 differing frequencies which will help your GPS figure out how much the signal is slowed by the ionosphere and can then make corrections (somewhat like limited WAAS) for a better position.

 

What don't you get till there are more new sats up? The full benefit of all of the above (as I understand it).

[+EraSeek]

OK here it does sound like there is some improvement in atmospheric mapping as well in the basic improvements. I don't know if this is part of the new sats or just the programing and monitoring:

 

"The L-AII upgrade allows the integration of data from up to 14 National Geospatial Intelligence Agency (NGA) monitor stations with data from six existing GPS monitor stations. The L-AII update has incorporated improvements in a variety of scientific knowledge areas, including: numerical standards, geopotential, monitor station site displacement, tidal variations in the earth's rotation, tropospheric delays, and satellite solar radiation pressure.

 

"With greater global coverage from the additional NGA monitor stations, operators will be able to monitor the GPS constellation in near real-time, allowing faster response to anomalies," said John Mengucci, Lockheed Martin' vice president and general manager of DoD systems. "The 10 to 15 percent accuracy improvement will be advantageous to all GPS users and will not require any modifications to their GPS receivers. This program is truly a win-win for both the operators and the users." "

[+Alan2]

I placed my PPC with a SirfIII CF GPS on top of a benchmark. After I let it sttle down for 30 seconds or so, the coordinates were exactly what the benchmark was. The distance kept switching from 0 feet to 3 feet to the waypoint. The PPC program I was using (Mapopolis) does not have EPE.

[+Muddler]

Some very interesting replys! But let me ask, if the data I am geting is better by 15 % and the best EPE (even if is is a rough estimate) was 10 feet, wouldn't I now be getting better accuracy and therefore a closer fix on the selected waypoint? What do you think, does the EPE get rounded up or rounded down? The Lawyers would probably want it to round up and marketing would want it to round down. With all that has been said and my further reading on the subject, I hope we are getting closer to the query and not knowing it!

[Keystone]

Moving to the GPS Units and Software Forum.

[arthurking83]

OK so the new, improved signal will lead to a 15% improvement accuracy?

 

15% improvement to what component of the accuracy?

 

15% of the positional measurement, or the probability of the positional estimate?

 

ie is the EPE now going to be 8.5ft (as opposed to 10ft), 95% probability,

or 10ft, 95.75% probability?

 

there is more to GPS accuracy than just the positional data, it also needs to consider the probability of the estimate to be within the bounds of the reported error.

 

EPE? Don't trust it!!