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tteggod trackers

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tteggod trackers

+tteggod trackers

Posted
Posted

i have etrex legend, i have the waas enabled but how do i know if its working? i think i read somewhere its one or two specific satellites it uses? number 33 springs to mind? i know the gps uses 12 satelites but howmany are there in total ?

Nellies Knackers

+Nellies Knackers

Posted
Posted

If you get a waas/egnos correction good enough to use you will get a 'D' displayed below the sattelite signal bars,doesn't happen often on a garmin though as the signal still carries a test flag.

Any sattelite above 32 is a waas/egnos sattelite.

You will often get a grey signal bar that never quite gets fully accepted due to the test flag.

Cryptik Souls Crew

+Cryptik Souls Crew

Posted
Posted

You will often get a grey signal bar that never quite gets fully accepted due to the test flag.

 

This signal bar will only turn solid black if you are receiving positioning data as well as correctional data from a WAAS/EGNOS satellite. Some of them only broadcast correctional data, in which case even when the "do not use" flag is not present you will only ever get a greyed out bar. This doesn't mean you aren't locked onto the satellite, just that it is not broadcasting a position signal.

 

You will see in this picture that satellite 44 is displayed as a greyed out bar, but corrections have been applied to several of the other satellites in view. This is because satellite 44 was used only to broadcast correctional data.

 

VistaEGNOSaktiv.jpg

Cave Troll and Eeyore

+Cave Troll and Eeyore

Posted
Posted

If you get a waas/egnos correction good enough to use you will get a 'D' displayed below the sattelite signal bars,doesn't happen often on a garmin though as the signal still carries a test flag.

Any sattelite above 32 is a waas/egnos sattelite.

You will often get a grey signal bar that never quite gets fully accepted due to the test flag.

I get the Ds every time i switch my Garmin on. <_<

Moote

+Moote

Posted
Posted

i have had mine enabled since day one. i travel all over europe but only once recall seeing a "d" in the screen, so i'll join you in sulking!!

Discussion

 

I often see the D's, I know Cave Troll also does as I have cached with him. Maybe it is:

  • The area we live
  • Model of GPS (We both have the same GPS)
  • Luck!

Pengy&Tigger

+Pengy&Tigger

Posted
Posted

I know for ages Mark (Cave Troll) complained because I got the Ds all the time and he never got them at all. One day he got them, and has never lost them since.

 

Could it be that once you have locked on to them once, you're more likely to get them next time?

 

T

wildlifewriter

+wildlifewriter

Posted
Posted
Could it be that once you have locked on to them once, you're more likely to get them next time?

In a sense, yes.

 

Once the GPSr has loaded the almanac for WAAS-type satellites, it then "knows" which ones cover the service area it's in, and which can be ignored.

 

On subsequent start-ups, it won't waste time looking for those signals again. Because of the way Garmin GPS units work, this is a real benefit.

 

-Wlw.

Moote

+Moote

Posted
Posted

ok so where is the best to get logged on to d's then moote?i've driven east to budapest south to gibraltar west to dublin and north as far as watford.should i venture further north maybe?

Joke

 

Well P&T CT&E and I all live within 25miles of Manchester So I reckon somewhere near Bolton might be a Hotspot!

 

N53°34.690', W2°25.846'

spannerman

+spannerman

Posted
Posted

My trusty GPSr is not WASS enabled and I have no immediate plans to upgrade it. Reading this thread has put a question in my head as to whether it would be a hindrance or help to find a cache which was set using a non WASS enabled receiver.

 

If I set a cache, my accuracy would be 15 meters according to Garmin, so if a searcher was using a WASS enabled receiver with a 3 meter accuracy, they could in theory be nearly 40ft from my cache. Am I right in thinking this. If I am right it maybe it's an idea to add a note in the cache description whether WASS was enabled or not in setting the cache.

 

I would be interested to know if anyone using a WASS enabled GPSr has found caching easier with it enabled. So far I have not had any problems with my old GPS12MAP and the accuracy has always been a lot less than than the figures quoted by Garmin. I guess this is because most caches I have done were set without WASS enabled GPSr's but is this likely to change as more cachers have WASS enabled.

Geo-Kate

+Geo-Kate

Posted
Posted

 

I would be interested to know if anyone using a WASS enabled GPSr has found caching easier with it enabled. So far I have not had any problems with my old GPS12MAP and the accuracy has always been a lot less than than the figures quoted by Garmin. I guess this is because most caches I have done were set without WASS enabled GPSr's but is this likely to change as more cachers have WASS enabled.

 

My GPSmap60c is WAAS enabled, and I often get a quoted accuracy of 5 or 6 feet, which is pretty good. Most of the time it is between 8 and 12 feet.

 

I think it is a good help finding caches, but as you say, the printed co-ords are only as accurate as the GPSr that placed it.

 

A good tip might be to log a position a few times, and then avaerage the results. This should help in cancelling the wandering of position sometimes found. Another good way is to let the GPSr take an everage reading over a period of time. This has often got an estimated accuracy of 3-4 feet! :lol:

The HERB5

+The HERB5

Posted
Posted

On hols in Devon last year, I could consistently get the D's.

However, the indicated accuracy on the GPS would be 5ish metres without but 10-12 metres with.

i.e. WORSE. :lol:

 

Is this the D's giving me a truer figure for accuracy or making it worse ?

The Forester

+The Forester

Posted
Posted

the indicated accuracy on the GPS would be 5ish metres without but 10-12 metres with.

i.e. WORSE. :laughing:

 

The indicated figure of "accuracy" is not an indication of accuracy.

 

To know how accurate the fix is, your GPSr would have to know the true value of the position fix. If it knew that, then surely it would tell you the true value and the "accuracy" figure would always be zero.

Geo-Kate

+Geo-Kate

Posted
Posted

On hols in Devon last year, I could consistently get the D's.

However, the indicated accuracy on the GPS would be 5ish metres without but 10-12 metres with.

i.e. WORSE. :laughing:

 

Is this the D's giving me a truer figure for accuracy or making it worse ?

 

With WAAS correction, the stated accuracy should be better than with it disabled. I don't know why it should get worse... :laughing:

 

Just been into garden, and couldn't get any correction signals, then again the satellites we need to see are quite low on the horizon, and I have buindings and trees all round so im not supprised.

The Blorenges

+The Blorenges

Posted
Posted

The satellites used to give the EGNOS signal are over the equator so appear low on our southern horizon, typically not more than 25 degrees or less - so the further north you go the less chance you have of a lock unless you have a clear view the south - as Bolton must do!

Chris

Geo-Kate

+Geo-Kate

Posted
Posted

the indicated accuracy on the GPS would be 5ish metres without but 10-12 metres with.

i.e. WORSE. :laughing:

 

The indicated figure of "accuracy" is not an indication of accuracy.

 

To know how accurate the fix is, your GPSr would have to know the true value of the position fix. If it knew that, then surely it would tell you the true value and the "accuracy" figure would always be zero.

 

:laughing: Huh?

 

Surely, the indicated figure of accuracy IS an indication of accuracy?!

 

The GPSr knows how strong and reliable the signal is and can give an estimate on how true it thinks the fix is.

 

For instance, if it was only recieveing poor signals from above, at would say 'location N X.00 E Y.00 arccuracy 30'. Or in other words 'you are at co-ords N X.00 E Y.00 +/- 30 feet.

 

Have I missed the point?

wildlifewriter

+wildlifewriter

Posted
Posted (edited)
:laughing: Huh?

 

Surely, the indicated figure of accuracy IS an indication of accuracy?!

Strictly speaking, it's not. The number shown is an estimate of the probability that the position shown will be found within a certain distance. This calculation takes a number of different factors into account. Where the receiver actually IS, is not one of them.

 

The Forester is right - but he's also being unnecessarily pedantic.

 

For practical purposes, the figure is a useful guide to how the unit is behaving - and "accuracy" is a useful word to describe it, since any alternative word would cause more confusion than otherwise.

 

-Wlw

 

 

[Edited for accuracy]

Edited by wildlifewriter
The HERB5

+The HERB5

Posted
Posted

For practical purposes, the figure is a useful guide to how the unit is behaving - and "accuracy" is a useful word to describe it, since any alternative word would cause more confusion than otherwise.

 

My understaning was that WAAS gave a correction so wouldn't the 'accuracy' however it's explained be the same, or is there more to it ?

Mr Nibbler

+Mr Nibbler

Posted
Posted

My sons (both on etrex camo) and my legend regularly get EGNOS lock here in Cambs. Nice to see all the Ds but doesn't seem to have any real effect on caches. The blindly stumbling about muddy woods looking under suspicious bits of innocent bark is half the fun for us and EGNOS doesn't alter our stupidity one iota.

dpoet

dpoet

Posted
Posted

My wifes geko 201 gets the Waas d's all the time, but my Legend does not.

I was told the software in the Legend will not use them with the test flag, but the Geko will

Geo-Kate

+Geo-Kate

Posted
Posted (edited)
:P Huh?

 

Surely, the indicated figure of accuracy IS an indication of accuracy?!

Strictly speaking, it's not. The number shown is an estimate of the probability that the position shown will be found within a certain distance. This calculation takes a number of different factors into account. Where the receiver actually IS, is not one of them.

 

The Forester is right - but he's also being unnecessarily pedantic.

 

For practical purposes, the figure is a useful guide to how the unit is behaving - and "accuracy" is a useful word to describe it, since any alternative word would cause more confusion than otherwise.

 

-Wlw

 

 

[Edited for accuracy]

 

Im not getting any further into this as i fear my brain may wave it's little white flag, or I will be corrected again, but I can't help feeling these are all acceptable and different ways of saying pretty much the same thing. :(

Edited by Geo-Kate
The HERB5

+The HERB5

Posted
Posted

On hols in Devon last year, I could consistently get the D's.

However, the indicated accuracy on the GPS would be 5ish metres without but 10-12 metres with.

i.e. WORSE. :)

 

Is this the D's giving me a truer figure for accuracy or making it worse ?

 

May I suggest checking out this website.

http://www.gpsinformation.org/dale/dgps.htm

 

 

Thanx for the link, found my answer.... :)

<quote>

It seems that Garmin will favor differentially corrected satellites, when at least four exist, to the exclusion of regular satellites. If the four are in a poor geometric relationship the epe number, and possibly the accuracy of the solution, can be worse that it was with a regular solution.

<quote>

The HERB5

+The HERB5

Posted
Posted (edited)

And....

 

Garmin are better than Magellan. :)

 

Discussing Magellan units.

<quote>

However they do not have a menu item to turn WAAS on or off. <snip> Note that the unit will continue to use WAAS corrections long after the signal is lost. Some report that corrections will be used for 50 minutes or longer as indicated by the WAAS averging indication.

<quote>

Edited by Nebias
Boardslider

+Boardslider

Posted
Posted

I've rarely seen the 'd's on my garmin etrex vista (mono) until the other weekend when I was in Jersey. I wish I'd photo'd it now, I noticed virtually a whole row of 'd's and the reported accuracy said 3ft!

The HERB5

+The HERB5

Posted
Posted

I've rarely seen the 'd's on my garmin etrex vista (mono) until the other weekend when I was in Jersey. I wish I'd photo'd it now, I noticed virtually a whole row of 'd's and the reported accuracy said 3ft!

 

The only time I've seen them was when on holiday in Devon.

Where are you from again ? :)

tteggod trackers

+tteggod trackers

Posted
  • Author
Posted

well i think i give up getting a full house of d's. since starting this thread i have flown to bahrain and not a sausage. i have also driven with gps on to south of spain and only this week been to austria and back,still nowt! consistantly getting sats 39 and 49 in light grey and a good signal,but not locking on. i did ages ago get some d's but can't for life of me remember where!! maybe its just my legend mono

iNiq

iNiq

Posted
Posted

well i think i give up getting a full house of d's. since starting this thread i have flown to bahrain and not a sausage. i have also driven with gps on to south of spain and only this week been to austria and back,still nowt! consistantly getting sats 39 and 49 in light grey and a good signal,but not locking on. i did ages ago get some d's but can't for life of me remember where!! maybe its just my legend mono

If you look back at post #3 in this thread, that guy explains that you’ll only get a grey bar, never a solid one… because of the “Do not use” tag… According to him. That’s the way it is on mine.

 

Use the following link to figure out where the sat is. And make sure you point your gpsr at it for several minutes.

PRN35 sat location http://www.lyngsat.com/tracker/inmar3f4.html

PRN47 sat location http://www.lyngsat.com/tracker/inmar3f3.html

 

The satellite, PRN 35 is “Inmarsat 3 f4” WAAS. This site even tells you that they are moving it 1.57°W per day…. Cool, eh? But 35 and 47 are for the North American Continent tho.

 

For those in Europe, try looking for PRN 33 and PRN 37. I guess even 44. Here is the links..

PRN33 sat location http://www.lyngsat.com/tracker/inmar3f2.html

PRN37 sat location http://www.lyngsat.com/tracker/artemis.html

These two are EGNOS

Sorry, but I don’t have any links for 39, 44 or 49…

 

I’m a novice at this, but I have had fun learning, and doing all the research into understanding how it all works…. I welcome any corrections, if I made a mistake… (I’m still learning)

martlakes

+martlakes

Posted
Posted

If you look back at post #3 in this thread, that guy explains that you’ll only get a grey bar, never a solid one… because of the “Do not use” tag… According to him. That’s the way it is on mine.

 

 

Hi

 

Just got back from a trip to Coniston. Today and the last couple of trips out I've noticed that the bar for 33 does indeed turn black, with a D as well, and I had nearly a full row of sats, all with Ds. :laughing:

 

I have a an etrex Venture by the way. The accuracy is quoted as 2m.

 

Cheers

Martlakes

Boardslider

+Boardslider

Posted
Posted

I've rarely seen the 'd's on my garmin etrex vista (mono) until the other weekend when I was in Jersey. I wish I'd photo'd it now, I noticed virtually a whole row of 'd's and the reported accuracy said 3ft!

 

The only time I've seen them was when on holiday in Devon.

Where are you from again ? :unsure:

Er, Devon :) North mind you.

 

When I was out at Arrakis yesterday I think it was 33 & 37 were showing but never locking.

The HERB5

+The HERB5

Posted
Posted

I've rarely seen the 'd's on my garmin etrex vista (mono) until the other weekend when I was in Jersey. I wish I'd photo'd it now, I noticed virtually a whole row of 'd's and the reported accuracy said 3ft!

 

The only time I've seen them was when on holiday in Devon.

Where are you from again ? :tired:

Er, Devon ;) North mind you.

 

When I was out at Arrakis yesterday I think it was 33 & 37 were showing but never locking.

 

We stayed near Clovelly last year, and will be near Sticklepath this year (1st week of June)

Jango & Boba Fett

+Jango & Boba Fett

Posted
Posted

Reading through this read I was almost enticed to go up into the attic and find a note book from 1994 when I used a clunky old yellow 8 channel magellan for some fieldwork in the Arctic. In those far off days your position would suddenly jump sideways 65 metres! Oh and the thing took 6AA batteries (I think), drained them in less than 4 hours and it was the size of a door stop.

 

What most users forget is that that ±3m figure is actually the resolution of the system (work it out for yourselves 1 minute of latitude = 1852m so 1/1000th of a minute = 1.825m) so in effect it is saying that it can display a figure ±1/1000th of a minute of Latitude.

 

The fact that a tiny box smaller than a mobile phone can do all that is pretty good so don't expect it to give you sub metric absolute accuracies as well - what are you trying to do call in a Scud Missile attack?

 

Have a look at http://www.ordnancesurvey.co.uk/oswebsite/...atisgps_08.html if you want to explore the issues of accuracy; in any cae no matter how powerful the algorythmns in your little hand held reciever any system depending on Broadcast Ephemeris is never going to give you an absolute accuracy better than ±10m even when it does constrain height - and who can trust it when it will not display cartesian coordinates anyway.

The Toughs

The Toughs

Posted
Posted

Reading through this read I was almost enticed to go up into the attic and find a note book from 1994 when I used a clunky old yellow 8 channel magellan for some fieldwork in the Arctic. In those far off days your position would suddenly jump sideways 65 metres! Oh and the thing took 6AA batteries (I think), drained them in less than 4 hours and it was the size of a door stop.

 

What most users forget is that that ±3m figure is actually the resolution of the system (work it out for yourselves 1 minute of latitude = 1852m so 1/1000th of a minute = 1.825m) so in effect it is saying that it can display a figure ±1/1000th of a minute of Latitude.

 

The fact that a tiny box smaller than a mobile phone can do all that is pretty good so don't expect it to give you sub metric absolute accuracies as well - what are you trying to do call in a Scud Missile attack?

 

Have a look at http://www.ordnancesurvey.co.uk/oswebsite/...atisgps_08.html if you want to explore the issues of accuracy; in any cae no matter how powerful the algorythmns in your little hand held reciever any system depending on Broadcast Ephemeris is never going to give you an absolute accuracy better than ±10m even when it does constrain height - and who can trust it when it will not display cartesian coordinates anyway.

 

Nope, completely lost me there LOL

What I was interested in most, was the appearance of the elusive D's and was wondering if anyone else was seeing them :mad:

Jango & Boba Fett

+Jango & Boba Fett

Posted
Posted

Nope, completely lost me there LOL

What I was interested in most, was the appearance of the elusive D's and was wondering if anyone else was seeing them :mad:

 

Put in simple terms, in the good old days of selective availability your position was good to the nearest 100m and jumped around, you needed an arm like a blacksmith to carry your "hand held" and it ate battries. The ±3m you see on your Garmin etc is ONLY the resolution of the thing (ie if you select DD MM.mmm then ±1/1000th of a Minute (remembering that there are 60 minutes in 1 degree and 1 minute of Latitude - the north/south bit is equal to 1 nautical mile or 1852m, thats 2025 yards, 1 foot and 1 2/5 inches). All the other magic stuff that effects the accuracy of your little Garmin thingy mean that if you intend to call in a pinpoint airstrike, or stand ontop of that allusive micro every time you need to buy a Military Spec reciever (which you can't) and go back 30 days after you took your observations because even dgps is only spot on if you are very close to the reference. To get accuracies good enough to measure the movement of tectonic plates, say, which may only be 2mm per year you need to use a completely different way of processing the satellite signals (phase differencing rather than pseudo ranging).

 

We use a bottom of the range Magellan eXplorist 100 and if you stand around at a position for 5 minutes anywhere in these Britanic Isles then WAAS is always activated (that's "we see D's" for those of you in Garmin land). Just to be complete for all those weird "Northing/Easting, feet and yards" people, just to show how basic our Magellan is it cost us £64, 19 shillings and 9 pennies and 3 farthings (that's pounds Sterling of course).

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