GPS Advice

On Fri, 7 Nov 2003 18:50:56 -0000, "www.amforbes.com - professional

photography said:

Ok thanks for the info - loads to think about and a few sites to visit.

You might add the newsgroups alt.satellite.gps and sci.geo.satellite-nav. There are some excellent
FAQ sites which you will find via these groups.

Quoted message said:

Is the idea to leave the thing switched on when I am walking and then upload it to my pc.

Do they come with maps built in or do I need to buy that later?

Depends on the make. Magellan only allow Magellan maps, Garmin have both Garmin maps and the
possibility (if you learn how, and its a bit complicated) of creating your own maps. All the
commercially available maps for the UK show only roads - footpaths & most tracks are missing, as are
any other detail useful to walkers.

I am busy creating my own footpath maps for my Garmin Vista. Cotswold Way, parts of Lakes & Brecons
so far. Quite laborious, and made no easier by the Ordnance Survey's attitude to copyright.

However, even without detailed maps I prefer to have a 'mapping' gps, which will at least show you
your track visually in relation to waypoints etc.

Incidentally, the discussions about WAAS are a bit irrelevant. Almost all GPS have it, but it
isn't any use in the UK at the moment - in fact it makes my Vista much slower to lock, and
REDUCES accuracy.

Quoted message said:

What about these american ones that have the 2 way radio built in - are they any good?

Sounds unlikely - 2-way radio is so short range, especially in hills.

Jim Hutton

Mark Cavendish said:

Trust me to get it wrong - it was the end of the initial test phase that I *thought* was the end
of testing! Put it down to EGONOrance!

Having said that I've never switched WAAS off and since I'm getting <3m accuracy have found
no need to

There may be a slight misunderstanding here. I routinely get 3-4m accuracy in the hills with my
GPS12 which has no WAAS, because of the clear sky views. I think the typical 15m quoted accuracy is
an average of typical conditions, and most people typically aren't on hilltops.

If a non-WAAS GPS gives 3-4m on the hilltops, then when WAAS is fully operational you should get sub-
1m accuracy up there.

Paul
--
The October Project 2003
wildwales.fsnet.co.ukoctober.htmlOpen ↗
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"Mike Clark" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

In article said:

"Mark Cavendish" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

On Fri, 07 Nov 2003 13:53:09 GMT, "Jiffy" <[email hidden]> wrote:

<snip>

Quoted message said:

Quoted message said:

Err, we're still in the test phase. Note this from gpsinformation.netwaasgps.htmlOpen ↗
"Europe's EGNOS system (compatible with WAAS but for operation in

Europe) is

Quoted message said:

Quoted message said:

in the test phase now and is transmitting a "do not use" flag. Magellan

GPS

Quoted message said:

Quoted message said:

receivers ignore this flag and use the signal anyway (for what it is

worth),

Quoted message said:

Quoted message said:

but Garmin receivers honor the flag's intent and will not use the EGNOS

data

Quoted message said:

Quoted message said:

as long as the "do not use" flag is set."

The April 2004 date for official launch is widely stated. For example:
pocketgps.co.ukegnos.phpOpen ↗

So be careful with the current Egnos signals otherwise you could be

Waasting

Quoted message said:

Quoted message said:

your time!

Cheers, Jiffy

Your wrong. The latest software updates for Garmin do allow the EGNOS signals to be used

I'm not wrong. The website quoted is wrong!

Cheers, Jiffy

Quoted message said:

How have you determined the accuracy? The estimated accuracy the receiver reports cannot be
relied upon.

Benchmarks for height - +/- 1 metre accuracy on my STP Combination of O/S maps and Fugawi which seem
reasonably accurate ;-) Car tracks are sufficiently accurate to determine that I've been driving on
the correct side of the road! Hiking slightly more difficult as O/S maps aren't always accurate (but
I usually find I've crossed a footbridge and not waded thru the river!) Since I'm also interested in
my total elevation climbed on a hike I also check total ascent vs total descent and these are
usually within 1-2 metres. Which ain't bad over 25km and 1500m! Mainly hilltops but also some steep
sided valleys/tree canopy in the mix. Certainly altogether more accurate than my fumbling around
with a compass/map (which I occasionally do to keep in practice for when my STP does let me down!)

Quoted message said:

There are plenty of satellites visible to the north of the UK over the pole. They are lower in the
sky than other directions but they are none the less useful as long as they are not obscured.

Whilst, yes there are often sufficient sats to the north, there are times when there are
insufficient, combined with poor line of sight (placed on dashboard so car body tends to block
sides/rear) resulting in loss of lock - just as I find the same problem in tunnels, the only other
place I lose lock ;-) Oh, yes, and occasionally lose lock from my window at home (faces east and
sometimes there are, again, insufficient sats). And yes I've used an app to track the azimuth and
elevation and watched as the sats disappear leaving me without lock!

Mark

In article <[email hidden]>, Jiffy

url=''URL:/url said:

"Mike Clark" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

In article <[email hidden]>, Jiffy "]<URL:[email hidden]>

Quoted message said:

"Mark Cavendish" <[email hidden]> wrote in message
"]news:[email hidden]...
> On Fri, 07 Nov 2003 13:53:09 GMT, "Jiffy" <[email hidden]> wrote:

<snip>

Quoted message said:

Quoted message said:

Err, we're still in the test phase. Note this from gpsinformation.netwaasgps.htmlOpen ↗
"Europe's EGNOS system (compatible with WAAS but for operation in

Europe) is

Quoted message said:

Quoted message said:

in the test phase now and is transmitting a "do not use" flag. Magellan

GPS

Quoted message said:

Quoted message said:

receivers ignore this flag and use the signal anyway (for what it is

worth),

Quoted message said:

Quoted message said:

but Garmin receivers honor the flag's intent and will not use the EGNOS

data

Quoted message said:

Quoted message said:

as long as the "do not use" flag is set."

The April 2004 date for official launch is widely stated. For example:
pocketgps.co.ukegnos.phpOpen ↗

So be careful with the current Egnos signals otherwise you could be

Waasting

Quoted message said:

Quoted message said:

your time!

Cheers, Jiffy

Your wrong. The latest software updates for Garmin do allow the EGNOS signals to be used

I'm not wrong. The website quoted is wrong!

Cheers, Jiffy

From <URL:http://www.garmin.com/support/>

For the Geko 201

Changes made from version 2.10 to 2.20:

* Improved WAAS/EGNOS satellite selection algorithm to select the satellite with the most
beneficial corrections given the unit's current position. A unit will not use a WAAS/EGNOS
satellite if the unit's current position is outside of a given WAAS/EGNOS satellite's
service volume.

If you turn on WAAS on a Geko 201/301 you will see that it sometimes uses the EGNOS information, and
sometimes it does not, depending upon your position within Europe, and the availability of the test
signals currently being transmitted.

The satellite display in Advanced mode shows for which satellites it is calculating Differential
information, by showing a D symbol on the strength of signal bar.

Mike <URL:http://www.path.cam.ac.uk/~mrc7/>
--
o/ \\ // |\ ,_ o Mike Clark <\__,\\ // __o | \ / /\, "A mountain climbing, cycling, skiing, "> ||
_`\<,_ |__\ \> | immunology lecturer, antibody engineer and ` || (_)/ (_) | \corn computer user"

Mark Cavendish <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Quoted message said:

How have you determined the accuracy? The estimated accuracy the receiver reports cannot be
relied upon.

Benchmarks for height - +/- 1 metre accuracy on my STP Combination of O/S maps and Fugawi which
seem reasonably accurate ;-) Car tracks are sufficiently accurate to determine that I've been
driving on the correct side of the road! Hiking slightly more difficult as O/S maps aren't always
accurate (but I usually find I've crossed a footbridge and not waded thru the river!) Since I'm
also interested in my total elevation climbed on a hike I also check total ascent vs total descent
and these are usually within 1-2 metres. Which ain't bad over 25km and 1500m! Mainly hilltops but
also some steep sided valleys/tree canopy in the mix. Certainly altogether more accurate than my
fumbling around with a compass/map (which I occasionally do to keep in practice for when my STP
does let me down!)

Quoted message said:

There are plenty of satellites visible to the north of the UK over the pole. They are lower in
the sky than other directions but they are none the less useful as long as they are not obscured.

Whilst, yes there are often sufficient sats to the north, there are times when there are
insufficient, combined with poor line of sight (placed on dashboard so car body tends to block
sides/rear) resulting in loss of lock - just as I find the same problem in tunnels, the only other
place I lose lock ;-) Oh, yes, and occasionally lose lock from my window at home (faces east and
sometimes there are, again, insufficient sats). And yes I've used an app to track the azimuth and
elevation and watched as the sats disappear leaving me without lock!

Mark

What makes you say that O/S maps are inaccurate, having used them for many years I find their
accuracy probably the best in the world. I use a mapping GPS and plan my routes using Fagawi which
include the
1:50,000 Landranger series. In every day use the route when overlaid by the GPS track the comparison
is spot on. I have no reason to doubt the mapping so I am curious about your remark.

In article <[email hidden]>, Nick Hopton

url=''URL:/url said:

In a recent message <[email hidden]>, Mike Clark
<[email hidden]> wrote.

[...]

Quoted message said:

If you turn on WAAS on a Geko 201/301 you will see that it sometimes uses the EGNOS information,
and sometimes it does not, depending upon your position within Europe, and the availability of
the test signals currently being transmitted.

I've not managed to get anything from the EGNOS test bed for the last couple of weeks. This is
using a Geko 301. Are other Garmin users finding the same thing? (Unspoken question; or is it
just me?)

It was working for me using a Geko 301 yesterday 9/11/2003 in Cambridgeshire.

Mike <URL:http://www.path.cam.ac.uk/~mrc7/>
--
o/ \\ // |\ ,_ o Mike Clark <\__,\\ // __o | \ / /\, "A mountain climbing, cycling, skiing, "> ||
_`\<,_ |__\ \> | immunology lecturer, antibody engineer and ` || (_)/ (_) | \corn computer user"

On 10 Nov 2003 03:28:42 -0800, [email hidden] (litherland-1)

Quoted message said:

Quoted message said:

Hiking slightly more difficult as O/S maps aren't always accurate (but I usually find I've
crossed a footbridge and not waded thru the river!)

Quoted message said:

What makes you say that O/S maps are inaccurate, having used them for many years I find their
accuracy probably the best in the world. I use a mapping GPS and plan my routes using Fagawi which
include the
1:50,000 Landranger series. In every day use the route when overlaid by the GPS track the
comparison is spot on. I have no reason to doubt the mapping so I am curious about your remark.

I'm not having a go at O/S (!) or complaining but occasionally I get paths, tracks, woods, fields
and even streams that are displaced despite them obviously existing for decades (if not
centuries). Using
1:25k which gives more detail - I'd probably find 1:50k alright as the main landmarks, roads, rivers
are spot on! Ironically, its the accuracy of my STP that highlights the errors - using map and
compass I'd be much more unlikely to notice

Mark

Mark Cavendish said:

I'm not having a go at O/S (!) or complaining but occasionally I get paths, tracks, woods, fields
and even streams that are displaced despite them obviously existing for decades (if not
centuries). Using
1:25k which gives more detail - I'd probably find 1:50k alright as the main landmarks, roads,
rivers are spot on! Ironically, its the accuracy of my STP that highlights the errors - using
map and compass I'd be much more unlikely to notice

The main landmarks are not spot on with 50k mapping though. Summit heights in particular are often
in slightly the wrong spot, whereas the 25k summits are usually pretty close. I have two tracks
through the same forest which don't match the 50k map. After the first walk I assumed the GPS to be
in error due to the trees, but the track from the second walk matched perfectly. When I checked the
25k map it turned out that the forestry track was a different shape to the 50k map, and guess what,
it matched the GPS tracks perfectly.

The 50k mapping isn't that accurate. It's pretty close and may seem to be accurate if you don't look
too closely, but over the years I've found many instances where my GPS tracks don't match the 50k
map features perfectly, but do match the 25k. Roads, paths, ROWs are often simplified for clarity,
with tiny twists and turns being smoothed out.

Paul
--
The October Project 2003
wildwales.fsnet.co.ukoctober.htmlOpen ↗
wilderness-wales.co.ukwilderness-wales.co.ukOpen ↗
photosig.comuserphotosOpen ↗