My other option for Christmas (see "Night Sight" thread :
Message-ID: <6xxZFBQ7lFl$ snipped-for-privacy@pigsonthewing.org.uk>)
is a GPS unit. I would want it for use in the field, and as an in-car aid.
I have a Compaq iPAQ, so could use one tat works with that.
Any thoughts/ FAQ?
Andy Mabbett Reply to [my first name] [at] pigsonthewing.org.uk USA imprisons children without trial, at Guantanamo Bay:
Why dont you keep this shit to yourself ? !
What's the matter? Does the truth hurt?
Probably more useful.
Try the newsgroup sci.geo.satellite-nav There's a good FAQ and an excellent website (reffed from the FAQ) that one of the regular posters maintains.
Most GPS are now pretty good, but some are still better than others - especially for mapping, which is now a near-standard feature. A surprising number have large inaccuracies in their conversion to GB OS grid refs though, which makes them damn near useless.
Inaccuracies, yes. Large, no.
No.
They were very useful even when SA was on, the conversion inaccuracies are way smaller.
Paul
In message <nqZkb.88895$ snipped-for-privacy@news-lhr.blueyonder.co.uk>, yup snipped-for-privacy@now.ta writes
So you don't give a f*ck then ?
Lucky it's not you this time eh ?
1/2km is a bit too big, IMHO.
Can't remember the model, this is a friend's (a Garmin, I think) bought just a few years ago. It was enough to put us on the wrong side of a woodland when out walking.
Does the iPaq have Bluetooth? You can get small (Swan Vesta matchbox sized) bluetooth GPS receivers that send their data to a connected device like a smartphone or PDA (do a search for "Emtac GPS" for an example). You then need software on your PDA to process the GPS data stream to do useful things with it. A neat solution if you are going to use the equipment indoors or in a car.
If you want to use the GPS outdoors for walking, then you're better going with the type of device you can buy from Field and Trek etc, since these will be weather proofed and have the right sort of navigation software on them.
tony
Sounds like he was using the wrong datum.
Paul
In article snipped-for-privacy@4ax.com, Andy Dingley snipped-for-privacy@codesmiths.com writes
That was not due to an error in the GPS conversions to OS grid. The datum transformations are accurate to a few metres (<10).
Most likely it was due to either poor satellite geometry / obstruction or user error in having the wrong datum set.
The most common error with setting up a Garmin for use with the OS is to select British Grid position format but not change the datum to the required Ord Srvy GB from the default WGS-84. That will lead to an extra
100m of error which is consistent. People also commonly miss read the grid ref reported by Garmins until they realise that it is a 10 figure ref.
Pot kettle black - does it really take that much attached junk to say one line?
In message <09$39sHcQRl$ snipped-for-privacy@dscs.demon.co.uk>, Dominic Sexton <{d-sep03}@dscs.demon.co.uk> writes [snip]
Except, of course, if you have purchased Memory-Map software and OS maps to go with your new Garmin.
Then you need to have the datum in your Garmin set to WGS84.
>
No you don't. Garmin units always send and receive data in WGS84 format, no matter what the datum is set to. Setting the OS datum simply affects the coordinates that are displayed on the unit, not how they are sent to the software.
I don't know about Memory Map, but with Ozi Explorer I set the upload/download datum to WGS84, so that the data is transferred correctly, but set the map datum to Ordnance Survey, so that the data is correctly shown on the map.
Setting your Garmin to WGS84 will give you incorrect readings.
Paul
In article <Q9xiDy3+Xal$ snipped-for-privacy@gododdin.demon.co.uk>, jake snipped-for-privacy@gododdin.demon.co.uk> writes
Not for the transfer of waypoints, routes and tracks as these use the Garmin Protocol which always uses WGS-84 no matter what datum the user has selected in their GPS.
However if you are using a program which takes the real-time NMEA information from the GPS to display the position on a map you may need to set the GPS datum to WGS-84 in order to have the position displayed correctly.
Wrong set-up, or very old unit. From the tracklog of my Garmin Vista you can usually see which side of the road I walked.
Jim Hutton
The first step is to look at the FAQ in sci.geo.satellite-nav. There are loads of links.
The choice depends on what you want most. I have a Garmin Vista, which I use for walking & cycling. It's not an ideal in-car unit (screen too small, likes to be flat so at the wrong angle to see the screen, no voice-prompt) but its the greatest for walking (small, likes to be flat .... etc). Other advantages are - batteries last all of a long day's walking, I can make my own maps, accurate, tough & waterproof.
The iPaq would be way too big and fragile for roughing it, and the battery life is NBG, but may be good for in-car.
Perhaps both ...!
Jim Hutton
Yes. Seems your right.
Just checked. My Garmin Map Datum is set to 'Ord Srvy GB'.
Now when memory-map displays the position where the cursor is sitting, it always appends '(WGS84)'
So a waypoint on a map is SP 75562 54701 (WGS84), but when down-loaded is displayed on the Garmin as SP 75561 54704.
Hmm ....... must try and understand all this one day ;-)
regards.
Actually that doesn't sound like WGS84, that sounds like the conversion to OSGB inaccuracy that Andy Dingley mentioned.
I've tried inputting a grid ref in WGS84 on my GPS and on OziExplorer, then changing the datum to OS and they both produce slightly different results. I think Ozi is more accurate because the conversion in a GPS is relatively simple.
I have two highly accurate lists of trig point waypoints in the UK, produced by the OS themselves, one in WGS84 Lat/Long format, the other in OS BNG format. When I enter the WGS84 waypoint (in either my GPS or OziExplorer) then switch to OS BNG, the result is different to the OS BNG coordinates (the OS use a much more complex conversion). The difference is usually only a few metres, sometimes more, but always less than 10 metres.
Paul
I think I'll keep quiet ;-)
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