In the same position as Mick W. Just bought a etrex to give me grid references in fog (can use the old compass & map - indeed prefer the compass once I know where I am). Anyway, how does the etrex give alititude (I know its not a barimetric altimeter) & where does it display it?
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 GPS provides a full 3D fix, provided you have at least 4 satellites in view.
The vertical accuracy isn't that good, though, due to the poor geometry of the satellite constellation.
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.jpg) Eddie when i had an Etrex the only way to get a height reading i think was to mark where you were and that then gave me a hieght ...if i remember correctly 
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 Height should be displayable on the same screen where you can scroll through information like position, time, ETA etc. It shouldn't require marking a waypoint.
Height info from a gps was atrocious before they turned off selective availability, but since then I've generally found it to be quite accurate most of the time.
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Matt i cant honestly remember my old Etrex having that feature but my Geko 201 does,but hey im not the best techie when it come to gadgets so i probably missed that,not sure.. The Etrex Legend/vista do have this function but the basic Etrex (YELLOW)i dont think does.could be wrong......
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| Edited: 26/10/07 16:36 |
No, I could be wrong Diddy, but I just know that, even on older Garmin gps units, many fields were selectable as to what info they displayed and on the two I've owned Altitude was certainly in there, so I'd expect the basic Etrex to offer it. It might be quicker to mark a waypoint though, lol! 
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Matt the Etrex definatley didnt have any featuers like the Geko 201 where you can select upto 30 differant options like you say eta/altitude/speed travelled/time travelled.it had none of that just very basic. Thats why i upgraded to the geko 201 loads more features and a lighter/smaller.. Can anyone else confirm this???
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Right, I'm happy to stand corrected on that one.....
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 matt. naturally errors don't matter in good visibilty. i was thinking more dark/fog where they may as you are more likely to be following shorter legs. more of a "be aware of the fact " than "wary"
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 Well folks, I haven't been near a PC for a few days, but thanx for all the input. I did another little walk with my GPS, and yes Matt, I was just using the 'GoTo' feature as you spotted! The next time, I also keyed in a 'finish' waypoint, and went to the 'GoTo' feature, but then switched back to the map page... ...that gave me my breadcrumb track to follow, complete with a little bloke - and it also connected my start waypoint to my finish waypoint with a straight line of a different type. Handy if you have to wander off course (me and the dogs took a wide detour round some bullocks on the return leg!) as it gives you an indication of where you have to get back to. Am I getting there? Oh, I also noticed a bit of a time delay of a few seconds on some things, such as altering course, and also that when in my pocket, the GPS didn't respond as readily. Is that due to the satellites needing to 'see' a flat, clear view of the GPS?
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 it's more likely to be that it has a pre SirF III chipset. earlier chipsets were notorious for needing to be out in the open with a clear line of site to open sky. The SiRF III chipset (the bit that actually receives the signal) is far more sensitive and can even pick up satellites indoors - older ones consistantly failed in urban canyons, trees, pockets etc. The latest Garmin H series use the SiRF III, as does SatMap Active 100.
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imo a gps is probably one of the most sensitive pieces of electronics, and the most accurate clock, you'll own. they pick up a very small signal from thousands of miles away. marvellous. sometimes they'll work in a pocket, sometimes not. this is just trial and error. the gps isn't really suited that well to walking for an instant repsonse as you don't move very far in say 5 secs so it has to wait and "think" about where it is when it receives a differential signal. i would recommend the trackback rather than the GOTO though. that way you can follow the arrow rather than looking at the map. if you stray off it will point you back in the right direction. it may not like tree cover very much as the leaves can block the signal (newer chipset models are more sensitive than the old ones). also beware of "spikes". this is where the gps gets itself in a tizz if it loses one or two of the satellites and will suddenly thinks it's 100m away before switching back to where you are; i've had a 1.5km "spike" before! however, you'll easily see this on the breadcrumb trail. i find waypoints more of an extra information service e.g. lunch, pub, bus stop, seat, view, a landmark en route. pleased to see you playing with it and this is the best way to learn its foibles and what you want to use it for.
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> and also that when in my pocket, the GPS didn't respond as readily
Well, it depends on the orientation in your pocket.
If the antenna isn't pointing up, it can't see all the sky, and so it won't see some of the satellites. Thus, it may not be able to provide a fix, or it will take longer to acquire a fix.
The antenna pattern varies with design, but, basically, it is usually designed assuming that the centre of the pattern points up, allowing all the sky to be seen (within reason; the response of the antenna will fall away towards the horizon). If you point the antenna horizontally, half of the antenna pattern is pointing uselessly into the ground, and it can't see anything behind it.
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-So it wants to be in the top pocket of my sack, or strapped onto the shoulder harness then. All good info, this, I'll have another play tomorrow morning when I take the dog for a walk on the moors. Looking forward to it already.
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slotted through a couple of shockcord loops on the shoulder strap works a treat, but your head can get in the way of the signal occasionally.
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What you need is the 'antenna hat'. Now don't laugh, but we had a team of engineers in here who were using sensitive GPS receivers for indoor positioning (we're using a different system). And yes, they had a hat with a GPS patch antenna on the top as they wandered around the building testing their system...
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I'm getting the hang of the Trackback feature now, thanx to Diddy's most excellent "Trackback for Idiots" post earlier on this thread. Cheers Diddy!
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Glad to help .. Have you got a case for it?Fleebay do some cheap cases that clip onto your pack and help keep the gps kinda pointing upwards/outwards depending where you clip it and with they only about a tenner and dont interfere with the signal. CASE HAVE A LOOK....
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| Edited: 31/10/07 17:05 |
