GPS - What's it all about?

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29/07/2008 at 20:23
Reasonably confident in using a map and compass, but know nothing about GPS. Don't want it as a replacement but would like to know basically what it does - I have no idea how it operates and what information it gives out and what needs to be input in the first place. Do they give your exact position and, if so, how? Anyone help?
29/07/2008 at 22:01

Yes they will give your exact position as a grid ref. You can also programme in a route using mapping software. i use memory Map. This will give you a trail to follow on the screen or the direction to the next waypoint you have set. I use mine as a safety measure as I usually walk alone. It is a comfort to know you are on the planned route. In the worst case scenario you can set it to 'back track' to retrace your route.

In the laKES LAST WEEK IN LOW CLOUD i MANAGED WITH MAP/COMPASS AS i WAS WILD CAMPING AND DIDN'T HAVE THE  ROUTES PROGEAMMED, BUT IT WOULD HAVE GIVEN ME A GRID REF IF i HAD NEEDED IT. ( caps lock)  It's a comfort as much as anything, It will also show where you actualy went if you get lost. can be quite usefull.

29/07/2008 at 22:59

How they work is basically: They receive signals from as many satellites as are visible, by comparing the time the signals took from the various satellites and comparing that with data of each satellite's position, the receiver (the device you take out for navigation) can triangulate your position very accurately.

The information a GPS gives can vary from a simple readout of your position in  OSGB (ordnance Survey Grid Reference) to showing your position liive on a scaleable OS map and your complete route to that point.

29/07/2008 at 23:47
Thanks for that guys, I want to use mine for interest as well as a useful tool.
What are Way Points and how are they used? Seen it mentioned that these have to input into the device.
30/07/2008 at 00:26


As you know what you are doing with a map and compass and sticking to fairly basic, common GPS features:

Think of a waypoint as being like a location you've marked on your map and labeled. On the GPS you are likely to mark (store) such a point in one of two ways. Either by storing the current  location (remember that the GPS knows where you are) as a waypoint, or by keying in a grid reference as a waypoint (there's a couple of other ways you might do it but they're a bit obscure).  Generally you can name these waypoints but most GPSs will automatically name them with numbers (001,002, etc.).

Once you have stored a waypoint you can then ask the GPS to navigate to it, it will then tell you the distance to the waypoint and the direction. If you have a compass built in to your GPS it will also point out the direction relative to the unit. One of the advantages GPS has over map and compass is that if you deviate whilst walking on a bearing to  point it can correct it without you even noticing. Most GPSs will also show you a map showing you in the middle and plotting the waypoints nearby.

Obviously travelling to a waypoint, selecting another, travelling to it etc. is a bit tedious so you can create a Route which is effectively an ordered list of Waypoints to visit. Bear in mind that this can be dangerous if you plot Waypoints which cannot be traversed in straight line segments.

A related feature is a track. Tracks are generally recorded by a GPS to provide functionality such as trackback where you can be lead through your walk, including any inadvertent detours in reverse to get back to the start. However, it is possible to upload routes plotted on computer as a track which can then be followed.

30/07/2008 at 09:41

the concept can require a bit of lateral thinking and, should you venture down the digital mapping path, a complete rethink depending upon what software you use. it seems confusing but isn't really.

to further what john said.

a waypoint is a point on the map (as if you put an X on the map). as far as the gps is concerned, a waypoint is more than just a grid reference. it also allows extra information to be stored with it e.g. a name, an icon. so simplisticly it is an information grid reference. by saving the list of input waypoints as a ROUTE, the gps can guide you from one waypoint to the next. in addition, you may dynamically record any waypoint i.e. a position as a separate waypoint e.g. where the car is in the car park, where's the tent, the pub, where the caravan was before the hurricane.

so, waypoints are what you enter into the gps, either by hand or via a mapping programme.

when you move, the gps will store the positions of where you've been (like laying a breadcrumb trail) which are called trackpoints. a trackpoint is purely a grid reference and time log (time is recorded so it knows what order the trackpoints are in, and as an aside the gps will probably be the most accurate timepiece you own)

trackpoints are what the gps records as you move (there is a lot more to this but that's another tale). you can save your walk as a TRACK. should you decide you don't want to go any further (e.g. bad weather or discover that you are investigating alternative destinations) you can ask the gps to trackback i.e. get it to show where you've been and it will guide you back along the way you have just come from.

you can use this saved track to repeat the walk, in either direction. you may also download the track into a mapping programme and see exactly where you've been.

so you may also share walks.

the only thing to be really, really aware of is that the gps may decide to direct you to the next waypoint that is nearest rather than the next waypoint. take three points a,b and c and these points are on the corners of a triangle (zig-zag). the gps may point you to point c as it's the nearest rather than directing you to c via b. as point c may be at the bottom of a cliff and b is the path down the cliff, you will appreciate that it is an important issue. so you have to be careful in picking where you place your waypoints. after all it is a dumb device and doesn't know where you want to go.

if you set the gps to navigate a route/track at the start of a walk. you can switch it off and switch it on again at anytime and it will continue to navigate to the end. it does this by telling you where the next nearest waypoint is and points you in the direction of it.

it really isn't all that confusing once you've played with one and they are a great tool. depending where you walk, a gps will not replace a map. one of the fun things with a gps is that it will show you that things on maps aren't always where the map says they are.

30/07/2008 at 10:57

How one uses a GPS may depend a lot on what sort of model it is.  Something like the Satmap 10, which shows a map with I Am Here clearly marked, has far less need for waypoints than most other units, for example: you don't need to tell it "show me the way to here", after all, you can see the way to there and see your progress towards it.

But there is no set "this is how you use it" routine: they're tools with features and how you use them depends on you and the task in hand.

Primary points are:

  • you can find exactly where you are
  • you can record information about where you've been, useful as a breadcrumb trail for return or logging your trips if you care about that sort of thing
  • you can enter a pre-planned route and follow it, or part of it (clumsy if done manually, easy with extra software but that means more money, mainly for the mapping licenses) 


30/07/2008 at 11:04
Really grateful for all your replies, it has given me a good insight into what is possible. Now my only issue is trying to find a local-ish outlet (Darlington area) which actually stocks different models - I like to get the info on what models can do what. Even my local Maplins doesn't stock hand-held models. Probably gonna have to go further afield.


30/07/2008 at 13:01

You can get an idea of what waypoints are, and what a digital mapping system might do for you by playing with WheresThePath.  This allows you to plot a route on a map (and see it on GoogleEarth satellite imagery).

If you hit the 'Track' button, you can start placing waypoints that define a route (they appear as little circles).  When you've finished the route, hit 'Stop', then 'GPX', and press the 'Export' button that appears in the pop-up box.  This will create a .GPX file that defines the route, and can be used with most modern GPS receivers.

I'd suggest making sure that any GPS receiver you think of buying is able to import and export these .GPX route files.

31/07/2008 at 08:50

Peter - don't know whether Nevisport is still operating in Middlesborough - the guys in there used to be pretty helpful. There was Simpson Sports in Darlington, but he retired last year - the shop is still in Post House Wynde, but not sure what it is now called and whether it has a range of gps. If you know of others I would be interested to know - it's usually the Lakes that I use and it's a pity to spend "hill time" in shops.

I've just acquired a gps - without trying in shops first - contact me if you want to play with it!

Edited: 31/07/2008 at 08:51
31/07/2008 at 20:37
CP and SD, thanks for that info - the import and export of these .GPX route files seems important to me. Yeah SD, the Simpsons Sports seems to be an outdoor fashion shop (of sorts) rather than equipment, but the Nevisport shop still seems to be there. Will give them a call to make sure and then visit.

PS - SandDancer, not a supporter of Darlo football team's local rivals by any chance?

31/07/2008 at 21:52
Peter - no. Just happen to live in Darlington now - brought up on the red n white side of South Shields.
16/10/2008 at 09:16

all this stuff makes for interesting reading but non of it is useful to a techno numpty, where can I get a simple, and I mean simple guide to my Garmin. I can read out a grid ref but that's it....

Don't advise me to grab a passing 5 year old as I think it's against the law.

Help. Calum

16/10/2008 at 09:20

What model of Garmin, and what are you trying to do?

And where are you (in general, not a 10 figure GR...)?  Easiest way is direct demonstration and there may be someone nearby willing to lend a hand.


17/10/2008 at 08:15

Hi Pete,

Thanks for the interest,

I have a new Garmin eTrex complete with the destruction manual.

I bought it after being slightly mislaid in the Sutherland hills, wrong hill, wrong glen, not serious as I carry my home on my back but the whisky was running low and I was making the map fit rather than!! well! you know!

I stay in Cardiff.


17/10/2008 at 08:54

Nowhere near Cardiff so I can't help directly...

The eTrex manual certainly used to bit of a Partial Success on the usefullness front, so I presume it still is... at what point is it all going Wrong with your efforts so far?

Have you got it turned on and set up for the UK, or not even that far yet?


17/10/2008 at 23:57


I live in Dinas Powys and I have a small book that may help. PM me.

"...the moral test of government is how that government treats those who are in the dawn of life, the children; those who are in the twilight of life, the elderly; those who are in the shadows of life; the sick, the needy the handicapped and submariners. " ~ Last Speech of Hubert H. Humphrey

15/12/2011 at 11:09

I suggested to a colleague at work he starts with the Garmin Etrex H - he just got one off Fleebay for £31.

I reckon they are great to start with then you can either sell, probably for the same money, and upgrade or stay with it.

19/11/2014 at 15:11

some good info here

considering a GPS myself. I tried to get my head around map reading but found it difficult to get time to practice.

19/11/2014 at 16:27

GPS Training have online courses  for basic gps use and using digital mapping at £10 per unit . Several people I walk with have used them and sing their praises.

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