using a GPS

[dannnnn]

hey all, i see a lot of chat on here about using GPS units, but i have not used one in the bush myself - i don't have one and none of my friends are keen enough walkers to have one either. so i am curious - how do they work?? not technically (i have enough of an understanding about that) - but practically. most of the GPS units i have seen do not have iphone-quality screens so i presume they don't work like google maps. and i also presume that they don't work like the tomtom in my car either so practically, how do you use one??

do they have all the same info that a 1:25,000 map has on it?? can you use it like a paper map to see what your surroundings are? can you use it to guide you on a path? can you easily get one to give you your location so that you can compare it to a paper map?? what other neat things do they do??

if it helps you to explain to me - please understand i am not an expert navigator by any imagination - most of the walks i have done are following well-formed tracks and usually i have just used a map to help me understand how far along i am and perhaps which way to turn at a junction.

cheers!

- dan

[icefest]

A GPS is in simplest terms a machine that tells you you location on the world (geode) as a series of numbers using satellites (and a while lot of relativity, chronology and mathematics).

You can do multiple things with this number

1) Put it onto a map and see where you are
2)Send someone else the number (so they can seee where you are), a la PLB.
3)display your location on a saved map. (no numbers needed.

Most forum members think that if you are not able to do 1 then you shouldn't use 3 as that leads to user error and inability to cope if things go wrong.

Lastly, 3 is only as good as your saved map. (Crap in crap out) There a decent free maps available and decent paid maps available. I use a combination of both.

Personally, I'd recommend going on a rogain to learn navigation first.

As far as models go, I have used an etrex and quest, both by garmin. I'll buy myself a new etrex 20 sometime this summer.

[GPSGuided]

Good explanation above from a purist point of view.

But for the lay people, a handheld hiking GPS unit is not that different to a TomTom in the car, if you have a mapping model. Similarly, the unit displays your present position and heading on a map underlay. The quality of map is of your choosing (some need to be purchased) and can vary from "toy" to highly accurate topo. It has a built-in compass and various features like overlay of planned route, just like a TomTom car navigation interface. You can also set waypoints (like in a car unit) and can set courses for them, but just not on established roads.

For people who are navigationally challenged, a mapping GPS with quality colour screen is desirable. Although colour screen will chew through batteries faster, it will make map features more readable. It's also worth staying with the major producers as they invariably have a feature set that suits.

[LandSailor]

With a GPS you can also do things like record a location or track and then load this data into Google Earth when you get home.

[MrWalker]

Because the GPS follows the twists and turns of your route all the way it can also give you a record of how far you have gone and based on the time taken, your average speed. When I started using a GPS I got a simple one with no maps included and used it mainly to find out how far along the route I was (or to find my location on a real map if I thought I was off the right track).

Now I use one that comes with maps equivalent to the 1:25,000, but most of the time I still keep it in my pocket and just check my distance from time to time to see how I'm going. However, a useful feature is to enter some points into the GPS before I start, so when I reach a track junction (or major feature if off-track) I can see where I should be going next and can make sure the route I am taking will get me there. This is much like the TomTom, except that the GPS doesn't talk me and tell me which track to take at the junctions.

[Scottyk]

A GPS is in simplest terms a machine that tells you you location on the world (geode) as a series of numbers using satellites (and a while lot of relativity, chronology and mathematics).

You can do multiple things with this number

1) Put it onto a map and see where you are
2)Send someone else the number (so they can seee where you are), a la PLB.
3)display your location on a saved map. (no numbers needed.

Most forum members think that if you are not able to do 1 then you shouldn't use 3 as that leads to user error and inability to cope if things go wrong.

Lastly, 3 is only as good as your saved map. (Crap in crap out) There a decent free maps available and decent paid maps available. I use a combination of both.

Personally, I'd recommend going on a rogain to learn navigation first.


As far as models go, I have used an etrex and quest, both by garmin. I'll buy myself a new etrex 20 sometime this summer.

Well said above

Remember that a map should ALWAYS be carried for the area you are walking (in addition to a GPS). Due to fact that electronics can stop working a paper map never stops working.

[icefest]

... until it gets wet, torn, or lost.

[Scottyk]

... until it gets wet, torn, or lost.

Are you saying you don't take a map?
Wet = Laminate it with contact used to cover school books
Torn = the above make it impossible to tear
Lost = well you can loose the gps too. Loose your map and well maybe you shouldn't be out there.

[perfectlydark]

I think the point is paper maps have every chance of "failing" as does tech without proper care

[GPSGuided]

Good retorts ScottyK! Another one on maps. Dingoes can't eat GPS but can turn a map (laminated or not) to a dog's meal.

[Scottyk]

Good retorts ScottyK! Another one on maps. Dingoes can't eat GPS but can turn a map (laminated or not) to a dog's meal.

Dingoes are one thing I have never considered
I have nothing against GPS at all but It is just plain foolish to not carry a map as well.

[puredingo]

It's also a lot harder to wipe your *&%$#! with a GPS...Now tell me a map doesn't win in that emergency situation!

[neilmny]

It's also a lot harder to wipe your *&%$#! with a GPS...Now tell me a map doesn't win in that emergency situation!

Either way your navigation capacity will turn to Sh1T

[GPSGuided]

Either way your navigation capacity will turn to Sh1T

ROTFL!!!!!

[McWade]

Good retorts ScottyK! Another one on maps. Dingoes can't eat GPS but can turn a map (laminated or not) to a dog's meal.

Sounds like a challenge..

[AlbinoNeutrino]

... so practically, how do you use one??
...what other neat things do they do??

I think the two most compelling reasons to own a GPS for bushwalking are the trackback feature and the compass.

Most of us don't stop every 50m and look behind, so when you do decide to turn around the track often looks completely unfamiliar in the other direction. If you decide to bail out you can use the trackback feature and follow your footsteps back to starting location, which is particularly useful if not on a well marked track.

If you are stuck in poor visibility conditions like cloud or a blizzard and you have had the foresight to mark the waypoint that you are trying to navigate to, the compass will point you in the direction you need to travel, regardless of your deviation from the course. Unlike a traditional compass, it knows where you are in relation to the thing you are trying to find. To find your way with a map and compass you would first have to find your position on the map, take a bearing and then walk a straight line course between sighted landmarks, all of which is difficult to do if you can't see 20m. With a GPS you just hit find and follow the arrow, and it doesn't care if you need to go off course to clear obstacles on the way.

GPS units offer some other features that are practical in the bush even if you aren't actually lost. The trip computer can tell you your elevation, the temperature, the distance you have covered, how fast you are moving, how long you have been moving/still, the distance to the next way point, etc etc ad infinitum. On my garmin you can customise the data fields it displays.

Elevation plotting is another feature that is quite useful and allows you to visualise the terrain.

Mine can track and plot changes in atmospheric pressure that can be used as a basic weather forecasting tool.

It also has a "sight and go" feature, so if you were, for example, standing on a hill in a city and wanted to navigate on foot to the bridge on the horizon, you can point the unit and take a bearing then descend into the city streets where the bridge is no longer visible, and the unit will point you towards the bridge until you get there.

There's the little stuff like the stopwatch and and alarm if you need to wake up at sunrise . And it will also tell you when sunrise is for that matter. And sunset. And tides.

Using it in conjunction with a computer allows you to do trip planning in advance and enter your tracks and way points, measure distances and plan campsites. All of which can be done with a map and a pencil, and there's a learning curve with the software, but it does add another layer to the experience.

With the usual caveats about the short comings and limitations of GPS, personally I find it gives some peace of mind to have it in the bag.

[dannnnn]

hmmm, sounds useful but not so great that you can forget the map like with the car GPS. is there anywhere i can go and have a good play with one??

[GPSGuided]

hmmm, sounds useful but not so great that you can forget the map like with the car GPS. is there anywhere i can go and have a good play with one??

You think so? Have you seen my SO driving in the city when her car GPS bummed out?

[jonnosan]

Remember that a map should ALWAYS be carried for the area you are walking (in addition to a GPS). Due to fact that electronics can stop working a paper map never stops working.

A paper map may not stop working (well unless it gets lost, or wet of course), but a compass sure can. I keep reading posts saying modern electronics are less reliable than map & compass , but have never seen any actual evidence to that effect.

[GPSGuided]

A paper map may not stop working (well unless it gets lost, or wet of course), but a compass sure can. I keep reading posts saying modern electronics are less reliable than map & compass , but have never seen any actual evidence to that effect.

Battery juice is finite, US military may at their discretion switch off or induce errors in their GPS network, solar storm may significantly interfere with the signal, electronic chips may fail, LCD screen may crack and so the list goes on. All have happened in the past, you just need to search for them but so are map eating dingoes.

[icefest]

I've had a map blown off a cliff when a huge gust of wind knocked me over.

Maps, compasses, and GPSs can all break/fail/get lost. Diversifying can improve safety at the expense of weight. There are some situations where each of them shine and others are less effective.

EDIT: The US also says that their new GPS satellites can not induce errors.

[GPSGuided]

I've had a map blown off a cliff when a huge gust of wind knocked me over.

Nooooo...!!! Photo/video or it didn't happen!

EDIT: The US also says that their new GPS satellites can not induce errors.

Being a strategic military asset, would you believe them? Fortunately we now have GLONASS compatible services on most of the newer unit. I further understand that China's system and European's system are all coming along quickly.

[icefest]

Both of them are at least another 8 years. Although Galileo will hopefully replace the current PLBs...

[GPSGuided]

Be interesting to know how the market place will select which system to use. Will there be any advantages in using signals from all the systems?

[icefest]

Be interesting to know how the market place will select which system to use. Will there be any advantages in using signals from all the systems?

Advantages: Improves accuracy, improved reception in difficult areas (both a function of more satellites), more future-proof (they will not all shut down at the same time).
Problems: Increased complexity (ergo weight)

[frenchy_84]

Be interesting to know how the market place will select which system to use. Will there be any advantages in using signals from all the systems?

they will use all of them just like glonass capable receivers at the moment. It doesn't matter whether they are US, Russian or euro, at the end of the day it's just a radio frequency beamed down from a satellite. It just gives you more satellites so more redundancy and therefore the ability to only need to use the ones which have a good geometry at the time. For example on my current work site, we have graders set up with machine guidance which can use both GPS and GLONASS however if its receiving signals from 20 sats (and corrections from base as its RTK) it's to much for the processor to handle (doesn't help that its a rubbish brand) so we set the base station to only transmit the 12 best satellites whether that's US or Russian

[GPSGuided]

That's very interesting. Didn't know that even with our current two system chips, data sources could be mixed in use at the triangulation level.

[icefest]

Forgot to mention this: When the time is sent on a different frequency it is easier to correct for ionospheric delays, this means that 2 satellites near each other but sending on another frequency improve accuracy more.

Rephase:
The ionosphere changes the speed of the signals coming from the satellites, but the amount of delay changes with time and frequency.
An extra GPS satellite in the same part of the sky does little to improve accuracy.
An extra GPS satellite in the same part of the sky but broadcasting at another frequency does a lot more to improve accuracy as it can be used to calculate the ionospheric delay.

Last edited by icefest on Fri 25 Oct, 2013 7:23 pm, edited 1 time in total.

[stry]

My head hurts

[icefest]

My head hurts

Sorry, I've fixed it and made it easier to understand.