GPS receivers

[Adi007]

The geocaching thread over at http://www.bushcraftuk.net/community/showthread.php?t=1101 has meant that I've had a few PMs relating to GPS receivers. As there seems to be a lot of interest, I thought I'd create this thread so that you can post your GPS related questions - I've been using GPS receivers for over 5 years extensively in recreation for a variety of applications and I'll do my best to answer your questions!
I look forward to your posts!

 

[Martyn]

OK, I'll start with an obvious question, which is probably rather stupid, but as I know absolutely nothing about them, it seems logical to me. Which one is the best? Accuracy, reliability, robustness, price etc.

I might be persuaded.

 

[familne]

Good idea Adi!

I've been using GPS in my work for the past seven years or more. I have tried several models but keep coming back to Garmin. For me they are the most compatible with other computer software (GIS etc) and equally relaible in the field. I like the way you can automatically update the software from the Garmin website without having to buy additional programs or send the unit off e.g Silva. I've recently got hold of the Geko 301 which has all the features of the Etrex Summit but is also EGNOS enabled - It's an excellent unit, very easy to use, small and compact. Garmin customer service is also excellent (unlike some others e.g. Silva)

There is also a thread on the OM forum regarding GPS:
http://www.outdoorsmagic.com/forum/forummessages/mps/dt/4/UTN/3682/srchdte/0/V/1/SP/

 

[Adi007]

Good question Martyn!

As for accuracy, since the system is a military system and as such the signal processing code is all standard, accuracy between one unit and another will be the same. Under clear skies all units should give you a position fix accurate to about 8 - 10 m. Under tree cover or on the side of hill or mountains or in valleys where part of the sky is obscured or reflected signals received from the satellites (called SV - space vehicles), then accuracy can drop. Trees are a particular problem because the chlorophyll in the leaves absorb the microwave signal at the freq that the GPS system uses.

If you want more accuracy, you now have the option to go for a WAAS GPS receiver (Wide Area Augmentation System). this receives an additional signal from a European satellite in orbit and can give your position to about 1 - 3 m (I've had some good accuracy with this).

But for accuracy of a standard GPS receiver, 8 - 10 m can be expected from the cheapest to the dearest - I've never seen any significant variation in accuracy related to price.

Best brands for reliability and robustness are Garmin and Magellan - I've standardized on Garmin because I found that their customer service is excellent.

Price ... begins at about £80 but if you'd like the ability to connect to a PC or PDA, go for one with a port on them ... worth the extra tenner i think!

The eTrex series by Garmin offer a full spectrum of price and features ... with the higher end receivers having barometers and electronic compasses build in. Another good range (albeit with fewer features) is the Gecko range.

Best prices ... www.globalpositioningsystems.co.uk

OK, I'll start with an obvious question, which is probably

rather stupid, but as I know absolutely nothing about them, it seems logical to me. Which one is the best? Accuracy, reliability, robustness, price etc.

I might be persuaded.

 

[Adi007]

Good points there ... Garmin and Magellan units can have their software updated by the user (although I've heard of quite a few Magellan units being messed up by this while I've yet to come across a Garmin unit fried by the update).

My model of choice is the Garmin Vista ... It's a great unit! All I'd suggest as extras are a set of rechargeable NiMH 2100 mAh batteries ... feeding it on Duracells can be expensive!

I've used the Geko a bit at a Geocaching meet and thought it was a well featured unit ... but I still like the slightly bigger screen of the etrex ... although if size/weight is an issue, the Gecko is a good unit.

Good idea Adi!

I've been using GPS in my work for the past seven years or more. I have tried several models but keep coming back to Garmin. For me they are the most compatible with other computer software (GIS etc) and equally relaible in the field. I like the way you can automatically update the software from the Garmin website without having to buy additional programs or send the unit off e.g Silva. I've recently got hold of the Geko 301 which has all the features of the Etrex Summit but is also EGNOS enabled - It's an excellent unit, very easy to use, small and compact. Garmin customer service is also excellent (unlike some others e.g. Silva)

There is also a thread on the OM forum regarding GPS:
http://www.outdoorsmagic.com/forum/forummessages/mps/dt/4/UTN/3682/srchdte/0/V/1/SP/

 

[Chopper]

I have been using GPS for about ten years and love it.
I started with a Magellan gps 2000, good bit of kit although as with all early products quite basic, it did however guide me through the gate to the farm we camp on some 300 miles away, the main thing to remember is that unless you are a map based gps the unit will always point directly at the target grid referance and give you a distance to be covered as the crow flys (in a straight line), ok if your travelling in a straght line to your target but can be very misleading if you are using it in your car, main draw back with this was the battery life, eight hours from 4 AA's.
I, a few years later upgraded to a Garmin Emap, and what a tool, map based, I now have world wide street level software, a 128meg memory card (got 95% of the UK street plan on it), power lead to run from the Lannys power supply and 17 hours from 2 AA's.
Because it is map based you can actually plan your journey street by street, route planning can be planned on you PC (easier than doing it on the GPS unit, but can be done if needs must) and uploaded to the unit.

One product that Garmin have in the States (but not here yet :-( ) is the Garmin Rino 120, a GPS and pmr radio all in one, the thing that I love about this is the fact that it will transmit you location to the other units in your group so that you can see each others locations on the screen of your unit, and they can see you on theirs, great for keeping an eye on your kids (and my Scouts). Unfortunatly the position sending fearure is not yet legal in the UK, and until the Radio communications agency realises the incredable safety featurs of this unit and gets the law changed we wont see it here, it is selling like hot cakes in the US and so it should, but dont be tempted to order them from over there as:

1, They are illegal to use in the UK.

2, The US pmr frequencies are not legel over here. US is on a different setup to the UK that will never be compatable with the UK, so your nice new Garmin Rino's will not be able to talk with any Uk spec pmr radios that you may already have.

3, If you do get tempted and get caught you wont like the fine of watching the judge using your nice new kit as a gavel block.

Be patient and play the waiting game and hopefully we may see them over here. :-D

 

[Adi007]

It's worth adding is that these GPS SV (space vehicles) orbit the Earth at an altitude of about 14,500 miles and each orbits the planet twice a day.

There are always at least 24 active satellites with a minimum of at least 3 above the horizon at any one time. Usually there are at least 6 visible.

The GPS signal is not affected by adverse weather.

Here is more information on the GPS system and the constellation of GPS SVs.

http://www.trimble.com/gps/

 

[Adi007]

If you plan on using your GPS in a car then you might also want one of these:

http://www.pocketgps.co.uk/reradiating.php

Depends on the car but I find that even if you don't have metalized windows in increases the signal strength dramatically and also make the GPS work better and be more accurate if you are driving along forest roads or valleys.

 

[mercury]

I bought a basic yellow garmin etrex last week and its amazing

It can keep sat loc in my car , in my pocket , I can connect it to my laptop and run it in my car

This weekend I'm taking the kids up to the North York moors to go walking and camping

The most exciting thing is the fact I can connect it to Autoroute, plot a course to the next continent and just follow the flashing icon

Brilliant

Oh and I use it for the geocaching malarky too

 

[Adi007]

Great bit of kit ... and if you have figured out how to combine it with mapping, you're onto a winner!

:biggthump

 

[Doc]

Interesting to hear about the Garmin Rino. Shame it's not legal here.

As yet, it is not legal to transmit data on PMR 446 radios. You can transmit data (including position reporting data from a GPS) on amateur radio (with appropriate license)

APRS (Automatic Position Reporting System) was invented to allow Amateur Radio operators to utilize Packet Radio (AX25) to exchange data over a wide area network of stations. That information is then displayed in a graphical format, super-imposed onto maps using suitable software. The information could include:

Position
Speed
Course
Station Type
Weather
Objects
Messages & Email
One of the most popular uses of APRS is to incorporate a GPS receiver to a radio and frequently beacon a Mobile Station's position into the network allowing it to be tracked to a high degree of accuracy. Originally APRS users were connected by Amateur Radio, but as time has gone on, many people are also using Internet Gateways (Igates) allowing them to use the Internet as their medium.

The American hams are mad keen on this. Loads of stuff about it on the net.

 

[Adi007]

Yeah, now that Garmin have ironed the bugs out of the Rino it sounds like a good bit of kit that could save lives.

 

[leon-1]

I have used Garmin Gps in Canada, U.K., Kenya and other places, but I have also used Trimble, Magellan(trailblazer and GPS2000) and can honestly say they are a usefull aide to navigation.
But we should never forget that they are just that an aide to navigation and no substitute for standard skills using map and compass.

I will echo the fact that of all the GPS that I have used, the best have been made by Garmin and I have had good customer service from Garmin (when the internal lithium battery died they replaced the unit there and then).

 

[Adi007]

I will echo the fact that of all the GPS that I have used, the best have been made by Garmin and I have had good customer service from Garmin (when the internal lithium battery died they replaced the unit there and then).

They did the same for me too at no cost for a unit that was well outside of the warranty period. Excellent company to deal with!

 

[Chopper]

ORIGINAL CONTENT REMOVED AS I DONT WANT LOADS OF PEOPLE TRYING TO GET FREE KIT


Lets just say that having both Garmin and Magellen GPS units and having delt with both companies customer services.
Garmin is very good, but Magellan is 500 times better.

:-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D

 

[Adi007]

Might have to try that wioth my old (now useless) Magellen 310!

 

[leon-1]

Hey Adi have you ever shopped at Gaynor Sports, I know it is a bit up country from you, but they do have some good kit at cheap prices (Lowe Alpine Flash Jackets £100 cheaper).

Well currently they are having offers on GPS http://www.gaynors.co.uk/acatalog/Catalogue_Contents_Navigation_Equipment___GPS_4.html have a look.

Also one of the guys mentioned memory map they appear to be selling that as well.

 

[Adi007]

Good prices! Thanks for posting that!

 

[Adi007]

With all this talk of GPS and connectionn ports to the PC I thought I'd add that one of the dearest parts to a GPS is the communication cable ... you'll pay between £20 and £30 for the geniune article. However, here is a place that sell good quality cables for connecting GPS to PC and iPAQ:

www.lynks.co.uk

 

[leon-1]

No probs. Check out the whole site. I was up there a few years ago when they had a delivery arrive, about £3,000,000 worth it lasted for about a week and then they had to re-stock.

Edited

Thanks for the link Adi, I have been after a a cable for an old GPS12XL for a time and most of the time they have been a lot more expensive then the ones on the above site.