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Richard's GPS Ramblings

This is a very brief introduction to GPS devices and their use, it is not intended to be exhaustive and is based on my own experience of using a dedicated GPS unit for cycling and walking and a smart phone app for car navigation.

GPS Functions

These will include one or more of the following:

  • Viewing a map
  • Following a pre-recorded journey (with or without audible prompts and directions)
  • Creating an on-the-fly journey
  • Automatic recalculation of a journey when off-course
  • Recording a journey
  • Recording other metrics such as heart rate, cadence, power meter data

When deciding on a GPS device, the relative need and importance of the above functions should be considered as this will influence the cost. In addition, thought needs to be given to factors such as screen size, resolution & clarity in daylight and whether the screen should be in colour or black and white.

Device Options

It is normally the case that a (fairly inexpensive) supplementary memory card card can be used to increase capacity to hold maps and journeys, if the native memory of the device becomes too full.

  • Dedicated GPS units – there are very many models. Generally, the larger the size of the unit, the greater the accuracy of the GPS location. The penalty of this and of screen size is increased power demand from the battery and also a heavier device. Very often, the claimed battery life falls well short of the manufacturers figures! Maps are pre-loaded onto the device. Some units have touch and swipe screen capability rather than buttons, and they increasingly have bluetooth and other wireless technology connectivity to communicate with phones and bike sensors such as for cadence. Examples are -
    • Bike specific units eg Memory Map 270, Garmin Edge
    • Multi-activity units eg for hiking, running eg Garmin Oregon – these may have restrictions on the maximum number of waypoints that can be used for turn-by-turn directions
  • Apps for smartphones – Android, iPhone, Windows
    • Examples – Viewranger, Google, Strava
    • They can be either free for a 'Lite' version with enhanced 'Premium' features available for a charge, or simply as a paid-for app.
    • Map data can be either obtained live 'online' as the app is being used, in which case this will use the mobile phone's data allowance, alternatively this data can often be pre-loaded before use and is hence termed 'offline'.
    • There will normally be a minimum version of an operating system required to run an app. So if you have an old phone it might not be possible to load a particular GPS app
    • It should be noted that GPS navigation creates a high power demand on a phone battery.


  • Internal batteries, either –
    • A pack (normally Lithium Ion)
    • Or conventional batteries eg AA - the best type of rechargeable is Hybrid Nickel Metal Hydride eg Sanyo Eneloop. These have no 'memory effect' ie you can recharge them when they are partially discharged, also they retain their charge for long periods.
  • External battery pack, often referred to as a 'Powerbank', normally contain Lithium Ion batteries. There are numerous makes available, the cheap ones tend to expire after a few months use – so it is worth paying £20-£25 or so for a good one. A consideration when choosing this option is where the pack can be conveniently hung/stashed on the bike.
  • To extend their life, Lithium Ion batteries should be fully discharged at least every 6 months (I do this every 3 months).
  • A dynamo or solar cells can be used to top up the battery/power a GPS device.


  • Mounting arrangement for device on bike
  • Weatherproofing your device – all dedicated GPS units should be designed to resist water ingress, however the same does not obtain for smartphones, waterproof cases are available but touch screen functionality can be compromised depending on the design.


  • Paid for eg Ordnance Survey or Memory Map
  • Open source (ie free!!) eg Open Street Map. You need to check if your unit can be uploaded with this type of map ie that the correct format is available. There are quite a few different types (eg bike specific, contours), but the important thing to ensure is that the map is routable. I regularly upload the latest Open Street Maps onto my Garmin Oregon, both for the UK and abroad – we have used this device in several countries especially to follow walking routes. For driving in the UK and abroad, I load the latest appropriate Open Street Maps onto a smartphone app called Map Factor Navigator. This gives voice-guided prompts for road journeys.

Journey Planning & Editing

  • On the device/app. This can be fiddly and apps are generally better suited to this feature when used for multiple points making up a route.
  • Using a web site -
    • You don't normally have to use the web site for your device to plan a journey eg the Garmin web site.
    • The Garmin web site and software can be rather impenetrable and daunting, I prefer to use an alternative: Ride with GPS. There are many such web sites to choose from and most do a similar job.
    • It is possible to edit journeys that you create and also copy and edit other people's journeys and save them for your own future use.
    • When creating a journey, there will be the option to make it public, so that others visiting the web site you use can see it and download it.
    • Most web sites will allow you to search for other people's journeys and download them.
  • There are two main file extensions for journeys -
    • .gpx includes info for the journey (a Track) or in addition, including turn by turn directions (a Route)
    • .tcx in addition to .gpx data this includes additional data with each track point (e.g. heart rate and cadence). The format was created by Garmin for their devices which record fitness metrics. Note that this format is the better choice for several Garmin Edge devices.

Recorded Journeys

Once you have returned home after your ride, there is the opportunity to record your accomplishment for posterity, either privately or publicly. You open your journey planning web site, then connect your device to your computer and download the GPX/TCX (or other format) file.

  • Metrics will be calculated for example - distance, average & maximum speed. In most cases, comparisons with other cyclists' times of segments (parts) of the journey will be displayed.
  • Examples of these web sites are Strava (the de facto standard) and Ride with GPS.
  • Your previous efforts on segments can be displayed so that performance over time can be compared.


  • If you require assistance with GPS, please mail me and I will try to put you in touch with someone who has the relevant knowledge.
  • My email is: cholladua(at)

Ted's GPS Ramblings

A GPS (which stands for - Global Positioning System) truly is one of those devices you never knew you needed....Mine takes me walking every week whether it's guiding me along a track, or recording where we've been, takes me cyclimg every week, sometimes guiding me, or just recording the miles and elevation covered, and has taken me to and from the Black Forest by motorbike. So it really is well worth making friends with your GPS.....

It's always good to read different perspectives on any complex topic and GPS's can be tricky. But if you can use a smartphone, for example, you'll easily be able to use a GPS. Using it is actually quite simple once you have the basics, but you do need to 'tell it' a few things along the way.

I had already written the 'bones' of the notes when Richard beat me to it, so here's my 'take' on GPSs, shared with you for what it's worth..

What Can I Do with a GPS?

Well, at its very basic level, a GPS will find your location and show you exactly where you are on a map. It may very well become the piece of kit you can’t do without, as it can do far more than that:

  1. Locate you on a map (known as a GPS lock)
  2. Record your journey in all of its detail (details depend on model) in a file called the current track so you can look at where you went later on your pc - how long it took you, how fast you went, how high you went etc. Most GPSs will have a trip computer, and a current track facility.
  3. If you know exactly where you want to go and how you want to get there (eg an off-road walk), it can put your pre-recorded track on a map for you to follow (typically the magenta line)
  4. If you know where you want to go, but you’re not too bothered by how to get there, put your pre-recorded route (note the difference from a track) on a map and allow you to follow it, with, or without turn-by-turn instructions.
  5. If you know where you want to go but haven’t been able to pre-prepare a route or track, it will allow you to set up a waypoint or two (simply where you want to go), and route you to it / them.
  6. If you’re stranded in some foreign part and are need accommodation, food or anything else, your GPS will find what you need and route you there (Points of Interest, or POIs). This depends on the amount of data on your mapset.
  7. Latest GPSs have good wireless communications with the outside world so you can share any of your data or photos (some GPSs include cameras) on Facebook, Strava and so on.
  8. Some GPSs also have cameras.

Why a GPS, not a Smartphone ?

Many people use smartphones quite happily to do GPS duties, but there are some advantages with purpose-designed GPSs. These advantages can be quite marginal or highly significant depending on the use you have for a GPS:

  1. Battery life is usually better with a GPS unit. My GPS batteries will last a full 2 days, whereas most smartphones will struggle to last a day without the support of an additional ‘donkey’ battery or other charging device on your bike.
  2. You will usually get a quicker (and stronger) 'GPS lock' on your location using a GPS. If you’ve flown to a foreign part, even a GPS can take some minutes to ‘find you’ and place you on the correct map. This can be important in cities, amongst tall buildings - even GPS's can struggle here.
  3. GPSs are usually designed to be outdoors, so are often waterproof. Smartphones notoriously aren’t. Look for the GPS's 'IPX rating' and Google what this means. Some are splash-proof, IPX5 or so, and some are guaranteed waterproof under pressure. The bigger the IPX number, the better the water-proofing.
  4. Your GPS will be designed to be attached to something, depending on model. So for a bike, purpose-designed GPSs will be able to be fixed reasonably securely to a handlebar. It’s best also to have a lanyard, too with the unit, so you can tie it on – many are the people who have hit a pothole and had the unit jump off. Smartphones are just not designed to attach to anything although there are some work-arounds.
  5. GPSs are usually a bit more rugged that smartphones and mine has survived jumping off the bike at speed.

What’s a Track and What’s a Route ?

Tracks are ‘pictures’ that you can put on your map. They won’t change regardless of where you go with the GPS. If you go off a track, you go off it and have to find a way back to it. This is important if you are following an audax track because you probably don’t want to deviate from it.

Routes are active. The GPS is calculating all the time the best way to get you to your destination. It can give you turn-by-turn instructions, and if you deviate from your set route, the Garmin may well re-calculate it with a new set of instructions and a completely different route. This is fantastic in a car because it means you can never actually go wrong – you’ll always get to your destination. On a bicycle this can be a bit worrying at times. And walking, you may find that your mapset does not allow the GPS to route you over footpaths, so beware.

To be safe I nearly always now navigate using a track, especially when walking, unless I am completely lost and want the Garmin to take me somewhere !! Confusingly, both route and track files are .gpx files, so you can’t tell which they are just by looking at the file name on your pc. I now keep routes and tracks in separate folders on my laptop, and sometimes add ‘rte’ or ‘trk’ to the filename.

You can generate tracks or routes from websites such as, BikeHike, RidewithGPS etc, or from apps on your computer or smartphone such as MemoryMap (OS mapping, which is what I use). I've always used the .gpx file format though.


A lot of mapping is available free of charge through the OpenStreetMap project. These are user-compiled maps, ordnance survey-based but the level of detail varies immensely depending on how much use there has been in the area you’re interested in. A website that we find very useful is, specifically designed to bust the myths around getting your rather user-unfriendly Garmin to do what you want without paying out shed-loads of cash. The guy who operates this also modifies and updates the OpenStreetMap mapsets and some are available free off his website, whilst others where he has added functionality to the OSM he charges a small fee for.

If you’ve got lots of dosh, though, you can buy full OS mapping for the UK, or the Garmin version, but this will be in the order of an eye-watering £250. The beauty of the free maps is that they are also available for other countries around the world, so when we went to Thailand we had full mapping – you don’t get that with your £250 OS map of UK!

Managing Garmin Map Files

Garmin map files are .img files, and they all have ‘GMAPSUP’ as part of their names (this might be changing with newer units) – I don’t think this is case-sensitive. Leave this bit out of the filename and your Garmin may not recognise them as maps. The Garmin Dakota looks for the maps on the micro-SD card, not, it seems, its own internal memory, but units vary. If true for your unit, you need to set up a folder called Garmin on the card, and put your map files in it. You can do this using your pc – you should have a card-reader slot. But if the card contains any other folders, my Dakota won’t 'boot'.

Quirks of Garmins and Mapping

The software is American, so 'toll roads' are motorways, and Devon country lanes come under either the 'off-road' or 'unmade roads' or ‘carpool lanes’ categories, which also includes bridleways and some footpaths. So if you use the unit as a 'satnav' for bike routes - which you can do - make sure you review the route before you set off to ride it. You can get over this problem, if the route goes over bridleways and other tracks, by inserting waypoints en-route to force the route to change to something more workable. Note also that you don’t need any Garmin software (Basecamp, Connect) to do any of this basic stuff.

Managing Track Files

If you use the tracking function, you’ll soon generate lots of files, so you’ll need your own system of naming. My unit has a current track folder, and an archive, both residing on the Garmin’s internal memory. It’s best to keep all tracks except those you are currently using, in the GPS’s archive and you can easily later transfer the files to your pc., to un-clutter your GPS I’ve learnt to prepare tracks in advance, and when I walk or cycle them, I make sure that tracking is on, so that the Garmin records what actually happens on the ground. For example, if a footpath has been diverted, the current track will record this. When I’ve done my walk or ride, I name my current track with the name of the track or route I’d prepared previously. I also added a date field, which tells me that I’ve walked or cycled it, so it’s not one off the map, and I can easily refer to a diary, or photos, for full recollection later I delete the original pre-prepared route or track, and store the track I’ve recorded and named - or that's the idea !!

My unit can store up to 200 tracks or 50 routes, but it gets grumpy if the memory is getting full. So it’s best to keep only a few on the unit. When it gets flustered, the display goes off and I have to switch it back on again and it always happens at times when I need it most !

Dakota 20 Specifics

Dakota is touch-screen. Not all GPSs are. It can be used with a gloved hand. It’s waterproof (IPX7) so you don’t particularly need to keep it out of the water or rain, although it can make reading the screen difficult The screen is easily scratched, so screen protectors should be used.

All the functions are accessed from icons on the screen (or desktop) which is the first screen you see when the unit is switched on. Use the scrolling arrows to see more icons. You can customise the desktop easily with those icons you find useful, and dump those you don’t. You can vary the strength of the backlight by quickly pressing the on/off button once if the screen is already lit, or twice if it’s not lit, and pressing the + or – to alter the brightness, then quickly pressing on/off to go back to the first screen. At any time if the screen is not backlit, the first tap on the screen or on/off always lights the backlight, so it’s the second tap that executes instructions.

There are 3 key functionalities which work independently:

1) The trip computer. This works automatically and so you don’t have to switch it on or off. But you do have to set it to zero at the start of your ride / walk / event, otherwise you get nonsense data Setup / Reset menu. Also, when you’ve completed your event you have to read off the data you want, there and then, or switch the unit off, otherwise it’ll continue recording until you get home....even if that’s by car

2) The Current Track. This simply tracks where you go and also gives you data about your track. Part of this function duplicates the trip computer, and as these work independently I’ve found that they come up with slightly different results – rarely much different. The current track has 3 settings in the Setup / Tracks menu, 1 ‘off’, 2 ‘on but do not show on map’, or 3 ‘on, show on map’. If you use this function (and I find it very useful) then you must remember to clear the current track register at the start of your event, (in the Setup / Reset menu) AND to switch it off at the end.

3) The SatNav / GPS function. This is comprehensive in Dakota.

a. Routes - You can put in a ‘Route’ and it will give you turn-by-turn instructions. You can also generate your own route or track on the Garmin, too, from places you want to go to called ‘waypoints’. You can generate waypoints any way you like, by a pin in the map, or from POIs (points of interest) listed on the Garmin, or ‘Cities’ (villages, towns etc). b. Tracks - You can also put in a track and this will put a red line (or other colour of choice) on your map for you to follow.

SD Cards, Batteries, Charging

The map-sets are recorded to the micro SD card on Dakota. That means if you want a better map-set than the standard base-map (which is useless for practical purposes) you need a micro SD card, unless you've bought a set of maps already on one. The maps don't occupy as much storage as you might think, with the UK Open-Street-Maps occupying less than 1GB on the micro SD card, although later sets are tending to be bigger files. Thus, unless you are planning to store lots of maps, a 4GB card would be ample. You certainly don't need the 16GB I opted for ! The more detail you have on the map-set, the longer it takes the unit to load, which can be a pain, so be careful about opting for full Ordnance Survey mapping, or keeping lots of mapsets on your GPS – there’s a trade-off.

I like my unit because it uses ordinary AA batteries – so easy to buy if you run out, or as I do, carry a few fully-charged with you, so I’ve never run out of power. I use a set of 2 Sanyo (or Panasonic) Eneloop batteries 1900 mah versions. These batteries are bomb-proof and will withstand all sorts of charging abuse. Remember to check that the unit knows what batteries you’re using. It’s best to use a dedicated charger. Apparently you can get 'higher powered' batteries, too, such as 2400mah, but blogs seem to report inferior performance in these applications, and the 1900 ones will give you about 2 days life as well as being robust to abuse like part-charging.

With built-in batteries, you don’t have a lot of options, typically add-on batteries, or a spare charged one.

Profiles – Dakota is designed to be used for walking, cycling, flying, sailing and as a car satnav. Each use needs a different set of maps and settings and these are called profiles. The 'profile' manager allows you to specify what settings you want the unit to use for each use you might give it. This is very useful, but be prepared for it to take quite a long time, and practice, for you to be able to use fully the functionality of the unit. It pays to ‘play with it’ a lot.

There's lots more stuff, but hope this helps.

Principles Bike Maintenance Skills GPS
New Riders Group Riding Shouts and Signals Leader Information Tips and Maintenance Resources
CTC Exeter Sunday Rides Coffee Pots Bike Bus Devon News