This is the web site of
Penrith Ramblers, Cumbria, England.
WELCOME!
Penrith Ramblers
 
Navigation. (Map, Compass and GPS.)
Table of Contents.

1. Introduction to the Ordnance Survey grid reference system.
2. How to Find an Ordnance Survey Grid Reference.
3. Check out a grid reference.
4. Getting a bearing in relation to Grid North.
5. How to travel to your destination.
6. GPS - a brief insight.
  Introduction
  Accuracy of a GPS
  Running a GPS
  GPS software
  Plus points of GPS
  Tips on use of GPS
  Thinking of getting more than a basic GPS.
  GPS in Wrist watches, smart phones & Personal Digital Assistants, (PDAs).
  Free GPS Programmes on the Internet.


  1. Introduction to the Ordnance Survey map reference system.

Generally locations on the earth are given by their latitude and longitude, in that order. The lines of latitude are a series of circles of varying radius, the largest being the equator. The circles are parallel to each other, with their centres on the earth's axis. The lines of longitude run at 90 degrees to the lines of latitude, and are furthest apart at the equator and meet at the North and South Poles so the lines of longitude are not parallel. The O.S. grid, or National Grid for England, Scotland and Wales represents a fairly small part of the earth's curved surface as a flat surface, with parallel vertical grid lines, one of which points to TRUE North. This is one of several datums in use throughout the world. Britain has just the one, which is a Transverse Mercator Projection based on an ellipsoid, representing the Earth, known as the Airy 1830 ellipsoid OSGB (1936). (The GPS uses a more accurate ellipsoid known as WGS80, which is 1km wider at the equator and flatter at the poles. The Navy has recently changed to ellipsoid WGS84.)
The grid is a rectangle 700km x 1300km and has a 'false' origin at 49° 45' 58"N 7° 33' 23"W, so as to include the Outer Hebrides and to eliminate negative numbers. (The grid for Ireland is separate.) The National Grid is split into 91 squares each100km x 100km. These squares have 100 horizontal and 100 vertical grid lines 1km apart drawn on them. These lines are numbered 00 through to 99.
The 100km x 100km squares are given letter codes.To Top

To Top
The diagram above shows the 91 large squares of the O.S. grid, together with their letter codes laid out flat. Seen through this is a portion of a globe showing the corresponding part of the British Isles, which the maps using the O.S grid cover. The grid squares are angled about the false origin, so that a vertical line, in the middle region of the grid, lines up with a line of longitude. The line of longitude chosen is 2°W and the corresponding vertical line on the OS grid is the only one, which passes through True North. This line stretches from Poole in the south to Berwick on Tweed, passing through Tewkesbury, Walsall and Skipton. The grid lines to the west of this line will point to the west of True North. Also the further west (and north) one goes the larger the angular divergence from TRUE North will be. It can be seen that nearly all of Scotland is to the west of 2°W. To the east of this line, the reverse happens and the grid lines will point to the east of True North.
The reader might consider why the line of longitude 0° was not chosen to be the only TRUE North on the O.S. grid. Also you may be tempted to try to work out which area any the letter coded squares represents from the diagram, This is not possible, with any accuracy, because the land in green is curved, while the grid is flat.

The Penrith Ramblers walk mostly in the Lake District, The Eden Valley, The Howgills, The Dales and The Pennines. The squares of interest will be the square covering the Lake District, which is NY and adjacent squares, which are given in the diagram below.
To Top


The vertical lines are known as Eastings and the horizontal ones are known as Northings. The Grid Reference takes on the form: letter-code Easting Northing. (Note that the vertical reference now comes before the horizontal one, the same as locations specified using longitude-latitude.) The way to remember is that Easting comes before Northing in the alphabet. The vertical line parallel to true north is the Easting 000 in square SZ and will be the Easting 000 in the squares SU, SP, SK, and so on. Continuing upwards, you can see that this line runs to the east of Penrith along the Easting 000 in square NZ, which is the right hand edge of square NY.

  1. How to Find an Ordnance Survey Grid Reference.

Although far from essential, a compass with Romar scales is a convenient instrument to estimate the O.S. grid references. Both the 'Silva 54 combi' and the 'Silva expedition 54' have them.

On a 1:25,000 scale map the interval between lines representing 1 km are 4cm and on a 1:50,000 these intervals are 2 cms. The Romar scale on your compass can be used to subdivide these intervals. Splitting the interval into tenths can usually be assessed by eye. Using the Romar scale on the compass, splitting into hundredths is just possible, especially on the 1:25,000 scale map, as in the diagram below.


To Top Romar scales on compass base plate.

Using Romar scales on compass to find map reference.To Top


The Romar scale for the 1:25,000 scale map are the two sets of graduations at right angles on the outer edge of the baseplate of the compass. Place the junction of these graduations over the location on the map, whose grid reference is required, as shown in the diagram. Write down your estimate and check your answer here. 
If the values are rounded to the nearest digit, then the 6 digit answer will be within ±50 metres and the 8 digit answer will be within ±5 metres.
The Romar scale for the 1:50,000 scale map is placed away from the edge of the baseplate and so one should try to look directly over the graduations to avoid parallax errors.
Some compasses have baseplates with the Romar scale in one direction only. This is not so convenient because the baseplate has to be turned through 90° between measurements.

A convenient device, which can be carried in your top pocket, is a grid reference finder or Romar. This is made of transparent, rectangular plastic and has square sections calibrated in 1 : 25000 and 1 :50000 Romar scales. For more information go to Where-Wolf.

To Top
  1. Check out a grid reference.

  • Do you have a grid reference relating to a (possibly unknown) location in the region, where the Penrith Ramblers hold their walks?
  • Do you also have no idea which map to use to find where this location is? (This can occur if you use the 'Find Place' facility with mapping software on your computer. You get a grid reference which is not covered by your software but have plenty of paper OS maps you can refer to - but which one?)
  • Using the grid reference checking facility. on this site could solve your problem and save you unfolding several maps before you find the right one. (It is often used for checking grid references before they are incorporated into the mapping facility on this site. )
    The facility should work on most modern browsers, if Javascript is enabled.
    1. Click on the underlined link above.
    2. Enter the grid reference.
    3. Press the submit button. Silly entries will be rejected. If the grid reference is on the map, it will be plotted. However, because of the small scale of the maps, the spot can only give a guide as to the position of the location.
    4. If the spot appears to be plotted correctly, click on the button 'Get OS Map Title' to find which OS map the grid location will appear on.
    5. If the location seems wrong, check the grid reference letter code and check if the eastings and northings are in the correct order.
To Top

  1. Getting a bearing in relation to Grid North.

  • Find a flat surface, out of the wind if possible, and place your map on it, having opened the map at the correct place.
  • Estimate the approximate direction of your destination from where you are, i.e. is it west? south-east? etc. This will be used as a check later.
  • Now place your compass on the map with the 'direction-of-travel' arrow pointing roughly in the direction you wish to go.
  • Line-up the long edge of the base plate of the compass so that it runs from your present position, PP, to your destination, D, see diagram below.
  • Rotate the compass housing (coloured green), so that its arrow (coloured yellow) points to the 'North on the map' or Grid North. (On O.S. maps this is parallel with the vertical edge of the map.) The North /South lines on the base of the compass housing should now be parallel to the North/South grid lines on the map.
  • The bearing from Grid North, is shown on the index line, which in the diagram is about 113 degrees. (You could set up your own compass and check if you agree - each small division is 2 degrees on the compass illustrated.) The position of the compass needle at this stage is immaterial.
To Top Image of compass being used to find a bearing.

Finding a bearing in relation to Grid North.

  1. How to travel to your destination.

As you are going to use the compass needle as your reference direction, when you travel, you have to convert your bearing in relation to Grid North to a bearing in relation to Magnetic North. You will be aware that the bearing from magnetic north varies as the position of the magnetic north varies, due to the movement of the molten magnetic core of the earth.
To Top
The 3 Norths.
The three Norths.
The direction of the Magnetic North and Grid North relative to True North depends on time and place.
The diagram is that for the Lake District at the start of the 21st century.

At the moment Magnetic North is to the west of True North in Britain, (though on the other side of the earth, say in Canada, it is to the east of True North). This angle is termed the declination.
The position of Grid North in relation to True North depends on where in Britain you are. The vertical line in the centre of OS map OL4 (NW lakes) is 1° 4' west of True North. For OS maps OL5 (NE Lakes) and OL21 (South Pennines) the corresponding angles are 42' and 4' repectively. Move further east and Grid North would be to the east of True North. (The value will be zero on the line of longitude 2° W.)To Top
Figures quoted by OS maps for the angle between Magnetic North and Grid North vary depending on the age of the map. One version of OL5 quotes a value of 5° in 1999, while an earlier version quotes 5° in 1997. Both state that the angle reduces by about ½° every 4 years. Thus a suitable value to use would appear to be 4° (or 3° 45') at the time of writing , i.e. 2007. An accurate value for the angle between Grid North and Magnetic North for any location in the British Isles can be found by going to the Geomag website. The value given for Penrith for July 2007 is 3° 7', a difference of more than ½° compared with the value derived from data given on OS maps. Fortunately it is unlikely that this small difference will prove to be of practical significance given the difficulty of walking on a bearing to this degree of accuracy using a simple compass like that above.

For this instruction, we shall use a value of 4° but you will need to amend this as time goes by. In a few years time the value will be small enough to ignore and by 2050 it should be a significant negative value and the rotation of the compass housing, mentioned below, will be clockwise - not anticlockwise.
To Top
  • Rotate the compass housing anticlockwise by 4°. This adds 4° to the reading and compensates for the difference in the angles between Magnetic North and Grid North in the British Isles.
  • Now hold the compass, so that it is flat in your hand, and turn yourself until the red end of the compass needle and the (yellow) arrow head in the compass housing line up. The 'direction-of-travel' arrow, marked on the clear base plate, now points in the direction of your destination, (D).
  • You should now try to locate a fixed distinguishing feature or 'marker' such as a tree, a bush, a rock or even a clump of grass on the line of the 'direction-of-travel' arrow. Check that this is roughly in the direction that you estimated at the start. You don't want to be going in the opposite direction to the one you want! If okay, you now head towards your marker. If you lose sight of your marker, due to undulations in the ground, check that the red end of the needle and arrow head in the housing continue to line up as you move. Always be careful not to turn the housing in relation to the baseplate.
  • When you have reached the first marker, repeat the process until (hopefully) your destination comes into sight.
To Top

  1. GPS - a brief insight.

Introduction.

The development of GPS units is fast moving and no attempt is made here to describe how to set up and use the numerous innovations on the latest models or even implement the user interface of basic models, which tend to differ in detail, even though their operation is similar. It is necessary, therefore, to consult the manufacturers manual on how to access the facilities provided by a GPS, how to select a suitable grid system and north reference, how to enter/delete waypoints, how to load and access/edit routes, etc. Instead, the more useful facilities that a handheld GPS can provide are discussed, besides providing information on accuracy, safety and some tips on use in the fells.


Before starting it is necessary to be aware that a GPS receiver needs information from satellites orbiting the earth, which tells the receiver where the satellites are. There are 24 satellites in precise orbits, transmitting information as they circle the earth, each doing this twice in less than 24 hours. This facility is provided by the 'US Department of Defense'. Your GPS receiver picks up this information and with the aid of a built-in clock and computer, it determines the time interval between the time the signal was transmitted and the time it was received. From this and knowing the speed of the signal, (which like all electro-magnetic waves is that of light), it calculates the distance of the satellite from the receiver. If there are 3 satellite signals, the receiver uses triangulation to calculate its location in two dimensions (latitude and longitude), With 4 satellite signals it can add altitude as the third dimension. Many receivers do not calculate altitude but use any extra signals to improve on the accuracy of the calculated position.
The latest GPS units have several parallel channels and these can process signals from several satellites at the same time, rather than processing the signals one after another, (in series). This helps reduces error, whichs averages about 10m from the stated position. There are GPS receivers with an average error of 3m. These make use of WAAS ('Wide Area Augmented System').
To Top
Accuracy of a GPS.

The accuracy of a GPS can be affected by a number of factors, all leading to an increase in error of the calculated position.
  • The accuracy of the built in clock has to be high. However it is not an atomic clock, unlike those on the satellites, so it is likely to be slightly out.
  • The speed of the signal can be affected by the atmosphere through which it passes by reducing it. This means that the calculated distance of the receiver from the satellite will be higher than it should be.
  • The orbits of the satellites are not perfect, even though adjustments are made to them during their time in space, again adding to error.
  • If reflected signals are picked up by the receiver, errors can result because their paths will be longer than those coming directly. Reflections can come off rock faces in the countryside or tall buildings in cities.
  • Calculations are less accurate when the signals are coming from satellites that are close together rather than when far apart.
  • As already mentioned, the more satellite signals the better, so errors can increase if there are only 3 or 4 satellite signals being received.
  • The GPS requires strong signals and early receivers could be badly affectd by foliage. Deep valleys caused poor signal reception. More modern GPS units have improved signal reception and amplification, so that foliage is less of a problem.
At one time the 'US Department of Defense' deliberately degraded the signal, known as L1, which was for civilian use. (Signal L2 was for the military.) This was done so that any foe using it was at a disadvantage. This action ceased in May 2000 and so one error source is no more.
When one considers that a TV signal often has 10,000 watts of power, is only up to 30 miles away and is received by a dish antenna usually over 1 foot in diameter on your roof and compare this with the 50 watt signal coming from a satellite 11,500 miles above the earth and is received by a small antenna inside a case, it is a wonder that any useful signal is received and the error is as small as it is!
For most civilian purposes an error of about 10m is no problem, e.g. a tent one might be searching for is easily visible from 10m and being at most some 20m from someone injured in dense undergrowth, who you are looking for, is better than having to search a whole wood. It is fortunate the user does not have to worry about the sophisticated computer inside the receiver, which has to deal with the complex science and mathematics and can concentrate just on using it.
To Top
Running a GPS.

Here is some information to help you get the best out of your GPS.
  • When starting a walk, a fully charged battery should be installed and a second charged battery in a waterproof container is advisable, especially if the unit is to be switched on for long periods.
  • Unlike a map but like a compass, it does not give positions of possible hazards, such as pot holes, steep cliffs, etc.
  • Cheaper GPs receivers do not indicate a true direction, while they are stationary, so you need to walk a number of steps at a reasonable speed in a straight line to get an accurate reading - something your companions may not understand, if they do not use a GPS.
  • After stopping on a route, it is possible to retrace the route inadvertently rather than proceed further along it, so check that the numbers associated with waypoints continue in the same direction before and after the stop. This error is easy to do in dense mist. (It follows that, if you are new to an area and you have installed a circular route, which you intend to follow, check that you start in the direction you intended! )
  • If left off for about 4 hours or more, the information, which tells the GPS receiver, where the satellite should be at any particular time, (known as ephemsis data), will be out of date and the GPS has to reload this information before it can calculate its position. This can take a few minutes. A page on the GPS can be selected, showing the progress of this process, the heights of vertical bars varying according to the signal strength of each satellite and changing colour when the full orbital information has been received. This is termed a 'cold' start and does not refer to the temperature of the GPS! A 'warm' start occurs when the orbital information does not need updating and the position can be calculated immediately.
Clearly, to rely on a GPS as the sole navigational aid is folly and may even been fatal. (See below.)
To Top
GPS software.

GPS software has been developed to enhace the operation of a GPS which can bring an extra dimension to a walk, e.g.
  • they allow you to enter a long list of waypoints into your PC and then upload them to your GPS, quickly and accurately - much better than doing this manually.
  • they allow you to plan a route on your PC, knowing its length and cumulative ascent/descent and upload this to your GPS, which you can walk later. This is useful, for those planning to do a walk they have not done before.
  • they allow you to download a tracklog of a walk, (perhaps a recce), amend it if necessary and save it as a route for future use.
Two popular Digital mapping companies are 'Anquet' and 'Memory-Map'. These use Ordnance Survey maps under licence. You can check them out before buying by requesting a demonstration CD Rom or visit their websites. Free software is also available , which can be downloaded from the internet but this does not have maps pre-installed. You have to do this yourself. (See the section: 'Free GPS Programmes on the Internet'.)

To Top
Plus points of a GPS.

Some ramblers disparage using a GPS receiver when rambling, saying that a map and compass are all you need but its use in some instances can sometimes be invaluable, e.g.,
  1. locating one's position when travelling over ground with few or no clear features in poor visibility.
  2. giving an accurate grid reference in the unlikely event that you or a colleague are severely injured and your position has to be passed on to Mountain Rescue.
Besides giving grid references, the basic GPS can record a log of the track one has taken on a walk, which can be useful in two ways::
  1. It enables one to retrace the walk, if considered sensible to do so, when difficulties arise, such as worsening weather conditions in snow or mist.
  2. It enables a record of the route of the walk to be saved later on a PC, if the PC is installed with suitable software.

Tips on use of GPS.
  • Fully acquaint yourself with how to access the various facilities that your GPS has to offer before using it in the fells. You can get an idea of the time it takes to make a cold start. You can enter some way points in the area you live and use the GOTO function - more on waypoints below. You can check its reception under tree cover or between high buildings. Having enabled tracklog operation, you can zoom in on the track of your walk on the map screen and check on how it corresponds to the track you have taken on the ground. You can read off your position at various places and check them against the appropiate OS map. After the walk check out the distance you have walked and your average speed. You can also familiarise yourself on how to delete the tracklog memory and reset the trip metres in readiness for your next walk.To Top

  • If waypoints have been loaded into your GPS, then these will be numbered in sequence and the GPS will display straight lines from one waypoint to the next in the sequence. (It is possible to go in reverse.)
    When in the fells, if the waypoints are far apart, this could mean that your path could cross dangerous ravines or deep lakes - not to be recommended if they are unsighted in a mist or in the dark. Thus extra waypoints will be needed so that you are led round such impassable places. Because it takes time and care to load waypoints by hand, some people use only a few waypoints, perhaps on prominent features. Others like to use waypoints at places where there is a choice of path or to negotiate around obstructions or points of danger. Loading a route from software on a PC is likely to produce many waypoints, their accuracy depending on how accurate the path was drawn on the PC. A disadvantage of this is that the limited number of waypoints that a GPS can hold, perhaps 500 or 1000, limits the number of routes, even though the theoretical limit may be 20 (or 50 on later models). This problem is easily overcome by storing the routes on your PC rather than your GPS.
    • To Top
  • The GPS needs to be set up with a suitable co-odinate system or datum. There are many in use throughout the world. The default datum is WGS84, which stands for 'World Geodetic System 1984 and if you are to use your GPS in Britain, this should be changed to the only British datum, which is OSGB (1936), Ordnance Survey Great Britain 1936, so that it lines up with the OS maps you will be using. Any software you use will need the datum setting too. Setting the GPS' datum can take many steps,, e.g. with the Garmin GPS60, you need to select the 'Main Menu' page, then 'Setup', then 'Units' and in 'Position Format' select 'British Grid' and in 'Map Datum' select 'Ord Srvy GB'. (Incidentally, having navigated this far, whilst in the 'Units' section, select the units of distance and elevation that you wish to use too.)

  • The way the GPS aligns the map can be adjusted. Choose 'Track up', if you tend to turn your map upside down when going south(!), otherwise choose 'North up'.

  • You can select whichever of the three North references the GPS uses. It is usual to select 'Grid North', if you have selected your datum as OSGB(1936) in the UK, because the position of the way points will use grid references. Use 'True North' if you are using latitude and longitude. perhaps outside the UK. Use 'Magnetic North' if you particularly want north on the GPS' electronic compass to line up with north on your magnetic compass.

  • BNG is a shorthand for British National Grid, which is the same as OSGB(1936) datum and is shown in the grid reference on some GPS models, as in this example appearing over 2 lines.
    NY 72318
    BNG 96523
    The letters NY are the two letter code for a 100km by 100km square mainly in Cumbria. The digits 72318 is the easting in the grid reference. The 96523 is the northing in the grid reference. Both the easting and northing use 5 digits, which means that together the area they repesent is a 1m by 1m square. Assuming the manufacturer round the measurement to the nearest (5th) digit, the centre of the square is positioned 72.318km from the west edge of the SD square and 96.523 km from the southern edge of the SD square. You might think that going from 4 digits to 5 digits for the easting and northing would improve accuracy 10 fold, i.e from a square 10m by 10m to one 1m by 1m. However you have to remember the latent inaccuracy in the information being displayed, which can have an error averaging 10m on cheaper GPS units. As a rough guide, this means the error will have been reduced from about 20m to about 11m, less than half! With a WAAS enabled GPS unit, the error will go from about 13 m to about 4m, a reduction of more than 2/3rds but not the 90% you might have thought.
    • To Top
  • If you have problems loading waypoints or routes into your GPS using GPS software on your PC, then make sure you have configured both your GPS and your software so that a physical connection between your GPS and your PC has been established.

  • The basic GPS also gives distance walked, its elevation and will display a pointer, which gives the direction to your next waypoint. However
    the pointer does not work when stationary,
     so you need to carry the GPS a few steps to be able to gain the necessary information for it to calculate the correct bearing.

  • As long as you keep your GPS switched on while you walk, you can read off your speed, average speed, maximum speed and the time you have been walking. You can save power by switching off the GPS when you are stopped for any length of time, such as a lunch stop but remember to switch it back on when you move off again! Switching it off when on the move and only having it on when really needed will save power but any readings of speed and distance walked will be more or less meaningless and the track log, if being recorded, will be very inaccurate, being a few straight lines joining the recorded positions made when the GPS was on.To Top

  • As mentioned already, it is important to start with fully charged batteries and ideally carry a spare set, if you are going to have the GPS on for several hours. (You won't lose any data while the batteries are swapped over.) Rechargeable batteries are cheaper and more environmentally friendly than non-rechargeable alkaline batteries. However if left unused, they will need recharging periodically. Nickel Metal Hydride, NiMH, batteries are to be preferred to Nickel Cadmium batteries as they can be recharged when only partly discharged, unlike Nickel Cadmium. Choose batteries with a high current capacity, i.e. 2500mAh rather than 1300mAh say. Eventually even your set of rechargeable batteries will need replacing. If possible select the battery setting on your GPS for either 'Alkaline' or 'NIMH' operation, whichever is appropiate.

  • It has been mentioned that the GPS needs to receive at least 3 satellite signals to get a good 2D fix and at least 4 to get elevation as well. Reception of satellite signals depends on the location of the GPS. In deep ravines or under heavy tree cover reception can be impaired significantly. Because the satellites are positioned mainly to the south of Britain, reception is improved if the GPS is carried so that there are no obstructions to the south of it. Reduction of signal due to nearby fells to the south of you probably can't be avoided but carrying the GPS on the north side of your body can. Your body acts as a shield. So try carrying the GPS on the south side, if signal strength is low. Keeping the GPS as high as possible also helps - perhaps in the top of one's rucksack, if you are only making a track log and not actually navigating with the GPS.To Top

  • Before starting a walk, the track log memory should be cleared and the trip odometer, the time and speeds set to zero. Then enable the tracklog feature before setting out. If you do this at home, before the walk, select the GPS OFF' setting, so that it is not trying to get satellite reception. Doing this prevents the GPS having a waypoint preset before the start of the walk. Also make sure you have the GPS switched off as you travel from your home to the start of the walk, otherwise you will be logging this journey too. Don't forget to switch it off at the end of the walk either. Doing this means that the track log will be a record of just the walk, without any 'extra bits'. The log can be uploaded onto your computer and saved for future reference. If the tracklog contains more than the actual walk, it is possible to select the section you require by first splitting the track/path at the start and/or end of the walk using the Anquet or Memory-Map software and then deleting the parts you don't want.

  • When in the fells, don't set the way point of a distant location into your GPS and then use the GPS to walk straight towards the location. As with a compass, you must first check on a map, that there are no hazards, such as precipices, pot holes, etc., between you and it. By simply following a pointer in thick mist, without checking for such hazards, some walkers have fallen to their deaths! If you do experience such conditions on the fell tops, where no distinguishing features are visible, you will be better off with a map and a working GPS, (with its grid reference display), than you would be with just a map and compass. Even if you know where you are at the start, following a compass bearing is not straight forward when you are forced to circumnavigate high peat hags or deep pools crossing your path. This would mean that you may soon be having to guestimate your position - far from ideal, if there are serious hazards to avoid!To Top

  • Some older models of GPS don't have a USB connector for connecting to a computer. This means that an (over-priced?) adapter may be needed to be able to connect such a GPS to your PC.


Thinking of getting more than a basic GPS. Then check for the following:
  1. a multi coloured display but make sure it can be read in bright sunlight, especially if you use it for biking.
  2. camera, e.g. Garmin Oregon 550t has 3.2 megapixel geotagging camera with 4 x zoom.
  3. use of parallel multi channels for receiving several satellite signals at once. (Automotive GPS units use 12 channels and so do most modern handheld units. If it incorpoates the SIRF Star III signal processor, all to the good.)
  4. electronic compass - even a triple axis digital compass, which can be read whichever orientation it is held in!
  5. barometric altimeter
  6. built in detailed topographic maps
  7. large internal memory, say 20MB (20 megabytes or 20 'megs' to some)
  8. At least 500 waypoints per route
  9. At least 20 routes, though routes can be stored on computer.
  10. touch screen
  11. 3D map viewing
  12. high screen resolution
  13. good size map area, which could conflict with light weight and low bulk
  14. expandable memory
  15. waterproof - GPS units designed for hikers will be
  16. ability to upload maps,
You get what you pay for, so the more of these features the GPS has, the more expensive it will be.
If you are going to include a map with sufficient detail to be of any real use, then a multi coloured screen is essential. However, the screen on a GPS is quite small and although it is possible to load routes from a PC to a GPS, it is not possible to load a real OS map. This is because the GPS manufacturers only allow the loading of their own mapping software - 'Mapsource' from Garmin, 'MapSend' from Magellan and 'MapCreate' from Lowrance, the three main GPS manufacturers. Basemaps on a small scale will probably be already loaded. However to get larger scale maps, extra sotware, which is quite expensive, has to be purchased. You have to weigh up, if the extra cost of a more expensive GPS with the extra memory and colour display, together with the cost of the extra software, is worth the extra benefit you get.
To Top

To get round the problem of the small screen on a GPS and the unwieldiness of plastic covered OS maps in the field, some ramblers produce their own A4 sized maps. On one side is the specific area and route of each walk, (especially useful if your walks involves more than one OS map) and on the other side a smaller scale map, giving a wider view of the area. Also, if the printouts are then laminated, they are durable in wet/windy weather. However, this does involve the purchase of suitable software for the PC, such as 'Anquet' or 'Memory-Map', already mentioned or scanning maps onto your computer and using 'stand alone' software.

GPS in Wrist watches, smart phones and Personal Digital Assistants, (PDAs).

Wrist watches with GPS are available, such as the Suunto X9i, which also includes an electronic digital compass, an altimeter and a barometer. Unlike many GPS models it gives cumulative ascent and descent. Waypoints, routes and tracks can be created using Memory-Map connected to a PC via a USB cable. When navigating on a pre-planned route, the Suunto X9i shows the direction and remaining distance to the next waypoint. It also indicates the current speed and distance travelled.using the GPS functions. There is a trackback facility which enables the user to retrace any recorded route and the route of a walk can be viewed after downloading it to a PC. Like many watches, it is water resistant down to 30 metres. Its main disadvantages are its cost, (about that of a top of the range GPS), its failure to give the grid reference of its position and the limited display on a watch's small dial. The Casio Pathfinder watches are examples of more limited GPS watches in only displaying a digital compass and elevation, though again they calculate and display cumulative ascent and descent.To Top

The latest smartphones can be used to view digital maps and plan routes. Some do not possess GPS but can be linked via wireless (Bluetooth) technology to a screenless GPS. Others now possess a built in GPS, such as Mitac Mio A701, which also has pocket PC functionality. They do of course have many extras such as digital cameras and the ability to send text and voice messages. Their main disadvantage is their lack of ruggedness compared to a standard GPS.


PDAs are handheld computers. They can be bought with navigation software and are used by motorists for in-car navigation. If a PDA does not have an integral GPS, it can be connected via a lead to a standard GPS or to a screenless GPS using wireless (Bluetooth) technology, the latter allowing the GPS to be positioned for better reception away from the PDA's screen.. Their main advantage over a top of the range GPS is their larger coloured screens, their ability to be fitted with extra memory and the wide range of software available. Also they are not tied to one manufacturer as regards mapping software and can use maps produced by Anquet or Memory-Map. Unfortunately they are not designed for tough outdoor conditions by not being either weatherproof or rugged. Also the battery life of about 4 hours, is much less than that of a basic GPS.
To Top
Free GPS Programmes on the Internet.

Besides using the software produced by digital mapping companies, such as 'Anquet', 'Memory Map' and 'Fugawi', there are a number of programmes, known as 'stand alone' software, which do not have maps included but will accept a bitmap, produced by scanning a section of a map into your computer. This bitmap has to be calibrated before the software can make use of it but once the bitmap is loaded and calibrated, the software operates in much the same way as the software of mapping companies, previously mentioned,

'Trailgauge' is a freeware programme. To calibrate a bitmap, it requires you to enter two points with their map refences. For accuracy the differences in both longtude and lattitude (Eastings and Northings), should differ as much as possible. This means that they should be as far apart as the bitmap allows on a diagonal starting and finishing in opposite corners. The first point sets the origin and the second sets the scale and rotation.


Another freeware program, 'GPS Utility' accepts between two and four calibration points. As before, the first two points are for origin, scale and rotation. The first extra point allows for any stretch or skew in the bitmap and the second extra point allows for any non-parallel grid distortion.To Top
(Two shareware programmes of a similar nature are 'Gartrip' (once freeware before recent updates) and 'OziExplorer'. The latter has geo-referencing built in thus simplifying map calibration for the user.


Because of the need to scan a map and the need for bitmap calibration, these programms are not so easy to use as those coming with maps provided. However, getting maps from the digital mapping companies is not cheap so there may be areas where you are not covered. In such cases scanning a paper map of the area and using one of the programmes mentioned may be your best option to enter a route into your GPS.


In conclusion, the GPS should be used to complement the use of map and compass, not replace them.

Go to the Top