Across Wales Walk: Maps, Route and GPS Navigation
Across Wales Walk: Maps, Route and GPS Navigation |
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This page contains information on maps, route descriptions and GPS data relating to the Across Wales Walk.
Whilst Landranger 135 and 136 maps cover the entire route, it is highly recommended that 1:25,000 maps be used for navigation, the principal benefit, in addition to the larger scale, being the clear identification of field boundaries.
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Explorer 213 Aberystwyth and Cwm Rheidol
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Below are route descriptions for the Across Wales Walk. Entrants must determine suitability of the route in relation to their own abilities. No liability for error, accident or any other arising is accepted or implied.
A two page narrative description of a route is available by clicking here (Word 2000 format)
Like many other outdoor enthusiasts, I am interested in the use of technology to aid navigation, particularly if it results in fewer people getting lost and more people to completing the event. I'm sure that many long distance walkers, novice and expert, are all too familiar with the disheartening consequences of making simple navigational errors during challenge walks. When compounded by fatigue and foul weather, navigation errors can potentially have serious consequences. Therefore I would like to encourage the use of GPS navigation receivers as an aid to safety but not as a substitute for map, compass and appropriate navigation skills.
Co-ordinate data for the route for most Garmin series of receivers will be available for direct downloading at the start of the event.
NOTE: the co-ordinate data provided comprises more than 130 waypoints spread over eight 'routes'. Some budget Garmin GPS receivers such as the 'Gecko' do not have the capacity to handle more than one route nor this quantity of waypoints. Please bear this in mind before purchasing or attempting to download the information.
This data, compatible with GPS Utility (se below) is also available from this website by clicking the appropriate links below:
awwiss06e.txt is a Route file containing waypoint and route information.
Note that the route file is basically a standard text file and may be read with any text editor. Thus the information may by read by those without access to GPSU software and perhaps converted to other formats.
Foremost amongst GPS data management programs is GPS Utility by Alan Murphy. I am still fully investigating this program's capabilities but so far I have found it to be excellent and would commend it to anyone interested in GPS. Click on the logo below for more information.
A total of 135 waypoints along the route of the walk have been defined either from OS 1:25,000 maps to a resolution afforded by 8 figure grid references, or by direct measurement with a GPS receiver in the field. These have been checked then converted to 10 figure references compatible with the GPSU software and are shown as separate eastings and northings.
Each waypoint has a six digit ident which may be either a reduction of a place name on or near the waypoint, or it may be a sequential ident such as 'road04' which, for example, is the fourth waypoint on a road along the route. Some waypoints also have an altitude (in metres) as determined from the map, however this information is incomplete, and pretty irrelevant anyway as altitude measurement is not a strongpoint of portable GPS receivers. Important waypoints also have a text description up to 16 characters in length. This description appears in the 'waypoint comments' field of the GPS at the 'waypoint' screen.
The waypoints are grouped into 8 routes as follows:
Although the interface on Garmin GPS receivers do not necessarily conform to an RS232 standard (accepting that there is no such thing as a standard RS232 interface!) it is possible to make a direct connection between a PC COM port and a GPS. Such a lead can be purchased from Garmin but it is possible to fix-up a cheap substitute. The original round connections are not easy to trace but, with care, a 5-pin 'domino' DIN female connector can be modified to suite. Note that possibly the centre pin will need to be removed and the remaining hole enlarged to take the centre peg found on some models of receiver such as the GPS38. For details of how to make such a connection try this link.
Each route should be made 'active' in sequence. This essentially transfers the active route into route 00 (which overwrites the previous content). The GPS should then identify which is the nearest waypoint and set a course for it. Once this is reached, the receiver should then identify the next waypoint in sequence and so on for all the route. When the end of a route is reached, the next route should be activated and so on. Note that no route passes through a checkpoint so a new route may be selected as part of your normal checkpoint routine.
I have used the Issue 02 route description extensively with my Garmin GPS38 receiver. In the clear parts of the route I have found its performance to be outstandingly good. Often one can count down the feet to the next waypoint with surprising accuracy. Across areas such as Plynlimon where the waypoints are widely spaced it gives good consistent bearings to one's next objective. However, where coverage is restricted, such as in the muddy depths of Mochdre Brook (typical of such places where detailed navigation assistance is so desirable) the limitations of these early GPS receivers become clearly apparent. In fact you might as well save your batteries and turn it off! I understand that the latest multi-channel receivers (such as the GPS III) still operate under tree cover: perhaps when all receivers have this performance then GPS will really be of benefit.
A further serious limitation of units such as the GPS38 is that they carry an internal antenna with no provision for an external one to be connected. Thus one has to walk around like a demented 'water diviner' in order to maintain an adequate signal. However, an external antenna is not the best solution either: does one really want to walk around looking like a mobile TV detector van?
Another limitation is that of battery life: I plan to make an external battery pack and dedicated lead (as for linking to a PC) to overcome this problem. However, for now the AA cells run down in no time - I would recommend the serious 'GPSer' carry at least three sets. I would also recommend that one purchases AA cells with care: some types (particularly Duracell with the integral 'power meter') are larger in diameter and stick into the battery holder. I have previously had to resort to chiselling them out with a screwdriver at great risk to the unit.
Those familiar with the principles of GPS will be aware that the 'Compass' function in the cheaper GPS receivers (a mimic of a compass dial to show the direction to the desired waypoint) is calculated by assessing the speed and direction of one's changing position. This may be fine if you are sailing a boat on a steady course, but on foot, in my experience this function is virtually useless. Typically, if one stands still or even travels slowly, the compass oscillates wildly. However, a GPS is basically effective in knowing where it is, not where it's going: it is therefore very good at calculating bearings to waypoints. Thus I have found the best system to be to carry both a GPS and a magnetic compass together, using the former to tell me the bearing and the latter to give me the direction. Until the price of GPS receivers with integral electronic magnetic compasses comes down, this will be the best compromise.
Overall, in my view GPS is a bit of useful fun that adds some interest. I don't necessarily see everyone carrying it in future, and if one is not careful use of a GPS can dominate a walk: one can spend far to much time looking down and fiddling with it. Perhaps its a bit like golf: a good walk spoilt? And who wants to look like a 'techno-dork' with wires going up your sleeve and antennae poking out of your KIMM sack? Not me, well not where I might be seen!
Be aware that 'Selective Availability', the deliberate reduction in accuracy of the GPS system by the US Department of Defence can induce errors. NB from 1 May 2000, SA was removed by the DoD: this has resulted in a significant improvement in accuracy, but SA can be put back on again at any time! In addition, vegetation, terrain and your body can obscure the GPS's view of the sky and cause loss of coverage or reduction in accuracy. Finally, all waypoints were derived by eye using a roamer to 8 figures and therefore errors on my part may have crept into data. However the data has been comprehensively checked and has been used on part of the route, but is basically provided in good faith for assistance with navigation. As stated in the details of the walk, traditional tools of navigation i.e. map and compass, must be carried as a primary means of navigation.
I hope you find the data useful and I would appreciate any feedback on its features or shortcomings.
Stuart Lamb
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