I don't know whether anyone is interested on an old world perspective on charts and co-ordinate systems, but in the UK probably the most widely used source of charts for paddling are not marine charts but the Ordnance Survey Land Ranger maps (analogous to USGS topo maps) at 1:50000 marked with the UK national grid in 1km increments. The UK national Grid is based on a Transverse Mercator projection very similar to UTM (different datum/UK grid is based on the airy rather than GRS80 spheroid for the technically minded). The advantages for coastal kayaking in the UK of using OS topo maps rather than charts are consistent scales and **much** greater coastal detail, and cost and availability - as a consequence if having a lot of coast for a little land you can get them for pretty much any kayaking location and they can be purchased pretty much anywhere. The disadvantage as I see it is not that the co-ordinate system isn't lat/long but that pilotage and tidal stream information is absent, and needs to be pencilled on from the pilot and almanac - but to me this adds to the fun of trip planning. Re: using grid co-ordinates ... it is pretty easy to estimate positions and grid references by eye for a 100m2 square on a map with 1km grids (100m2 = six figure reference). However it may be of interest that virtually all of the full size base plate orienteering compasses (silva, suunto etc) have a roamer marked on the protractor base plate for grid squares on 1:50000, 1:25000 and 1:63000 (inch to the mile) scale maps. Use of the roamer scale could not be simpler: put the corner of the base plate on the map at the point of interest, and read off the grid reference values on the compass base plate against the grid lines or ticks marked on the map. Silva style orienteering compasses were inexplicably given a bad press a while ago on this list, but for me this style of compass is indispensable: taking bearings and measurements from a map, roamer scales are useful for pinpointing positions, and you always have a spare working and rough hand bearing compass. Cheers Colin Calder 57º19'N 2º10'W *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Fri Apr 09 1999 - 04:29:51 PDT
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