After a recent "adventure", which involved sailing about 6 miles down Loch Lomond in near zero visibility conditions (5 to 10 yards max :O), I decided to brush up on my navigational skills. We were pretty well equipped and the journey was uneventful, albeit slow, due to having both GPS and compas as well as the appropriate map. I have been using a Garmin E-trex for a few years now and it has never let me down before, but if I hadn't had a compass as well, it would have been an unplanned night on the islands, again not a great problem, but not ideal with no beer....
Basically the problem was, in a small boat in zero visibility, it is pretty much impossible to tell if you are going in a straight line at low speed, so the GPS which relies on movement to determine your bearing is pretty much useless, apart form telling you where you are. Without both GPS to establish position, and compass to establish and follow a bearing, the journey would have been foolhardy to make.
Anyhoo, enough of the drivel, I decided I wanted a new compass which was capable of taking accurate bearings to position myself without the electronic wizardary, as well as doing the map work, so after some research, it was between the Silva Ranger 15TDCL or the Recta or Suunto equivelant, and the Silva Expedition 54. I decided to go for the Expedition 54 in the end as part of my birthday present and it duly arrived from www.maps-warehouse.co.uk on Thursday, having been ordered on Tuesday. This was the cheapest I could find it in the UK.
The 54 appears just like any other full size baseplate compass with the various romers and scales, but is different in that it incorporates a prismatic sighting system into the bezel, which allows sightings accurate to half a degree to be taken easily. I think it would be fair to say that it is generally accepted that a prismatic compass is the most accurate way to read a bearing, but traditional prismatics are not really suitable for map work in the way that a baseplate compass is.
The prismatic compass is simplicity itself to use, you simply bring the compass up to your eye and line the sighting mark up with your target and your bearing appears to "stand up" from the disc. The Silva website shows this in a sketch, and I have, semi-successfully, attempted to capture the process in a photo, showing, I hope, that with a steady hand that it really is possible to take readings accurate to half a degree with this compass. The disc is graduated for reading both forward and back bearings, which can save some mental arithmatic.
So much for all the blurb, does it actually work?
I live on a bit of a hill, and at the end of the street you can see down over the town and looking south east can see right down over the next town and easily pick targets anywhere between a mile and probably 20 miles and further.
Armed with my new compass and a pencil, I headed down to the end of the road and took bearings to six prominent landmarks ranging from about a mile to about 6 miles away, and noted them all. I then went back to the house and took bearings from the map to the six landmarks. Once I had added three degrees to the map bearings to compensete for grid / magnetic north, I was extremely impressed to find that 5 of the six readings were an exact match, and the last one was one degree out. The 54 has proved to be very accurate, and I very much doubt that I could have achieved the same results with a mirror sighting compass.
Do you actually need this much compass, I don't know, but its nice to have. The only niggle that I could pick with this compass, is that at this price point, perhaps it should have correction facility for magnetic deviation, but perhaps Silva feel that the target market for this compass is the experienced navigator and such a feature is not required.
If you are looking for a new compass, I would say that this is as good as you are going to get, and I would highly recommend it!
Basically the problem was, in a small boat in zero visibility, it is pretty much impossible to tell if you are going in a straight line at low speed, so the GPS which relies on movement to determine your bearing is pretty much useless, apart form telling you where you are. Without both GPS to establish position, and compass to establish and follow a bearing, the journey would have been foolhardy to make.Anyhoo, enough of the drivel, I decided I wanted a new compass which was capable of taking accurate bearings to position myself without the electronic wizardary, as well as doing the map work, so after some research, it was between the Silva Ranger 15TDCL or the Recta or Suunto equivelant, and the Silva Expedition 54. I decided to go for the Expedition 54 in the end as part of my birthday present and it duly arrived from www.maps-warehouse.co.uk on Thursday, having been ordered on Tuesday. This was the cheapest I could find it in the UK.
The 54 appears just like any other full size baseplate compass with the various romers and scales, but is different in that it incorporates a prismatic sighting system into the bezel, which allows sightings accurate to half a degree to be taken easily. I think it would be fair to say that it is generally accepted that a prismatic compass is the most accurate way to read a bearing, but traditional prismatics are not really suitable for map work in the way that a baseplate compass is.
The prismatic compass is simplicity itself to use, you simply bring the compass up to your eye and line the sighting mark up with your target and your bearing appears to "stand up" from the disc. The Silva website shows this in a sketch, and I have, semi-successfully, attempted to capture the process in a photo, showing, I hope, that with a steady hand that it really is possible to take readings accurate to half a degree with this compass. The disc is graduated for reading both forward and back bearings, which can save some mental arithmatic.
So much for all the blurb, does it actually work?
I live on a bit of a hill, and at the end of the street you can see down over the town and looking south east can see right down over the next town and easily pick targets anywhere between a mile and probably 20 miles and further.
Armed with my new compass and a pencil, I headed down to the end of the road and took bearings to six prominent landmarks ranging from about a mile to about 6 miles away, and noted them all. I then went back to the house and took bearings from the map to the six landmarks. Once I had added three degrees to the map bearings to compensete for grid / magnetic north, I was extremely impressed to find that 5 of the six readings were an exact match, and the last one was one degree out. The 54 has proved to be very accurate, and I very much doubt that I could have achieved the same results with a mirror sighting compass.
Do you actually need this much compass, I don't know, but its nice to have.
The only niggle that I could pick with this compass, is that at this price point, perhaps it should have correction facility for magnetic deviation, but perhaps Silva feel that the target market for this compass is the experienced navigator and such a feature is not required.If you are looking for a new compass, I would say that this is as good as you are going to get, and I would highly recommend it!
