/ Silva expedition 4 vs 54
Any practical thoughts people? ( aware of price difference)
I've got the 4 and have never wished I had a sighting compass. I thought sighting compasses went out with the dinosaurs!
Hey! Have you seen it? It's basically a baseplate with a little added extra, not the hinged mirror etc
the one with a prism in the bezel? either way, why do you need a sighting compass?
I got an expedition 4 that I got from Amazon via Germany. It is not stocked in the uk. But it's an awesome compass because of the chunky bezel and bright Orange colour scheme.
Because you can take a more accurate bearing with it?
Indeedy, which is why I bought one. Main diadvantage over the Type 4 is the lack of luminous blobs for night nav, and because of the disc it's harder to orient the bezel with the grid on the map.
Thanks guys. I'm 50/50 on it at the moment.
The Parallax effect happens either way, with or without a sight - so the're both only as reliable as your ability to place yourself (and your line of sight) at 90 degrees to the plain of the sight.
unless you're aiming artillery then i don;t think you'll see much advantage.
On the other hand if you like all the best toys - knock yourself out.
As others have said, it depends on where you are and what you're doing. I find there's no difference (I use both the Exped 4 and the Exped 15TDCL, and have previously used the Exped 54) when taking bearings off a map and walking on it (there are far more errors introduced by your ability to walk straight), so for most things the 4 is fine. The only time it makes a noticeable difference is if you're doing lots of resections (eg nav specific training), need accurate resections (eg teaching more advanced nav) or are taking resections off fewer defined points (eg sparse or very distant reference points).
Overall, however, I find the 4 too fragile (broken dials and base plates on several), the 54 too fiddly and the sighting tricky to use and prefer the 15 (yes the mirror occasionally gets in the way, but the dial is chunkier, the plate shorter but not detrimentally so and the mirror acts as a protecting cover for the dial).
Thank you. Exactly the sort of info I was after.
A 4 is the workhorse and I've only ever properly broken one (shut it in a car door) and worn out 3 or 4 (well, one of those was cracked, but some Araldite held it together for years.
For most purposes it's fine as you're taking a bearing off a map and following an indicated direction, with inevitable slight meanderings. A big base plate is easier with frozen, icy gloves.
Accurate bearings from an object is only really relevant when directing artillery. For resections, you'll be lucky to have two precisely identifiable points, or the conditions in which to plot accurate lines anyway (if you did, you wouldn't be lost to the extent that you need to do accurate resections).
For artillery though it is important to have an accurate bearing so that 'Left 200, Drop 200' actually gets the rounds to move in the right direction when that instruction from the observer's point of view is interpreted at the guns. The guns don't fire conveniently along the observer's line of sight and the observer doesn't know where the guns are. The guns however know the location of the target (if the observer can read a map) and the bearing from the observer to the target. They fire the first round at the grid ref the observer gave, and then make adjustments based on what the observer sees and tells them to do.
(This is the steam-driven version)
Brilliant. Going to go for the 4. Thanks.
Rumour has it that this is going to be added to the ML syllabus
Suunto M-3G, you wont regret it.
Serious question, not being versed in the dark arts of the Drop Shorts. If the observer doesn't know where the guns are, how does "Left 200" work? Or do they know the observers position and back calculate it from his viewpoint?
The observer tells the guns the target's grid position and the bearing of the target from the observer. The guns plot the target location and that bearing and work out the changes based on the directions given by the observer. So, if the gun were firing from 90 degrees to the left of observer's line of sight, 'Right 200' as seen by the observer would be 'Add 200' from the guns' position.
As I say, steam gunnery, but the principles are still the same when you add computers and GPS.
It is, as someone observed, a critical skill for anyone in the mountains with a sighting compass.
The guns use the bearing from the observer to the target to "fine tune" the observer's corrections then?
You never know when you might need a fire mission on Cleator Moor.
Not so much 'fine tune' as make sense of them, i.e 'left' only makes sense if you're looking from the same point of view as the observer. To someone looking in the opposite direction, it's 'right'.
The corrections are necessary because the grid reference the observer originally gave may not be quite right (hopefully it's nearly right), and weather etc will affect the flight of the shell.
And Cleator Moor - you can't be too careful, especially when the natives are restless.
Ta. The ones I have looked at online don't seem to have romer scales.
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