Silva Expedition 4 / 4MD

[Rob]

Hi, I've just purchased what I thought was an Expedition 4 compass but found an Expedition 4MD in
the box. The instructions however don't mention use of the mm scale on the bezel which is,
apparently, for measuring distances to a point by triangulation. Does anyone have any information /
instructions for this so I can decide whether it's a useful feature or whether I should simply have
it replaced with an Expedition 4. Thanks, Rob

 

[Peter Clinch]

rob wrote:

> I've just purchased what I thought was an Expedition 4 compass but found an Expedition 4MD in the
> box. The instructions however don't mention use of the mm scale on the bezel which is, apparently,
> for measuring distances to a point by triangulation.

Sounds like you've got a military one with a scale in mils. There are 640 rather than 360 in a
circle and the military prefer to work in them rather than degrees. AFAICT nobody else does, and
there's no clear advantage in doing so, so I'd take it back and get the plain 4 with clearer
scale marking.

Pete.
--
Peter Clinch University of Dundee Tel 44 1382 660111 ext. 33637 Medical Physics, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK net [email protected]
http://www.dundee.ac.uk/~pjclinch/

 

[Roger]

The message <[email protected]>
from [email protected] (rob) contains these words:

> I've just purchased what I thought was an Expedition 4 compass but found an Expedition 4MD in the
> box. The instructions however don't mention use of the mm scale on the bezel which is, apparently,
> for measuring distances to a point by triangulation. Does anyone have any information /
> instructions for this so I can decide whether it's a useful feature or whether I should simply
> have it replaced with an Expedition 4.

Do you mean mils? I have a type 4/54 (graduated in mils and cheap to clear) and I didn't notice it
was in mils until I came to use it but as it also has a degree scale within the ring I don't find
using it a problem.

A mil is 1/640 of a full circle or 0.5625 degrees but, more importantly to the Army, subtends
(approximately) an offset of 1 unit at the range of 1000 units.

--

Roger

 

[Anonymous]

In article <[email protected]>, Roger <[email protected]> writes
>The message <[email protected]> from [email protected] (rob)
>contains these words:
>
>> I've just purchased what I thought was an Expedition 4 compass but found an Expedition 4MD in the
>> box. The instructions however don't mention use of the mm scale on the bezel which is,
>> apparently, for measuring distances to a point by triangulation. Does anyone have any information
>> / instructions for this so I can decide whether it's a useful feature or whether I should simply
>> have it replaced with an Expedition 4.
>
>Do you mean mils? I have a type 4/54 (graduated in mils and cheap to clear) and I didn't notice it
>was in mils until I came to use it but as it also has a degree scale within the ring I don't find
>using it a problem.
>
>A mil is 1/640 of a full circle or 0.5625 degrees but, more importantly to the Army, subtends
>(approximately) an offset of 1 unit at the range of 1000 units.
>

It may be marked on the ring as 640 but there are actually 6400 mils in a circle. Otherwise one mil
at 1000m would equal ~10m.

Trying to mark in thousands instead of hundreds would be a wee bit impractical on a small compass.

--

http://www.dscs.demon.co.uk/

 

[Roger]

The message <[email protected]>

> >A mil is 1/640 of a full circle or 0.5625 degrees but, more importantly to the Army, subtends
> >(approximately) an offset of 1 unit at the range of 1000 units.

> It may be marked on the ring as 640 but there are actually 6400 mils in a circle. Otherwise one
> mil at 1000m would equal ~10m.

> Trying to mark in thousands instead of hundreds would be a wee bit impractical on a small compass.

Clang! It must be the imminent onset of old age. I managed to get that wrong even after checking the
definition in a dictionary (one sixty-four-hundredth) and the accurate figure (0.00981.......) on a
calculator. Now was it the 'hundredth' in the definition or the 2 leading zeros in the tangent that
led me astray.

--

Roger

 

[Rob]

Thanks for the replies chaps. Have returned it to the suppliers. The soft glow of the tritium on the
baseplate in the understairs cupboard was qute exciting for a short while but when have I ever had
to navigate at night? Never. Don't you need glow-in-the-dark OS maps

Cheers, Rob

Roger <[email protected]> wrote in message news:<[email protected]>...
> The message <[email protected]>

>
> > >A mil is 1/640 of a full circle or 0.5625 degrees but, more importantly to the Army, subtends
> > >(approximately) an offset of 1 unit at the range of 1000 units.
>
> > It may be marked on the ring as 640 but there are actually 6400 mils in a circle. Otherwise one
> > mil at 1000m would equal ~10m.
>
> > Trying to mark in thousands instead of hundreds would be a wee bit impractical on a small
> > compass.
>
> Clang! It must be the imminent onset of old age. I managed to get that wrong even after checking
> the definition in a dictionary (one sixty-four-hundredth) and the accurate figure (0.00981.......)
> on a calculator. Now was it the 'hundredth' in the definition or the 2 leading zeros in the
> tangent that led me astray.