Silva Expedition 4 / 4MD

rob said:

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 hidden]
dundee.ac.uk~pjclinchOpen ↗

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

Quoted message said:

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

In article <[email hidden]>, Roger <[email hidden]> writes

Quoted message said:

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

Quoted message said:

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.

--

dscs.demon.co.ukdscs.demon.co.ukOpen ↗

The message <[email hidden]>

Quoted message said:

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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

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 hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

The message <[email hidden]>

Quoted message said:

Quoted message said:

Quoted message said:

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.

Quoted message said:

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.

Quoted message said:

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. :-)