# The 25 m rule

Hello to all

One of the local rule here says that a maximum distance of 25 meters below a summit is admissible for an activation. But if that rule is used (if we are 25m or less vert from a summit), then, what is the maximum horizontal distance admissible from that same summit? If it not defined, it would mean that any neighboring mountain could be used (HI)?

From the general rules:-

Vertical Distance
The maximum permitted drop in height at any point along the straight line between the Summit and the Operating Position.

No horizontal distance is defined, in this country we have some plateau-type summits where the activation zone, the minus 25 metres contour from the summit, has an area measured in square miles. At the other extreme we have at least one summit that no more than a few people would fit onto at any one time, and its no place for vertigo sufferers!

If the rules are obeyed no neighbouring mountain could be used unless the col was less than 25 metres below the activated summit!

73

“in a straight line”. That is an interesting complication to the rule that I hadn’t realised before. It just so happens that I had been reading up on Gisborough Moor recently. This has the main top in square NZ6312 at a height of 329M, with a subsidiary top 1.9km to the NW at a height of 324M. There is a ridge connecting the two, curving slightly, with both summits and the ridge being wholly enclosed by the 310M contour. Hence I thought the NW top would be well within the activation zone.

However, if a straight line is plotted between the two tops, the lowest point on the straight line falls outside of the 300M contour; my version of Memory Map showing the lowest point as 298M. Therefore the NW top is outside of the activation zone.

Even more interestingly (if you are pedantic or like mathematical curiosities), you could pick a point say 200M west of the NW top (and about 14M below it), for which a straight line to the main SE top doesn’t fall below 304M, (actually about 309M).

Is that what was really intended? Without in any way wishing to start an argument (as I think the group who originally formulated the rules did a very good job), I would be interested in knowing why the word straight was put in the rule.

Richard
G0IBE

Not wishing to add to any (non-existent) argument ;)))

I’d of thought the straight-line to be straight when viewed from above only and in the other plane for it to be along the ground.

At least, that makes the most sense to me and I think to be the only way you could have the rule at all.

You draw a straight line on a map between the summit (point A) and your operating position (point B). Any decrease in height against the height of the summit, exceeding 25m, along that “straight line” would make that operating position (Point B) invalid.

All the best,

Rob G7LAS

And don’t even get me started about the fact that we’re all modelling this on a hypothetically flat earth in the first place! ;)))

Surely, the essence of the argument is that there must be a route from the actual summit to the operating point that remains in the operating area, ie, within 25M of the summit. You have no need to use that route, or even go via the summit, to reach your chosen operating point.

In the dim and distant past, my maths master (Mr Dyne - no word of a lie) demonstrated the Calculus by treating a curve (function known) as being made up of a series of straight lines. This defeats the use of the word ‘straight’ in the argument.

Tom can now put me and my memory in their proper place.

Regards, Dave, G6DTN

You (and your memory) are in the correct place Dave AFAIAC! And yes, the intention of the activation zone rule is that you describe. I wasn’t aware that the vertical separation definition in the General Rules still mentioned a “straight line”. I thought that had been dealt with.

Tom MO1EYP

And yes, the intention of the activation zone rule is that you describe. I

wasn’t aware that the vertical separation definition in the General
Rules still mentioned a “straight line”. I thought that had been
dealt with.

Tom MO1EYP

We have redefined a few things, Tom, but I don’t think the new definitions have been applied yet.

I’ve always thought that the “straight line” bit was utter nonsense, anyway. Take the hypothetical case of activating a volcano, even if the whole rim of the crater is within 25 metres of the summit height, a straight line to any position not adjacent to the highest point would be crossing a void. Come to think of it, many of our British hills have quite serpentine ridge lines and a straight line path would be - shall we say a little eccentric? The obvious case (at least, to me!) is the Inaccessible pinnacle on Skye, where the summit of Sgurr Dearg is within the activation zone by virtue of also being enclosed by the -25 metre contour, but a straight line between the two summits crosses a void whilst a simple track with a right angle bend takes you from the foot of the short side of the In Pin to the summit of the Sgur with no need for hand work!

73

To put it in laymans terms - if you can walk from the summit to the operating position without descending more than 25m (50m in the Alps) the operation is ok.

So just to close this topic off, is the rule going to be amended to be a little more as people interpret it, when the rules are next revised?

Thanks

Richard

G0IBE