By: Blonde One
Copyright Ordnance Survey
If you want to find a pinpoint feature that you’ve seen on a map, you need to have at least one attack point to get to it. In this case we were at Hameldown Beacon and wanted to go and find the two cairns that are at the right of the map screenshot. We could have set a bearing from our location and walked directly to the cairn. There were two reasons that we didn’t: 1. the route was very prickly and I didn’t have long trousers or gaiters. 2. It would have been easy to get the bearing slightly off and miss the cairn completely.
Here’s what we did instead:
We walked south down the path 500 meters to get to the feature on the contours. Although the contour feature on the map is very small, the re-entrant was very clear from the path. This was our first attack point.
Next we followed the contour feature for approximately 25 meters east downhill towards the water feature.
It was again obvious when we got to this feature as we began to get wet feet and the cutting flattened out.
From this final attack point it was a straightforward, short leg to navigate slightly uphill the 200 meters to the cairns which were easily visibly now.
Simples!
Impressive! But, from my experience I wouldn’t want to rely on the map indicating the exact point of the source of the stream – that would probably depend on how dry the weather had been and the possibility of it just being some indeterminate seepage spread over fifty metres or so. In your case you say you could see the cairns anyway, but that would not have been the case in bad visibility so your plan would have done the job.
I understand this post is for the purpose of illustration and instruction, and I understand your reasons for not taking a direct bearing which I think I would have done. I would have taken a bearing on the mid point between the cairns and estimated the distance at 0.5km. and say about eight minutes walking depending on how rough was the terrain, and then start looking carefully from six minutes in. But in truth I would be following the GPS position on my Memory Map iPhone, but at least you can see I would have some idea if the gadget was not functioning.
I have just looked at a magnified version of the map on my computer and I see there is a water feature which I don’t recognise just north of the bifurcated sources of the stream – perhaps you could enlighten me.
Have you ever experienced reverse polarity – I posted about this happening to me recently?
It’s always important to be able to use several different methods of locating a point. I take your point completely about the source of the water but in this case the re-entrant took us to the right spot (it was quite dry though). The symbol that you refer to indicates a marsh.
I haven’t ever experienced a complete compass malfunction like that except for a very foggy day when it did some strange spinning! It suited the mood of the weather but it was very strange!