A-Frames, A-Frames, A-Frames! Who’d a thought I would get so excited about A-Frames. Imagine the scene… I’m standing, outside in the orchard at Stanmer Park, clearly visible in my fluorescent cycling garb and woolly hat, looking like Where’s Wally meets Moby meets the Health & Safety Executive (not pretty basically), and scratching my chin while trying to understand just exactly WTF our course tutor is trying to tell me.
Something is ringing a bell in my mind but for the life of me my cortex is not responding to the chime. I’ve seen Ordnance Survey Maps and spent enough time reading them on the fells of the Lake District to know not to try and run down the bit of the hill with lines really really closer together. I recall maths lessons walking around a cold playing field with a wooden wheel on a stick and noting down distances. I remember A-Frames… A-Frames…. BUT HOW DO THEY WORK!?
Here’s my notes… I reckon if I drink enough alcohol, one day I will understand them as well as I did when I wrote them down:
So, look – I did eventually get what was going on… the A-Frame allows you to map contours onto a 2-D basemap when you’re woking with a landscape that slopes. Why are slopes important? All sorts of reasons, but one of them is that slopes naturally shift water around in different ways than flat surfaces. For a really great explanation, watch this vid on Keyline Water Systems. Any why are key line water systems useful? Because they work with nature (not against) in order to get the best yield and use out of the naturally available water in any environment. Remind you of anything? (Ahem… Permaculture Design Principles). Have I lost you yet? No. Good. I know the links are getting heavy.
So here’s me marking out the A-Frame – what this does is mark the place where the plumb-line (that’s the dangling water bottle to you) will be when the two feet of the A-Frame are level on the ground. Why is this important? Well, when you do this in sequence, several times, perpendicular to the slope, you can map out the contour at the same level…. *sigh*…. look, this is really hard to put into words OK? You have to get out there and do it… make an A-Frame. I’m going to.
You can see the marker points beginning to map out the contour line using rope.
Several contours now being built up…
Where’s Wally? He’s in the fluorescent jacket. Someone with a rather long 1m step sneaking behind!
Completely oblivious to the Bangles Walk Like An Egyptian situation going on. It is hard work you know!
You know, for a better description than I can do justice to, I kinda like this dude’s explanation: