Saturday, December 21, 2013

Tools for Surveying


 When communities approach us with petitions, we rely on quick, reliable, and easy methods of surveying to determine, with the community, whether we can assist them or not.  Learning and behavior change will solve many of the problems that we get petitions for, but for others some sort of practical structure is needed to address their need.  We are usually involved when something needs to be built, but perhaps not to the extent that you would guess.  As a rule, we do not do anything that communities can do for themselves.  We come in with the extra boost of support that they need to get the job done.  This usually involves accurate surveying that can be used to inform the community of their options, and help them move toward making project decisions and plans. 

I said above that survey methods must be quick, reliable, and easy.  If these criteria are not met, there is no way that we will transfer the capacity of surveying on to the communities that we are working with.  This means that expensive GPS equipment is out. 

Here are a few low-tech survey tools that we have borrowed from books and fit to our purposes.  The first is an A-frame:


A-frames are extremely simple; they can be made with tree branches, a piece of string, and a rock.  Poor farmers in many developing countries use A-frames to make terraces in their fields.   In 2009 a colleague made an aluminum A-frame for surveying the slope of a planned 700-meter pipeline.  It worked wonderfully.

Next is a fluid communicating vessel:

                                      

I found the idea for this survey tool in a FAO publication.  Whereas the A-frame is great for leveling and carefully measuring slope 1 meter at a time, we needed that would cover ground faster without losing accuracy.  What you see is two 2-meter boards with rulers and a clear hose running the full height of them.  The hose runs between the two boards, with slack, and a 5-meter chain links the bottom of the boards.  To use this, the boards are stood upright and water is dripped into them until they’re even at 1-meter height of water.  Then the surveying is as simple as taking water readings from both the front and the rear sticks, every 5 meters.  Crunch the numbers as you go or when you’re done, and you can quickly draw a line graph of the slope.  I was very pleased with how well this worked.

I don’t have a picture of the 3rd surveying technology I want to share with you, but I can describe it easily enough! 

For surveying long stretches, nothing beats the simplicity of a small spirit level that clips onto a string!  In any hardware shop here we can find small plastic spirit levels, no bigger than your finder, and they clip onto a tightly held string.  Two people take the ends of that string, stretch it out for up to 20 meters, find level, and measure the difference.  It’s not as accurate as the former two methods, but it’s a great tool for when you just need to make sure that a long ditch (over 1 kilometer) is still going downhill!

There you have it, 3 surveying tools that can be built for under $10.  One for short and super-accurate work, another for medium distance and detail, and the last for longer distances.  When used right, these provide communities with the information they need to see their options and make their action plans.

No comments:

Post a Comment