Map Making- Tool of the Trade
The tool for measuring the angles you must measure for this type of map making is called a transit. I have enjoyed a quest for the perfect 'home built' transit for over 20 years. If you think you can design the best possible answer in 20 minutes, good luck to you... but you're going to miss some of the fun I've had on my quest. My current transit, excluding my camera tripod on which it is mounted, cost me about $30. Off the top of my head (I'll try to give you a better indication later!), I think it can make readings good to a tenth of a degree.
As you think about how you are going to build your transit, think about measureing devices in general. If you are organising this as a school activity, you might want to make a 'game' along the following lines:
Set up for the class five angle measuring exercises. Get each participant to measure each angle. Rule out any clearly wrong measurments; average the remainder. Now score each participant on how little his/ her readings vary from the class's average.
An alternative test for your transit is to go to a large field. Along one edge, mark perhaps 5 locations all in a straight line, perhaps 50 feet apart. (Use a longer distance if you can measure it accurately, and space allows. (You can see they are in line by looking along it!) About 150 feet from the baseline, at a point perpendicular to it's middle, stick a pole in the ground. (The location does not have to be precise.) Now measure angles between the baseline and the pole at each of your locations. Next, prepare a map of what you have measured. Start by drawing a line on a piece of paper. Mark 5 evenly spaced points along it. Draw the angles you recorded. The lines going away from the baseline should all met at one point if your readings are accurate.
Remember: Any measuring device must be able to return the same reading every time it measures the same angle, weight, length, etc. It must give the answer in usable units.
With the transit, a major element in achieving success will be your skill in devising something that will allow you to point directly at the distant objects which define the direction of the two arms of the angle.
How you read off how far around your pointer has swung will be another critical area.
When you are thinking about the design, remember that the simpler you can make it, the less chance there will be for inaccuracies to creep in. Attack the problem from both ends: What do I want to make? What can I (easily) make?
Click here to go on to my answer to the challenge of making a usable transit at a reasonable cost.
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