Thursday 16 October 2014

How to measure the area of an irregular shape

This article uses Meander for Mac OSX, which has a free trial period

1. View your shape on your screen using any app. This can be a map, satellite view, drawing or anything else.

2. Start Meander. The acetate window should cover the screen. You can resize this if you want to but the acetate should at least cover your shape.

3. Set the scale by dragging the cross-hairs to two points on your map or drawing which are a known distance apart. Type the known distance, not forgetting to select the appropriate units.

4. Trace your shape by pointing and clicking. You can change the style of the line you're drawing by going to Meander > Preferences (cmd-comma). Double-click to finish the line.

5. If you need to , you can adjust your line. Go to Line > Modify points (cmd-R) and drag individual points around.

6. Read off the area and line distance (perimeter). Note that you can choose your units for distance and area.

7. If you need to adjust the distance or area to take account of gradient / hilliness (for example, if you're measuring land for sowing seed), go to Meander > Preferences (cmd-comma) and adjust the slider. (The slider starts off at 'flat' for each new line you draw).

The slider's full setting is equivalent to a gradient (up or down) of 66% / 32 degrees over the entire length of the route or over the entire enclosed area. The slider is liner (eg half-way is equivalent to a constant 33% / 16 degrees) but note that the results aren't linear, and this is as it should be.

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