Large map area measuring grid
Images courtesy of Abbie Gordon, Banchory.
The large area dot planimeter was a very convenient way of measuring areas on maps of various scales fairly accurately without the need to resort to the expensive wheeled planimeter.
The text on the planimeter reads as follows:
How to use the dot planimeter
1. Place the planimeter over the area to be measured.
2. Count all the dots which fall completely within the area.
3. Count only one type of dot which falls on the boundary line.
4. Take several readings, placing the planimeter at random angles in order to get an average reading.
5. Obtain the area measurement by multiplying the average reading by the appropriate scale factor.
(list of scale factors written below)
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