How do trig points actually work? (or learning maths by applying maths - is a good way to understand it)

The way these were used was the same in every country. In America they’re called Trigonometrical stations, in the UK Trig Points, Australians calls them Trig Stations and in France they’re called geodesic terminals. . <br> <br>This video will explain how the theory behind how they were used to create extremely accurate maps. <br> <br>NOTE - at 15.05 there is a graphics typo. I dropped the results on to the wrong sides of the triangle when I did this in graphic in Photoshop. Obviously the longer side (on the left) should been 13 and the shorter side (on the right) shout have been 11, ooops ?, sorry