noun

1. Surveying, Navigation the process of determining the distance between points on the earth's surface, or the relative positions of points, by dividing up a large area into a series of connected triangles, measuring a base line between two points, and then locating a third point by computing both the size of the angles made by lines from this point to each end of the base line and the lengths of these lines
2. the triangles thus marked out

Etymology: ML triangulatio