  in trigonometry and geometry, triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly (trilateration). the point can then be fixed as the third point of a triangle with one known side and two known angles. triangulation can also refer to the accurate surveying of systems of very large triangles, called triangulation networks. this followed from the work of willebrord snell in 1615â17, who showed how a point could be located from the angles subtended from three known points, but measured at the new unknown point rather than the previously fixed points, a problem called resectioning. surveying error is minimized if a mesh of triangles at the largest appropriate scale is established first. points inside the triangles can all then be accurately located with reference to it. such triangulation methods were used for accurate large-scale land surveying until the rise of global navigation satellite systems in the 1980s. == applications == optical 3d measuring systems use this principle as well in order to determine the spatial dimensions and the geometry of an item. basically, the configuration consists of two sensors observing the item. one of the sensors is typically a digital camera device, and the other one can also be a camera or a light projector. the projection centers of the sensors and the considered point on the objectâs surface define a (spatial) triangle. within this triangle, the distance between the sensors is the base b and must be known. by determining the angles between the projection rays of the sensors and the basis, the intersection point, and thus the 3d coordinate, is calculated from the triangular relations. == distance to a point by measuring two fixed angles ==  right|200px|triangulation the coordinates and distance to a point can be found by calculating the length of one side of a triangle, given measurements of angles and sides of the triangle formed by that point and two other known reference points. the following formula apply in flat or euclidean geometry. they become inaccurate if distances become appreciable compared to t
Angle Elementary_geometry Euclidean_geometry Surveying Wireless_locating