baseline

In surveying, a baseline is generally a line between two points on the Earth's surface and the direction and/or distance between them.
In a triangulation network, at least one distance between two stations needs to be measured to calculate the size of the triangles by trigonometry.
In relative Global Navigation Satellite System (GNSS) surveying, a baseline is the line between two GNSS receivers to determine the 3D coordinate difference.

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