Calculate coordinates (an angular resection(notch))

It is necessary for user to specify a basic line on a map. The choice of a basic line can be carried out by two ways: by the consecutive indication of two point objects (the first point - the initial point, the second point - a terminal point) and by a choice of a piece of the metrics of linear or polygon object. Then in the corresponding dialogue to enter parameters of construction (an angle onto an observed point from an initial and final point of basis).  

Coordinates of a picket point are on crossing of two rays dropped from initial and final points of basis of construction, under angles specified by the user.  

The user can create points, as on the right, and to the left of basis. See terms.

Description of dialog: Calculation of coordinates (method of angles).