Geometric constructions on a map |
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Basic line (basis of construction) - a starting line, coordinates of initial and terminal point of which are known. Initial point of a basic line — a point on a map at which coordinates are known, and together with a terminal point it forms a basic line and from it the measurement of distance and corners from a basic line is made. Terminal point of a basic line — a point on a map at which coordinates are known and it together with initial point forms a basic line. Picket point — a point of district which coordinates are calculated. For an execution of geometrical constructions it is necessary 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 a choice of a piece of the metrics of linear or polygon object.
Following variants of construction are possible:
After a choice of basis of construction the user carries out input in corresponding dialog of the measuring data, necessary for calculation of coordinates of a picket point. In a dialogue of data input there is a figure which evidently explains what information it is necessary to enter for calculations. Calculations of coordinates of a picket point can be executed to the left and to the right of basis of construction. To set the side for calculations, and as to change a direction of basis of construction (to interchange places the initial and final points) it is possible during input of the information, having set necessary value of corresponding elements of dialog.
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At an execution of geometrical constructions on a map the following basic concepts are used: 
