﻿ Object metric

# Object metric

 The metric of object of a map can contain coordinates of points in two-dimensional, three-dimensional or four-dimensional system. The first two coordinates can have values in meters in a flat rectangular cartographical system in which the X axis is directed onto the north, Y axis - onto the east or in radians in geodetic system in which the X axis is a latitude, and Y axis  - a longitude. The third coordinate contains the value of the height in meters in the given system of heights (relative to the mean sea level, relative to the given spheroid, and so on). The first three coordinates can be in meters in the geocentric elevation system relative to the center of the given spheroid. The fourth coordinate can contain some characteristic of the object at the point. For example, the time of passage of a point, the speed of movement, or other information.   The metrics of different objects can have the different format of storage and dimension. Reason of variety - necessity to provide a high speed of data processing and files compactness at observance maximum accuracy of coordinates. The object metrics of an digital vector map can have some components: the metric of properly object and metric of subobjects. Object metrics may consists of components: metrics of main object and metrics of subobjects. The assignment of subobjects depends on a character of localization. For polygon objects the metric of the object describes an external outline, and metric of a subobject - internal outline ("cheese holes"). For example: an outline of glades in a forest, outline of islands on the river and so on. For line objects the metric of a subobject is prolongation of the metric of the object after an enforced rupture. For example: the field road at an intersection of the river can be torn in a place of ford. But the given recording capability of the metric is not applied to the denotation of dashed objects. The way of object visualization should not influence its coordinates. Multiscale linear and areal objects can have several additional contours created in the Sorting procedure using the generalization method. Additional contours are formed for smaller scales of display - 1/4 1/16, 1/64 from base scale of a map and are recorded into the object metrics together with the main contour. When compressing the map, those contours of objects that are closer to the current display scale will be automatically displayed. This speeds up the display of complex objects and makes the image of the terrain more visual. At any editing of the map and when performing calculations by the metric of object, the main contour of the multiscale object is processed. Multi-scale objects are one of the elements of a multiscale map that changes its view when changing the scale of displaying. Application of multiscale maps in packed MPTZ project allows to reduce number of created scales (layers) of maps in system of storage, finishing and application of topographic and geodetic information. The metric of a subobject is applied for labels, when the text must be placed into several strings or  to place characters by special way or for the description of complex labels including graphics units as a line or the dot sign. The coordinate axes direction is based on Russian geodetic system (X - to the north, Y - to the west).