Elevation matrix

Elevation matrix - 3D  ( three-dimensional )  raster model of area, created by conversion of the initial vector data of region into raster sort and further filling of raster model by method of  interpolation.

The element  of  matrix corresponds to a square plot of area, the size of which side is named as precision of  matrix.

The elevation matrix  can contain an absolute relief of area, relative elevations of objects  or   sum of  absolute relief and relative elevations of objects.

The surface appropriate to an absolute relief of terrain can be built by method of «weighted-average interpolation» or by method of «linear interpolation by net of elevations». At building matrix of relative  heights the surface is formed as the plane with zero height.

All elements of an absolute relief matrix can conditionally be divided into two groups. The element belong  to the first group, if its value is defined at the beginning of matrix building by map objects information. The element belong to the second group, if its value is evaluated with usage of the nearest elements of the first group.

If the surface appropriate to an absolute relief is created by a method of «linear interpolation by net of elevations» then at definition of elements  values of the first group the following map objects are used:

- point objects having the characteristic «true altitude»;

- point objects having the three-dimensional metrics.

If the surface appropriate to an absolute relief is created by a method of «weighted-average interpolation», then at definition of elements values of the first group the following map objects are used:

- Objects having the characteristic «absolute elevation»;

- Objects having the 3D - metric;

- Area objects of a hydrography with a constant elevation (lake, water storage basin etc.), not having characteristics    «absolute  elevation»;

- Line objects of a hydrography with a variable elevation (rivers, brooks  etc.).

If object has 3D - metric and the characteristic «absolute  elevation», then elevations  of   3D -metric  will be used.

To skip 3D - metric of map objects  You must use auxiliary text file (keyword PROCESS_3D_METRIC=NO).

To define the first group element values following map objects  type uses  :  line, polygon, dot, vector.

At processing the line object the elements are filled in which are intersected by a polyline connecting point of  the metric of the object.

At processing the area object the elements are filled in which are covered by the polygon appropriate to the given area object.

At processing the dot object the element  is filled in, in which the given dot object hits.

At processing the vector object the element is filled in, in which the central point of the segment connecting the first and second points of the metric of the given vector object hits.

At processing the line object with the characteristic «absolute elevation» the elements of a matrix are filled in with one value, equal absolute elevation of the object.

If inside area limited closed horizontal, there are no objects with absolute elevation, in that area the surface appropriate to a local extremum of a relief (a hole, a mountain) is created.  Height  of  a  relief cut is used for construction of this surface. If height of a relief cut is missed in the passport of a map, the held back significance, dependent on scale of a map, is used. If the local extremum is represented by dot object of a planimetric-high-altitude fundamentals (for example by mark of height, item GGS etc.), the surface is created with allowance for of this dot object. Construction the surfaces appropriate to local relief extremums is carried out if  the mode «Make extremes»  is  active.

At processing the linear object having 3D metric, the elements are filled in with different values appropriate to altitudes of points of 3D metric.

If an area object has 3D metric, it is handled as a line one.

For area objects of a hydrography with a constant elevation not having characteristic «absolute elevation» (lake, water storage basin etc.), the elements are filled in with one value, which is evaluated on the basis of elevations of the nearest enclosing objects of a map.  

For line objects of a hydrography with a variable elevation (river, brooks etc.) the elements  are filled in with different values appropriate to elevations of a map objects, with which the given object of a hydrography is intersected.

It is considered, that the line object of a hydrography is intersected with the dot object of a hydrography «water boundary», if the orthogonal coordinates on a plane in meters of one of points of the linear object metric coincide appropriate coordinates of the «water boundary» object till 0.01 of meter on area. If the given object of a hydrography does not intersect objects with the high-altitude characteristics, it is not handled.

The area objects of a hydrography not having characteristics «absolute elevation», and also line objects of a hydrography with a variable elevation can be included in processing only at usage of the auxiliary text file, in which the codes of these objects are enumerated.

At definition of elements values of the first group the map objects are handled in the following order:

- Line and polygon objects having the characteristic «absolute elevation» or 3D metric;

- Polygon objects of a hydrography with a constant elevation without the characteristic «true elevation»;

- Linear objects of a hydrography with a variable elevation;

- Dot objects having the characteristic «absolute elevation» or 3D metric.

At filling in a matrix of absolute elevations of objects there can be an overlay of elevations  ( hit in the same element  of two or more objects with absolute elevation).

In Height if superposition window of Matrix builder dialog you can set mode of elevations  filling  in case of superposition.

If the mode Height if superposition - Average is preset then an average arithmetic available value of the given element  and absolute elevation of the object which has hitted in the given element is recorded into an element.

If the mode Height if superposition - Maximum is preset, maximum of elevations of the objects which have hitted into the given element is recorded into an element.

Height of superposition mode does not influence filling in a matrix of dot objects  with  an absolute elevation. The absolute elevations of dot objects are recorded into an element  irrespective of its contents.

In case of superposition of relative elevations of objects the maximum relative elevation is always recorded into an element.