Building a matrix of slopes

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ic_8145 This task is used for building a matrix of the qualities reflecting directions of slopes of a terrain relief.

Creation of a matrix of slopes can be done at presence of the open data about a terrain relief - matrixes of heights MTW, matrixes of layers MTL, MTD-models, TIN-models.

The size of an element of a created matrix of slopes is defined by the size of an element of the open matrix of heights, and at absence of a matrix of heights is defined from scale of MTD-model or TIN-model.

Element size of a created matrix of slopes can be set by the user in a window of editing Element size (meters).

Result of building is the file of a matrix of qualities (*.mtq) which name the user can set by using the button «…» to the right of a field Matrix name. Into a matrix the values of angle of a slope in degrees are placed: for northern slopes - negative values of angle(shades of blue color of a palette), for southern slopes - positive values of angle(shades of pink color of a palette), for absence of a slope - the values of angle close to zero (white color of a palette).

Value of an angle of slope for a defined element with coordinates of the center (x0, y0) is calculated with use of three heights:

1) height in a defined point (x0, y0);

2) height in northern point concerning a defined one (xN, yN);

3) height in a southern point concerning a defined one (xS, yS).

 

Coordinates of northern (xN, yN) and southern (xS, yS) points are calculated with use of a direction "north-south" in view of obliquity of the ecliptic (22,5 degrees).

Coordinates of northern point:

xN = x0 + Elem;

yN = y0 + Dy

Coordinates of a southern point:

xS = x0 - Elem;

yS = y0 - Dy;

where:

Dy = Elem * tan (22.5);

Elem - the side size of a matrix element in meters;

tan (22.5) - a tangent of angle 22,5 degrees.

The request of the average values of absolute heights from a matrix of heights MTW is carried out by a method of triangles with use of heights of the elements surrounding the specified point.

 

Value of the exposition of a slope is value of one of 16 angles of the direction having the greatest in absolute size the angle of slope. Exposition of slope is measured in degrees and has the value equal to i * 22,5 where i is varies from 0 to 15. Exposition is the angle between «direction to the north» and «direction of slope». Direction of slope is one of 16 directions around the specified point (x0, y0), corresponding to the angle (maximal in absolute size) of a surface's slope. Direction to the north is the vector of the X-axis of a map, rotated clockwise onto the angle ECLIPTIC = M_PI/8 (22,5 degrees).

Palette of matrix of slopes can be specified by the element of Palette type dialog in the Palette group. Palette type can have the following values:

1) for exposition;

2) for angle (regular);

3) for angle (nonregular).

 

If the palette type for angles (nonregular) is set, then the palette contains 17 colors corresponding to the following ranges of the angle of slope of a surface in degrees:

1)  from-90 up to-15

2)  from-15 up to-10

3)  from-10 up to-7

4)  from-7 up to-5

5)  from-5 up to-3

6)  from-3 up to-2

7)  from-2 up to-1

8)  from-1 up to-0.5

9)  from-0.5 up to 0.5

10) from 0.5 up to 1

11) from 1 up to 2

12) from 2 up to 3

13) from 3 up to 5

14) from 5 up to 7

15) from 7 up to 10

16) from 10 up to 15

17) from 15 up to 90

 

Display of borders of diapasons and corresponding colors of a palette of slopes matrix can be received by means of the menu Tools-Map Legend, a Matrix bookmark.

For setting palette it is necessary to press the button «>> » in Palette group.

To choose a palette from the previously created matrix of quality (*.mtq) it is necessary to press the button of choosing a palette «…» in the Palette group.

The matrix of slopes can be built onto the region or onto the specified in region a frame of district provided by data about a relief : matrixes of heights (*.mtw), matrixes of layers (*.mtl), MTD-models (*.mtd), TIN-models (*.tin). For building a matrix of slopes onto the region it is necessary to include a mode All region in group Output area. For building a matrix onto the specified rectangular frame of district it is necessary to press the Select button in Output area group and to choose a frame of district on a map by two clicking of the left mouse button. To change borders of a frame - to press the Change button and execute change by using the left mouse button. The completion of the change mode is the double click of the left mouse button. For building a matrix onto the site of the district limited by the closed contour, it is necessary to press the By contour button in Output area group and to set a contour by pressing the left mouse button. Completion of a mode of the specifying a contour is the double pressing of the left mouse button. For  building a matrix onto the site of the district limited by closed object, it is necessary to press the By object button and to choose the closed object of a map.

For entering into a created matrix of slopes of passport data from an existing vector map it is necessary before pressing the Build button to choose a vector map by using the button «…» Passport's data from map.