Spatial analysis in GIS Wednesday is based on complex techniques, the results of which depend on the raw data.
One of the fundamentals of spatial analysis techniques based on digital hypsometric model is the development of maps of the angles. She gained widespread use, from morphogenetic and geological-engineering perspective to the agrarian and territorial planning
Program ArcMap provides the ability to quickly prepare this type of cards based on raster model hypsometric territory. To calculate the slope of a surface that is specific to a particular screen, used values of absolute height, raised eight surrounding screens (Figure 1). The calculated values of the two parameters (ɑ and b), proportional average slant of slope (respectively on the x and y axis) according to the following formulae [1-4].
ɑ = (h3+2h6+h9-h1-2h4 - h7 )/8L ......(1)
b = (h1+2h2+h3-h7-2h8 - h9)/8L
h1 = the absolute height of the surface of the territory in (i) -OM image according to figure1.
L = raster measurement.
The angle of the slope, plant in the central point is call
I. In the menu Spatial Analyst pick Surface Analysis, then Slopethat will lead to opening the window method.
II. With list boxes Input surface Choose created a digital model of the hypsometric of Azerbaijan.
III. The main unit can be marked graphs slope measurement slope on the resultant map-in variant degrees ( Degree) or as a percentage (option) Percent .
IV. Graphs Z Factor and Output cell size perform the same role as
in the Hillshade. Leave them automatic size.
V. In the graph Output raster point localization and name of the
source file, then- OK.
VI. After completion of the analysis of the source layer appears in
the map image.
Change the layer display mode according to the technique
described previously. The final effect should be similar to Figure 2.
The following method of broad application that is based on digital
hypsometric model is the definition of exposure. Under slope
Exposition, understand the direction (azimuth) slope steepness of
most to the sides of the horizon. This option is very important for
those kinds of analysis that takes into account the difference of
thermal balance of the northern and southern slopes. This is the
initial value for aspects such as the time of occurrence of snow
cover duration of vegetation period etc. The method of calculation
is similar to the method Slope . It also used high-altitude data from
screens placed in the immediate vicinity of the Central screen, for
which the calculation of parameters a and b (in accordance with
Exposition of slope is calculated as:
tanβ = a / b (3)
If b positively, the largest ß necessary Add 180°, that allows to take into account the magnitude of the azimuth from 0 to 360°.
1. In menu Spatial Analyst choose a Surface Analysis, then Aspect-method dialog box appears (Figure 3)
2. In box Input surface traditionally make the filename digitally hypsometric model.
3. In box Output cell size leave unattended.
4. In box Output raster denote localization and name of the
source file, click OK to start following their completion,
payments to the image will be added effective map. After you
change the display card is similar to Figure 3.
Next, consider the way to an integrated spatial analysis based
on raster maps. For example, suppose you want to select a specific
localization hypothetical potential investments on the territory of
Azerbaijan. Investor demands that the investing territory meets
certain conditions. First, the angle of the slopes in the territory’s
investment should not exceed 10°. Secondly, the investment should
be within the absolute height of surface from 100 to 500nm. Using
GIS and digital hypsometric model of Azerbaijan (with derived
layers), the definition of localizations of this investment takes a
few minutes. In menu Spatial Analyst toolbar Select position Raster
Calculator. A dialog box appears, represented in the left part
of the window, in the Layers highlighted all raster layers project.
With right sides are mathematical logical operators that can be
used for entering formulas. The formulas are based on arithmetic
operators, and the results have a numeric expression. For example,
if you want to double increase digital hypsometric model, it is
possible to formulate a simple expression [9-12]:
[CGM] * 2 (3)
where instead of CGM , you must enter the name of the selected
raster layer surface model. As a result of this operation received
a raster map, where each point in discrete space is assigned a
numerical value, which corresponds to doubling the height of
the territory. Such arithmetic operations can be applied to other
For example, having a layer of embossed field precipitation,
as well as layer with spatial distribution of filtration coefficient,
obtained by multiplying the two layers you can obtain the spatial
distribution of effective infiltration of precipitation. Often also
used the differencing method. In this way, create a differential
maps that document the temporarily-spatial variability of the
investigated phenomenon. For example, as a result of the seizure
of average precipitation from the actual over the past two years, it
is possible to define the territory increases and regression of this
phenomenon. Use this type of expression to identify the territory
within Azerbaijan, which satisfies the conditions of investra. First
define the territory where the inclination does not exceed slopes
This requires the formulation of the next task [13-15].
[Slope] < = 10. (4)
Where on the graph Slope you must submit the name of a
bitmap layer with angles of inclination of slopes.
Formulation of issues using Windows Raster Calculator is
1. In the graph Layers Select the name of the layer with the angles
of inclination of slopes. Note that added layer automatically
enclosed in quotation marks.
2. Of the symbols of the operators choose < = This results in
adding this element to the expression.
3. Using digital signs in a window or on the keyboard, type 10 in
the end of the expression.
4. The formula is ready, you can go to to do so. Evaluate.
Upon completion of the calculations in the working area of the
project will add a new layer using the program Calculation . Layer
is only with greatness and 0 1. Screens marked digital 1, satisfy the
conditions of maximum slope slopes up to 10 largest° . Now you
must select the area that meets the requirements of investra for its
absolute height. To do this, construct the following expression (5):
[CGM] > = 100 and [CGM] < = 500 (5)
On site CGM enter the name of a raster layer with digital
hypsometric model territory. For formulating expressions use
window Raster Calculator [16-18] .
i. In Windows Raster Calculator Select layer with digital
hypsometric model of Azerbaijani territory in the graph Layers.
ii. press the key with the operator > =
iii. Enter the value 100
iv. Push And
v. Again click on the layer name in the CGM graph Layers.
vi. Push the button with the < = operator
vii. Enter the value 500
viii. Check the correctness of the formula and select Evaluate.
The result of the calculations is a raster layer named program
Calculation . 2. similar to the previous layer here showing screens
marked cifroj1 that identify the territory, where high-rise relevant
criteria. now you must connect both layers to define the territory
corresponding to two requirements-surface height and tilt. Use
the method the Raster Calculator .
i. press twice on the layer Calculation in the graph Layers.
ii. Select the = operator
iii. Enter the value 1.
iv. Choose the logical operator And
v. twice click on layer Calculation2.
vi. Select the = operator
vii. Enter the value 1. The final expression must be of the
form:(Calculation) = 1 & (Calculation2) = 1
viii. Click on Evaluate. In the working area will be added a new
layer with the designated (red) territory, which satisfies the
requirements of the investor (Figure 4).
The resulting image points to a very extensive array, located
in the foothill zone of Azerbaijan. It is clear that in such a large territory does not satisfy any investor to potential localization
object. In this regard, you can narrow the boundary parameters
of each criterion. For example, the choice of the territory where
the inclination does not exceed 1 degree. In the analysis process
can also take into account additional criteria, such as location,
investment plot at a distance of not less than 500m from the nearest
coastline and 1000m from the urban areas. The possibilities are
endless and depend solely on the needs of the user of GIS and
spatial information availability.