Map Algebra - PowerPoint PPT Presentation

1 / 35
About This Presentation
Title:

Map Algebra

Description:

Map algebra is a high-level computational ... Zonal functions ... Zonal Functions. Dr. Robert C. Frohn, Department of Geography, University of Cincinnati ... – PowerPoint PPT presentation

Number of Views:248
Avg rating:3.0/5.0
Slides: 36
Provided by: THo48
Category:
Tags: algebra | map | zonal

less

Transcript and Presenter's Notes

Title: Map Algebra


1
Map Algebra
2
Map algebra
  • Map algebra is a high-level computational
    language for performing spatial analysis using
    gridded (raster) data.

3
The Map Calculator
4
Map Calculator Syntax Rules
  • Grid names are always in square brackets (e.g.,
    Slope).
  • Strings are in quotes.
  • Optional blank spaces can be used to separate
    objects, requests, and parameters. Grid1
    Grid2
  • Expressions are evaluated from left to right,
    regardless of the mathematical operator.
    Grid1(Grid2Grid3)
  • You may nest expressions, as long as the entire
    expression evaluates to a grid. The inner most
    parentheses set is evaluated first, then outward.
  • ((Grid1 Grid2) 0.40) (((Grid3
    Grid4) 0.10) ((Grid5 Grid6) 0.50))

5
Map algebra operators
  • Arithmetic operators
  • basic math operators.
  • Boolean operators
  • logically examine the input grids. The integer
    output grid will contain values of 0 (FALSE) and
    1 (TRUE).
  • Relational operators
  • compare two numbers. If the result is true, 1 is
    returned, otherwise, a 0 is returned.

6
Arithmetic Operators
7
Relational Operators
8
Boolean Operators
9
Map Algebra Functions
  • Local
  • Neighborhood
  • Zonal
  • Global

10
Local Functions
  • Local functions perform cell-by-cell processing.
    The output value at each location is only
    dependent on the input cell at that location

11
Local Functions
  • arithmetic,
  • trigonometric,
  • exponential,
  • logarithmic,
  • reclassification,
  • extraction,
  • statistical.

12
IsNull
13
SetNull
14
Neighborhood (Focal and Block) Functions
  • Depends on value of pixel and its neighbors

15
Resample
16
Zonal functions
  • A zone is defined as all cells in a grid that
    have the same value, regardless of whether or not
    they are contiguous.

17
Zonal Functions
18
Global functions
  • Global functions compute an output grid where the
    value for each output cell is potentially a
    function of all the input cells

19
Global functions
20
RegionGroup
  • The RegionGroup request creates regions for an
    input grid. A region is a group of connected
    cells with the same value. A zone is a group of
    connected or disconnected cells with the same
    value.

21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
(No Transcript)
34
(No Transcript)
35
(No Transcript)
Write a Comment
User Comments (0)
About PowerShow.com