Raster Math: Algebraic Expressions and Map Analysis

A method of treating raster layers as algebraic expressions, using arithmetic operators, mathematical functions, and comparison operators for spatial analysis. Explore examples like calculating the probability of encountering the cascade treefrog in Australia's forests. Learn about common functions, mathematical functions, and comparisons in raster math and map algebra.

• - Raster Math - Map Analysis - Spatial Analysis - Algebraic Expressions

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Uploaded on Mar 02, 2025 | 0 Views

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1. Raster Math Dana Tomlin and Joseph Berry (1970 s) A method of treating individual raster layers as members of algebraic expressions. 2 * LayerA

2. Raster Analysis Map Algebra Examples: Fire Hazard: [Fuel Density Hazard] + [Slope Hazard] + [Veg Type Hazard] Probability of encountering the cascade treefrog (Litoria pearsoniana) within the forests of eastern Australia: 1 / (1 + exp(10.48 2.204 * log10(RAINFALL) 2.037 * PALMS)) RAINFALL= the annual volume of rain falling in the watershed above the stream PALMS = 1 if palms are present at the site and 0 otherwise.

3. Raster Math LayerA + LayerB Arithmetic Operators (+, -, *, /) Mathematical Functions (Sqr, Sqrt, Log, Abs, exp, int, etc.) Comparison Operators (>, >=, =, <>, <, <=) Boolean Operators (AND, OR, NOT, XOR)

4. Raster Calculator Toolbox Spatial Analysis Tools Map Algebra Raster Calculator

5. Test Yourself 3 2 4 3 0 2 1 9 = -

6. Analysis Environment Spatial Reference (Coordinate System) Make them the same Extent Area of interest All rasters should overlap Cell Size Largest of all rasters or larger

7. Raster Math Raster Math Vector or Linear Algebra 1 + 12 = 13 1 2 2 3 12 13 9 10 13 11 = + 15 13

8. Common Functions Local: Arithmatic: +,-,/, *, MOD (Modulo): returns the remainder Boolean: OR: If either input is true, output is true AND: If both inputs are true, output is true CON (Conditional)

9. Mathematical Functions Abs (absolute): flips negatives to positive Ceil (ceiling): float to integer next highest integer value (i.e. 1.1 -> 2) Floor: float to integer giving next lowest integer value (i.e. 1.1 -> 1) Int (integer): truncates float to integer

10. Comparisons <> (Not Equals) == (Equals) < (Less than) <= (Less than or equal to) > (Greater than) >= (Greater than or equal to)

11. Raster Math: Comparisons 1 > 2 = 0 1 2 2 3 2 3 2 2 0 0 = > 0 1

12. Raster Math: Boolean AND 0 AND 1 = 0 0 1 0 1 0 0 1 1 0 0 0 1 = AND AND works but the calculator will insert &

13. Raster Math: Boolean OR 0 OR 1 = 1 0 0 0 1 1 0 1 1 1 0 1 1 = OR OR works but the calculator will insert !