Map Algebra and Beyond: 1. Map Algebra for Scalar Fields Xingong Li University of Kansas 3 Nov 2009. Topics. The conventional map algebra Local operations Focal operations Zonal operations Global operations. Map Algebra.
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Precipitation

Losses (Evaporation, Infiltration)
=
Runoff

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3
2
4
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2
3
5
2
Global
Local
Focal
Zonal
Images are from: http://rs.gso.uri.edu/amy/avhrr.html
Feb.
Apr.
Jun.
Dec.
Aug.
30Year (19712000) Monthly PRISM PrecipitationHow do we define seasonality of precipitation at a single location?
Total = 18.69”
[4.01 3.48 2.69 1.30 0.48 0.11 0.01 0.02 0.19 0.74 1.57 4.09]
y=p*cos(monthAngle)
Monthly Precipitation as a Vector QuantityEach month’s duration is equivalent to a 30° angle
Monthly data are plotted at midpoint: 15°, 45°, 75°, ……
y=p*cos(monthAngle)
Seasonality AnalysisMonthly precipitation (in inches):
[4.01 3.48 2.69 1.30 0.48 0.11 0.01 0.02 0.19 0.74 1.57 4.09]
Add all vectors = Resultant vector
12.41
22.25°
Measurement spatial resolution
model/application resolution
p1
p2
a2
a1
a3
a4
p3
p4
Calculating Subwatershed Precipitation Depthpi—precipitation depth in an hour
ai—portion of the watershed that falls in the ith cell
Buffers can be delineated from the distance raster
friction
CostDistance OperationUnit of the friction raster:
days per unit distance
Friction = 1 / speed
What do the values mean on the cost raster layer?
The days that the fungus will take to reach a cell
April
The least cost between A and B and passes through a cell.
Corridor = accumulative cost < a threshold value