RS_MapAlgebra

Introduction: Apply a map algebra script on a raster.

Format:

RS_MapAlgebra (raster: Raster, pixelType: String, script: String)

RS_MapAlgebra (raster: Raster, pixelType: String, script: String, noDataValue: Double)

RS_MapAlgebra(rast0: Raster, rast1: Raster, pixelType: String, script: String, noDataValue: Double)

Since: v1.5.0

RS_MapAlgebra runs a script on a raster. The script is written in a map algebra language called Jiffle. The script takes a raster as input and returns a raster of the same size as output. The script can be used to apply a map algebra expression on a raster. The input raster is named rast in the Jiffle script, and the output raster is named out.

SQL Example

Calculate the NDVI of a raster with 4 bands (R, G, B, NIR):

-- Assume that the input raster has 4 bands: R, G, B, NIR
-- rast[0] refers to the R band, rast[3] refers to the NIR band.
SELECT RS_MapAlgebra(rast, 'D', 'out = (rast[3] - rast[0]) / (rast[3] + rast[0]);') AS ndvi FROM raster_table

Output:

+--------------------+
|              raster|
+--------------------+
|GridCoverage2D["g...|
+--------------------+

Spark SQL Example for two raster input RS_MapAlgebra:

RS_MapAlgebra(rast0, rast1, 'D', 'out = rast0[0] * 0.5 + rast1[0] * 0.5;', null)

For more details and examples about RS_MapAlgebra, please refer to the Map Algebra documentation. To learn how to write map algebra script, please refer to Jiffle language summary.