BSL {landsat} | R Documentation |
Bare Soil Line
Description
Finds Bare Soil Line (BSL) and maximum vegetation point.
Usage
BSL(band3, band4, method = "quantile", ulimit = 0.99, llimit = 0.005, maxval = 255)
Arguments
band3 |
File name or image file (matrix, data frame, or SpatialGridDataFrame) for Landsat band 3 DN (red). |
band4 |
File name or image file (matrix, data frame, or SpatialGridDataFrame) for Landsat band 4 DN (NIR). |
method |
Either "quantile" or "minimum" – describes way in which soil line is identified. |
ulimit |
Upper limit for quantile of band ratios (ulimit < 1). |
llimit |
Lower limit for quantile of band ratios (llimit > 0). |
maxval |
Maximum value for band data; default of 255 for Landsat 5 and 7. |
Details
Finding the BSL requires identifying the lowest NIR values for each level of red. The quantile method takes the lowest set of points, those with a NIR/red ratio less than the llimit-th quantile. The minimum value method takes the lowest NIR value for each level of red. However they are found, these points with low NIR for their red values are used in a major axis regression to find the Bare Soil Line. This function also identifies the full canopy point (maximum vegetation), by using the ulimit to identify the top points, with NIR/red ratio greater than the ulimit-th quantile, and with high NIR values. Red or NIR values of 255 (saturated sensor) are omitted when calculating the BSL.
Value
BSL |
Regression coefficients for the Bare Soil Line |
top |
band 3 and band 4 values for the full canopy point |
Author(s)
Sarah Goslee
References
Maas, S. J. & Rajan, N. 2010. Normalizing and converting image DC data using scatter plot matching. Remote Sensing 2:1644-1661.
Examples
data(nov3)
data(nov4)
nov.bsl <- BSL(nov3, nov4)
plot(as.vector(as.matrix(nov3)), as.vector(as.matrix(nov4)))
abline(nov.bsl$BSL, col="red")
points(nov.bsl$top[1], nov.bsl$top[2], col="green", cex=2, pch=16)