modiscloud (version 0.14)

extract_bit: Get the value of a particular bit in a byte

Description

In many MODIS products, the information for each pixel is stored in a byte, which represents numbers between 0 and 255. A byte is made up of 8 bits, and is a base 2 representation of the number. In the MODIS cloud product, each bit encodes information; see documentation of the MODIS cloud product in question.

Usage

extract_bit(intval, bitnum)

Arguments

intval

An integer between 0 and 255

bitnum

The bit number to return, between 1 and 8

Value

bitval The value of the bit (0 or 1).

Details

This function takes a byte and extracts the bits. The bits are in whatever order they are in the byte. If reading in the reverse direction is needed, the user should use rev.

References

Ackerman S, Frey R, Strabala K, Liu Y, Gumley L, Baum B and Menzel P (2010). "Discriminating clear-sky from cloud with MODIS algorithm theoretical basis document (MOD35)." MODIS Cloud Mask Team, Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin - Madison. .

GoldsmithMatzkeDawson2013

See Also

byteint2bit

get_bitgrid_2bits

Examples

intval = 123
extract_bit(intval, bitnum=1)
extract_bit(intval, bitnum=2)
extract_bit(intval, bitnum=8)