Global Monthly Vegetation Cover Quality Description Files

Introduction Page, Digital Data Information

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The 8-bit QD files were generated for each month to describe some of the inherent statistical characteristics. The following table describes how each bit was assigned:

BIT NUMBER	CRITERIA/COMMENT	BIT VALUE
1	nobs = 0 or 1 (mostly cloudy)	1, else 0
2	nobs = 2 or 3 (moderately cloudy)	1, else 0
3	nobs = 4 or 5 (mostly clear)	1, else 0
4	|sva| < 20 deg (near nadir)	1, else 0
5	sva > 20 deg (forward scatter bias)	1, else 0
6	sva < -20 (back scatter bias)	1, else 0
7	sza < 50	1, else 0
8	sza > 50	1, else 0

where "nobs" is the number of clear weekly observations per month per pixel, sva is the satellite viewing angle, and sza is the solar zenith angle.

To illustrate, examples of the images representing metadata for the vegetation cover data for April, July and October 1985 are given below. The first row shows the cloud bits: mostly cloudy - red, moderately cloudy - green, and mostly clear - blue. The second row shows the satellite viewing angle bits: near nadir - red. forward scatter - green, and backscatter - blue. The third row shows the solar zenith angle bits: smaller than 50 deg - red, and greater than 50 deg - green. To see the annual and interannual variability in these metadata, the user should read all the data files and use some image processor to display the bits of the QD files.

Cloud	April 1985	July 1985	October 1985
Viewing geometry	April 1985	July 1985	October 1985
Sun angle	April 1985	July 1985	October 1985

Note: Because of space restraints on this CD-ROM, the digital QD files for 1985 were eliminated, but the samples above should give the user some indication of how the QD files looked for 1985.