i Detection of Smoke and Dust Aerosols Using Multi-sensor Satellite ...

Total 4.656% 2
35
34.577% 2
1
The threshold of BTD (3.7, 12) is 15 K for pixels over land and 9 K for pixels over
ocean.
2
The total errors of both over land and over ocean are not equal to the summation of
errors from each test because the overlap exists among tests.
3
The pseudo-NDVI and NDDI is only applied over land.
3.3.2 Flowchart
Fig. 3.8 is the flowchart of smoke detection algorithm. The whole swath of L1B
measurements is input and divided into two branches with land/sea mask product stored
in L1A file: smoke over land and smoke over ocean. In land branch, the process is
comprised with four tests, orderly for classifying vegetation, soil, cloud, and noise
(including water). The first test employs a pseudo-NDVI to examine vegetated pixel. The
NDDI is applied in the second test for differentiating smoke from bright surface. In the
third test, the BT11 and BTD (3.7, 11) are used to discriminate smoke from cloud, as well
as the reflectance at the 1.38μm band. The goal of last module is to filter out the noise
pixels (mainly water pixels) with the normalized Ratio (R3, R8) and single of reflectance
of band 8. In ocean branch, the process is relatively easy, which is comprised of two steps
only. At the end of process, an additional test named “noise-elimination test” is executed
to further filter noise pixels. In view of the smoke continuity, although a pixel is
identified as smoke pixel but it is not close to other smoke pixels, this pixel will be
considered as noise pixels and deleted from smoke images.