Investigating availability of cloud free images with cloud masks in relation to satellite revisit frequency in the Northwest of England

Ebenezer Yemi OGUNBADEWA

Ebenezer Yemi OGUNBADEWA Remote sensing GIS Unit, Geography Department Adekunle Ajasin University, Akungba-Akoko, Ondo-State, Nigeria

Keywords: investigating, cloud free, satellite revisit, cloud masks

Abstract

The aim of this study is to determine the availability of cloud free images
in relation to satellite revisit periods for the UK and in particular for the Northwest of
England. Cloud free pixels were analysed with cloud masks from AVHRR/APOLLO and
TERRA/MODIS satellite cloud products. Availability of cloud free images was determined
from revisit frequency and the numbers of monthly images from Landsat ETM+,
ASTER, Quickbird and SPOT satellite sensors series. The average number of cloud free
days at Risley Moss and Charter’s Moss is five days per month with a minimum of one
cloud free day. The results show that satellite revisit periods and cloud free days are
a major determinant of satellite data availability and in this study it was also found
that contrary to popular opinion, satellite overpass does not necessarily mean imaging
opportunity and additional cloud free images could be obtained when there are no satellite
overpasses. The number of cloud free images at a given site may be increased by
combining data from different satellites.