207
21. LIGHT SCATTERING MODELS AND REFLECTANCE
MEASUREMENTS IN REMOTE SENSING OF SNOW
provide the highest frequency in observing the snow. As a result of this
modeling of snow-covered area and snow water equivalent can be
interpreted.
As can be seen the work for modeling is huge and it only can be solved
by starting from some in situ measurements of the BRDF and then
continuing with mathematical approximations and by finishing with tests and
control by using satellite images and the estimated incoming radiances.
4.
DISCUSSION AND CONCLUSIONS
The most important optical sensors for snow cover monitoring will be in
future MERIS and AATSR in ENVISAT, GLI in ADEOS II and VIRSR in
METOP-1. The estimated radiometric accuracy figures of MERIS and
AATSR shows that the sensors themselves will be sensitive enough for
registering the reflectance changes caused by snow metamorphism. This
opens the way for more accurate snow cover monitoring (presence, depth,
albedo and melt) if only we can estimate the BRDF of different snow types
and increase the accuracy of atmospheric correction of satellite images.
In snow measurements most efforts shall be concentrated in estimating
the BRDF of snow by starting with in situ measurements. When this has
been done or simultaneously with this, present satellite data can be analyzed.
A very valuable sensor in this modeling is the POLDER on ADEOS I and
coming ADEOS II, because some parts of the BRDF can be estimated over
large areas
using this sensor.
When the BRDF of snow is known the modeling of the reflectance of
snow covered terrain shall be studied. Ordinary satellite images will help in
this modeling even they do not give very many representative incidence
angle values for modeling. When this modeling gives useful results it is
possible to monitor the snow cover much better than earlier with optical
satellite sensors.
21. LIGHT SCATTERING MODELS AND REFLECTANCE
MEASUREMENTS IN REMOTE SENSING OF SNOW
provide the highest frequency in observing the snow. As a result of this
modeling of snow-covered area and snow water equivalent can be
interpreted.
As can be seen the work for modeling is huge and it only can be solved
by starting from some in situ measurements of the BRDF and then
continuing with mathematical approximations and by finishing with tests and
control by using satellite images and the estimated incoming radiances.
4.
DISCUSSION AND CONCLUSIONS
The most important optical sensors for snow cover monitoring will be in
future MERIS and AATSR in ENVISAT, GLI in ADEOS II and VIRSR in
METOP-1. The estimated radiometric accuracy figures of MERIS and
AATSR shows that the sensors themselves will be sensitive enough for
registering the reflectance changes caused by snow metamorphism. This
opens the way for more accurate snow cover monitoring (presence, depth,
albedo and melt) if only we can estimate the BRDF of different snow types
and increase the accuracy of atmospheric correction of satellite images.
In snow measurements most efforts shall be concentrated in estimating
the BRDF of snow by starting with in situ measurements. When this has
been done or simultaneously with this, present satellite data can be analyzed.
A very valuable sensor in this modeling is the POLDER on ADEOS I and
coming ADEOS II, because some parts of the BRDF can be estimated over
large areas
using this sensor.
When the BRDF of snow is known the modeling of the reflectance of
snow covered terrain shall be studied. Ordinary satellite images will help in
this modeling even they do not give very many representative incidence
angle values for modeling. When this modeling gives useful results it is
possible to monitor the snow cover much better than earlier with optical
satellite sensors.