The calibration of
dard. The panel has
very high spectral
height of about one
rea with a diameter
value of ratio index
measurements were
Veasurements were
rocks, water bodies,
NDI and Spectral
ious terrain surfaces
in Table 5.,6.7. The
e compared directly
This is because the
e constituents of the
int between the two
snow. This clearly
| and identify snow
igher. However, for
ratio indices could
er bodies and snow
spectral reflectances.
es would help as an
ninate between snow
s satisfactorily in the
X (RI)
M TYPICAL
0.55
0.71
0.88
13.20
38.50
us terrain surfaces in
RENCE INDEX
JM _ TYPICAL
- 0.30
- 0.17
- 0.10
0. 80
0.93
ous terrain surfaces in
IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India,2002
Target Spectral Reflectance (%)
Minimum Maximum Typical
(0550 (91625 |@550 |@1625 |@550 |@1625
Soil 6 15 30 37 20 25
Sand 20 30 27 39 24 40
Rocks | 11 20 30 28 28 22
Water | 3 0.09 S 1 4 0.5
Bodies
Snow | 47 0.8 99 S 80 1:3
Table 7. Range of measured Spectral Reflectances for various
terrain surfaces in the Himalaya region.
8. FUTURE SCOPE, UTILITY AND APPLICATIONS
At present, the instrument is designed with the bands useful for
snow and glacial studies. The instrument has flexibility to
incorporate any two spectral bands in the range from 400 to
1800 nm. Hence with proper selection of spectral bands it is
possible to use the instrument to generate databases of spectral
reflectances, spectral radiance, and to obtain spectral indexes
for other applications such as agricultural, geological,
atmospheric etc. This information will be ultimately useful for
satellite image analysis and interpretation.
The instrument with proper spectral bands would be also
helpful for on-board calibration of various satellite sensors like
IRS, TM, INSAT etc., by collecting concurrent radiometric data
at multiple sites and over different terrain with these units.
9. SUMMARY AND CONCLUSIONS
A portable, battery operated field instrument, Ratio Radiometer,
has been indigenously designed and developed for various
remote sensing applications. The instrument simultaneously
produces two outputs in two different wavelength bands. The
instrument is useful for "in-situ" measurements of spectral
reflectance with respect to standard reflectance panel and
spectral radiance.
The present model has been developed for snow and glacial
applications. Two spectral bands with central wavelengths 550
nm and 1625 have been incorporated in this model to derive
snow indices. The instrument is being used to collect
radiometric data, which would be useful for analysis and
interpretation of satellite imagery for snow monitoring/
mapping. It has been found that it works satisfactorily under the
typical environmental conditions of Himalayas. The field data
obtained with the instrument is found to be encouraging. The
ratio index along with the values of spectral reflectances would
be useful to classify/identity snow packs and their conditions.
The instrument has flexibility in incorporating any two spectral
bands in the range from 400 nm to 1800 nm. Hence with
proper selection of spectral bands, the instrument has capability
to tune it for any specific remote sensing application.
Consequently, the instrument becomes versatile to use it for
various other applications of remote sensing.
Its specially designed software processes the data for offset
correction and temperature correction and also compute the
spectral indices viz. ratio index and normalized difference
index. The database of these measurements along with spectral
indices would subsequently be used to classify, identity various
terrain surfaces and to develop suitable spectral indices such as
ratio index, normalized difference index, etc. for the
interpretation and analysis of satellite images for any desired
applications of remote sensing.
Acknowledgements
The author gratefully acknowledges Mr. A. S. Kiran Kumar,
Group Director, EOSG/SEDA, Mrs. Gunbala Navlakha, Head,
SFSD/EOSG/SEDA and DR. S. R. Nayak Head
MWRD/RESA for their support and comments on this work
and manuscript. The encouragement, logistic as well as ground
measurements support provided by Gen. (Retd) S. S. Sharma,
Director, Mr. Amod Kumar, Scientist, SASE, Chandigarh, is
greatly acknowledged. Mr. P. Narayanbabu, Scientist,
SFSD/EOSG/SEDA is kindly thanked for his help in software
development. The author gratefully acknowledges Dr. V. D.
Mishra, Scientist SASE, Chandigarh his participation in field
data collection.
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