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Monitoring India’s Forest Cover through Remote Sensing
Landsat (TM) imageries of 1985-87 were used for the second cycle of forest cover assessment. Interpretation was done visually at 1:250,000 scale. With better spectral and spatial resolution of satellite data, higher scale of interpretation and more extensive ground truthing led to improvement in estimation of forest cover. The results published in the form of SFR 1989 estimated forest cover of the country as 640,134 km˛ (19.47% of country’s geographical area). Same satellite data and scale of interpretation was used for the third and fourth assessments. However, a significant development during this period had been the procurement of the then state of art computer (VAX-11/780) in 1989 for digital interpretation of satellite data. During the fourth assessment, satellite data of some parts of four states namely Bihar, Himachal Pradesh, Madhya Pradesh and Uttar Pradesh were also interpreted digitally.
In the mean time, India launched its remote sensing satellite (IRS). The fifth assessment (1995) was based on visual interpretation of imageries from IRS-1B (LISS-II) data was used, while for subsequent assessments (1997 and 1999) was based on data from IRS-1C (LISS-III). Scale of interpretation remained same (1:250,000 scale) and interpretation technique was largely visual with increasing input of digital interpretation.
Development of efficient digital image processing software (such as, ERDAS Imagin) and availability of reasonably priced powerful workstations and capacity building of its technical manpower, enabled FSI to completely switch over to digital interpretation of satellite data. Consequently, FSI interpreted the satellite data of the entire country through digital image processing at 1:50,000 scale during its latest assessment of forest cover assessment (2001), the eighth in the series. This improvement in the methodology has led to generation of a new baseline data on forest cover as for the first time FSI could map forested areas as small as 1 ha in extent while in the previous assessments this limit was 25 ha. As per SFR 2001, the forest cover of the country has been assessed to be 675,538 km2 (20.55% of the geographic area of the country).
A summary of important features of satellite data, sensors and their properties used for various assessments carried out so far for monitoring the forest cover of the country is given in table 1.
Table 1: Satellite Data for Forest Cover Assessments from 1987 to 2001
| Assessmentand Year |
Data Period |
Sensor |
Data Form |
Spatial Resolution |
Spectral Resolution |
Scale of Interpretation |
| I 1987 |
1981-83 |
Landsat – MSS |
Hard Copy FCC |
80 m |
4 Bands |
1:1 million |
| II 1989 |
1985-87 |
Landsat – TM |
Hard Copy FCC |
30 m |
7 Bands |
1:250,000 |
| III 1991 |
1987-89 |
Landsat – TM |
Hard Copy FCC |
30 m |
7 Bands |
1:250,000 |
| IV 1993 |
1989-91 |
Landsat – TM |
Hard Copy FCC |
30 m |
7 Bands |
1:250,000 |
| V 1995 |
1991-93 |
IRS-1B LISS II |
Hard Copy FCC |
36.25 m |
4 Bands |
1:250,000 |
| VI 1997 |
1993-95 |
IRS-1B LISS II |
Hard Copy FCC |
36.25 m |
4 Bands |
1:250,000 |
| VII 1999 |
1996-98 |
IRS-1C/1D LISS III |
Hard Copy FCC |
23.5 m |
4 Bands |
1:250,000 |
| VIII 2001 |
2000 |
IRS-1C/1D LISS III |
Digital |
23.5 m |
4 Bands |
1:50,000 |
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