ICAR AIEEA-PG — Physical Science group (sub-subject 3.6 Environmental Science) · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersWatching land, water, vegetation and carbon from space and analysing it spatially: sensors, indices, classification, change detection and the open datasets used in sustainability work. Precision-agriculture uses of the same tools are in the crop sciences.
In the exams: ICAR AICE subject 71 Unit 3 (RS and GIS for ecosystem analysis); ICAR AIEEA-PG Physical Science Unit IV; UGC NET Unit 9
How our questions for ICAR AIEEA-PG spread across the units of Remote Sensing & GIS for Environmental Monitoring. Difficulty: 26 easy, 4 medium, 0 hard.
| Electromagnetic spectrum and spectral signatures | 4 | |
| Sensors and platforms: optical, thermal, radar, LiDAR, UAV | 4 | |
| Vegetation and water indices: NDVI, EVI, NDWI | 3 | |
| Image classification and accuracy assessment | 3 | |
| GIS data models, projections and spatial analysis | 3 | |
| Digital elevation models and watershed delineation | 3 | |
| Image pre-processing and corrections | 2 | |
| Land-use and land-cover change detection | 2 | |
| Remote sensing of biomass and carbon | 2 | |
| Open Earth-observation data and cloud platforms | 2 | |
| GNSS and field data collection | 2 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Using Wien's displacement law (λmax = 2898 µm K / T), at roughly what wavelength does the emission of a land surface at 300 K peak?
C. 9.7 µm
λmax = 2898 / 300 = 9.66 µm, in the thermal infrared window. 0.50 µm is the Sun's peak at about 5800 K; multiplying instead of dividing, or inverting the ratio, gives the other values.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
Which surface has almost no reflectance in the near infrared and shortwave infrared?
D. Clear, deep open water
Water absorbs strongly beyond about 0.7 µm, so clear deep water is dark in NIR and SWIR. Dry sand and senescent grass reflect increasingly with wavelength; snow is bright in the visible though dark in SWIR, and still reflects some NIR.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
A synthetic aperture radar operates at 5.405 GHz. What is its wavelength (c = 3 × 10⁸ m s⁻¹)?
B. 5.55 cm
λ = c/f = 3 × 10⁸ / 5.405 × 10⁹ = 0.0555 m = 5.55 cm, the C band. The other values come from slipping a factor of ten in unit conversion or multiplying c by f.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
A LiDAR pulse returns from the ground 6.67 µs after it was emitted. How far is the ground from the sensor (c = 3 × 10⁸ m s⁻¹)?
C. 1000 m
Range = c × t / 2 = 3 × 10⁸ × 6.67 × 10⁻⁶ / 2 ≈ 1000 m. Forgetting to halve the two-way travel time gives about 2000 m.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
A three-class error matrix (rows = map, columns = reference) has forest row 45, 3, 2; cropland row 6, 38, 6; grassland row 1, 7, 42. What is the overall accuracy?
C. 83%
Overall accuracy = (45 + 38 + 42)/150 = 125/150 = 83.3%. 90% is the forest class's user's accuracy, not the map's overall accuracy.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
Which change-detection method directly produces a 'from–to' transition matrix?
D. Post-classification comparison
Classifying each date and cross-tabulating gives from–to classes. Differencing, ratioing and PCA indicate where change occurred, not its class transitions.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
At a map scale of 1:50,000, what ground distance does 4 cm on the map represent?
D. 2 km
4 cm × 50,000 = 200,000 cm = 2,000 m = 2 km. 200 m and 20 km are factor-of-ten slips; 12.5 km divides instead of multiplying.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
Under Strahler ordering, a second-order stream joined by a first-order tributary becomes:
A. Second order
The order increases only when two streams of the same order meet (2 + 2 → 3). A lower-order tributary does not change the order.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
A forest has 200 t ha⁻¹ above-ground dry biomass. Using a carbon fraction of 0.47, how much CO₂ equivalent does this represent?
A. 345 t CO₂ ha⁻¹
Carbon = 200 × 0.47 = 94 t C; CO₂ = 94 × 44/12 = 345 t. 94 stops at carbon; 733 skips the carbon fraction; 25.6 inverts the 44/12 ratio.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
An image has 10,000 × 10,000 pixels, 10 bands and 16-bit values. What is its uncompressed size?
C. 2 GB
10⁴ × 10⁴ × 10 × 2 bytes = 2 × 10⁹ bytes ≈ 2 GB. 1 GB treats 16 bits as one byte; 16 GB counts bits rather than bytes.
Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU
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