Indian Forest Service Examination (IFoS) — Forestry optional · India · Union Public Service Commission
Original practice questions written to the published syllabus · not past papersReading the forest from above: aerial photographs and satellite images, spectral behaviour of vegetation, image classification, change detection and forest-cover monitoring.
In the exams: IFoS Forestry Paper II Section A (forest mensuration and remote sensing); ICAR AIEEA-PG Group 09 (aerial photo interpretation and remote sensing); ICAR AICE-JRF 59 Unit 4
How our questions for Indian Forest Service Examination spread across the units of Remote Sensing & Photogrammetry for Forestry. Difficulty: 4 easy, 24 medium, 10 hard.
| Aerial photographs: scale, stereoscopy, parallax and tree height | 6 | |
| Vegetation indices (NDVI and others) | 5 | |
| Forest cover and change detection | 5 | |
| National forest-cover monitoring systems | 5 | |
| Photo-interpretation keys for forest types | 3 | |
| Satellite sensors and resolutions: spatial, spectral, temporal, radiometric | 3 | |
| Image classification: supervised and unsupervised; accuracy assessment | 3 | |
| Radar (SAR) in forestry | 3 | |
| Electromagnetic spectrum and spectral signatures of vegetation | 2 | |
| Drones (UAVs) for forest survey | 2 | |
| Fire detection and burned-area mapping | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Compared with a healthy tree, a tree defoliated by insects usually shows:
B. Higher red and lower NIR reflectance
Less chlorophyll raises red; less leaf area and damaged mesophyll lower NIR.
A camera with a 152 mm focal length is flown 3,040 m above flat ground. What is the photo scale?
D. 1:20,000
Scale = f ÷ (H − h) = 0.152 m ÷ 3,040 m = 1 ÷ 20,000, so 1:20,000. Forgetting to convert 152 mm to metres gives the wrong 1:20 or 1:200,000-type slips; 1:2,000 drops a zero.
On a single photo, which part appears at the largest scale?
C. A hilltop
Scale = f ÷ (H − h): higher ground is closer to the camera, so its scale is larger.
Trees planted in regular rows are most readily recognised on photographs by:
C. Pattern
Pattern is the spatial arrangement of objects; plantations show rows and grids.
A forest pixel has NIR reflectance 0.45 and red reflectance 0.05. Using NDVI = (NIR − red) ÷ (NIR + red), NDVI is:
A. 0.80
NDVI = 0.40 ÷ 0.50 = 0.80. 9.00 is the simple ratio NIR ÷ red.
The soil adjustment factor L in SAVI is most commonly set to:
B. 0.5
L = 0.5 suits intermediate vegetation cover; L = 0 makes SAVI equal NDVI.
Omission error for a class is the complement of:
B. Producer's accuracy
Omission is the share of reference samples of the class that the map missed.
A national forest-cover assessment counts all lands of more than 1 ha with canopy density above 10% as forest cover. Which rule makes such a cover figure differ from the recorded (legal) forest area?
A. It ignores ownership and land use
Cover is counted irrespective of ownership, legal status and land use, so orchards and tree plantations outside recorded forest are included, while recorded forest without canopy is not. Recorded forest area is a legal designation, not a canopy measurement.
A national forest agency's satellite fire-alert system typically:
B. Sends satellite fire detections to forest officers
Such systems take MODIS/VIIRS active-fire detections that fall in forest areas and send them to field officers by text message or email for ground verification and response. They do not measure severity in the field or forecast lightning.
In a forest-cover report that maps forest wall to wall with a 1 ha minimum mappable unit but estimates 'tree cover' separately by sampling, 'tree cover' refers to:
A. Tree patches under 1 ha outside recorded forest
Tree cover means patches of trees outside recorded forest areas that are smaller than the 1 ha minimum mappable unit, so they cannot be mapped and are estimated by sampling. Canopy above 70% is the very dense class, a different thing.
Ten here, 38 in the app. The Laisha app has every practice question we have written to Indian Forest Service Examination in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
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