CUET-PG Remote Sensing & GIS for Environmental Monitoring: practice questions

CUET-PG — Environmental Sciences · India · National Testing Agency

Original practice questions written to the published syllabus · not past papers

6worked here, free

16written to this exam in this subject

10syllabus units

What this subject covers

Watching 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

Electromagnetic spectrum and spectral signatures
Sensors and platforms: optical, thermal, radar, LiDAR, UAV
Image pre-processing and corrections
Vegetation and water indices: NDVI, EVI, NDWI
Image classification and accuracy assessment
Land-use and land-cover change detection
GIS data models, projections and spatial analysis
Digital elevation models and watershed delineation
Monitoring deforestation, drought and crop condition
Remote sensing of biomass and carbon
Open Earth-observation data and cloud platforms
GNSS and field data collection

Where the 16 questions fall

How our questions for CUET-PG spread across the units of Remote Sensing & GIS for Environmental Monitoring. Difficulty: 15 easy, 1 medium, 0 hard.

Vegetation and water indices: NDVI, EVI, NDWI	3
Electromagnetic spectrum and spectral signatures	2
Sensors and platforms: optical, thermal, radar, LiDAR, UAV	2
GIS data models, projections and spatial analysis	2
GNSS and field data collection	2
Image pre-processing and corrections	1
Image classification and accuracy assessment	1
Land-use and land-cover change detection	1
Digital elevation models and watershed delineation	1
Open Earth-observation data and cloud platforms	1

6 practice questions, worked

Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.

1 · Electromagnetic spectrum and spectral signatures · easy

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?

0.50 µm
0.87 µm
9.7 µm
0.10 µm

Answer and working

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

2 · Electromagnetic spectrum and spectral signatures · easy

Which surface has almost no reflectance in the near infrared and shortwave infrared?

Dry, bright sandy soil
Fresh snow on a glacier
Senescent grass canopy
Clear, deep open water

Answer and working

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

3 · Sensors and platforms: optical, thermal, radar, LiDAR, UAV · easy

Why are most land-observation satellites placed in sun-synchronous orbits?

They remain fixed above one point on the equator through the whole day
They are positioned to image the whole Earth every fifteen minutes
They are able to avoid passing through the Earth's shadow at night
They cross a given latitude at the same local solar time on each pass

Answer and working

D. They cross a given latitude at the same local solar time on each pass

A sun-synchronous orbit keeps illumination comparable from date to date. Staying over one point and imaging a hemisphere every few minutes describes geostationary orbit.

Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU

4 · Vegetation and water indices: NDVI, EVI, NDWI · easy

What is the theoretical range of NDVI?

0 to 1
0 to 100
−100 to +100
−1 to +1

Answer and working

D. −1 to +1

A normalised difference of two non-negative reflectances lies between −1 and +1. Water and snow are usually negative.

Further reading: See the manual sources: Lillesand et al.; Jensen; Campbell and Wynne; Longley et al.; Olofsson et al. 2014; IPCC 2006 AFOLU

5 · GIS data models, projections and spatial analysis · easy

At a map scale of 1:50,000, what ground distance does 4 cm on the map represent?

200 m
20 km
12.5 km
2 km

Answer and working

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

6 · Digital elevation models and watershed delineation · medium

Under Strahler ordering, a second-order stream joined by a first-order tributary becomes:

Second order
Third order
First order
Fourth order

Answer and working

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

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