Geographical Techniques Questions and Answers

Q: Which one of the following is an equal area projection ?

The equal area projection is Bonne's projection.Bonne's projection is a modified conical projection in which every parallel is drawn true to scale and the central meridian is also true, so areas are preserved everywhere, though shapes are distorted away from the centre. It was long used for atlas maps of continents such as Asia and Europe.The simple cylindrical and simple conical projections preserve neither area nor shape exactly, and the Mercator projection is conformal (shape-preserving), with areas greatly exaggerated towards the poles.

Q: If a map is drawn on the R. F. = 1 : 50,000 but when the same map is redrawn on R.F. = 1 : 2,50,000. The status of redrawn new map is :

The redrawn map is reduced by 5 times.The representative fraction compares map distance with ground distance. At 1 : 50,000, 1 cm represents 50,000 cm; at 1 : 2,50,000, 1 cm represents 2,50,000 cm. The same ground distance therefore appears on the new map at\[ \begin{aligned} \frac{1/250000}{1/50000} &= \frac{50000}{250000} \\ &= \frac{1}{5} \end{aligned} \]of its original length, so the map is reduced five times in linear scale (and 25 times in area). It is not enlarged, because the denominator has grown, and 2.5 is a misreading of the 2,50,000.

Q: Which GIS data model represents geographic features using points, lines, and polygons?

The model is the Vector data model.A vector model stores geographic features as geometry defined by coordinates: a well or a sampling site is a point, a road or a river is a line, and a field or a district boundary is a polygon. Each feature carries its own attribute record, which makes vectors suited to discrete objects with sharp boundaries.A raster model instead divides the area into a regular grid of cells or pixels, each holding one value, as in a satellite image or an elevation surface. Grid and pixel are simply the parts of a raster, so they are not separate models that use points, lines and polygons.

Q: Georeferencing an image in GIS means to :

Georeferencing means to assign real world coordinates to the image so it aligns with other spatial data.A scanned map or an aerial photograph starts with only pixel positions. Georeferencing links known points on the image, called ground control points, to their real coordinates and then transforms the whole image into a map projection. After that it overlays correctly on roads, field boundaries and other layers in the GIS.Compressing an image only reduces file size, converting it to vectors is digitising or vectorisation, and changing the colour depth only affects display. None of these gives the image a location on the earth.

Q: Which index uses Short-Wave infrared (SWIR) and Near-infrared (NIR) bands to assess crop water stress ?

The index is NDWI, the Normalized Difference Water Index.In the form proposed by Gao in 1996, NDWI compares the near-infrared and short-wave infrared bands:\[ \text{NDWI} = \frac{N - S}{N + S} \]where \(N\) is the near-infrared reflectance and \(S\) the short-wave infrared reflectance.Short-wave infrared is strongly absorbed by water in leaves, while near-infrared is scattered by leaf structure, so the index falls as the canopy loses water. That makes it suited to detecting crop water stress.NDVI uses red and near-infrared bands and measures greenness and vigour. SAVI is NDVI corrected for soil background, and EVI adds the blue band to correct for the atmosphere and dense canopies; neither of them uses SWIR.

Q: Cartosat series satellites are primarily designed for

Cartosat satellites are designed for high resolution land use mapping and agriculture monitoring.The Cartosat series of the Indian Space Research Organisation carries panchromatic and multispectral cameras with very high spatial resolution, below one metre in later satellites, and can take stereo images. They are used for cartography, cadastral and large-scale mapping, urban and rural planning, and land use and crop monitoring.Weather forecasting is the job of the INSAT and Meteosat-type meteorological satellites, and ocean studies of the Oceansat series. Mineral exploration uses remote sensing too, but it is not what Cartosat was built for.

Q: Which of the following is used for precision agriculture ?

The answer is All of these.Precision agriculture manages variation within a field by applying the right input, at the right rate, at the right place and time. GIS stores and analyses the spatial data, such as soil maps and yield maps. GreenSeeker is a hand-held or tractor-mounted optical sensor that reads crop NDVI and guides variable-rate nitrogen application. Drones capture high-resolution images for crop scouting and are also used to spray inputs on targeted spots.All three are standard precision agriculture tools, so no single option is complete on its own.

Q: Topographical map of India is approved by

Topographical maps of India are approved by the Surveyor General of India.The Survey of India, headed by the Surveyor General, is the national mapping agency. It prepares and publishes the topographical maps of the country and certifies the external boundaries and coastline shown on maps.The Archaeological Survey of India protects monuments, and the survey that studies rocks and minerals is the Geological Survey of India. Neither approves topographical maps.

101.

Which one of the following is an equal area projection ?

A.Cylindrical projection
B.Conical projection
C.Bonne's projection
D.Mercators projection

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: C

The equal area projection is Bonne's projection.

Bonne's projection is a modified conical projection in which every parallel is drawn true to scale and the central meridian is also true, so areas are preserved everywhere, though shapes are distorted away from the centre. It was long used for atlas maps of continents such as Asia and Europe.

The simple cylindrical and simple conical projections preserve neither area nor shape exactly, and the Mercator projection is conformal (shape-preserving), with areas greatly exaggerated towards the poles.

Discuss in Forum

102.

If a map is drawn on the R. F. = 1 : 50,000 but when the same map is redrawn on R.F. = 1 : 2,50,000. The status of redrawn new map is :

A.Reduced by 5 times
B.Reduced by 2.5 times
C.Enlarged by 5 times
D.Enlarged by 2.5 times

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: A

The redrawn map is reduced by 5 times.

The representative fraction compares map distance with ground distance. At 1 : 50,000, 1 cm represents 50,000 cm; at 1 : 2,50,000, 1 cm represents 2,50,000 cm. The same ground distance therefore appears on the new map at

\[ \begin{aligned} \frac{1/250000}{1/50000} &= \frac{50000}{250000} \\ &= \frac{1}{5} \end{aligned} \]

of its original length, so the map is reduced five times in linear scale (and 25 times in area). It is not enlarged, because the denominator has grown, and 2.5 is a misreading of the 2,50,000.

Discuss in Forum

103.

Which GIS data model represents geographic features using points, lines, and polygons?

A.Raster
B.Vector
C.Grid
D.Pixel

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: B

The model is the Vector data model.

A vector model stores geographic features as geometry defined by coordinates: a well or a sampling site is a point, a road or a river is a line, and a field or a district boundary is a polygon. Each feature carries its own attribute record, which makes vectors suited to discrete objects with sharp boundaries.

A raster model instead divides the area into a regular grid of cells or pixels, each holding one value, as in a satellite image or an elevation surface. Grid and pixel are simply the parts of a raster, so they are not separate models that use points, lines and polygons.

Discuss in Forum

104.

Georeferencing an image in GIS means to :

A.Compress the image to reduce file size
B.Assign real world coordinates to the image so it aligns with other spatial data
C.Convert the image into a vector layer automatically
D.Change the image colour depth for display purposes

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: B

Georeferencing means to assign real world coordinates to the image so it aligns with other spatial data.

A scanned map or an aerial photograph starts with only pixel positions. Georeferencing links known points on the image, called ground control points, to their real coordinates and then transforms the whole image into a map projection. After that it overlays correctly on roads, field boundaries and other layers in the GIS.

Compressing an image only reduces file size, converting it to vectors is digitising or vectorisation, and changing the colour depth only affects display. None of these gives the image a location on the earth.

Discuss in Forum

105.

Which index uses Short-Wave infrared (SWIR) and Near-infrared (NIR) bands to assess crop water stress ?

A.NDVI
B.SAVI
C.NDWI
D.EVI

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: C

The index is NDWI, the Normalized Difference Water Index.

In the form proposed by Gao in 1996, NDWI compares the near-infrared and short-wave infrared bands:

\[ \text{NDWI} = \frac{N - S}{N + S} \]

where \(N\) is the near-infrared reflectance and \(S\) the short-wave infrared reflectance.

Short-wave infrared is strongly absorbed by water in leaves, while near-infrared is scattered by leaf structure, so the index falls as the canopy loses water. That makes it suited to detecting crop water stress.

NDVI uses red and near-infrared bands and measures greenness and vigour. SAVI is NDVI corrected for soil background, and EVI adds the blue band to correct for the atmosphere and dense canopies; neither of them uses SWIR.

Discuss in Forum

106.

Cartosat series satellites are primarily designed for

A.weather forecasting
B.ocean studies
C.mineral exploration
D.high resolution land use mapping and agriculture monitoring

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: D

Cartosat satellites are designed for high resolution land use mapping and agriculture monitoring.

The Cartosat series of the Indian Space Research Organisation carries panchromatic and multispectral cameras with very high spatial resolution, below one metre in later satellites, and can take stereo images. They are used for cartography, cadastral and large-scale mapping, urban and rural planning, and land use and crop monitoring.

Weather forecasting is the job of the INSAT and Meteosat-type meteorological satellites, and ocean studies of the Oceansat series. Mineral exploration uses remote sensing too, but it is not what Cartosat was built for.

Discuss in Forum

107.

Which of the following is used for precision agriculture ?

A.GIS
B.Green Seeker
C.Drone
D.All of these

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: D

The answer is All of these.

Precision agriculture manages variation within a field by applying the right input, at the right rate, at the right place and time. GIS stores and analyses the spatial data, such as soil maps and yield maps. GreenSeeker is a hand-held or tractor-mounted optical sensor that reads crop NDVI and guides variable-rate nitrogen application. Drones capture high-resolution images for crop scouting and are also used to spray inputs on targeted spots.

All three are standard precision agriculture tools, so no single option is complete on its own.

Discuss in Forum

108.

Topographical map of India is approved by

A.Archaeological Survey of India
B.Geographical Survey of India
C.Surveyor General of India
D.None of these

Exam Year(s)

Tripura Public Service Commission - 2021,

Answer: C

Topographical maps of India are approved by the Surveyor General of India.

The Survey of India, headed by the Surveyor General, is the national mapping agency. It prepares and publishes the topographical maps of the country and certifies the external boundaries and coastline shown on maps.

The Archaeological Survey of India protects monuments, and the survey that studies rocks and minerals is the Geological Survey of India. Neither approves topographical maps.

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