GIS - Geographic Information System Remote Sensing and Imagery Questions and Answers

Question 1

An agricultural analyst needs to monitor the health of crops throughout a growing season to detect stress and optimize irrigation. This requires frequent observation of the same area to track changes in vegetation vigor. Which type of remote sensing resolution is most critical for this application?

Accepted Answer

Temporal Resolution

Answer

Temporal resolution refers to the revisit frequency of a satellite or sensor over a specific location. For monitoring dynamic phenomena like crop growth, high temporal resolution (i.e., frequent revisits) is essential to capture changes as they happen. [2, 7]

Question 2

An analyst is performing a land cover classification. They have extensive ground-truth data and need to create a map with specific, predefined classes such as 'Urban', 'Coniferous Forest', and 'Agriculture'. Which image classification method is most appropriate for this task?

Accepted Answer

Supervised Classification

Answer

Supervised classification requires the analyst to provide the algorithm with 'training sites'—representative samples of known land cover types. The algorithm then uses the spectral signatures from these sites to classify the rest of the image into the predefined classes. [3, 8, 11]

Question 3

The Normalized Difference Vegetation Index (NDVI) is a widely used indicator of live green vegetation. Its calculation relies on the unique reflectance properties of plants in which two portions of the electromagnetic spectrum?

Accepted Answer

Red and Near-Infrared (NIR)

Answer

NDVI is calculated using the formula (NIR - Red) / (NIR + Red). It leverages the fact that healthy vegetation strongly absorbs red light for photosynthesis and strongly reflects near-infrared light due to its cellular structure. [4, 9, 13]

Question 4

A remote sensing satellite with high radiometric resolution is particularly valuable for which of the following tasks?

Accepted Answer

Detecting subtle variations in water turbidity or soil moisture.

Answer

Radiometric resolution refers to the sensor's ability to discriminate very slight differences in energy, which translates to the number of brightness values it can record (e.g., 8-bit vs. 12-bit). [19, 29, 30] High radiometric resolution is crucial for applications that require detecting subtle changes in surface properties, such as water quality or soil moisture content.

Question 5

A GIS analyst has a high-resolution (1-meter) panchromatic image and a lower-resolution (4-meter) multispectral image of the same area, acquired at the same time. To create a single, high-resolution color image that combines the spatial detail of the first image with the spectral information of the second, which image processing technique should be used?

Accepted Answer

Pan-sharpening

Answer

Pan-sharpening is an image fusion technique that uses a higher-resolution panchromatic (grayscale) image to increase the spatial resolution of a lower-resolution multispectral (color) dataset. The result is a single image with the best characteristics of both inputs: high spatial detail and multiple spectral bands. [1, 6, 18]

GIS - Geographic Information System Practice Test

GIS - Geographic Information System Practice Test

GIS - Geographic Information System Remote Sensing and Imagery Questions and Answers