Remote Sensing: Introduction to Technology Application in Agriculture (Chapter 2)

Question-and-answer flashcards summarising key concepts, platforms, sensors, and applications of remote sensing in agriculture.

What is remote sensing in the context of agriculture?

The detection and/or identification of an object, series of objects, or landscape without the sensor being in direct contact with the target.

What are the three broad categories of remote sensing platforms?

Ground-based, airborne, and spaceborne platforms.

Define electromagnetic radiation (EMR).

A wave of the magnetic field generated by the sun and propagating through space while carrying electromagnetic radiant energy.

Which four regions of the electromagnetic spectrum are commonly exploited for remote sensing data?

Ultraviolet, visible, infrared, and microwave regions.

Give three examples of instruments used to collect electromagnetic data in remote sensing.

Cameras, sensors or linear arrays, and lasers mounted on aircraft or spacecraft.

Place these types of electromagnetic radiation in order from longest to shortest wavelength: radio, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.

Radio → Microwaves → Infrared → Visible light → Ultraviolet → X-rays → Gamma rays.

What is the first step of the remote sensing process?

Emission of electromagnetic radiation (EMR) from a source.

How do passive sensors differ from active sensors?

Passive sensors detect energy emitted or reflected by the landscape, whereas active sensors emit their own signal and measure the part reflected back (e.g., radar, sonar).

Give two common forms of ground-based remote sensing platforms.

Hand-held devices or tripods, and towers or cranes.

For what purpose are permanent ground platforms often used?

Long-term monitoring of atmospheric phenomena or terrestrial features.

Why were spaceborne photographs particularly valuable during the Cold War and in modern archaeology?

Their high spatial resolution helps study areas where the landscape has changed dramatically due to human activities such as agriculture and urbanization.

What is a satellite?

A body that orbits around another body in space.

Differentiate natural and man-made satellites with one example each.

Natural satellites are celestial bodies like the Moon; man-made satellites include MEASAT or RazakSAT.

How do satellites transmit information to Earth?

They use radio waves that are captured by ground antennas and then processed.

What does GPS stand for and what three data types does it synchronize?

Global Positioning System; it synchronizes location, velocity, and time data.

State two advantages of satellite-based remote sensing.

It is fully autonomous after launch and offers wide accessibility to nearly any spot on Earth.

When and how were the first aerial images captured?

In 1859 with a camera carried aloft by a balloon.

What remote sensing technique was extensively used for military reconnaissance during World War I?

Black-and-white aerial photographs taken from airplanes.

How did infrared and multispectral photography enhance aerial archaeology in the 1970s?

They extended the visible range, enabling better detection of differences in soil moisture and crop growth.

What is an unmanned aerial vehicle (UAV) or drone?

An aircraft controlled remotely or autonomously via software-controlled flight plans, often integrated with sensors and GPS.

List three types of agricultural insights obtainable from drone data.

Crop health assessment, irrigation monitoring, and yield prediction.

Why are drone views less affected by clouds than satellite imagery?

Because drones fly below most cloud cover and are less influenced by atmospheric perturbations.

Compare rotary-wing and fixed-wing drones in terms of one advantage and one disadvantage each.

Rotary-wing drones can take off/land vertically and hover (pro) but their batteries drain quickly (con); fixed-wing drones cover larger areas faster with longer battery life (pro) but need runway-like space to land (con).

Name five types of sensors commonly carried by UAVs.

RGB cameras, multispectral cameras, hyperspectral cameras, LiDAR sensors, and thermal cameras.

How does an RGB camera generate a color image?

By capturing reflected energy in the red, green, and blue bands of the visible spectrum.

What is the main difference between a multispectral and a hyperspectral camera?

Multispectral cameras capture a few discrete wavelength bands, whereas hyperspectral cameras capture hundreds of narrow, contiguous bands.

What does LiDAR stand for?

Laser Imaging, Detection and Ranging.

Explain how LiDAR creates a high-resolution digital elevation model (DEM).

It measures the time taken for emitted laser pulses to hit the ground and return, converting these times into precise 3-D distance measurements that form a DEM.

Give three practical applications of LiDAR.

Flood modelling, land-use planning and urban design, and ecosystem or wildlife habitat assessment.

What does a thermal camera detect, and why is this useful in agriculture?

It detects infrared radiation (heat) patterns, allowing identification of issues like water stress, pest or disease outbreaks, improper irrigation, and nutrient deficiencies.

Name two veterinary applications of thermal imaging.

Detecting inflammation or arthritis in joints and locating hot/cold spots in veins or skin for quick diagnosis.

List six agricultural applications of remote sensing mentioned in the lecture.

Crop disease & pest observation, soil & water status assessment, weed detection, crop & livestock monitoring, weather prediction, and estimating harvest time.