Geospatial and Monitoring Technology

Smart Pigs (Pipeline Inspection Gauges) are sophisticated tools that can be equipped with GPS for tracking, magnetic sensors for detecting metal loss/corrosion, and ultrasound scanners for measuring wall thickness. All these technologies work together for comprehensive pipeline monitoring.

The primary purpose of IRS satellites is natural resource management - monitoring agriculture, water resources, forests, and disasters. While they can measure various environmental parameters, their core mission is resource management, not precipitation or radiation specifically. Option 'All' is too broad.

Radar (Radio Detection And Ranging) systems use radio waves to detect objects. Radio waves are a type of electromagnetic wave, but the specific answer expected is 'radio waves' as radar uses the radio frequency portion of the electromagnetic spectrum. It does not use ultrasonic waves (sound).

Night vision apparatus uses infrared waves (also called thermal radiation) to detect objects in darkness based on their heat signatures. All objects emit infrared radiation, which is invisible to human eyes but can be detected by specialized sensors that convert it into visible images. Radio waves and microwaves have much longer wavelengths and don't provide the spatial resolution needed for imaging. Night vision specifically operates in the infrared spectrum.

Pilotage is navigation by visual reference to landmarks. The passage describes pilots using visual references (natural features) and switching to instruments like radar/GPS when visibility is poor. Radar and radio navigation rely on instruments, not visual landmarks. Dead reckoning calculates position using course, speed, and time without visual references.

RADAR, VOR (VHF Omnidirectional Range), and GPS are all commonly used navigation aids in modern aircraft. SONAR (Sound Navigation and Ranging) is used underwater for submarines and ships, not for aircraft navigation. Therefore, SONAR (Option C) is the correct answer as it is NOT an aircraft navigation aid.

Night vision apparatus works by detecting infrared radiation, which is emitted by all objects based on their thermal energy. Infrared waves have longer wavelengths than visible light, making them invisible to the human eye but detectable by specialized equipment.

Night vision devices work by detecting infrared radiation, which is emitted by all objects based on their temperature. This allows visualization in darkness by sensing heat patterns rather than visible light.

SONAR (Sound Navigation and Ranging) works on the principle of echo - sound waves are emitted, reflected back from objects, and the time delay gives distance/depth. Superposition principle refers to wave interference, which is not the core concept here.

RADAR stands for Radio Detection And Ranging, which is a detection system that uses radio waves to determine the range, angle, or velocity of objects. It was developed in the 1930s-1940s and played a crucial role in World War II for aircraft detection. Modern radar is used in weather forecasting, air traffic control, and navigation.

GIS is defined by its five core functions: capture (data collection), storage (database), retrieval (querying), analysis (spatial operations), and display (mapping). GPS is for positioning, surveying is for measurement, and remote sensing is for data collection - none include all five functions.

Remote sensing involves collecting data about objects or areas from a distance, typically using satellites or aircraft, without physical contact. Surveying (C) involves ground-based measurement, and photogrammetry (A) is a specific type of remote sensing using photos - remote sensing is broader than just that.

This technique is a front end to a massive database of satellite images, aerial photographs and topo maps of much of earth's surface.

Space modulation is a radio amplitude modulation technique used in instrument landing systems that incorporates the use of multiple antennas fed with various radio frequency powers and phases to create different depths of modulation within various volumes of three-dimensional airspace.

Ongoing scanning at an almost unconscious level is passive scanning. No effort is made to select a particular information resource to scan. Only ad hoc decisions are made on the results of this type of scanning.