Remote Sensing in a Nutshell

According to the National Oceanic and Atmospheric Administration (NOAA), remote sensing is a science that obtains information regarding objects or areas from a distance,  typically using aircraft or satellites to take radar or infrared photography. In 1972, a joint initiative between the U.S. Geological Survey (USGS) and NASA launched the first earth resource satellite (Landsat-1). The Landsat Project is the world’s longest continuously acquired collection of space-based moderate-resolution, land remote sensing data.  The remote sensing data collected has been used by agriculture, commercial, education,  emergency response geology, government, forestry, industry, and military and many other communities.

According to the International Society for Photogrammetry and Remote Sensing (ISPRS), satellite observation has several advantages. It allows users to observe a broad area for a long period, including change detection and invisible information on the electromagnetic spectrum without visiting the area.

NASA Earth Observatory describes two types of remote sensing technology methods – passive and active sensors. Remote sensing technology continues to change as technology innovations occur giving remote sensing professionals access to more information about the world.

Passive sensors record information that comes from natural energy from Earth’s surface and thermal radiation in the visible and infrared of the electromagnetic spectrum.  Because passive sensors respond to external stimuli and do not emit their own radiation, reflected sunlight is the most common source of external energy restricting it to daylight. LANDSAT is the most famous example of a passive sensor.  Created in a joint initiative between the U.S. Geological Survey (USGS) and NASA, the Landsat Project and resulting data. 

Active sensors collect data from Earth using internal stimuli, which means that the active instruments provide their own energy. This means that active sensors have no spectral characteristics like passive sensors. Lidar (Light Detection and Ranging) is an example of an active sensor. Lidar uses a laser (Light amplification by stimulated emission of radiation) to observe scenes and illuminate objects. A pulse of energy is sent to the object, and then the radiation that is reflected from that object is received.

Remote Sensing images collected from passive or active sensor data are often in the form of digital images with the help of image processing techniques. This helps with the visual interpretation, and corrects or restores an image that has been distorted by blurriness or degradation. One of the most important skills of a remote sensing professional is the ability to interpret and understand remote sensing data and images.

The Government of Canada lists some universal uses of remote sensing. Remote sensing has geographical uses that can include tracking changes on Earth’s surface. In geology, remote sensing can be used to detect significant minerals. Environmentalists find much use in remote sensing which detects allows them to follow movements of pollutants on the ocean floor. Uses can even be as simple as detecting patterns involving retail and market share by counting cars in parking lots, counting polar bears to keep track of sustainable population levels, and even keeping track of algae growth as an indicator of environmental health.

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