1. What is remote sensing?
Starting with a strict definition "remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object"
This definition is very broach and as a consequence includes vastly different domains like optical imaging, radar imaging, altimetry, magnetometry etc
2. Is earth observation different from remote sensing?
Yes it is different, but still similar. Remote sensing as defined above is the science of measuring and estimating parameters of an object/phenomenon from a distance. So this object/phenomenon can be actually anything. On the other hand, earth observation refers only to part of remote sensing that observes the earth. So we could say that earth observation is included in the broader domain of remote sensing.
3. What is remote sensing technology?
This one is very simple. It refers to the technological sensors used to acquire remote sensing data. And as you see in the next question we actually have different types of remote sensing based on these technologies.
4. What are the types of remote sensing?
Based on the technology used to capture remote sensing data, we define different types of remote sensing. We have two broad categories passive and active. It refers to whether the signal measured is emitted from the sensor (active) or not (passive)
4.1 passive remote sensing
4.1.1 multispectral, hyperspectral
Multispectral and hyperspectral remote sensing refers to the measurement of the reflected spectrum ranging from UV wavelengths to shortwave infrared (i.e. 200nm - 25000nm)
Thermal remote sensing refers to the measurement of the emitted thermal infrared radiation in the 11 - 15 μm spectrum
4.2 active remote sensing
SAR or Synthetic Aperture RADAR refers to the measurement (in the form of imagery) of the backscatter of the microwave pulse emitted from the sensor.
4.2.2 LiDAR and altimetry
LIDAR, which stands for Light Detection and Ranging, is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the object sensed. Altimetry is a very similar to the concept of LiDAR, i.e. it measures distances, but it does this with a vertical radar sensor instead of a pulsed laser.
5. What is remote sensing data?
The measurements and information acquired by the sensors. To give a few examples. A multispectral image captured by the multispectral camera is remote sensing data. The information (or metadata) that accompany this image is part of the remote sensing dataset, but as standalone it cannot be considered as such. Also the spectral measurements from a spectrometer (consider it as a one pixel hyperspectral/multispectral image) is also remote sensing data
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