Difference between revisions of "Remote Sensing"
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===NIR (Near-Infrared)=== |
===NIR (Near-Infrared)=== |
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| − | The electromagnetic spectrum covers many more wavelengths than what humans can see, |
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Many satellite imagery providers (e.g. Planet 0.5m) include NIR bands. NIR puts particular emphasis on plants and vegetation, and can be used with other bands to detect regions of ice, vegetation, fires, etc. A common method of analysis is to simply use the imagery as you would optical, but replace the "red" band (e.g. in Qgis) with the NIR data. |
Many satellite imagery providers (e.g. Planet 0.5m) include NIR bands. NIR puts particular emphasis on plants and vegetation, and can be used with other bands to detect regions of ice, vegetation, fires, etc. A common method of analysis is to simply use the imagery as you would optical, but replace the "red" band (e.g. in Qgis) with the NIR data. |
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Revision as of 12:43, 16 July 2022
Remote Sensing is a generic term for types of satellite or high-altitude aviation imagery that contains bands outside of the visual spectrum, or uses a novel method of capturing images that the human eye would otherwise be unable to see.
"Where we're going, we won't need eyes to see" - Sam Neill, Event Horizon
Sources
As with most imagery, remote sensing data tends to fall into one of two categories: freely available and low resolution (to a technical user), or high quality and easy to use but absurdly expensive. If you have to ask how expensive, odds are you simply don't have the money.[1] This is all to assume that you can even open the data and use it- the software to do so is either proprietary, clunky, or both.[Citation NOT needed but provided anyways][2]
However, as time goes on, more and more is slowly becoming available.[3] (Todo: if anyone can figure out the prices for various providers, here would be a good place to put them)
Free
- NASA (EarthExplorer, various)
- ESA (Sentinel-1)
Paid
- Capella (SAR)
- Hawkeye 360
- ICEYE
Types
NIR (Near-Infrared)
Many satellite imagery providers (e.g. Planet 0.5m) include NIR bands. NIR puts particular emphasis on plants and vegetation, and can be used with other bands to detect regions of ice, vegetation, fires, etc. A common method of analysis is to simply use the imagery as you would optical, but replace the "red" band (e.g. in Qgis) with the NIR data.
SAR (Synthetic Aperture Radar)
A satellite in space shines radar light on the Earth and records the result, and using special processing fairly high resolution spatial images can be created. However, while the results look similar to images recorded by a normal camera, they are not actually formed by anything close to the same process as what normal cameras use, and special care must be taken when interpreting because the intuition you have from using your eyes all day does not always apply.
Theory of Synthetic Aperture Radar
GPS Mediated Ionosphere Monitoring
By processing recordings of the GPS signals from satellites, it is possible to identify changes in the electron content of the ionosphere, and by monitoring it detect the travelling ionospheric disturbances caused by rocket launches.
Social Media
If you're new, you wouldn't believe the stuff people posts on social media.
Truly this is more of a "near" sensing method since usually the most interesting material are images and video posted by people on the ground and nearby to the events. Nevertheless, this is highly valuable data can be collected by people very far from the events of interest.
Other
todo: talk about how you can detect ice, snow, fire, etc. by doing veeery specific band math in e.g. qgis. Maybe write a guide on it?