Discover Satellite Images & Remote Sensing
Ever wonder how satellite images are made? We use remote sensing technology to make these images and many others. But how does that work?
What is Remote Sensing?
Remotely sensed imagery provides aerial views of the Earth’s surface. These images are used in many ways, from natural resource management (as we are using them in the Seagrass Adventure) to disaster management to weather monitoring.
Remotely sensed imagery comes from camera-like sensors that are either attached to a satellite in space or attached to an airplane or helicopter. This imagery provides aerial views of the world by collecting and storing data about the energy that is reflected off of the Earth’s surface.
Our sun emits light at different wavelengths in the electromagnetic spectrum and everything reflects this light in a certain way. Once the sensor records the light, it sends the information back to computers on Earth to be converted into images. It is the differences in how the light is reflected that allows us to distinguish between features on the landscape.
Exploring Different Types of Remotely Sensed Imagery
There are many different types of remotely sensed imagery that are used, each with different characteristics. The type of imagery that we choose depends on how we are going to use it. Each type of imagery has a different spectral and spatial resolution.
The spectral resolution describes the number of wavelengths in the electromagnetic spectrum (see the picture below) that is collected. Aerial photos from airplanes and helicopters usually collect reflectance data from one to three wavelengths, while satellites can collect reflectance data from three to several hundred wavelength bands. For the Seagrass Adventure, we’re using imagery from the Quickbird satellite, which has a relatively small spectral resolution (4 bands).
Spatial resolution refers to the area of earth that each pixel represents—a fine spatial resolution would be 3 meters compared to a coarser spatial resolution would be 30 meters. The satellite imagery we’re using in the Seagrass Adventure has a relatively fine spatial resolution of approximately 2 meters. Because we are looking at small area and we need to detect small changes in seagrass density, it is best to use imagery that has a fine spatial resolution.
Remotely sensed imagery can be manipulated in many ways to make features of interest easier to detect.
The satellite imagery that we are using in the Seagrass Adventure was manipulated so that it’s easier to see the seagrass on the ocean floor. We used different wavelength/band combinations and adjusted the brightness and contrast. A ‘true color’ visualization of an image shows the colors as we see them. A ‘color enhanced’ visualization of an image uses different colors to highlight components of the map, depending on what you are interested in looking at determines which color you choose for the ‘color enhanced’ images.
Want to Learn More about How Satellites Work?
Check out the following NASA websites:
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