|Title||Predicting risk of invasive species occurrence - remote-sensing strategies|
|Publication Type||Government Report|
|Year of Publication||2014|
|Authors||Young K, Schrader T. S|
|Edition||Scientific Investigations report 2012-5162|
|Publisher||US Department of Interior; US Geological Survey|
|ARIS Log Number||316420|
Remote sensing is a means to describe characteristics of an area without physically sampling the area. Remote sensors can be mounted on a satellite, plane, or other airborne structure. Remotely sensed data allow for landscape perspectives on management issues. Sensors measure the electromagnetic energy reflected from an object or area on the Earth’s surface. These sensors measure energy at wavelengths that are beyond the range of human vision. The guiding principal is that different objects (for example, soils, plants, buildings, water) reflect and absorb light differently at varying wave¬lengths. Graphically plotting the amount of radiation reflected at a given wavelength provides a unique signature for an object, especially if there is sufficient spectral resolution to distinguish its spectrum from those of other objects. Reflectance of clear water is typically low, with initial higher reflectance values in the blue end of the spectrum, which decreases as wavelength increases. Vegetation reflectance is typically low in both the blue and red regions of the spectrum due to absorption by chlorophyll. Because reflectance values peak at the green region, vegetation appears green. In the near infrared (NIR) region, reflectance is much higher than that in the visible bands due to leaf cellular structure. Therefore, vegetation can be identified by the high NIR but generally low visible reflectance. Spectral reflectance curves can be used to discriminate between vegetation types or plant species.