Wildlife & Remote Sensing
Landsat
Known as the oldest continous global record ever. There have been eight different Landsat satellites. Landsat 8 being the most current. Each Landsat has carried different sensors inlcuding, but not limited to; the multispectral scanner (MSS), the Thematic Mapper (TM), the Enhanced Thematic Mapper plus (ETM+), and the Operational Land Imager (OLI). Each Landsat satellite has a temporal reolution ranging from 18-16 days. This means that it takes 18-16 days to cover the entire Earth. The Earth Satellite Corportaion was contracted by NASA to obtain the best availible Landsat images and to orthorectify them. These images are availible from the USGS and can be easily used for mapping habitat and habitat change. With such an abuncance of Landsat imagery, it is no surprise that it is so commonly used in wildlife research and management.
Image Credit: Nasa's Goddard Space Flight Center
Thematic Mapper​
This is an MSS upgrade. It simultaneously scans the Earth's surface in seven different spectral bands. One of which (Band 6) detects thermal infrared radiation and is only used for night scenes. TM is a passive sensor that was carried on Landsat 5 & 4.
TM image from Landsat 5. Yukon Delta National Wildlife Refuge, Alaska. 5/9/05. USGS
MSS​
The Multispectral Scanner System is a passive sensor that was carried on the first five Landsat satellites. It observed and measured the reflectance of the Earth's surface in four different spectral bands.
MSS image from Landsat 1. Wrangell-St. Elias Park and Wildnerness Reserve. 7/8/73/ USGS
How it works
There are two different types of sensors with which observations are made: passive and active. Passive sensors only sense radiation that is emmited by the object (such as thermal radiation) or that which is emmited by an external source (such as the sun) and then reflected back by the object. Active sensors emmit their own source of radiation (such as radar or microwaves) which is then reflected back by the object and then captured by the sensor.
Each of these different sensors observe different parts of the electromagnetic spectrum, called spectral bands. Some sensors only measure microwaves or radar, whiles others measure visual light (that which we can see) and/or infrared. Each sensor has different spatial resolutions as well, this is a measure of how small an object can be "seen" by the sensor.
The sensor selected for a study is based on the following considerations; the type of data needed, the area to be observed and the limitations of the sensor. Sensors can be limited by how often it visits the area in question, or its temporal resolution. Environmental factors play a roll such as weather, clouds, and time of day. In observing wildlife, species behaviors and habits must be considered, as this may affect the method in which data is collected.
Below can befound information about the platforms and the sensors that are commonly used in wildlife sudies and wildlife management. Click on the platform or sensor name to learn more about the each one, click on the image see more.
Platforms
ETM+
The Enhanced Thematic Mapper plus is an upgrade to, and replaced the TM. This sensor simultaneously scans the Earth's surface with eight different bands, including thermal infrared. The ETM+ is the passive sensor that is carried on Landsat 7.
ETM+ image from Landsat 7. Yellowstone National Park. 5/16/07. USGS
The Advanced Very High Resolution Radiometer can be found on the NOAA's Polar Orbiting Environmental Satelites or POES. AVHRR is a passive sensor that measures the intesnity of the visible, infrared and thermal parts of the electromagnetic spectrum. Images are used for landcover mapping, vegetation and fire monitoring, and more.
AVHRR image of fires in a boreal forest east of St. Petersburg, Russia, 1998. NOAA.
Terra & Aqua
Terra and Aqua are two different satellites that circle and observe the Earth's surface. Each satellite has different sensors onboard which are designed to collect different types of data. Terra carries with it five different sensors, including MODIS and ASTER. These sensors are geared towards observing the atmosphere, land surface, oceans, snow and ice, and energy budget. Aqua carries six different sensors, which also includes MODIS. Each sensor is geared towards observing all parts of Earth's water cycle.
Image Credit: Nasa's Goddard Space Flight Center
MODIS
Moderate Resolution Imaging Spectroradiometer. It records images in 36 different spectral bands which vary greatly in function: from land and cloud imaging, to temperature recording, and phytoplankton detection. MODIS is a very versitile passive sensor that can be found on the Terra and Aqua satellites.
MODIS image from Terra. Landcover Mapping in Eastern Canada. 2005. CSA.
Sensors
OLI
The Operational Land Imager is carried by Landsat 8 and is the most improved passive Landsat sensor. It captures images in the visible, near infrared and short wave infrared parts of the spectum. Its new "push-broom" scanning pattern uses 7000 seperate detectors instead of mirrors to make it more sensitive.
OLI image of Western Austrailia. 5/12/13. USGS
Water and land sperately enhanced to show nutrients in estuary & condition of vegetation
RADARSAT
Is a Canadian owned and operated active sensor. It is used for environmental monitoring applications in Canada and around the world. Using radar waves, RADARSAT is able to pentrate clouds to "see" what is below.
Left Landsat 1985, right RADARSAT image 2005, of shrinking lakes in Denali, Alaska. CSA
Planes, Helicopters, and Drones
Several different sensors can be used in conjuction with these platforms such as digital cameras, thermal infrared or Forward Looking Infrared. The cameras are either handheld or attached to the platform and then flown above the area of interest. Images are captured by the sensor and later interpreted. If a digital camera is used, imagies can be viewed while still in flight. In some cases, very high definition cameras are used capture images and video from great distances so as not to disturb the species being viewed.
Image Credit: James Junda
ASTER
The Advanced Spaceborne Thermal Emission and Reflection Radiometer view the Earth using 14 different spectral bands ranging from visible to thermal to infrared. It is used to map land surface temperature, elevation and more.
ASTER image of deforestation in Mato Grosso. ASTER Science Team