1a. In its broadest sense, how would you describe remote sensing?1b. What platform was first used to acquire aerial photographs?
2a. What are four domains of information obtained from remotely sensed data.?
2b. What is a pixel?
2c. What is an advantage to using multitemporal imagery?
3a. What is spectral resolution?
3b. What is spatial resolution?
3c. What is spatial scale?
3d. What is temporal resolution?
4a. What are some advantages of using satellite platforms?
4b. What is a limitation to using passive sensors?
4c. What are two common active sensors used in remote sensing?
5a. State briefly the difference between a geostationary satellite and a satellite having a Sun synchronous orbit.
5b. What is the Earth Observing System (EOS)?
ANSWERS
1a. Remote sensing involves methods that acquire information about an object by means of "remote" examination, that is, with no direct contact of the object. See Introduction and 3.1.2.
1b. Balloons. See Section 1.
2a. Four domains of information gathered from remotely sensed data are spectral, spatial, temporal, and bidirectional (angular). See Section 2.
2b. A pixel or "picture element" is the smallest element that makes up an image. Each pixel has associated spatial and spectral information. See Section 2.2.
2c. Multitemporal imagery and data are useful for studying changes in the environment and to monitor various processes. See Section 2.3.
3a. Spectral resolution refers to the width of the spectral portion being sampled by a given band or channel. Broad bands measure a wide wavelength interval lumped together; narrow bands measure very restricted portions of the spectrum separately. See Section 2.1.
3b. Spatial resolution corresponds to the spatial area each displayed or printed pixel represents on the ground. See Section 2.2.
3c. Spatial scale is the ratio of a distance on a map or image to the actual distance on the ground that the map distance represents, for example, if one inch on a map equals 1000 inches in actuality on the ground, then the scale of that map is 1:1000. See Section 2.2.1.
3d. Temporal resolution refers to the time period between successive multitemporal data sets or images.
4a. Satellites are more stable, they can orbit continuously for several years, and they can potentially obtain global coverage.
4b. A major limitation of passive systems is that in most cases they require sunlight in order for valid and useful data to be acquired. Consequently, deployment of and/or data acquisition by passive sensors is very dependent on lighting (time of day, time of year, latitude) and weather conditions. See Section 3.3.
4c. Two common types of active sensors are radar and lidar.
5a. A geostationary satellite has a period of rotation equal to that of Earth (24 hours) so the satellite always stays over the same location on Earth. A satellite having a Sun synchronous orbit does not stay over the same location on the surface, but instead moves around Earth maintaining the same relative position with respect to the sun.
5b. The Earth Observing System (EOS) is a series of satellite platforms designed to carry a variety of new sensors, with each platform and sensor complement aimed at gathering data for specific research questions and applications. Launches of EOS satellites will begin soon and continue throughout the next several decades.
|
|
|
|