what does blue do in the the electromagnetic spectrum?
it absorbs red wavelengths and reflects blue, such as water
what does green in the spectrum do and what is an example?
it absorbs red and blue wavelengths but reflects green, such as chlorophyl
what is remote sensing?
images that view our universe at wavelengths far greater than those of visible light
what do spaceborn sensors assist with?
crop forecast, weather prediction, mineral exploration, pollution detection, commercial fishing
what is an atmospheric window?
those areas of the spectrum that are not severely influenced by atmospheric absorption and are useful to remote sensors
what are passive sensors?
satellite and airborne-based systems that detect the ultramagnetic energy reflected and emitted by things on earth
(landsat, spot, meteorological satellites)
what are active sensors?
systems that: can provide their own source of energy and operate day and night, operate independently from solar illumination (radarsat 1 and 2, lidar)
explain digital image analysis
the pixels have an image color and tone which are assigned digital numbers and values
what does tm 1 do in the thematic mapper
it's wavelength is blue and it distinguishes soil and forest(.45-.52 hertz)
what is tm4?
it is near infrared and distinguishes between plant types, soil moisture, and health and biomass content(wavelength .76 to .90)
what is tm 7?
short-wave infra-red that distinguishes mineral and rock types, sensitive to vegetation moisture content (2.08-2.35)
what is photogrammetry?
the science of making reliable measurements by the use of photographic or video imagery; it uses photographs, video, ccd cameras or radiation sensors
what is stereophotogrammetry?
an airplane flying in a certain area takes photos with a special camera straight down and overlaps photos creating vertical aerial photographs
what is paralax
a shift in position of the object in a background because of change in observer position ( can give a 3d look)
advantages and disadvantages of lidar
they are cheap and immediately digital, but files are big and may not see through water
what is dem
digital elevation models; a 3d depiction of the ground surface using contour maps, also referred to as dtm
what is non-spatial information?
the digital database that can be linked with map and topographical features, creating a gis
what is the common purpose for gis?
it is for decision-making in use of land, resources, transportation, retail, and oceans or spatial distributed entities
when do you use a vector model?
when the data has been accessed by coordinated consistent field work or digital map