manufacted to record green, red and the photographic portion of the near-ir scene energy.

the dyes developed in each layer are cyan, magenta and yellow.

'false color' film

uses a yellow filter

blue=black

green=blue

red=green

red=green

near ir=red

ex. active vegetation=red/magenta, brown gravel=white, red roofs=greenish yellow

what is NDVI?

what satellite does it come from?

used to measure and monitor plant growth, vegetation cover and biomass production.

comes from AVHRR 1km in the visible and near ir bands

vigorously healthy vegetation has low red reflectance and high near ir reflectation so it has high NDVI values, shows in shades of green to indicate levels of growth.

valus range from -1 to 10.

inherently raster. raw images can be easily included directly as layers in a raster-based GIS

raster images have finite set of digital values called pixels

mixed pixels=several objects, classes or features are present in the target area. (# of mixed pixels increases as spatial resolution decreases)

pure pixels=occupies a completely single homogenous class of information or feature.

aka along track

record multispectral image data along a swatch beneath an aircraft. Doesnt use scanning mirror but instead uses linear array of detectors.

use of forward motion of the aircraft to build up a 2D image by recording successive scan lines that are oriented at right angles to the flight direction

typically consist of numerous CCDs (charge coupled device) positioned end to end. they are very small and a single array can have over 10,000 individual CCDs. each spectral band needs its own array.

located in the focal plane of the scanner perpindicular to flight path

cheaper and lighter

ALI (advanced land imager)

pushbroom vs whiskbroom characteristics?

pushbroom

wide swath

filters and sensors used

short dwell time

pixel distortion

simple optics

whiskbroom

dispersion grating and ccds

long dwell time

no pixel distortion

complex optics

expensive and wear out quickly

Landsat

monochromatic

to obtain full color, each photosite of the CCD is covered with blue, green or red filter. photosites are square with alternating blue, green and red sites arranged in bayer pattern. GBRGBRGBR...

the 2 missing colors at each site are interpolated from surrounding sites

at any instant in time, the scanner 'sees' the energy within the systems IFOV (instantenous field of view).

normally expressed as the cone angle within which incident energy is focused on the detector.

sensors supply or send out their own electromagnetic energy and then record what comes back to them.

radar

detect naturally reflected or radiated energy

ikonos

Light Detection and Ranging

active remote sensing

involves transmitting pulses of laser light toward the ground and measuring the time of pulse return. the return time of each pulse back to the sensor is processed to calculate the disances between the sensor adn the various surface present on (or above) the ground.

airborne and spaceborn radar remote sensing systems are called imaging radar. modern methods are referred to as synthetic aperture radar(SAR)

produce continuous strips of imagery depicting extensive ground areas that parallel the platforms flight line.

is an active day or night imaging system

radar systems record the intensity of the radiation that is backscattered.

=the fraction of the incident energy that is reflected directly backwards towards the sensor.

 active veg appears green, bare soil and fallow fields are red-brown, and urban structures are purple, clear water appears black, dirty water appears dark blue