EM 1110-2-2907
1 October 2003
NAD83--North American
NAD83 is an Earth-centered datum and uses the Geodetic Reference
Datum of 1983
System 1980 (GRS 80) ellipsoid, unlike NAD27, which is based on an
initial point (Meade's Ranch, Kansas). Using recent measurements with
modern geodetic, gravimetric, astrodynamic, and astronomic
instruments, the GRS 80 ellipsoid has been defined as a best fit to the
worldwide geoid. Because the NAD83 surface deviates from the
NAD27 surface, the position of a point based on the two reference
datums will be different.
Nadir
Point on the ground directly in line with the remote sensing system and
the center of the earth.
NAPP--National Aerial
NAPP was established to coordinate the collection of aerial
Photography Program
photography covering the 48 contiguous States and Hawaii every five
years. NAPP's goals are to ensure that photography with uniform scale,
quality, and cloud-free coverage be made available to meet the
requirements of several Federal and State agencies. The program was
initiated in 1980 as the National High Altitude Photography (NHAP)
program. In 1987, the program was renamed to NAPP when the flying
height for the program changed from 40,000 feet to 20,000 feet. NAPP
photography is available in black and white, and in most cases, color-
infrared. The program is administered by the U.S. Geological Survey's
National Mapping Division. NAPP imagery is used by the USGS for
photo revision and land use land cover characterization work on the
standard series maps at 1:24,000; 1:100,000 and 1:250,000 scales.
NASA
National Aeronautical and Space Administration.
NDVI--Normalized
The NDVI is computed by calculating the ratio of the VI (vegetation
Difference Vegetation
index, i.e., the difference between Channel 2 and 1) and the sum of
Index
Channels 2 and 1. Thus NDVI = (channel 2 - channel 1) / (channel 2 +
channel 1).
Nearest Neighbor
When correcting image data points, the nearest neighbor technique
Resampling
assigns for each new pixel that pixel value which is closest in relative
location to the newly computed pixel location.
Near infrared (NIR)
The shorter wavelength range of the infrared region of the EM
spectrum, from 0.7 to 2.5 m. It is often divided into very-near infrared
(VNIR) covering the range accessible to photographic emulsions (0.7 to
1.0m), and the short-wavelength infrared (SWIR) covering the
remainder of the NOR atmospheric window from 1.0 to 2.5m.
Near range
Refers to the portion of a radar image closest to the aircraft or satellite
flight path.
Negative photograph
Photograph on film or paper in which the relationship between bright
and dark tones is the reverse of that of the features on the terrain.
NESDIS--National
NESDIS is the element in NOAA that is responsible for establishing a
Environmental Satellite,
digital archive of data collected from the current generation of NOAA
Data and Information
operational polar orbiting satellites
Service
NHAP
National High Altitude Photography program of the U.S. Geological
Survey.
NOAA
National Oceanic and Atmospheric Administration.
Noise
Random or repetitive events that obscure or interfere with the desired
information.
Nondirectional filter
Mathematical filter that treats all orientations of linear features equally.
Non-selective scattering
The scattering of EM energy by particles in the atmosphere which are
much larger than the wavelengths of the energy, and which causes all
wavelengths to be scattered equally.
Non-spectral hue
A hue which is not present in the spectrum of colors produced by the
analysis of white light by a prism of diffraction grating. Examples are
brown, magenta, and pastel shades.
Glossary-20
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