|
|
Earth Imaging Glossary
A,
B,
C,
D,
E,
F,
G,
H,
I,
J,
K,
L,
M,
N,
O,
P,
Q,
R,
S,
T,
U,
V,
W,
X,
Y,
Z
" R "
RADAR ALTIMETER
Instrument for measuring altitudes or elevations with respect to a reference level, usually
mean sea level. A radar altimeter determines the height of an aircraft above the terrain by
measuring the time required for an electromagnetic pulse to travel from aircraft to the ground
and back again.
RADIAN
A radian is a unit of angular measure equal to the angle subtended at the center of a circle by
an arc of length equal to the radius of the circle equal to approximately 57 degrees, 17
minutes, 44.6 seconds.
RADIANCE
Measure of the energy radiated by an object. In general, radiance is a function of viewing
angle and spectral wavelength and is expressed as energy per solid angle.
RADIOMETRIC
A radiometer is a device used for detecting and measuring radiation. These measurements of
electromagnetic radiation are referred to as radiometric measurements.
RAMP/AUTO CALIBRATION
Diagnostic measurements pertaining to the linear electrical performance of the sensor.
RASTER
A raster image is a matrix of row and column data points whose values represent energy
being reflected or emitted from the object being viewed. These values, or pixels, can be
viewed on a display monitor as a black and white or color image.
RASTERIZE
The process of converting vector points, lines, and areas into raster image format.
RBV--Return Beam Vidicon
The RBV system on Landsats 1 and 2 consisted of three television-like cameras aimed to
view the same 185 km-by-185 km area as the multispectral scanner (MSS) sensor. The RBV
system did not contain film. The images were exposed by a shutter device and stored on a
photosensitive surface within each camera. This surface is then scanned in raster form by an
internal electron beam to produce a video signal.
The RBV system instantaneously imaged an entire scene, had greater inherent cartographic
fidelity than imagery acquired by the Landsat MSS sensor, and contained a reseau grid in the
image to facilitate geometric correction of the imagery. This resulted in an array of tick
marks that were precisely placed in each image.
The RBV system on Landsat 1 produced only 1690 scenes between July 23 and August 5,
1972, when a tape recording switching problem forced a system shutdown. The RBV system
on Landsat 2 was operated primarily for engineering evaluation purposes and only occasional
RBV imagery was obtained, primarily for cartographic uses in remote areas.
These images are no longer available.
REFLECTANCE
Reflectance is the fraction of the total radiant flux incident upon a surface that is reflected
and that varies according to the wavelength distribution of the incident radiation.
REGISTERED USER
A GLIS user who has established a userkey and completed the USER INFORMATION
screen is a registered user. Registering automatically gives the user enhanced GLIS features
including the ability to save session information and results from previous searches.
NOTE: A registered user who has signed on as a guest cannot switch to a "registered user"
status within the same session. The user must exit GLIS and login as a registered user.
REGISTERED USER FUNCTIONS
GLIS users who are registered have the following additional options which are not available
to the guest.
* User information for order requests are saved across sessions.
* Review, save, and restore flagged inventory items, search criteria, and results
between sessions and in the event of a system crash.
* Customize the presentation of inventory search results and save custom formats.
* Additional options for inventory search output (fax, communications, GLIS printer,
etc.).
RELATIONAL DATABASE
A way of modeling information in a database by relations between the features. Relations are
usually represented as a collection of tables where each table contains the occurrences of a
particular feature. Each column of the table corresponds to an attribute and each row is an
instance of the feature. For example, two related tables might be created to describe types of
transportation networks in a data set. The first table has columns that uniquely identify the
transportation feature, and another that contains codes that describe the transportation type
(trails, roads, railways, ferries, etc.). A second table, which relates to the first, might contain
columns that list the transportation codes used in the first (related) table, and a second
column that defines, in further detail, the definition of the code (gravel, asphalt, concrete, etc)
and road maintenance schedule for that type of road surface. The benefit of a relational
database is that repetitive information is not recorded numerous times in a table, but instead
is pointed to in related tables. Also referred to as Relational Database Management Systems
(RDBMS).
REMOTE LINK
A remote link is a direct connection to a computer-based system located at another data
center. Links are established via wide area networks and are initiated by the GLIS software.
Once connection is established, the control of the user's session is passed to that system.
RESEAU GRID
An array of tick marks precisely placed in an image.
RESIDUAL ANOMALY
Residual anomalies are geophysically defined features that represent the difference between
total (actual) and regional (modeled) geophysical fields; i.e. residual field or anomaly.
RMSE--Root Mean Square Error
The RMSE statistic is used to describe accuracy encompassing both random and systematic
errors.
The square of the difference between a true test point and an interpolated test point divided
by the total number of test points in the arithmetic mean. The square root of this value is the
root mean square error.
Did we miss something?
Send your submission to imaging@geocomm.com
Glossary Home
Initial content for this Glossary of terms has been graciously supplied by RADARSAT International - www.rsi.ca
|
|
Sponsored by:
For information
regarding
advertising rates
Click Here!
|
