Exam 1 Flashcards
What is the Definition of Remote Sensing?
The science & Art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the objects, area, or phenomenon under investigation
Major Components of RS
1) Energy source, 2) Radiation & Atmosphere, 3) Interaction with the Target, 4) Recording of Energy by sensor, 5) Transmission, Reception, Processing, 6) Interpretation & Analysis, 7) Application
What are some advantages of Remote Sensing?
1) Large area coverage: low cost, uniform manner, 2) Extended Spectral range 3) Geometric Accuracy 4) Real time data acquisition 5) Permanent Record 6) Can combine with other digital data 8) Manipulate and enhance data
What is Image scale and how can it be expressed?
The relationship of the image distance between two points and the actual distance between the two corresponding points on the ground. Word Statement (One inch equals one mile) Representative Fraction (1:50,000)
IFOV
Instantaneous field of view; a measure of the ground area viewed by a single detector in a given instant, and is the primary determinant of spatial resolution.
What are some image characteristics?
`1) Data Model Raster 2) Image Resolutions 3) File Types 4) Image Dimension 5) Image/Raster types 6) Projections or georeference
What is the difference between image and photographs?
Images are any pictorial representation of image data, while photographs are images that were detected as well as recorded on film.
Relationship between map scale, spatial scale, and image spatial resolution?
With a fine spatial resolution you have a small resolution size with fine details shown, and a large scale map.
Coarse spatial resolution there is a lg resolution with less detail and a smaller scaled map
What is Spatial Resolution?
the size of the smallest object that can be resolved on the ground
What is Radiometric resolution?
the ability of an image system to record many levels of brightness
What is Spectral resolution?
The ability of a sensor to resolve spectral features and bands in to their separate components Hyperspectral Images (fine spec res); Multispectral images (low spec res); Panchromatic images (very low spec res)
What is Temporal Resolution?
the frequency at which images are recorded/captured in a specific plane on the earth
What is the relationship between spatial, radiometric, and spectral resolution?
An increase in spatial and spec res result in a decrease in the energy available to be sensed (decreased radiometric res)
What is the relationship between spatial and temporal resolution?
Increasing the spatial res means a small ground area to be sensed at any instant in time (decreased temporal res)
Why is IFOV important?
Establishes a limit for the level of spatial details that can be represented in a digital image.
What is the relationship between spatial resolution and pixel size?
The spatial resolution of an image is limited by its pixel size and an image sampled at a small pixel size does not necessarily have a high resolution.
What is electromagnetic radiation (EMR) and how does it originate?
A form of energy with the properties of a wave. It originates from vibrating electrons, atoms, and molecules with the sun being the most obvious source.
What is the atmospheric window?
Wavelengths of the electromagnetic spectrum that can be transmitted through the earth’s atmosphere
What is spectral Reflectance?
Reflectance characteristics of the earth’s surface features and may be quantified by measuring the portion of incident energy that is reflected.
What are spectral signatures?
specific combination of emitted, reflected or absorbed EMR at varying wavelengths which can uniquely identify an object.
What are the two principal measures for EM waves?
Electric field
Magnetic Field
What are the major divisions in the electromagnetic spectrum?
Radio, microwave, infrared, visible, ultraviolet, x-ray, and gamma ray
What are the three major EMR interactions with the Earths Surface?
Reflectance (EMR is turned back), Absorption (EMR is absorbed), and Transmittance (EMR passes through)
Why are reflectance properties so important in RS?
Many remote sensing systems operate in the wavelength regions in which reflected energy predominates.
How does RS differentiate water, vegetation, and soil?
It uses the reflectance properties of each given feature under different wavelengths to create different signatures we can use to distinguish the three.
Why are spectral signatures important in RS?
This allows us to identify certain features of interest by looking at there spectral response, such as separate kinds of crops, forests or minerals.
What are some advantages of aerial photography?
1) easier to obtain than a map 2) Provide day-to-day comparison of selected areas 3) Provides permanent record of day-to-day changes
Advantages of vertical photography
1) uniform scale 2) Can use as a map 3) stereoscopic study
What are the advantages of digital cameras over film cameras?
1) Data in digital formats 2) economical for storage, processing, and transmission of data 3) sensors can differentiate a wider range of brightness values 4) economical operation costs
What are the two major geometric distortions and how are they solved?
1) Relief displacement 2) Tilt distortion
Geometric correction involves calculating the distortion at each point, and then shifting the image location accordingly.
What is relief displacement and what causes it?
the radial displacement of objects that are at different elevations.
It is caused by the terrain, height of features, and increasing distance.
What is tilt distortion?
When the optical axis points at a non-vertical angle and results in perspective convergence (objects farther away appear to be closer together than objects of equal distance apart that are closer to the observer)
What is Orbit?
Path followed by a satellite
What is swath?
the portion of the earth’s surface that is seen by the sensor as ti orbits around the earth`
Two most common types of orbits?
Geostationary orbit
Sun-synchronous orbit
What is Geostationary orbit and give one example?
The orbital period of the satellite is equal to the earths rotation .
Ex: Meteorological Satellites
What is Sun-Synchronous orbit?
Orbital plane satellite moves about the Earth at the same angular rate that the earth moves above the sun.
Ex: used by earth observation satellites
What are the two main modes of scanning employed to acquire multispectral image data?
Across-Track Scanners
Along-Track scanners
What are Across-Track Scanners?
Scan the earth in a series of lines using a rotating mirror to scan from one side of the sensor to the other.
What are Along-Track Scanners?
Uses a linear array of detectors instead of a scanning mirror. Each detector measures the energy for a single ground res cell and thus the size and IFOV of the detectors determines the spatial res of the system
Advantages of Along-Track Scanners
1) Longer period of time to measure energy from the ground resolution cell
2) More energy can be detected (higher radiometric res)
3) Detectors last longer due to no moving parts
Disadvantages of Along-Track Scanners
Cross-calibrating thousands of detectors to achieve uniform intensity across the array is necessary and complicated
What are common characteristics of weather satellites?
1) Very coarse spatial res 2) Very high temporal res 3) Large area maps with low detail 4) Light computer load for data processing
One example of a meteorological system satellite
NOAA (National Oceanic & Atmospheric Administration
GOES (Geostationary Operational Environmental Satellite)
One example of a marine system satellite
USA - Nimbus - 7 CZCS (Coastal zone color scanner)
Janpan - MOS ( Marine Observation Satellite)
One example of a Earth Resource system satellite
USA - Landsat Program
India - IRS (Indiana Remote Sensing) Satellite systems
One example of a High Resolution system satellite
IKONOS
Spaceborne RS advantages & disadvantages
1) Lower detail 2) Expanded spectrum 3) Inherently digital 4) higher flight paths 5) inexpensive for large areas
Airborne RS Advantages & Disadvantages
1) Higher details 2) Less expensive for small areas 3) Flexible repeat time 4) Fly under clouds 5) Simple handling
What is a pixel?
a picture element represents a single brightness value or digital number (DN) in an image
What are digital images?
Composed of pixels in geographically ordered and adjacent to one another consisting of ‘n’ pixels in the x direction and n pixels in the y direction
What are image channel/band?
where information from narrow wavelengths is stored
What is a multiband image?
Images sensed simultaneously from essentially the same geometric vantage point but in different bands of the EM energy spectrum.
What is a false color composite image?
the color of a target in the displayed image does not have any resemblance to its actual coor
What is a true color composite image?
images sensed simultaneously from essentially the same geometric vantage point but in different bands of the EM energy spectrum
