Introduction to Remote Sensing Flashcards
List 2 energy sources.
Passive (naturally available energy)
Active (own energy source)
What are the 4 orbit types?
Near polar
Sun synchronous
Geo synchronous
Geostationary
What is near polar orbit and 1 usage:
In conjunction with earth’s rotation (at low altitude) north-south orbit
Covers most of the earth’s surface over period of time
Inclination relative to a line running between N and S poles
What is sun synchronous orbit and 1 usage:
Covers each area at local solar time with consistent illumination conditions
Changes between images
Any given latitude, the position of the sun in the sky will be the same within the same season
What is geo synchronous orbit and 1 usage:
Orbital period that matches earth’s rotation around its axis (at high altitude 36,000km)
What is geostationary orbit and 1 usage:
In earth’s equatorial plane, seeming stationary to earth’s surface
Weather and communications satellites
Circular geosynchronous orbit
List differences between Landsat 8/9 and Sentinel-2 Orbits
Landsat repeat cycle: 16 days for 1 satellite
Sentinel repeat cycle: 10 days for 1 satellite or 5 days for 2 satellite
Landsat Altitude: 705km
Sentinel Altitude: 786km
Landsat Swath Width: 185km
Landsat Swath Width: 290km
What is resolution? List 4 types
The level of detail at which data is captured and displayed on a spatial dataset, indicating the size of the smallest discernible unit
Spatial or Temporal or Radiometric or Spectral
What is spatial resolution?
Size of the individual pixel
Higher spatial representation = smaller pixels = greater representation
Feature to be detected = size has to be equal to or larger than resolution cell
The average brightness of all features in a cell will be recorded if too small (can dominate a sell if their reflectance is high)
What is temporal resolution?
Length of time it takes to revisit an area at the same viewing angle
Spectral characteristics of features may change over time, detected by collecting and comparing multi-temporal imagery
What is radiometric resolution?
The sensitivity of a sensor to detect the magnitude (or intensity) of the EMR
Ability to discriminate very slight differences in energy recieved (greater quantisation levels = greater detail in information collected).
Actual information content in an image
What is spectral resolution? List 2 types
The ability of sensor to define fine wavelength intervals.
The finer the spectral resolution, the narrower the wavelength range for a band.
Multispectral (5-7 bands) or Hyperspectral (contiguous bands)
Panchromatic produces a greater spectral resolution.
What is a swath?
Corridor of a surface that is covered by a remote sensing instrument during a single scan
Why is indices important?
Useful for imagery analysis to derive insights about certain features (vegetation, soil properties, moisture content), using the differences in how the feature reflects and absorbs different wavelengths of light.
How is imagery data represented?
What does this concern?
By positive digital nimbers varying from 0 to selected power of 2
Sensors ability to differentiate among subtle variations in brightness (gray level values the sensor can record between brightess to darkest)
Max number of brightness levels depends on number of bits used in saving the brightness
