GIS Section 5.2 Flashcards
What is remote sensing?
the science/art of acquiring information about an object (ex earth’s surface)
What data model does remote sensing use?
raster
What is RADAR?
Radio Detection and Ranging
What are the seven elements of remote sensing?
- Energy source (illumination)
- Radiation and the atmosphere
- interaction with the target
- recording of energy by sensor
- transmission/reception/processing
- interpretation/analysis
- application
What regions of the EM spectrum are used in remote sensing?
- visible
- infrared
- microwave (RADAR)
- ultraviolet, visible, near infrared (LiDAR)
What visible colour has a shorter wavelength?
violet
What EM range is infrared?
0.7-100micrometers
what is infrared light useful for detecting?
- chlorophyll activity (plants)
- emitted/thermal IM (temperature
What EM range are microwaves in? (RADAR)
1micrometer to 1m
What is RADARSAT?
Canada’s instrument to detect changes, especially in far north
Does cloud cover prevent RADAR sensing?
Nope! RADAR penetrates cloud cover
What 3 forms of interaction can take place when energy hits a target?
- absorption
- transmission
- reflection
Why does water look blue?
stronger reflectance of non-blue colours
What can easily be confused with shallow water?
water with lots of sediment
How do we ensure constant light conditions in satellite images?
at a given latitude, the sun will be in the same position in the sky during the same season
- ie. imaging is ‘sun-synchronous’ and covers each area at a constant local ‘sun time’
How has remote sensing evolved recently?
moving from analog to digital
how can a satellite image be displayed?
- pixels
- each pixel represents radiation/brightness with a digital number
How does georeferencing work?
-Ground Control Points
- match GCPs to known locations
What five categories of image processing are most common?
- Pre-processing
- Image enhancement
- image transformation
- image classification
- analysis of special feature/data integration
What is pre-processing in image analysis?
- radiometric corrections: correct for sensor irregularities and unwanted noise
- geometric corrections: correcting for distortions due to sensor-earth geometry, conversion to coordinates
What is image enhancement in image analysis?
operations to improve appearance of imagery for visual interpretation
What are the three operations in image enhancement (for image analysis)?
- contrast stretching: increase tonal distinction
- spatial filtering: to enhance specific spatial patterns (filter)
- atmospheric corrections
What is contrast stretching?
changing digital values to use more available visual range
What are common forms of noise in imagery?
- striping/banding, or dropped lines
