5210 exam 2 study 2
What are the advantages/disadvantages of satellite imaging systems relative to aerial imaging systems?
++ very high perspective, which significantly reduces terrain caused distortion ++very precise control of pointing direction disadvantages cost may be high if only a small area is desired acquisition is less flexible, relative to a pilot flying on short notice
what are the advantages and disadvantages of using UAVs/drones?
+++ low cost high data resolutions --limited datat collection rates
Aerial photographs are captured with how much overlap? Illustrate. _________sidelap __________endlap
20-30% sidelap 60% endlap These help prevent lack of coverage because of drift and crab
An image must be captured with less than_____ of tilt to be considered "vertical"
3 degrees
What is LiDAR?
Laser shot down from an arieal platform to measure height. The strength and time of return is used to estimate height of canopy, mountain etc..
Satellite scene location may be specified by a path/row number, because a set of approximately ______paths are designated, with approximately ___________rows identified across the paths
North south East west
The orbits of imaging satellites are usually_________and ____________________
Polar Sun synchronous
What is a stereopair? What is parallax?
Stereo pairs- over lap photos Parallax- Apparent change in the position of an object on an air photo because of a change in the position of observation
What are the primary sources of distortion in aerial photographs and satellite images?
Terrain camera tilt
How is imagery typically collected by a satellite
across track direction, __perpendicular___ to the flight path __Along Track__ directon, parallel___to the flight path AKA push broom
What does discrete return LiDAR collect?
collects x,y,z coordinates for 3 dimenational space result= point cloud
Why were infrared sensors originally developed?
developed by military for camouflage detection purposes original concept was to separate signatures for live vegetation from simulated vegetation
What is the difference between a true color image and a false color infrared image?
false color - there is infrared incorporated
How are false color images created?
green, red, and near infrared channels of the image are assigned the blue, green, and red colors in a computered displayed system Referred to as false color images
What are the approximate resolutions of "high", "medium", and "coarse" resolution satellite systems?
high= finer than 3m Medium = 5m - 100m coarse= more than 100m
solar radiation is either
infrared ultraviolet ...??
What is the difference between low oblique and high oblique?
low- horizon is not shown High-horizon is shown
What is the difference between orthographic view and perspective view?
ortho- looking down at all locations ( google maps) Perspective- being able to see the sides of buildings ( air plane view)
What is the difference between passive and active sensors?
passive- run off of renewable energy Active- operate at night -sonar, radar, Lidar
What are the elements of photointerpretation?
size- Shape Shadow Tone/color Texture Pattern Site, situation, and association
Explain spectral reflectance curves
surface features color can be characterized by the % of energy it reflects
What are sources of distortion in aerial photographs and satellite images?
terrain Camera tilt Film deformation Camera lens Sensor defects or other camera errors Atmospheric bending
What are the common characteristics of terrain distortion in vertical images?
terrain distorions are radial Relief distortions affect angles and distances on an image Scale is not consistent on aerial images A vertical aerial image taken over varied terrain is not orthographic
Differentiate roll, pitch, and yaw. Illustrate. Which result in tilt distortion?
tilt results in roll and pitch Yaw: does not result in tilt
What is the most common form of solar radiation emitted by the sun?
ultraviolet
What does the red on a false color infrared image indicate?
vegetation
What is the difference between vertical, oblique, and horizontal?
vertical- taken staright down, like a map Oblique- taken at an angle