Active Sensors, LIDAR
1) How does a LIDAR operate? How does it measure the distance to a target?
2) Name a US LIDAR sensor on a satellite.
3) Aircraft LIDAR sensors typically provide an image showing ground or tree canopy
heights. Describe an optical/mechanical approach that could be used to scan the laser
beam across track as the aircraft flies forward, thereby obtaining the data needed for
creating an image. (Hint: consider the system used on Landsat 1 and also on early
remote sensing aircraft.)
Active Sensors, microwave
1) Microwave SAR imagery of an area is
a) black in P, L, C and X band data. What can you say about the surface? What might
the surface be – give two possibilities.
b) black in P band but bright in C band. What can you say about the surface? What
might the surface be – give three possibilities.
c) bright in P, L, C and X band data. What can you say about the surface? What
might the surface be – give one possibility. (Hint: look at John Jensen’s web site
http://www.cas.sc.edu/geog/rsbook/ Click on the Powerpoint slides for our
textbook. Login to the ftp site using ID=rs, Password=rs; Under Lectures_RSE,
drag Chapter09_Radar.ppt to your desktop; open it and look specifically at slide
number 66 that illustrates ‘Surface roughness in radar imagery.’)
2) Microwave SAR imagery of San Francisco reveals an area south of Market street is
exceptionally bright – much brighter than any other area of the city. Explain what
process might cause the increased brightness in imagery of the area south of Market.
Discuss how this same process could be used to estimate the stocking density of a
forest (# of trunks/ unit area).
3) A Microwave SAR is used to image a wetland that includes an open water area and,
closer to shore, a dense patch of reeds. How would you expect the image to appear
(i.e. black, grey or white) for each of the following:
___________________|||||||||||||||||| shore
open water reeds
