1. Garvin
et al. 1998 - "The Shuttle Laser Altimeter (SLA)..."
2. Blair, Rabine, Hofton
1999 - "The Laser Vegetation Imaging Sensor (LVIS)..."
3.Dubayah, Blair et al., 1997
- "The Vegetation Canopy Lidar (VCL).."
4."Laser altimetry simulator
version 3.. " which briefly explains the lidar concept.
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Assignment #1
Go to the class directory and redo the steps outlined on the worksheet
dated 9/9/99 to review how to look at data using IDL.
1. Using the techniques you used in the IDL class, cut out a box in
the flightline within the following latitude and
longitude:
N36.4734 E241.2214
N36.4734 E241.2659
N36.5312 E241.2659
N36.5312 E241.2614
Save these data in an array called 'cc'.
a. These data were collected by LVIS in October 1997. Where were these data collected (hint: plot the longitude vs latitude to find out).n_elements command).
c. How many beams was LVIS configured to during this flight. (The number of beams corresponds to the number of cross-track footprints in the swath).
d. If the footprints are separated by 8m from each other, what is the total width of the LVIS swath (in meters).
e. What is the minimum, maximum, and mean elevation of the ground in your subset of data. What is the minimum, maximum and mean height of the canopy within your data subset. (Hint: use IDL functions ).
f. Which shots (i.e., what is the array index number) have the minimum and maximum ground elevation (hint: use "where" command and the results from question 1e).
g. Which shots have the minimum and maximum canopy heights.
h. Make a histogram of the canopy heights within your subset using a binsize of 2 m (hint: see class worksheet on how to do this).
2. Using your data subset, grid the ground elevations using an 8m horizontal ground spacing. Repeat using the canopy top topography (i.e., ground elevation + height). (Hint: use the worksheet from the IDL class).
a. Produce a plot with the following four panels and save in GIF format.
-plot footprint latitude vs. longitude of whole data set
and overplot the locations of your subset in a different color.
-plot elevation vs. array number and overplot canopy top
topography in a different color.
-plot a 3-d image of the gridded ground topography (using
shade_surf procedure)
-plot a 3-d image of gridded canopy heights (note: you
will have to form this from your gridded canopy top data set and your ground
topogrpahy data set).
Label the axes appropriately.
b. Briefly describe the general topography of the region. Is there any relationship of canopy height with elevation (hint: use your cc array to plot the height array vs elevation array and determine if there is a relationship).
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Assignment #2
Carefully read the Means, et al, Lefsky et al, and Magnussen papers.
Compare the methods section of each paper. What are the questions that
each methodology was structured to answer? How were the field methods
and sampling protocol different in each case? The data analysis
methods? How do the differences in lidar data acquisition (large
foot
print lidar vs small footprint) come into play in methods and analysis?
Please write a brief summary of your thoughts on these questions (to
be
turned in) that will form the basis of our discussion the next class
meeting.
Magnussen, S. and P. Boudewyn, "Derivation of stand hights from ariborne
laser scanner data with canopy-based quantile estimators", Can. J.
For.
Res. 28: 1016-1031 (1998)
===> Pay attentention to the underlying assumptions the authors make
in
this paper and think about how justified they are for this specific
anlaysis, and also in
more general terms. Also how much of the methodology is a direct result
of the advantages/limitations
of small footprint lidar first/last return lidar, vs. large footprint,
full waveform digitization
lidar?
There is a related paper by Magnussen et al. (1999) in For. Sci, August,
but this paper is even more difficult to get through methodologically;
however, it does
present a a more generalized approach (at least in the mind of the
authors).