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FOR 220 Aerial Photo Interpretation and Forest
Measurements
Lecture 5 Fixed Area Sampling
Avery and Burkhart, Chapter 10
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Fixed Area Plot Sampling
Two general methods Strip cruising
Plot cruising
Sample area
Sample area
X
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Strip Cruising
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Strip Cruising
Nominal cruise intensity How much of the land
was sampled? (Wstrip width, Ddistance
between strips) Examples strips 1 chain
wide, 10 chains apart strips 1/2 chain wide,
10 chains apart
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Strip Cruising
Actual cruise intensity How much of the land was
sampled Example area cruised was 10 acres,
stand area was 200 acres
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Strip Cruising
Expansion factor What does each sample
represent? Examples Cruise intensity was
10 Cruise intensity was 5
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Strip Cruising
Computing total stand area from a strip
cruise Acres sampled Estimate of stand
area
(Remember 10 sq. chains 1 acre)
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Strip Cruising
Computing total stand area from a strip
cruise Example 1 chain strips, 15 chains
apart, total length of strips 145 lineal chains
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Strip Cruising
Advantages of strip cruising 1. Less time
wasted between sample areas than for a fixed plot
method of equal intensity. 2. Fewer borderline
trees, because the total perimeter of the sample
area is smaller than with fixed plots. 3. Less
risk to personnel in remote areas two people
generally work together.
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Strip Cruising
Disadvantages of strip cruising 1. Inaccurate
estimation of strip width may lead to errors. 2.
Difficult to maintain a straight strip
centerline. 3. Brush and windfall are more of a
hindrance in this system. 4. Spot-checking the
cruise is difficult strip centerline is rarely
marked.
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising
Nominal cruise intensity How much of the land
was sampled? Examples 1/10 acre plot on a
2 x 5 chain spacing (remember 10sq. ch. 1
ac.) 1/5 acre plot on a 4 x 5 chain spacing
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising
Plot cruise planning 160 acre tract 10
cruise (sample) 1/5 acre plots
Given
1. Area to be sampled
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising
Plot cruise planning 160 acre tract 10
cruise (sample) 1/5 acre plots (0.2
ac.plots) area sampled 16.0 ac.
2. No. of plots needed.
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising
Plot cruise planning 160 acre tract 10
cruise (sample) 1/5 acre plots area sampled
16.0 ac. 80 plots needed
3. Samples represent how much area?
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising
Plot cruise planning 160 acre tract each
represents 2 acres (20 sq. chains) 10 cruise
(sample) 1/5 acre plots area sampled 16.0
ac. 80 plots needed
4. Plot spacing? Distance between plots
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising
Plot cruise planning 160 acre tract each
represents 2 acres (20 sq. chains) 10 cruise
(sample) 5 chain spacing between lines 1/5 acre
plots area sampled 16.0 ac. 80 plots needed
5. Plot spacing? Distance between lines
FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising

• Plot cruise planning
• 160 acre tract
• 10 cruise (sample)
• 1/5 acre plots
• Area sampled 16.0 ac.
• 80 plots needed
• Each represents 2 acres (20 sq. chains)
• 5 chain spacing between lines
• 4 chain spacing between plots

FOR 220 Aerial Photo Interpretation and Forest
Measurements
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Fixed Area Plot Sampling
Plot Cruising

• Some advantages of plot cruising
• 1. Suitable for one-person cruising.
• 2. Cruisers do not have to tally trees while
  following a compass line.
• Cruisers pause at plot centers, allowing more
  time to check
• measurements.
• 4. Tree tally is separated by plots can
  separate the plots into sets to calculate volumes
  for different timber types, etc.

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Measurements
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Fixed Area Plot Sampling
Purposes
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Fixed Area Plot Sampling - Different plots for
different purposes
Inventory Plots

• Not very precisely installed and not well
  monumented
• Round plots are common
• Standard procedures for measurements
• Not re-measured at periodic intervals
• Purpose To measure forest conditions (volume,
  etc.)

Example Lab 2
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Fixed Area Plot Sampling - Different plots for
different purposes
Permanent Plots

• Installed very precisely and monumented
• Square plots are common
• Standard procedures for measurements
• Re-measured at periodic intervals
• Purpose To measure changes in forest conditions
• Can determine causes of change

Example Forest Inventory and Analysis (FIA)
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Measurements
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Fixed Area Plot Sampling - Different plots for
different purposes
Permanent Plots
F.I.A.
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Measurements
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Fixed Area Plot Sampling - Different plots for
different purposes
Regeneration Plots
Not installed and nor monumented Purposes To
evaluate regeneration status To demonstrate
compliance with laws To determine effectiveness
of regeneration treatments To identify
additional treatments needed To collect data to
predict growth and yield

• Stocked-quadrat method (proportion of land
  utilized)
• Plot-count method (number of trees per acre)
• Staked-point method (like permanent plots)

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Measurements
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Where, in the U.S. are we?
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What is this guy doing?
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Kite Aerial Photography
http//arch.ced.berkeley.edu/kap/kaptoc.html
FOR 220 Aerial Photo Interpretation and Forest
Measurements