Field Survey & Data Collection Flashcards
7 cards from real SAF practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Field Survey & Data Collection flashcards as text
When measuring slope distance to convert to horizontal distance, a forester records a slope of 30% over 100 feet of slope distance. The horizontal distance is approximately:
Answer: 95.4 feet
For a 30% slope (angle ≈ 16.7°), horizontal distance = slope distance × cos(16.7°) ≈ 100 × 0.954 = 95.4 feet.
What is the standard diameter at breast height (DBH) measurement point in the United States?
Answer: 4.5 feet above ground
In the US, DBH is measured at 4.5 feet (1.37 m) above the ground on the uphill side of the tree.
In a two-phase (double) sampling design for forest inventory, Phase 1 typically involves:
Answer: Rapid, inexpensive measurements on a large sample to stratify the population
Phase 1 collects inexpensive auxiliary data (e.g., aerial photo interpretation) on many points used to stratify before the smaller, costlier Phase 2 ground sample.
Which instrument is specifically designed to measure the diameter of standing trees at heights above ground without climbing?
Answer: Optical dendrometer
An optical dendrometer (such as the Wheeler pentaprism or Barr & Stroud) allows measurement of stem diameter at any height without climbing.
A forester uses a Biltmore stick to estimate tree diameter. The stick works by holding it at a fixed arm's length distance and reading the scale. This method relies on the principle of:
Answer: Similar triangles using the eye as the apex
The Biltmore stick uses similar triangles: the stick at arm's length, the eye, and the tree diameter form proportional triangles, allowing diameter estimation.
When measuring crown closure (canopy cover) with a spherical densiometer, readings are taken in how many directions?
Answer: 4 (north, south, east, west)
Standard spherical densiometer protocol calls for four readings—north, south, east, and west—which are then averaged to estimate canopy cover.
In forest inventory, 'cruise control' or 'quality control' checks are best performed by:
Answer: An independent checker re-measuring a random subset of plots
An independent checker measuring a random subset of plots detects both systematic bias and random error without the original cruiser's influence.