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Huge Trees to the South
BAD
: This site is not suitable for GPS observation because of large trees to the south:
Southern sky is fully blocked and trees obscure view directly overhead.
We can debate:
leaves on, leaves off
pine needles vs. broad leaves
length of pine needles
size of tree-trunks
size of branches
But trees above 10° to the East, South or West are bad and 100% canopy is really bad.
Huge Trees Overhead
Trees (with or without leaves) directly above the antenna prevent the receiver from having a clear
view of the sky. Even though this location has open water to the South, it is directly underneath
large trees. Water can also be a source of significant multipath (see the next section). This is a
BAD
location:
Large Reflective Surfaces Nearby
Your receiver trusts that the signals that it receives have traveled directly from the satellite to your
antenna. Large nearby surfaces present opportunities for the receiver to have signals arrive having
taken multiple paths (multipath) or entirely the wrong path.
Not only do these tanks block the view to the South, but they also have metal-reflective surfaces
that provide a multiple length signal path for every signal from every satellite to the observation
area: