iGage iG9 User Manual
67
Large Structures to the South
This 8-story parking garage is 40 feet to the southeast of the brass rivet in the street. The red arrow
points South.
This is a
bad
location because
the structure completely blocks the antenna’s view to the South and
East.
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:
