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GNSS (GPS) PRECISION AND SYSTEM TIMING
Exaggerated Animation (from BT Controller Status & Signal GUI) for Illustration ONLY
example GPS with SBAS

  PDOP (Position Dilution Of Precision):
Error related to relative position of tracked satellites.
When satellites spread apart more precise PDOP.
      1 Ideal   1 - 2 Excellent
As PDOP ↑ both Horizontal and Vertical precision ↓

example GPS tracked
example GPS tracked

   1 PPS Pulse from GPS Module
←   As may be selected on "Signals" GUI
    Reference Sync for All receivers

 Can Be Precise to Billionths of a Second (ns)
1PPS Accuracy
Goal: Impulse TOA Time Stamp precision ⋜ 1 µSec
  1 µSec = 300m location error. (Deviation)

Antenna Types, Filter settings, (e.g.) will affect
Signal's Time Stamp referenced to GPS 1PPS

Server understands the designed circuit and filter
settings, and specified antenna type descriptions.
Unusual antenna configurations, circuit changes
may result in dramatic locating errors . (deviation)

Check Controller GPS Satellites tracked against those visible at your location Live at In-The-Sky.org
Set "View Sky" = "Above", and for Northern Hemisphere "Orientation" = "South"

'Real Time' Global GPS Satellite Position and Status
3 min UpDate ± 1 min Delay
SBAS Satellites (Geostationary) numbered 120 to 151
Blitzortung GUI may display SBAS using NMEA IDs, 33-64. (Add 87) ie. "44" = "131"
In November 2018 the FCC issued waiver for certain US technology to utilize EU Galileo GNSS, but older BT systems may lack capable modules.
 
 
'Real Time' Global GPS PDOP
3 min UpDate ± 1 min Delay
 
'Real Time' North America Geomagnetic — Ionospheric Influence and Compensations
15 min UpDate ± 8-12 min Delay
GNSS data can be affected by extreme GeoMagnetic Activity Background Info
3 min UpDate ± 1 min Delay — CLICK GRAPHIC for full size image
WAAS corrections applied to GPS Timing NORTH AMERICA
"GIVE"
= Vertical Error
"DELAY"
= Position Error

SBAS enabled attempts some corrections if SBAS satelite in view.