Software Setup & Processing
• Precise Point Positioning (PPP) Method
• 27 hour Observation Window
• Fixed GPS Clocks and Orbits: IGS Finals
• Elevation Angle Cutoff: 7 degrees (Receiver Dependent)
• Troposphere Mapping Function: GMF (Global Mapping Function)
• A Priori Troposphere Estimate: Dry Niell Model
• Temporal Resolution: 5 minutes
• Relative A Priori Sigmas: 1 mm (ZTD), 0.1 mm (Gradients)
• Latency: 3 weeks (Result of Using IGS Finals)
• First Day Processed by USNO: DOY 107 of 2011 (April 17, 2011)
• Not a Combination Production Like Other IGS Products
• Generated Using Bernese 5.0 Software and USNO Developed Routines
• RINEX Data Pre-Filtered for Missing Data
• Post Estimate Screening for Product Quality
Quality Screening • Improved RINEX Data Retrieval Algorithm to
Download More Stations for Processing
• Revised Station List to Increase Stations Downloaded
• Robust Data Getting Commands
• Search Multiple RINEX Data Extensions (Ex: *.14d And *.14o) to Retrieve a Station’s Observations
• Upgraded Observation Data Screening Procedures
• TEQC Processing Routines
• Checks for Station Data Gaps or Insufficient Station Data
• Upgraded Post Processing ZPD File Screening
• Ongoing Improvements
IGS Final Troposphere Product Update S. Byram and C. Hackman
United States Naval Observatory, Washington DC, USA
Purpose
• Describe Processing of IGS Final Troposphere by USNO
• Status Update of IGS Final Troposphere Processing
• Future Plans
Summary • Produced Using a PPP Method at USNO, Not
a Combination Product
• Number of Stations per Day Variability Due to Improved Post Processing Screening for Data Quality, Revised Station List, and Improved RINEX File Routines
• Station Repeatability Consistent Over Time Demonstrating Excellent Internal Stability of the Processing (and Improving)
• Many Future Plans including Repro2 Models and Upgraded Software
Troposphere Products Available Online: ftp://cddis.gsfc.nasa.gov/gps/products/troposphere/zpd/ USNO Archive: ftp://maia.usno.navy.mil/GPS/tropo/
For more information: Sharyl Byram, US Naval Observatory, 3450 Massachusetts Ave NW, Washington, DC 20392, USA. Telephone: (202) 762-0185. email: [email protected].
Future Plans
• Incorporate the Recommendations of the Troposphere Working Group
• Incorporate Other GNSS Signal Data (Maybe Improve Estimates at Higher Latitudes?)
• Participation in Repro2 Processing (Waiting on Repro2 Orbit Products)
• Incorporate Repro2 Models/Standards in Daily Processing
• Upgrade to Bernese 5.2 Software (Testing Now)
Background image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center
ZPD File Production • Produce Estimates for ~325 stations/day (2013 Average)
• 10.3 Million Files Downloaded from CDDIS FTP Site in 2013
• Variability Due to Availability of Station Data at 3 weeks Latency, Improved Post Processing Screening for Data Quality, Revised Station List, and Improved RINEX File Routines
Current Operations Status
Number of Stations/Day Since Start of USNO IGS Final Troposphere Estimates Production
Coordinate Repeatability • Coordinate Comparison of ~325 Stations
Over Each Ten Day Period for DOYs 112 through 142 of 2014 (Most Recent)
• Outliers Screened Out (~10 Stations/Period)
• Same Stations Filtered Out of File Submission for Quality at End of Troposphere Estimate Processing
• ~10-20% Improvement from 2012 in All Directions (2012 Average Values: N 1.85, E 2.85, W 5.33 mm)
DOYs of 2014 N [mm] E [mm] U [mm]
112-121 1.50 2.58 5.10
122-131 1.44 2.24 4.48
131-141 1.43 2.48 4.68
average 1.45 2.43 4.75
Station Repeatability Associated with IGS Final Troposphere Estimates in Ten Day Increments
200
220
240
260
280
300
320
340
360
380
400
11 1
07
11 1
22
11 1
37
11 1
52
11 1
67
11 1
82
11 1
97
11 2
12
11 2
27
11 2
42
11 2
57
11 2
72
11 2
87
11 3
02
11 3
17
11 3
32
11 3
47
11 3
62
12 0
12
12 0
27
12 0
42
12 0
57
12 0
72
12 0
87
12 1
02
12 1
17
12 1
32
12 1
47
12 1
62
12 1
77
12 1
92
12 2
07
12 2
22
12 2
37
12 2
52
12 2
67
12 2
82
12 2
97
12 3
12
12 3
27
12 3
42
12 3
57
13 0
06
13 0
21
13 0
36
13 0
51
13 0
66
13 0
81
13 0
96
13 1
11
13 1
26
13 1
41
13 1
56
13 1
71
13 1
86
13 2
01
13 2
15
13 2
30
13 2
45
13 2
60
13 2
75
13 2
90
13 3
05
13 3
20
13 3
35
13 3
51
13 3
64
14 0
14
14 0
29
14 0
44
14 0
59
14 0
74
14 0
89
14 1
04
14 1
19
14 1
34
Sta
tion
s
Year and Day of Year
Improved Post Processing Screening
Revised Station List
Improved RINEX Data Retrieval
