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: sharyl.byram@usno.navy.mil.

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