1 / 17

On the use of Numerical Weather Models to Predict Neutral-Atmosphere Delays

On the use of Numerical Weather Models to Predict Neutral-Atmosphere Delays. Felipe G. Nievinski. The curse of tropospheric delay in GPS positioning. One of main error sources in medium- to long-range kinematic applications. Estimation more challenging than in static app.

Download Presentation

On the use of Numerical Weather Models to Predict Neutral-Atmosphere Delays

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. On the use of Numerical Weather Models to Predict Neutral-Atmosphere Delays Felipe G. Nievinski

  2. The curse of tropospheric delay in GPS positioning • One of main error sources in medium- to long-range kinematic applications. • Estimation more challenging than in static app. • Due to, e.g., time-varying height. • A better a priori prediction would be valuable. • Whether estimating or only correcting for tropospheric delay.

  3. Numerical Weather Models: a better picture of today’s weather? • Typical tropospheric delay prediction models: (i) Climatological models (ii) Surface-measured pressure, temperature, humidity • NWM aims at representing (i) The daily weather (ii) The entire 3-dimensional weather field. Northern half of 3D refractivity (unitless) field on Aug 16, 2004, 22:45 UTC (vertical scale 100x)

  4. Methods • 1. How to predict delays with NWM • 2. How to test if the delays are not wrong • 3. How to assess whether the delays improve GPS applications

  5. Numerical integration: Coordinate conversion: Interpolation: Refractivity calculation: Predicting delays with NWM

  6. Tropospheric corrections: NWM–radiosonde discrepancy Total (cm) Hydro- static (cm) Non- hydro- static (cm)

  7. GPS positioning • Two scenarios for kinematic processing: • Moving rover: on board ferry boat • Stationary rover: one of two base stations • In each scenario, test and reference solutions:

  8. Impact assessment • 3 tropospheric prediction models assessed: • NWM • UNB3m • Saastamoinen with standard weather parameters • uncorrected observations (no model) • Criteria: • Discrepancy in rover position between test and reference solutions • RMS of observation residuals

  9. Stationary rover:test–reference discrepancy

  10. Saint John Digby Moving rover: discarding unreliable epochs

  11. Moving rover (1): test–reference discrepancy

  12. Moving rover (2): test–reference discrepancy

  13. Conclusions and future work • NWM has only marginal improvement on that particular 70 km baseline. • Validation: vertical coordinates in NWM • Study how it is handled in data assimilation • Test it with GPS-equipped radiosondes • Impact assessment: varying-length baselines • Kinematic processing at stationary rover • From 100 to 1,000 km

  14. Publications • Paper at ION AM 2005 in Boston, MA • Poster at AGU Joint Assembly in Washington, DC • Paper at ION GNSS 2006 in Fort Worth, TX

  15. Thanks!Questions? Felipe G. Nievinski

  16. satellite receiver Neutral-Atmosphere Delays • GPS signals are refracted in the Earth’s neutral atmosphere. • Hence timings (rangings) are delayed (increased). • ~ 2.5 m at zenith direction, ~ 25 m at 5º elevation angle (for a station on the geoid)

  17. Tropospheric corrections: NWM self-discrepancy NWM Ray-trace vs NWM Saastamoinen Hydro- static (cm) NWM Ray-trace vs Radiosonde ray-trace Hydro- static (cm)

More Related