1 / 18

Staggered PRT Algorithm Update

Staggered PRT Algorithm Update. Sebastian Torres and David Warde CIMMS/University of Oklahoma and NSSL/NOAA. Data Quality MOU – Technical Interchange Meeting Norman, OK 1 December, 2009. SPRT Algorithm Evolution. 2003 : 2/3 PRT ratio with DC filter NSSL Report 7

sophia-rosales
Download Presentation

Staggered PRT Algorithm Update

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. Staggered PRT Algorithm Update Sebastian Torres and David Warde CIMMS/University of Oklahoma and NSSL/NOAA Data Quality MOU – Technical Interchange MeetingNorman, OK 1 December, 2009

  2. SPRT Algorithm Evolution • 2003: 2/3 PRT ratio with DC filter • NSSL Report 7 • 2005: SACHI filter (standalone) • NSSL Report 9 • 2008: Any PRT ratio with DC filter • NSSL Report 12 • 2009: 2/3 PRT ratio with SACHI filter • Separate document delivered on 03/09 • 2009: 2/3 PRT ratio with SACHI filter and overlaid echo recovery • Separate document delivered on 07/09 • NSSL Report 13

  3. 2009 SPRT AEL (07/09) • Notation standardization • Clutter filtering update • SACHI on Segments I and II • Functionality same as in Report 11 • Adapted to “fit” signal processing pipeline • Steps described in algorithmic form • DC removal on Segment III • Recovery of overlaid echoes • Segment III data reconstruction • Overlaid echo determination

  4. Recap: Squeezing SACHI in • Strong-point clutter canceling • Inputs: P, R1, and R2 • Outputs: P, R1, and R2 • SACHI needs to return P, R1, and R2 • Derived from SACHI’s outputs: S, v, and sv • In the absence of SPC, the spectral moment computations should produce S, v, and sv again! SACHI SPC Removal Spectral moment computations Conversion V S v sv P R1 R2 P R1 R2 S v1, v2 sv

  5. Recap: Clutter Filtering Logic • Segments I and II • SACHI • Output: “manufactured” P, R1, and R2 • Segment III • DC removal • Output: a dwell of time-series data • Power and correlation computations • Output: P1, P2, R1, and R2 • Combined power computation • Output: P

  6. Further AEL Updates • Handling overlaid echoes • Better performance from using short PRTs • Algorithm modifications • Segment-III data “reconstruction” • R1 and R2 are computed for all range gates • Handling overlaid echoes • Detecting and flagging • Ground clutter filtering • Rules to handle overlaid clutter • Overlaid power correction for SACHI ra,2 ra,1 rmax

  7. Segment-III Data Reconstruction Segment I Segment II Segment III 1 S1 S2 S1+S3 R1 Available only within ra1 Available within ra2 2 S1+S3 S2 S3 R2 3 S1 S2 S1+S3 S1+S3 S2 S3 4 S1 S2 S1+S3 M -1 M S1+S3 S2 S3 ra2 ra1 T1 T2 I II III I II III I II I II III

  8. Handling Overlaid Echoes Segment I Segment II Segment III • Segments I and III may contain overlaid echoes • Overlaid echoes appear on every other pulse • Correlations are not biased • Overlaid echoes do not contaminate reflectivity • Combined powers use only “clean” data • Moment-specific overlaid power thresholds are used to recover velocity and width for the strong trip • Segment II does not contain overlaid echoes T1 S1 S2 S1+S3 T2 S1+S3 S2 S3

  9. Clutter Filtering Logic Segment I Segment II Segment III • Algorithm assumes no clutter beyond ra1 • No clutter in Segment III • Segment I gates • Segment I clutter (C1): SACHI • Overlaid power correction (S3): computed from T2 pulses • Segment II gates • Segment II clutter (C2): SACHI • Segment III gates • Segment I clutter (C1): DC removal on T1 pulses T1 S1 S1+C1 S2+C2 S2 S1+S3 S1+S3+C3 S1+C1+S3 S1+C1+S3 T2 S1+C1+S3 S1+S3+C3 S1+S3 S1+C1+S3 S2 S2+C2 S3 S3

  10. Overlaid Correction for SACHI Segment I Segment II Segment III • SACHI is not designed to handle overlaid echoes • After perfect filtering, it would return S = S1+S3/2 • Need to remove S3/2 • S3 is computed from the T2 pulses • S3/2 is subtracted from the power estimates that are used to produce the manufactured outputs T1 S1+C1 S2 S1+C1+S3 T2 S1+C1+S3 S2 S3

  11. Final SPRT AEL (I)

  12. Final SPRT AEL (II)

  13. Computational Complexity (I) • The most computationally intensive step in the SPRT algorithm is SACHI • For SACHI, complexity is mainly driven by • DFT of the extended time series • O(Mx2) = 6.25 O(M 2) • Matrix multiplications • Two complex matrix multiplications • 5-by-5 times 5-by-Mp : 2x5x5xM real multiplications ≈ O(M ) • One real matrix multiplication • 5-by-5 times 5-by-Mp : 5x5xM/2 real multiplications ≈ O(M ) • SACHI is not recursive and other steps involve routine computations performed in the FFT mode • The GMAP notchwidth computation does not require an additional DFT nor the recursive part of GMAP

  14. Computational Complexity (II) • VCP 221 vs. VCP 222 • DFT for SPRT compared to DFT for Batch • Mx = (5/2) MSPRT = (5/2) (MSPRT /MBATCH) MBATCH • O(Mx2) = [(5/2) (MSPRT /MBATCH)]2 O(MBATCH2)

  15. RVP-8 CPU Load • Extracted from Steve Smith’s presentation to the SREC (Jun 2008)

  16. Computational Complexity (III) • Back of the envelope computations • Assume that CPU load in Batch mode is ~10% • This includes GMAP for the short PRT pulses (all bins?) • Number should not depend on coverage • Batch mode • Assume that DFT takes ~33% of total computations for the Batch mode • DFT CPU load is ~3% • “Other steps” CPU load is ~7% • SPRT algorithm • Assume that DFT in the SPRT algorithm takes 10 times longer • DFT CPU load is ~30% • Assume “other steps” in the SPRT algorithm take 4 times longer than the “other steps” in the Batch mode • Total CPU load of ~30% + 4x7% ≈ 60%

  17. Conclusions • Provided a new AEL for staggered PRT with updates in the following areas: • Notation standardization • Incorporation of SACHI • Handling of overlaid echoes • Computational complexity of SACHI is predicted to be within current processing capabilities • SPRT should not require new hardware • Could it be “the straw that breaks the camel’s back”? • Final version of the algorithm is complete! • Will support ROC’s implementation and validation

  18. Questions? Staggered PRT(k = 2/3, same DT) Batch ModeVCP 11 March 3, 20042.5 deg ra = 147 km, va = 28.8 m/s ra = 184 km, va = 45.1 m/s

More Related