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Thinning Procedure for Shiptracks

Thinning Procedure for Shiptracks. David Rosenfield Research Associate NOAA National Coastal Data Development Center 1021 Balch Boulevard, Suite 1003 Stennis Space Center, MS 39529 9/11/2012.

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Thinning Procedure for Shiptracks

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  1. Thinning Procedure for Shiptracks David Rosenfield Research Associate NOAA National Coastal Data Development Center 1021 Balch Boulevard, Suite 1003 Stennis Space Center, MS 39529 9/11/2012

  2. U:\Okeanos Explorer 2008-2009-2010-2011\2010\EX1004_Indonesia\NODC\data\0-data\vessel\EX1004_Leg3\Ship_Navigation\CNAV\: CNAV-GGA_20100722-004127.Raw CNAV-GGA_20100722-073052.Raw CNAV-GGA_20100722-101604.Raw CNAV-GGA_20100723-000000.Raw CNAV-GGA_20100724-000000.Raw CNAV-GGA_20100725-000000.Raw CNAV-GGA_20100726-000000.Raw CNAV-GGA_20100727-000000.Raw CNAV-GGA_20100728-000000.Raw CNAV-GGA_20100729-000000.Raw CNAV-GGA_20100730-000000.Raw CNAV-GGA_20100731-000000.Raw CNAV-GGA_20100801-000000.Raw CNAV-GGA_20100802-000000.Raw CNAV-GGA_20100803-000000.Raw CNAV-GGA_20100804-000000.Raw CNAV-GGA_20100805-000000.Raw CNAV-GGA_20100806-000000.Raw CNAV-GGA_20100806-150855.Raw CNAV-GGA NMEA SCS Date(MM/DD/YYYY),SCS Time(hh:mm:ss.sss),Sentence Label(None),CNAV-TIME(hhmmss),CNAV-LAT(deg),CNAV-LAT Units,CNAV-LON(deg), 07/26/2010,00:00:01.471,$GPGGA,000001.00,0216.124127,N,12449.075605,E,2,09,1.1,22.604,M,65.744,M,10.0,0025*44 07/26/2010,00:00:02.471,$GPGGA,000002.00,0216.124154,N,12449.075612,E,2,09,1.1,22.566,M,65.744,M,10.0,0025*42 07/26/2010,00:00:03.471,$GPGGA,000003.00,0216.124176,N,12449.075607,E,2,09,1.1,22.682,M,65.744,M,9.0,0025*76 07/26/2010,00:00:04.472,$GPGGA,000004.00,0216.124197,N,12449.075601,E,2,09,1.1,22.797,M,65.744,M,10.0,0025*45 07/26/2010,00:00:05.472,$GPGGA,000005.00,0216.124185,N,12449.075604,E,2,09,1.1,22.801,M,65.744,M,10.0,0025*42 07/26/2010,00:00:06.472,$GPGGA,000006.00,0216.124119,N,12449.075601,E,2,09,1.1,22.772,M,65.744,M,10.0,0025*4A 07/26/2010,00:00:07.472,$GPGGA,000007.00,0216.124052,N,12449.075599,E,2,09,1.1,22.741,M,65.745,M,10.0,0025*46 07/26/2010,00:00:08.472,$GPGGA,000008.00,0216.124001,N,12449.075584,E,2,09,1.1,22.700,M,65.744,M,10.0,0025*47 07/26/2010,00:00:09.472,$GPGGA,000009.00,0216.124011,N,12449.075558,E,2,09,1.1,22.693,M,65.744,M,9.0,0025*75 07/26/2010,00:00:10.472,$GPGGA,000010.00,0216.124038,N,12449.075558,E,2,09,1.1,22.742,M,65.744,M,10.0,0025*43 07/26/2010,00:00:11.472,$GPGGA,000011.00,0216.124050,N,12449.075586,E,2,09,1.1,22.717,M,65.744,M,10.0,0025*4F 07/26/2010,00:00:12.456,$GPGGA,000012.00,0216.124051,N,12449.075614,E,2,09,1.1,22.669,M,65.744,M,10.0,0025*4D 07/26/2010,00:00:13.472,$GPGGA,000013.00,0216.124051,N,12449.075625,E,2,09,1.1,22.666,M,65.744,M,10.0,0025*41 SCS Date(MM/DD/YYYY), SCS Time(hh:mm:ss.sss), Sentence Label(None), CNAV-TIME(hhmmss), CNAV-LAT(deg), CNAV-LAT Units, CNAV-LON(deg), CNAV-LON Units, CNAV-Fix Quality(*NONE*), CNAV-Sat(*NONE*), CNAV-HDOP(*NONE*), CNAV-Alt(Meters), CNAV-Alt-M(*NONE*), CNAV-Geoid(*NONE*), CNAV-Geoid-M(*NONE*), CNAV-?(*NONE*), CNAV-GGA-Chksum(*NONE*)

  3. thinshiptrack.m • octave> [ipos,opos]=thinshiptrack(eps,dist,nsec); • Three step process • Save record every ‘nsec’ seconds • Save ‘ipos’ as ascii file • Save ipos as a workspace variable • Perform Douglas Peucker optimization • octave> list=douglaspeucker(x,y,points,eps,dist); • octave> opos=ipos(:,list); • Save ‘opos’ as ascii file • Save opos as a workspace variable • Convert to (and save) a .kml file

  4. STEP 1 of thinshiptrack.m • Save record every ‘nsec’ seconds For each file: if nsec=6 for example… CNAV-GGA_20100722-004127.Raw CNAV-GGA_20100722-073052.Raw DateString,Tag,Date#,Lon,N,Lat,E,,,,,,Elev,,,, CNAV-GGA_20100722-101604.Raw ---------------------------------------------- CNAV-GGA_20100723-000000.Raw CNAV-GGA_20100724-000000.Raw CNAV-GGA_20100725-000000.Raw CNAV-GGA_20100726-000000.Raw CNAV-GGA_20100727-000000.Raw CNAV-GGA_20100728-000000.Raw CNAV-GGA_20100729-000000.Raw CNAV-GGA_20100730-000000.Raw CNAV-GGA_20100731-000000.Raw CNAV-GGA_20100801-000000.Raw CNAV-GGA_20100802-000000.Raw CNAV-GGA_20100803-000000.Raw saves variable creates ascii file CNAV-GGA_20100804-000000.Raw CNAV-GGA_20100805-000000.Raw DateString Date# Lon Lat Elev CNAV-GGA_20100806-000000.Raw ---------------------------------- CNAV-GGA_20100806-150855.Raw ipos is a [4x100K] matrix in Octave/MATLAB workspace ipos=[Date#;lon;lat;elev] 07/26/2010,00:00:01.471,$GPGGA,000001.00,0216.124127,N,12449.075605,E,2,09,1.1,22.604,M,65.744,M,10.0,0025*44 07/26/2010,00:00:02.471,$GPGGA,000002.00,0216.124154,N,12449.075612,E,2,09,1.1,22.566,M,65.744,M,10.0,0025*42 07/26/2010,00:00:03.471,$GPGGA,000003.00,0216.124176,N,12449.075607,E,2,09,1.1,22.682,M,65.744,M,9.0,0025*76 07/26/2010,00:00:04.472,$GPGGA,000004.00,0216.124197,N,12449.075601,E,2,09,1.1,22.797,M,65.744,M,10.0,0025*45 07/26/2010,00:00:05.472,$GPGGA,000005.00,0216.124185,N,12449.075604,E,2,09,1.1,22.801,M,65.744,M,10.0,0025*42 07/26/2010,00:00:06.472,$GPGGA,000006.00,0216.124119,N,12449.075601,E,2,09,1.1,22.772,M,65.744,M,10.0,0025*4A 07/26/2010,00:00:07.472,$GPGGA,000007.00,0216.124052,N,12449.075599,E,2,09,1.1,22.741,M,65.745,M,10.0,0025*46 07/26/2010,00:00:08.472,$GPGGA,000008.00,0216.124001,N,12449.075584,E,2,09,1.1,22.700,M,65.744,M,10.0,0025*47 07/26/2010,00:00:09.472,$GPGGA,000009.00,0216.124011,N,12449.075558,E,2,09,1.1,22.693,M,65.744,M,9.0,0025*75 07/26/2010,00:00:10.472,$GPGGA,000010.00,0216.124038,N,12449.075558,E,2,09,1.1,22.742,M,65.744,M,10.0,0025*43 07/26/2010,00:00:11.472,$GPGGA,000011.00,0216.124050,N,12449.075586,E,2,09,1.1,22.717,M,65.744,M,10.0,0025*4F 07/26/2010,00:00:12.456,$GPGGA,000012.00,0216.124051,N,12449.075614,E,2,09,1.1,22.669,M,65.744,M,10.0,0025*4D 07/26/2010,00:00:13.472,$GPGGA,000013.00,0216.124051,N,12449.075625,E,2,09,1.1,22.666,M,65.744,M,10.0,0025*41 07/26/2010,00:00:14.472,$GPGGA,000014.00,0216.124072,N,12449.075628,E,2,09,1.1,22.669,M,65.744,M,10.0,0025*45 07/26/2010,00:00:15.456,$GPGGA,000015.00,0216.124079,N,12449.075626,E,2,09,1.1,22.751,M,65.745,M,9.0,0025*72 07/26/2010,00:00:16.472,$GPGGA,000016.00,0216.124060,N,12449.075623,E,2,09,1.1,22.826,M,65.744,M,9.0,0025*72 07/26/2010,00:00:17.472,$GPGGA,000017.00,0216.124028,N,12449.075627,E,2,09,1.1,22.814,M,65.744,M,10.0,0025*42 07/26/2010,00:00:18.472,$GPGGA,000018.00,0216.124035,N,12449.075640,E,2,09,1.1,22.725,M,65.744,M,10.0,0025*4D 07/26/2010,00:00:19.472,$GPGGA,000019.00,0216.124065,N,12449.075641,E,2,09,1.1,22.693,M,65.744,M,10.0,0025*44 07/26/2010,00:00:06.472 3.971281 124.817927 2.268735 22.772 07/26/2010,00:00:12.456 3.971350 124.817927 2.268734 22.669 07/26/2010,00:00:18.472 3.971420 124.817927 2.268734 22.725

  5. STEP 2 of thinshiptrack.m • Perform Douglas Peucker optimization Simple lines of several points are reduced to a 2 point line. n=6n=2 More complex paths are broken down to smaller lines... n=13 ...and each are reduced to a 2 point line. n=4 This method is called “recursion.”

  6. STEP 2 of thinshiptrack.m • Standard Douglas Peucker optimization • Epsilon: some small % of total distance max perpendicular dist epsilon * total dist total distance n=15

  7. STEP 2 of thinshiptrack.m • Addition to Douglas Peucker optimization • BaseDistance: some small (1-1000m) distance When total distance is smaller than BaseDistance, all points within the line are removed. And we’re done! n=7

  8. thinshiptrack.m • Overview

  9. thinshiptrack.m • Evaluation In your “C:\Octave\student\” directory there is a file you will run in Octave called thinshiptrack.m (runs douglaspeucker.m) open Octave in Octave: Octave>cd ../../student octave>eps=0.01;dist=1;nsec=600; octave>[ipos,opos]=thinshiptrack(eps,dist,nsec); Octave>nsec=6; octave>[ipos2,opos2]=thinshiptrack(eps,dist,nsec); octave>whos Details on ipos, ipos2, opos and opos2 come up on your screen. Exploring your student directory, you should see two new *.kml file that you just created. Open Google Earth and drag both of these into it. Change one shiptrack’s color to red. Repeat this method to help fill out the following table.

  10. thinshiptrack.m • Evaluation • Otherwise use eps=1%, nsec=60, and dist=10m

  11. Thanks!Any Questions?

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