ASAR practical training session

Transcription

1 ASAR practical training session Dr. Fabrice Collard and Dr. Vincent Kerbaol, BOOST Technologies, Brest, France Prof. Johnny Johannessen NERSC, Bergen, Norway

2 2 Presentation of the company The activities of BOOST Technologies focus on the monitoring of marine environment using Remote Sensing data. Research: High level of expertise in Synthetic Aperture Radar (SAR) Software development SARTool software to produce SAR derived marine products (on the fly or embedded in operational processing chain) Value-added services: Oil spill monitoring, SAR wind products

3 3 Presentation of the company Reference Research Definition, development and validation of ENVISAT ASAR level 2 wind, waves and currents products (ESA) Software: SARTool Oil: SARTool Wind : SARTool Ships : SARTool Waves: CEDRE (F) Kongsberg Satellite Services (N) NURC (NATO) NOAA (US) Value added services Oil spill detection service provider for the French end-users

4 4 Plan Introduction to SARTool software Ship detection Oil spill detection Wind field retrieval Surface currents Waves retrieval Coastline delineation

5 5 Introduction to SARTool software Architecture SARTool Explorer (GUI) SARTool Ships SARTool Oil SARTool Wind SARTool Waves Database Selection Module SARTool common Features basis Option Under dev elopment

6 6 Introduction to SARTool software Designed to demonstrate the capabilities of SAR imagery over marine scenes and to generate value added products Supported format: Mission Products Format Type of Input ASAR ENVISAT level1 products IMS_1P, APS_1P, IMP_1P, APP_1P, IMM_1P, APM_1P, WSM_1P ENVISAT Payload Data Segment (PDS format) Path name of the file of standard ASAR ENVISAT L1B product ERS-1/2 level1 products RADARSAT-1 level1 products SLC PRI Standard modes, ScanSAR Narrow/Wide, Extended modes CEOS CEOS Path name of the directory containing standard CEOS Path files name of the directory containing standard CEOS files

7 7 File menu : Access to SAR data Configuration Tab widget to access image parameters: Information at Cursor Information on SAR Data Information on Quicklook Tab widget to setup geographic parameters: Overlay grid Overlay bathymetry Tab widget to setup levels parameters: Min/max value Levels number View histogram

8 8 Introduction to SARTool: exercise ENVISAT ASAR Wide Swath 11 November 2002 File > Open File > ENVISAT ASAR Select 6 th file in folder named ws ASA_WSM_1PXPDE _104431_ _ 00180_03741_0009.N1 Improve display of quick-look Rotation 180 Correct for signal attenuation over ocean

9 9 Platform heading (descending path) Main parameters of SAR image: Image size Pixel spacing Aspect ratio Detection mode Range projection Polarization Mean incidence angle Track angle (heading) Display of the pathoriented image Important attenuation in the acrosstrack (line-of-sight) direction

10 10 Visualization menu Display the image with original intensity values Apply histogram equalization Correct for variations of the SAR image intensity in the range direction Apply a 180 rotation

11 11 Visualization menu Nice display Correct for the variations of intensity in the Range direction Range spreading loss Attenuation of! 0 with increasing incidence angle Antenna pattern (e.g. ENVISAT ASAR IMS products) 2 2 " Pt $ G $! 2 2 e 3 4 % Pt & % & Pr = ' ( G ' ( A = $ " ) 4# R * ) 4# R * 4# $ R ( ) Rotation 180 Apply a 180 rotation on the quick-look. Useful to display descending path images in a more realistic way (i.e. North on the top).

12 12 Orientation after 180 rotation Display rotated image Uniform display of SAR intensity over water areas

13 13 Access to Full Resolution Open Full Resolution menu Select the dimensions of the full resolution image Pre-selected dimensions (recommended) User-defined dimensions Move the cursor to the area of interest A box at the specified dimensions will follow your cursor. Click the left mouse button to select area The full resolution image will the be displayed in a pop-up window (Ximagette module)

14 14 Orientation of the full resolution image Profile of the azimuth line at cursor position Profile of the range line at cursor position Tab widget to access image parameters: Information at Cursor Information on SAR Data Tab widget to setup geographic parameters: Overlay grid Overlay bathymetry Tab widget to setup levels parameters: Min/max value Levels number View histogram

15 15 Mapping in SARTool Select Image mapped in the Map menu From the main window of SARTool From the Ximagette module Image mapping uses display settings of the Quicklook or Full resolution image. Before mapping, it is then recommended to : Apply Nice display Adjust min/max clipping (CONTRAST TUNING on the right panel)

16 16 Tab widget to access image parameters: Information at Cursor Information on SAR Data Tab widget to setup geographic parameters: Overlay grid Overlay bathymetry Tab widget to setup display parameters: Size of plot Sampling factor Tab widget to setup levels parameters: Min/max value Levels number View histogram

17 17 Mapping in SARTool How can I change/add geographical information? Select Charts tab widget in the GEOGRAPHIC PARAMETERS frame Droplist to display land mask Droplist to select quality level of land mask and shoreline Toggle button to display cities Toggle button to draw EEZ boundaries Toggle button to display shoreline Toggle button to draw political boundaries Press the button

18 18 Mapping in SARTool How can I visualize topography/bathymetry information? Select Topo/Bath tab widget in the GEOGRAPHIC PARAMETERS frame Toggle button to display topography Editable widget to set isobaths Toggle button to display bathymetry Editable widget to set lowest bathymetry level Editable widget to set highest bathymetry level Press the button

19 19 Mapping in SARTool How can I change limits of the displayed map? Select Limits tab widgets in the GEOGRAPHIC PARAMETERS frame Editable widgets to set geographical limits Button to zoom in/out the map window Button to move map window to the left/right Button to move up/down the map window Press the button

20 20 Mapping in SARTool How can I change limits of the displayed map? Move the cursor in the main mapping window 1. Press and hold the left mouse button to mark first corner limits 2. Release the left mouse button to mark the second (opposite) corner limits How can I come back to original mapping limits? Move the cursor in the main mapping window Click on the right mouse button

21 21 Introduction to SARTool software Others features Sub-look extraction (Complex data only) Spectral analysis And also... Azimuth cutoff analysis Statistical analysis...

22 Ship detection

23 23 Ship detection Delivered information on detected targets Date/Time Geographical position Size If allowed by spatial resolution Route If allowed by spatial resolution or if trailing turbulent wake is visible Speed if trailing turbulent wake is visible Potential synergy Coupling with Automatic Identification System may enable identification of polluters Applications Illegal fishing activities Illicit oil discharges monitoring Monitoring support to Vessel traffic

24 24 SAR imagery processing Processing of other data type VTMS Vessels Traffic Management System AIS Automatic Identification System Synergy within EO data Synergy within Identification Systems Discrimination Comparison Report

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26 26

27 27 Ships detection: exercise 1 ENVISAT ASAR Wide Swath 3 August 2006 File > Open File > ENVISAT ASAR Select 1st file in folder named ws ASA_WSM_1PNDPA _211904_ _00115_ 12694_0020.N1 Relevant features: Atmospheric lee gravity waves over the Gulf of Asinara in Sardinia What is the typical wavelength of these wave? Several linear oil slicks in the South of French Riviera What is the wind speed (Ancillary > Wind > ECMWF 1/2 ) Find the three main targets located approx. 40 kms in direction ~145 from Saint Tropez Visualize them in a 512x 512 full resolution image

28 28 Ships detection: exercise 1 Perform ship detection (Applications Menu) Change False alarm probability (e.g ) Apply Wake Detection (Detection Settings widget) Perform manual Ship Wake Detection 1. Press <Shift> key and keep holding 2. Press Left Mouse button to point at one side of the trailing wake and keep holding 3. Release Left Mouse button to point at the other side of the trailing wake 4. Release <Shift> key 5. Associate a target to the outlined wake

29 29 Detecting ships from SAR Probability Prescreening CFAR detection Probability Density Function for Background Probability Density Function for target Threshold False Alarm Probability Image intensity

30 30 Measuring ship speed using SARTool 15.4 knots 42 N E Route: 86.4 Speed: 15.4 knts 43 N E Route: Speed: 23.8 knts 42 N E Route: Speed: 20.6 knts

31 31 Ships detection: exercise 2 ENVISAT ASAR Single Look Complex 9 March 2003 File > Open File > ENVISAT ASAR Select 2 nd file in folder named im ASA_IMS_1PNUPA _102259_ _00280_05344_00 26.N1 Relevant features: Sand banks SAR signature caused by local wave-currents interactions Backscattered signal in open water modulated by swell Look at 2-D complex spectrum (Processing > 2D-spectrum) Refraction of swells in the lee of Guernsey Island Find the targets located North of the harbour of Cherbourg Visualize them in a 512x 512 full resolution image

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33 33 Ships detection: exercise 2 Perform ships detection (Applications Menu) Identify azimuth ambiguities of strong signals in Cherbourg Azimuth ambiguities are caused by PRF sampling Ambiguity: part of the spectrum folded over the +/- PRF interval Browse sub-looks Processing > Sub-looks extraction Use LMB on Left window to change sub-looks

34 Oil detection

35 35 Monitoring of marine oil pollution Delivered information on polluted areas Geographical areas Surface, size, Potential source (ships, platforms) Metocean conditions Early warning system: Semi-automatic detection scheme Validation by a trained operator 2 output classes: oil and feature of interest Synergy Ancillary information to reduce FAR (ambiguous slicks) Coupling with Automatic Identification System (AIS) Applications Operational surveillance of illicit oil discharges Crisis situation (accidental pollution) Oil discharge Pollutant

36 Oil detection report 27 September NRT satellite receiving Ground station Acquisition Transmission Centre for SAR images Reception Analysis Early-warining Coast guards Customs Operational drift forecasters Others Earth observation satellite Observation Detection AIS Aerial surveillance Surveillance Validation Identification Report

37 37 Reduction of the False Alarm rate Wind information to assess the feasibility of slicks detection Coupling SAR/AIS to help in ship identification Ancillary information to reduce false alarm rate

38 38 Introduction to SARTool: exercise ENVISAT ASAR Wide Swath 11 November 2002 File > Open File > ENVISAT ASAR Select 6 th file in folder named ws ASA_WSM_1PXPDE _104431_ _ 00180_03741_0009.N1 Identify Prestige ship located at 42 N N 10 W Open 512 x 512 full resolution image over prestige and trailing leak

39 39 Introduction to SARTool: exercise Open SARTool Oil module from full resolution image window Applications > Oil detection Start automatic oil detection Press button == DETECT == Measure individual slicks Connect spills using water shed algorithm Classify detected area Export > Global map of detected slicks

40 40 Oil Spill catalogue (1) Decision criteria to classify slick as oil Shape criterion Linear feature opening out away from polluting ship Recent pollution (OSD report) Few hours old pollution (OSD report) Intermittent linear dark feature 4 August 2005(OSD report) 3 August 2004(OSD report) Dark feature with sharp edge on one side and diffuse on the other side (wind effect) 1 October 2005 (OSD report) 4 November 2005 (OSD report)

41 41 Oil Spill catalogue (2) Decision criteria to classify slick as oil Contrast criterion Dark feature with sharp features with high uniform backscattered signal area 23 April 2004 (OSD report) 7 August 2004 (OSD report)

42 42 Oil Spill catalogue (3) Decision criteria to classify slick as oil Analysis of the local environment Proximity of main navigation route Radar signature typical of ships operation

43 Wind field retrieval

44 44 High resolution wind fields Tramontane Main properties Coverage up to 500 km x 500 km High resolution (as high as 500 m x 500 m) Accuracy 2 m/s (wind speed), 25 (direction) Applications Near real-time: High resolution coastal wind field measurement Inputs for oil spills/ships detection systems Long term: Understanding costal dynamics Monitoring and study of meteorological phenomena Wind farm design, wind resource assessment. Wind acceleration Relief shadowing

45 45 Main principles The Normalized Radar Cross Section (NRCS) or! 0 depends mainly on: Radar wavelength Polarization Incidence angle Local wind vector (speed and direction) Scattering mechanisms Specular reflection Bragg scattering 2-scale composite models [Valenzuela, 1978]

46 46 Main principles Empirical scattering models Fourier development at 2 nd order State of the art of L-band models Limited to the range (Shimada et al., 2003) State of the art of C-band models CMOD_IFR2 (Quilfen et al. 1998) CMOD2-I3 (Bentamy et al. 1999) CMOD4 (Stoffelen and Anderson 1997) CMOD5 (Hersbach 2004) State of the art of Ku-band models SASS-1 (Schroeder et al., 1982), SASS-2 (Wentz et al., 1984)

47 47 Main principles State of the art of the polarization ratio models at C-band: Thompson et. al. 1998, ( 0.4 < " < 1.2, usually " = 0.7) (!) Elfhouhaily, 1996, (!) Mouche et. al., model1, 2004, (",!) Mouche et. al., model2, 2004 (! )

48 48 Wind retrieval : exercise 1 ENVISAT ASAR Wide Swath 4 March 2005 File > Open File > ENVISAT ASAR Select 5 th file in folder named ws ASA_WSM_1PNTSS _100339_ _ 00151_15736_0000.N1 Relevant features: wind-related features: Atmospheric front Rain cells Wind streaks Atmospheric gravity waves

49 49 ENVISAT Wide Swath 4 March 2005 Atmospheric signatures Wind streaks Atmospheric gravity waves Rain cells Atmospheric front

50 50 Wind retrieval : exercise 1 Open 256 x 256 Full resolution image over areas with wind streaks Estimate wind direction Using FFT method Applications > Wind retrieval > Wind direction > FFT method Estimate wind direction Using Radon method Applications > Wind retrieval > Wind direction > Radon method

51 51 Retrieving wind field from SAR Wind direction retrieval from SAR imagery Objective: Detect the SAR signature of wind streaks Typical wavelengths: between 1 and 2.5 km Conditions of development: Thermal instability Dynamic instability

52 52 Wind retrieval : exercise 1 Draw wind direction manually The idea is to over-plot arrows oriented in the direction the wind is blowing to almost the same way to measure distance between points 1. Press and hold the SHIFT key 2. Press the left mouse button to select starting point (The point at which the wind direction will be set). A green cross with white number 1 will appear at the exact position that you just selected. Hold the left mouse button pressed. 3. Holding the left mouse button pressed, move the cursor to the ending point. A straight line starting from starting point will follow the cursor with bearing indications. 4. Important: The length of the arrow does not matter anything (only starting point and direction are important) 5. Release the left mouse button at ending point. A green cross with white number 2 appears at the exact position that you just selected. The direction in which the wind is blowing to is printed close to the ending point. 6. Release the SHIFT key

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54 54 Wind retrieval : exercise 1 Open Wind retrieval module Applications > Wind retrieval > Wind vector Choose the output wind cell size Number of pixels and pixel dimensions of full resolution SAR image Number of wind cells and cell dimensions of retrieved wind field

55 55 Wind retrieval : exercise 1 Retrieve wind vector using wind directions set manually Press button to retrieve wind Retrieve wind vector using wind directions given by numerical wind prediction model (NWP) model Using Hirlam 1/5 NWP model Using ECMWF 1/2 NWP model

56 56 ENVISAT Wide Swath 4 March 2005 Hirlam atmospheric model

57 57 Non-physical decay due to Incorrect radiometric calibration

58 58 Wind retrieval case studies (1) Atmospheric fronts Map of sea surface roughness Low pressure situation Map of sea surface roughness SAR derived wind field

59 59 Wind retrieval case studies (2) Wind acceleration and atmospheric lee gravity waves Map of sea surface roughness Land breeze Sea surface roughness Map of sea surface roughness

60 60 Atmospheric front

61 61 Low pressure

62 62 Wind retrieval : exercise 2 ENVISAT ASAR Wide Swath 28 August 2005 (Katrina) File > Open File > ENVISAT ASAR Select 2 nd file in folder named ws ASA_WSM_1PNPDE _155008_ _ 00183_18273_6424.N1 Relevant features: wind-related features: Hurricane eye Rain Huge swell systems

63 OCEAN CURRENT EFFECT 1 File ws/asa_wsm_1pnpde _ Actions 1 : Nice Display + Map image and zoom over Agulhas current (South Africa) 2 : Anciliary -> sea surface temperature -> MODIS 1km -> A LAC visible -> chlorophyl A 1km -> A LAC 3 : Zoom ASAR Map over Agulhas current (South Africa) + interzoom SST and Ocean color.

64 OCEAN CURRENT EFFECT 2 File ws/asa_wsm_1pnpdk _ Actions 1 : Nice Display + zoom over surface natural slicks. Guess what are the white tracks. 2 : Adjust contrast : min ~600 and max ~2000. Look for eddies signatures. 3 : for a combination of sea surface roughness and Doppler shift go

65 SURFACE MOTIONS IN HURRICANE File ws/asa_wsm_1pnpde _ Action 1 : go

66 OCEAN SURFACE WAVES 1 File ws/asa_wsm_1pnpde _ Actions 1 : Nice Display + Map image and zoom over Agulhas current (South Africa) 2 : Anciliary -> sea surface temperature -> MODIS 1km -> A LAC visible -> chlorophyl A 1km -> A LAC 3 : Zoom ASAR Map over Agulhas current (South Africa) + interzoom SST and Ocean color.

67 File OCEAN SURFACE WAVES 2 im/asa_ims_1pndpa _ Actions 1 : Make a full res 512x512 around CAP DE LA CHEVRE 2 : Make a full res 512x512 in open ocean -> Processing -> sublook extraction : waves are mooving 3 : Make a full res 512x512 in open ocean -> Processing -> 2D spectrum : compare Abs. Spectrum and Imag spectrum

68 CAP DE LA CHEVRE

69 OCEAN SURFACE WAVES 2 cont. Actions 4 : Application -> wave analysis -> inversion 5 : wave animation : SARTOOL demo version available at :

70 Coastal delineation

71 71 Coastline delineation Many places suffer from inaccurate recorded coastline: Risk to shipping Inefficient coastal management Satellite imagery enables to periodically monitor and refine the current official recorded coastline boundary SAR images allow precise coastline detection over cloudy areas (e.g. inter-tropical zones)

72 72 Coastline delineation

73 73 Thank you for your attention Vincent KERBAOL BOOST Technologies 115, rue Claude Chappe, Plouzané, France Tel: Fax: