SAR interferometry applications for emergency mapping

Transcription

1 SAR interferometry applications for emergency mapping D.Grandoni (e-geos S.p.A.) Copernicus EMS Annual User Workshop Ispra, June 21 st June 2016 e-geos

2 Introduction: SAR Interferometric coherence (1/2) Interferometric coherence is generated from the analysis of phase information of two SAR images collected in interferometric mode. It displays, with a color scale ranging from black to white, the coherence of each pixel in the two images. White pixel, with high coherence, are related to stable target, such as buildings, rocks, infrastructures, bare soil. Progressively darker pixels, indicating medium to low coherence, are related to unstable targets, such as vegetation and water First SAR image SAR Amplitude Second SAR image SAR Amplitude 07 June 2016 e-geos2016 SAR Interferometric Coherence 2

3 Introduction: SAR Interferometric coherence (2/2) Coherence map can be seen as the comparison in amplitude and phase between the two signals received during two consecutive acquisitions with the same orbit pass, look direction, incidence angle and polarization (i.e. interferometric acquisitions) over the same area. Coherence map; 8 days, Mekong delta, Vietnam Coherence map; 8 days, Qom, Iran 07 June 2016 Mean value 0.24; Max value 0.59 e-geos Mean value 0.81; Max value

4 SAR interferometric products Product name Image sample Short description MultiTemporal Coherence (MTC) MultiTemporal Coherence (MTC) combines one pair of SAR images acquired in interferometric mode and is useful both for change detection and for thematic mapping as the use of coherence facilitates the detection of some land cover classes (e.g. urban, water, vegetation) Multi-Coherence Map (MCM) Multi-Coherence Map (MCM) combines two pairs of SAR images acquired in interferometric mode and is useful for change detection associated to significant coherence losses/gains (e.g. building destruction/construction) Damage Proxy Map (DPM) Damage Proxy Map (DPM) is a derived product from the Multi-Coherence Map where coherence difference values are normalized, filtered and classified to generate a proxy map of damage assessment 07 June 2016 e-geos

5 Product 1: MultiTemporal Coherence (MTC) The product is generated by composing an RGB images with the following base images: COSMO amplitude, collected on the first date (red channel) COSMO amplitude, collected on the second date (green channel) Coherence between the two COSMO images (blue channel) PETRANA COSMO Spotlight-2 27/08/16 PETRANA COSMO Spotlight-2 28/08/2016 PETRANA COSMO Spotlight-2 Coherence 27/08/ /08/ June 2016 PETRANA e-geos2016 COSMO Spotlight-2 MTC 5 27/08/ /08/2016

6 Product 2: Multi-Coherence Map (MCM) The product is generated by composing an RGB images with the following base data: COSMO coherence between two pre-event acquisitions (red channel) COSMO coherence between one pre-event and one post event acquisitions (green channel and blue channel) SOMMATI PRE/PRE CSK HI Coherence 06/06/ /06/2016 SOMMATI PRE/POST CSK HI Coherence 24/06/ /08/2016 SOMMATI PRE/POST CSK HI Coherence 24/06/ /08/ June 2016 e-geos2016 SOMMATI CSK HI MCM 6 06/06/ /06/ /08/2016

7 Product 3: Damage Proxy Map Damage Proxy Map is a point map obtained by analyzing the coherence between two pairs of COSMO SkyMed images - Pair 1: PRE- PRE; Pair 2: PRE-POST Damage Proxy Map is generated with the following steps: In the coherence from image pair 1 are extracted all pixels with higher coherence For all these pixels is analyzed the coherence from image pair 2. Only pixels with high coherence decrease are extracted and inserted in the Damage Proxy Map The process includes also histogram matching to make the two coherenc ehistograms comparable Damage Proxy Map is a vector product from the Multi-Coherence Map, obtained by discretizing the RGB imagery Damage Proxy Map Coherence from image pair 1 PRE-PRE Coherence from image pair 2 PRE-POST with high coherence decrease points 07 June 2016 e-geos

8 Satellite input data requirements 1. Interferometric acquisitions = same sensor, same geometry, same polarization - Sentinel-1A/B acquire interferometric pairs every 5 days (systematically) - COSMO-SkyMed constellation acquires interferometric pairs every 4 days (on average, on demand, but with a large background acquisition mission e.g. over all cities pop.> worldwide) 2. Timeliness = availability of pre and post event images close to the event date (short temporal baseline) - one (or more) pre-event images and one (or more) post event images - Time interval between the acquisitions (1, 3, 4, 8,. days) 3. Geometric fit = orbital distance between the two passes (short spatial baseline) - This influences the quality of interferometric coherence estimation 4. Geometric resolution = level of detail of detectable changes - Normally interferometric coherence is estimated after a multilooking process (3-4 looks) to reduce noise - This means that Sentinel-1 is while COSMO-SkyMed 07 June 2016 e-geos

9 Case Study #1 Earthquake in Central Italy Event description: In the first hours of 24th August 2016 an earthquake occurred in the centre of Italy involving a very large territory including several Regions (Lazio, Abruzzo, Umbria) and Municipalities. After the main shock several others occurred in the areas producing casualties and damages on structures and infrastructures. Triggering entity: Italian Civil protection activated the Copernicus EMS Rapid Mapping at 10:13 UTC on 24/08/ areas of interest have been mapped using both aerial and satellite data, producing and delivering almost 60 grading maps 07 June 2016 e-geos

10 COSMO SkyMed Data used for SAR Products generation First CSK UTC 24/08/ Himage (3m) 8 images (5 pre + 3 post) - 24/08-07/08-23/08-08/06 24/06 26/08-20/08 28/08 Spotlight 2 (1m) 4 images (post event) 27/08 28/08 27/08 28/08 Copernicus first set of AOIs 07 June 2016 e-geos

11 Multitemporal Coherence Map (MTC) PRE/POST COSMO-SkyMed Himage (5m) PRE-POST Amplitude 24 June 2016 Amplitude 26 August 2016 Coherence (24/06 26/ ) Concentraiton of damages 07 June 2016 in the historic center e-geos

12 MultiTemporal Coherence (MTC) PRE/PRE Detection of roads Detection of water areas Woody area Detection of built up area COSMO-SkyMed Himage (5m) PRE-PRE Amplitude 06 June 2016 Amplitude 24 June 2016 Coherence (06-24 June 2016) Detection of grassland divided by edge rows 07 June 2016 e-geos

13 MultiTemporal Coherence (MTC) POST/POST AMATRICE COSMO Spotlight-2 MTC. Images dates 27/08/ /08/2016 COSMO-SkyMed Spotlight-2 (2m) PRE-PRE Amplitude 27 August 2016 Amplitude 28 August 2016 Coherence (27-28 August 2016) 07 June 2016 Parking area with e-geos2016 Tents camp and Vehicles and 13 vehicle movement vehicle movement material movement

14 Multi-Coherence Map (MCM) Pescara del Tronto Grisciano Colle Accumoli COSMO-SkyMed 08/06/ /06/ /06/2016 Amatrice One single pass, acquired most of the affected area Urban areas appearing in red (even of small dimensions) have been effectively affected by the earthquake 07 June 2016 e-geos

15 Multi-Coherence Map (MCM) COSMO-SkyMed Himage (5m) 08/06 24/06 pre-pre Coherence 24/06 26/08 pre-post Coherence Sommati Quick detection of changes over urban areas Prato Colli Amatrice S. Benedetto Mosicchio Over the built-up areas (small town and villages) the reddish pixel identify buildings and infrastructures possible affected by the earthquake 07 June 2016 e-geos

16 Coherence Pre-post Coherence pre-pre Interferometric Coherence Himages: 08/06/2016; 24/06/2016; 26/08/2016 Teramo (not affected) Amatrice (affected) Illica (affected) 07 June 2016 e-geos

17 SAR Interferomtric products on Amatrice 07 June 2016 e-geos

18 Damage Proxy Map Damage Proxy Map enhances the area where has been detected, in the pre-post image pair, a strong decrease of coherence in the high coherence data in the pre-pre image pair Decrease can be associated with roofs large movement or building destruction Coherence decrease is color coded in the Damage Proxy Map, with darker area showing higher decrease Coherence Decrease AMATRICE COSMO SkyMed H1 Damage Proxy Map. 08/06/ /06/ /08/ June 2016 e-geos

19 Case Study #2 Oklahoma City Tornado Event description: On the afternoon of May 20, a large, violent tornado touched down west of Newcastle, Oklahoma and impacted the town of Moore, causing severe damage to residential areas as well as Plaza Towers and Briarwood Elementary schools. The Oklahoma Office of the Chief Medical Examiner has confirmed several fatalities, at least 200 people injured. Triggering entity: e-geos has been proactively acquiring COSMO-SkyMed images before and after the event, generating damage assessment maps provided to US Government. e-geos has been regularly acquiring also optical data for optical-sar combined analysis. 07 June 2016 e-geos

20 Damage assessment Open data Damage assessment map generated less 24 hours after the event by analyzing and georeferencing information from open data (tweets, video, ) 07 June 2016 e-geos

21 Damage assessment Optical Damage assessment map generated based on WorldView-1 image acquired on May 22nd, June 2016 e-geos

22 Damage assessment SAR Damage assessment map generated based the interferometric analysis of a COSMO-SkyMed pair. Red: Amplitude CSK May 17th, 2013 Green: Amplitude CSK May 25th, 2013 Blue: interferometric coherence 07 June 2016 e-geos

23 Damage assessment SAR/Optical Combination of SAR based damage assessment with Optical based damage assessment. 07 June 2016 e-geos

24 Conclusions SAR Interferometry applications can contribute operationally to satellite emergency mapping, subjec to the availability of suitable datasets Advantages: - All-weather, day-night acquisition capabilities complementary to optical sources - Quick overview over large areas to detect affected settlements - High sensitivity also to «small effectes» depending on the used SAR band (in particular, X- band), coherence loss is registered also for «deformations» in the order of few centimeters - Fully automated processing Limitations: - Availability of suitable pre-event images necessary conditions, not always satisfied. Need for systematic colelctions (e.g. Sentinel-1, COSMO-SkyMed background mission) - Geometric resolution in some cases (e.g. Sentinel-1) not enough to detect damages to buildings 07 June 2016 e-geos

25 All COSMO-SkyMed images ASI - Agenzia Spaziale Italiana e-geos S.p.A L.O. Contrada Terlecchie snc Matera / HQ Via Tiburtina, 965 Roma