COD - Coherence Difference

Owned by Shi Tong Chin
Last updated: Apr 01, 2020
3 min read

slcp2cod

This repository contains jobs to convert S1-SLCP products to Coherence Differences (CODs) for creating Damage Proxy Maps v1 (DPMv1).

A COD is created based on the below pairing system, using 3 SLCs --> 2 SLCPs --> 1 COD: 

Associated job:

Job 1: S1 COD - Network Selection

This job does network selection / pairing of pre-event SLCPs with the co-event SLCP in the specified AOI to submit to the S1 COD job (Job 2 below) to create CODs

  • Type: Individual

  • Facet: Not needed

  • User inputs:

Fields

Description

Type

Example

Fields

Description

Type

Example

dataset_tag

Suffix dataset tag to append at the end of the dataset id for differentiating events or settings

string

'standard'

project

Project category for possible queue propagation later

enum

'ariamh'

slcp_version

SLCP version to pair CODs for. Default is v1.2

string

v1.2

aoi_name

Dataset ID of AOI to find SLCPs for CODs creation based on AOI's coordinates, start, end and event time

string

'AOI_Japan_Earthquake'

track_number

Optional) Specific track number (only one allowed) of SLCPs overlapping AOI to process CODs for. If not specified, creates CODs for all tracks overlapping AOI.

int

171

overriding_range_looks

(Optional) Range looks to override SLCP's range looks to create CODs in the format: subswath1, subswath2, subswath3. If not specified, uses the range looks stored in SLCP for all subswaths.

int,int,int

16,16,16

(Recommended defaults)

overriding_azimuth_looks

(Optional) Azimuth looks to override SLCP's range looks to create CODs in the format: subswath1, subswath2, subswath3. If not specified, uses the azimuth looks stored in SLCP for all subswaths.

int,int,int

4,4,4

(Recommended defaults)

min_match

Minimum number of CODs to created. Priority of creation is based on temporal baseline. (See Notes below)

int

1

(Recommended defaults)

min_overlap

Minimum ratio of overlap between pre-event_SLCP and co-event_SLCP. Should be < 1. (See Notes below)

float

0.3

(Recommended defaults)

 

  • Important outputs:

    • No products will be directly generated, only S1-COD jobs will be submitted based on pairing results. (Expect 1 job for each subswath)

  • Notes:

    • The COD network selector pairs SLCPs to submit to the S1-COD job based on the following workflow:

      1. Gather pre-event_SLCPs + co-event_SLCPs from GRQ. Search criteria:

        1. SLCPs are pre-event if SLCP_end_time < AOI_event_time

        2. SLCPs are co-event if SLCP_start_time < AOI_event_time < SLCP_end_time

      2. Match pre-event_SLCP and co-event_SLCP pairs if:

        1. pre-event_SLCP[‘master_time’] - co-event_SLCP[‘master_time’] < 1 day

        2. area_intersect(pre-event_SLCP,co-event_SLCP) / area(co-event_SLCP) > min_overlap

      3. Creates and returns minmatch or valid SLCP pairs for COD based on shortest temporal baseline, where

        • temporal baseline = co-event_SLC['slave_time'] - pre-event_SLCP['slave_time']

     

    • Hence, if there are multiple pre-event SLCPs as per the following: 

      •  

        • If minmatch = 1, only COD 1's job will be submitted

        • If minmatch = 2, both COD 2 and COD 1 will be submitted

Job 2: S1 COD

  • Type: Individual

  • Facet: Not needed

  • User inputs:

Fields

Description

Type

Example

Fields

Description

Type

Example

dataset_tag

Suffix dataset tag to append at the end of the dataset id for differentiating events or settings

string

'standard'

project

Project category for possible queue propagation later

enum

'ariamh'

url1

Pre-event SLCP dataset's s3 url

string

s3://s3-<region>.amazonaws.com:80/
<bucket_name>/datasets/slc_pair/v1.2/
<year>/<month>/<day>/<S1-SLCP_ID>

url2

Co-event SLCP dataset's s3 url

string

s3://s3-<region>.amazonaws.com:80/
<bucket_name>/datasets/slc_pair/v1.2/
<year>/<month>/<day>/<S1-SLCP_ID>

overriding_range_looks

(Optional) Range looks to override SLCP's range looks to create CODs for that specific SLCP subswath.

int

16

overriding_azimuth_looks

(Optional) Azimuth looks to override SLCP's azimuth looks to create CODs for that specific SLCP subswath.

int

4

 

  • Important outputs:

Product

Description

Example

Product

Description

Example

Coherence Difference

Geocoded, multilooked CODs.
Band 1 - Pre-event SLCP's Amplitude.
Band 2 - Coherence Difference (pre-event - co-event).

diff_cor_[burst]_[range_lks]_[az_lks].cor.geo

Pre-event SLCP Coherence

2-Band geocoded, multilooked coherence (COR) of pre-event SLCP.
Band 1 - Amplitude.
Band 2 - Coherence.

cor_[burst]_[range_lks]_[az_lks].cor.geo

Co-event SLCP Coherence

2-Band geocoded, multilooked coherence (COR) of co-event SLCP.
Band 1 - Amplitude.
Band 2 - Coherence.

cor2_[burst]_[range_lks]_[az_lks].cor.geo

 

  • Notes:

    • The CODs in this PGE are computed as such (from burst_coherence_diff.py):

where COR = Coherence of given co-registered SLCP

=> Positve values correspond to decreased coherence after event and possible damage due to event.