LAR - Log Amplitude Ratio

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

slcp2pm (LAR)

SLC Pair to Log Amplitude Ratio

This repository contains jobs to convert S1-SLCP products to Log Amplitude Ratios (LARs) for creating Flood Proxy Maps v1 (FPMv1).

A LAR is created based on the below pairing system, using 2 SLCs --> 1 SLCP --> 1 FPM: 

Note: Since SLCP:LAR is 1:1, the pairing of SLCPs is not required to make LARs. Hence, user simply needs to facet on target SLCPs to execute the LAR job on.

Job 1: S1 Log Amplitude Ratio

  • Type: Iterative

  • Facet: SLCPs to create LARs from

  • User inputs:

Fields

Description

Type

Example

Fields

Description

Type

Example

lar_range_looks

Range looks to create LARs. (Overrides looks in SLCP's metadata)

int

7

lar_azimuth_looks

Azimuth looks to create LARs. (Overrides looks in SLCP's metadata)

int

2

  • Important outputs:

     

Product

Description

Example

Product

Description

Example

Log Amplitude Ratio Products

Geocoded, multilooked LARs

logr_[burst][range_lks][az_lks].float.geo

Amplitude Products

Geocoded, multilooked amplitudes stored in 2 bands. Band 1 - Master scene's amp. Band 2 - Slave scene's amp.

amp_[subswath][range_lks][az_lks].amp.geo

Notes on S1 Log Amplitude Ratio

The LARs in this PGE are computed as such (from log_ratio.py):

  • (Latest) From dataset v2.0 onwards:

where A = Amplitudes of SLCs of the given date in the co-registered SLCPs

=> Negative values / darker pixels correspond to decreased amplitudes in the post-event scene and possible open-water flood.

  • Before dataset v2.0 (v1.x etc):

 where A = Amplitudes of SLCs of the given date in the co-registered SLCPs

=> Positive values / brighter pixels correspond to decreased amplitudes in the post-event scene and possible open-water flood.

(Below section was moved from hysds-core wiki https://hysds-core.atlassian.net/wiki/spaces/HYS/pages/28540951/Product+Generation)

How to Generate LAR Products

  1. Facet on the SLCP's from which LAR products will be generated.

  2. Click the On-Demand button to bring the action parameters modal up.

  3. Select the S1 Log Amplitude Ratio action. Default parameters are shown.

 

  1. Enter a tag.

  2. Select the priority and queue for the job.

  3. Click the Process Now button to submit the job that will create the LAR products.