The ESA NRT River&Lake System

J.L. Wheeler

P.A.M. Berry

R.G. Smith

J.L. Wheeler

P.A.M. Berry

R.G. Smith

Overview

• Context / Background

• River&Lake Processor

• Altimeter products used

• Global Statistics

• Example products

• Data analysis and validation

• River&Lake website

• User analysis

• Discussion

• Context / Background

• River&Lake Processor

• Altimeter products used

• Global Statistics

• Example products

• Data analysis and validation

• River&Lake website

• User analysis

• Discussion

Context

• Ability of satellite radar altimeters to obtain accurate inland water heights known for several years

• Lakes were the first focus as they are large targets and it is relatively straightforward to obtain measurements

• Rivers are more complex as they are smaller and often located within steep terrain

• Improvements in retracking and accurate target location have make it possible to retrieve water heights globally

• Ability of satellite radar altimeters to obtain accurate inland water heights known for several years

• Lakes were the first focus as they are large targets and it is relatively straightforward to obtain measurements

• Rivers are more complex as they are smaller and often located within steep terrain

• Improvements in retracking and accurate target location have make it possible to retrieve water heights globally

River&Lake Processor – overview

•Mask : selects R&L Waveforms (1 pixel = 30”x30” = 1km at equator)

•Retracker : identifies ‘wet echoes’ and corrects height

•Boxes : fix target locations (correct for local geoid and seasonal mean heights)

•Filter : removes noise from height profile

•Mean : mean height used for RLH product

•Mask : selects R&L Waveforms (1 pixel = 30”x30” = 1km at equator)

•Retracker : identifies ‘wet echoes’ and corrects height

•Boxes : fix target locations (correct for local geoid and seasonal mean heights)

•Filter : removes noise from height profile

•Mean : mean height used for RLH product

Near-Real-Time altimeter products used

EnviSat RA2: IGDR + Level1B• repeat cycle: 35 days

• Orbits in cycle: 501

• Track separation: 80km (equator)

• Data availability: 2-3 days

• Archived data: 6½ years

EnviSat RA2: IGDR + Level1B• repeat cycle: 35 days

• Orbits in cycle: 501

• Track separation: 80km (equator)

• Data availability: 2-3 days

• Archived data: 6½ years

Jason-2:SIGDR (replaces Jason-1)• repeat cycle: 10 days

• Orbits in cycle: 124

• Track separation: 315km (equator)

• Data availability: 1-2 days

• Archived data: 1 year

Jason-2:SIGDR (replaces Jason-1)• repeat cycle: 10 days

• Orbits in cycle: 124

• Track separation: 315km (equator)

• Data availability: 1-2 days

• Archived data: 1 year

Global target coverage

Total targets: 1341 EnviSat: 1229 Jason-2: 112Total targets: 1341 EnviSat: 1229 Jason-2: 112

Lake Erie

Lake Michigan

Lake Tana

Lake Tanganyika

Lake Victoria

Data analysis – alongtrack height dispersion

Measurement uncertainty:

Mean uncertainty indicates data quality:

€

σ h

€

σ h

Height dispersion >= 0.3mHeight dispersion >= 0.3m

Height dispersion < 2cmHeight dispersion < 2cm

Data analysis - curve-fit R2

Fit 8th order sinusoid to timeseries.

Coefficient of determination (R2) is an indication of data quality

Fit 8th order sinusoid to timeseries.

Coefficient of determination (R2) is an indication of data quality

Timeseries with a strong sinusoidal trend

Timeseries with a strong sinusoidal trend

Curve-fit not possibleCurve-fit not possible

Data anlaysis - curve-fit residuals

Standard deviation of curve-fit residuals can provide an indication of measurement error

Standard deviation of curve-fit residuals can provide an indication of measurement error

Timeseries having residuals < 0.5m of sinusoidal model Timeseries having residuals < 0.5m of sinusoidal model

River and Lake Website

Updated daily *

Automated product delivery *

~120 registered users *

~160 subscriptions *

Updated daily *

Automated product delivery *

~120 registered users *

~160 subscriptions *

www.earth.esa.int/riverandlake/www.earth.esa.int/riverandlake/

Website usage according to city

• Widespread global usage

• Main users: research centres

• Remote user interest continues to grow

• Widespread global usage

• Main users: research centres

• Remote user interest continues to grow

Discussion

• Jason-2 successfully replaced Jason-1 as a data source and has augmented the number of global targets for the river and lake processor

• Although some targets will disappear when EnviSat enters a geodetic orbit phase (Sep 2010) we hope to replace these with data from CryoSat2 and Sentinel3

• Next generation altimeters will offer potential enhancements to the River&Lake processor due to their increased along-track sampling rate

• Work is underway to improve the global mask resolution and will potentially reveal smaller river targets

• The River&Lake website’s global user community continues to grow – including interest from the developing world

• Jason-2 successfully replaced Jason-1 as a data source and has augmented the number of global targets for the river and lake processor

• Although some targets will disappear when EnviSat enters a geodetic orbit phase (Sep 2010) we hope to replace these with data from CryoSat2 and Sentinel3

• Next generation altimeters will offer potential enhancements to the River&Lake processor due to their increased along-track sampling rate

• Work is underway to improve the global mask resolution and will potentially reveal smaller river targets

• The River&Lake website’s global user community continues to grow – including interest from the developing world

Thank you for listening.Thank you for listening.