2. Towards achieving continental scale field validation and multi-sensor interoperability of satellite derived surface reflectance in Australia Medhavy Thankappan1, Guy Byrne1, Fuqin Li1, Simon Oliver1, Tim Malthus2 , Cindy Ong2 , Ian Lau2 1Geoscience Australia 2Commonwealth Scientific and Industrial Research Organisation

3. Outline Digital Earth Australia National validation campaign
Protocols /planning / logistics
Validation sites
Field instrument calibration
Data collection - Lake George
National spectral data repository
Multi-sensor interoperability
Summary

4. Digital Earth Australia
Australian digital infrastructure for analysis of Earth observations
Aim - to streamline government business and support economic growth
Provide Australian industry with standardised, analysis ready data for innovative products / services
Australian Government funding of $15.3M over two years

5. National validation campaign
Continental scale validation of surface reflectance
Project Agreement with GA (16 Feb 2018), for CSIRO to coordinate field data collection
Two phases of field data acquisition, near-coincident with satellite overpass
Field data to be managed as a national collection

6. Protocols/ planning / logistics
Best practice protocols for validation
Field data collection schedule linked to satellite overpass calendars
Common protocols for coordinated data acquisition by multiple teams
Multi-temporal field data

7. Validation sites

8. Field instrument calibration
QA/QC of field spectroradiometers
Dark noise, noise equivalent delta radiance (NE L), wavelength check, signal-to-noise ratio
Cross calibration of instruments / reference panels
NE L
Dark noise

9. Recent field tests at Lake George, NSW

10. Early results from field testing
Tested measurement protocols and instruments in the field
Spectral data collection
Reflectance
Reflectance
Central Wavelength (nm)
Wavelength (nm)

11. Validation system elements1
Protocols and sampling strategy 3 4
QA4EO protocols, best practice guidelines for EO validation
Validation campaigns
Validation system
Sampling strategy for field measurements
Scheme for airborne measurements
Database sub-system
Coordinated ground airborne and satellite based data collection in line with sampling strategy and protocols 2
Field sites for observing multiple variables (Supersites) and instruments
Scale transform sub-system
Field / airborne measurements at different scales
Upscaling
Accuracy evaluation sub-system
Field instrument calibration / cross calibration

12. National spectral data repository
Proposal to establish a national spectral library for validation
Host field and reference spectral data obtained by spectroradiometers using SPECCHIO
Community based governance model with open access

13. Multi-sensor interoperability of Analysis Ready Data
Sensitivity Analysis for:
Solar angle: BRDF normalized to 25, 45 (control) and 70 degrees.
Aerosol change: aerosol optical depth 0.05, 0.15, (control: best observed)
Water vapour: 0.5, 2, 3.5 (control: NCEP)
BRDF: temporal average (control: MODIS MCD43)

14. Temporal stability of Analysis Ready Data
GA NBAR/T/Lambertian and LEDAPS/LaSRC
Statistical summaries:
Invariant targets within scene
Points coincident with field spectra
Polygonal statistics over homogenous targets
Tools for future inter-comparison e.g. GA NBAR vs sen2cor

15. Summary
The Digital Earth Australia initiative is supporting continental scale validation of surface reflectance using best practice protocols
A nationally coordinated effort will enable field data collection synchronous with satellite overpass, across multiple sites
Field data will be managed as a national collection with open access, and contribute to development of an end-to-end validation system
Work on interoperability of multi-source Analysis Ready Data is progressing and will benefit from field validation