Radiometric homogenisation of aerial images by calibrating with satellite data

Harris, Dugal; Niekerk, Adriaan van

doi:10.1080/01431161.2018.1528404

Cited by 2 publications

(1 citation statement)

References 26 publications

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“…The NGI imagery contains variations due to BRDF and atmospheric effects, which makes it poorly suited to quantitative remote sensing techniques. The imagery was consequently radiometrically homogenised through the application of a surface reflectance estimation technique (Harris & Van Niekerk 2019). This technique corrects for coarse scale atmospheric and BRDF effects using a well-calibrated, concurrent and collocated surface reflectance satellite image as a reference.…”

Section: Radiometric Homogenisationmentioning

confidence: 99%

Regional mapping of spekboom canopy cover using very high resolution aerial imagery

Harris

Vlok

Niekerk

2018

J. Appl. Rem. Sens.

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My sincere thanks to my supervisor, Adriaan van Niekerk, for his valuable technical input and guidance and for all the patient encouragement. Jan Vlok was instrumental in this research, and he is gratefully acknowledged for his vision, support and remarkable field expertise. Special thanks to Julie Verhulp, Raoul Duesimi and Aslam Parker of Chief Directorate: National Geospatial Information, for their generous provision of aerial imagery and related support. The Centre for Geographical Analysis, especially Garth Stephenson, Theo Pauw and Jascha Muller, graciously assisted with data, computing and software resources. Ilze Boonzaaier beautified some of the maps and Helene van Niekerk assisted with editing. Camera calibration software was kindly provided by Adrian Roos of Intergraph SA. Bernhard Jacobs of GeoSpace International assisted with valuable calibration discussions and data. Andrew Knipe, of the Gamtoos Irrigation Board, helped with funding administration. Finally, to Mireille van Reenen, for your moral support and great companythank you.

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Section: Radiometric Homogenisationmentioning

confidence: 99%

Regional mapping of spekboom canopy cover using very high resolution aerial imagery

Harris

Vlok

Niekerk

2018

J. Appl. Rem. Sens.

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OLCI A/B Tandem Phase Analysis, Part 1: Level 1 Homogenisation and Harmonisation

Lamquin¹,

Clerc²,

Bourg³

et al. 2020

Remote Sensing

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Copernicus is a European system for monitoring the Earth in support of European policy. It includes the Sentinel-3 satellite mission which provides reliable and up-to-date measurements of the ocean, atmosphere, cryosphere, and land. To fulfil mission requirements, two Sentinel-3 satellites are required on-orbit at the same time to meet revisit and coverage requirements in support of Copernicus Services. The inter-unit consistency is critical for the mission as more S3 platforms are planned in the future. A few weeks after its launch in April 2018, the Sentinel-3B satellite was manoeuvred into a tandem configuration with its operational twin Sentinel-3A already in orbit. Both satellites were flown only thirty seconds apart on the same orbit ground track to optimise cross-comparisons. This tandem phase lasted from early June to mid October 2018 and was followed by a short drift phase during which the Sentinel-3B satellite was progressively moved to a specific orbit phasing of 140° separation from the sentinel-3A satellite. In this paper, an output of the European Space Agency (ESA) Sentinel-3 Tandem for Climate study (S3TC), we provide a full methodology for the homogenisation and harmonisation of the two Ocean and Land Colour Instruments (OLCI) based on the tandem phase. Homogenisation adjusts for unavoidable slight spatial and spectral differences between the two sensors and provide a basis for the comparison of the radiometry. Persistent radiometric biases of 1–2% across the OLCI spectrum are found with very high confidence. Harmonisation then consists of adjusting one instrument on the other based on these findings. Validation of the approach shows that such harmonisation then procures an excellent radiometric alignment. Performed on L1 calibrated radiances, the benefits of harmonisation are fully appreciated on Level 2 products as reported in a companion paper. Whereas our methodology aligns one sensor to behave radiometrically as the other, discussions consider the choice of the reference to be used within the operational framework. Further exploitation of the measurements indeed provides evidence of the need to perform flat-fielding on both payloads, prior to any harmonisation. Such flat-fielding notably removes inter-camera differences in the harmonisation coefficients. We conclude on the extreme usefulness of performing a tandem phase for the OLCI mission continuity as well as for any optical mission to which the methodology presented in this paper applies (e.g., Sentinel-2). To maintain the climate record, it is highly recommended that the future Sentinel-3C and Sentinel-3D satellites perform tandem flights when injected into the Sentinel-3 time series.

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Radiometric homogenisation of aerial images by calibrating with satellite data

Cited by 2 publications

References 26 publications

Regional mapping of spekboom canopy cover using very high resolution aerial imagery

Regional mapping of spekboom canopy cover using very high resolution aerial imagery

OLCI A/B Tandem Phase Analysis, Part 1: Level 1 Homogenisation and Harmonisation

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