Next Article in Journal
Monitoring of Land Use/Land Cover and Socioeconomic Changes in South China over the Last Three Decades Using Landsat and Nighttime Light Data
Previous Article in Journal
Influence of Landscape Heterogeneity and Spatial Resolution in Multi-Temporal In Situ and MODIS NDVI Data Proxies for Seasonal GPP Dynamics
Article Menu

Export Article

Open AccessArticle

Radiometric Calibration of ‘Commercial off the Shelf’ Cameras for UAV-Based High-Resolution Temporal Crop Phenotyping of Reflectance and NDVI

1
Department of Geography, King’s College London, London WC2B 4BG, UK
2
Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
3
National Centre for Earth Observation (NCEO), King’s College London, London WC2B 4BG, UK
*
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(14), 1657; https://doi.org/10.3390/rs11141657
Received: 3 June 2019 / Revised: 3 July 2019 / Accepted: 9 July 2019 / Published: 11 July 2019
(This article belongs to the Section Remote Sensing in Agriculture and Vegetation)
  |  
PDF [11196 KB, uploaded 12 July 2019]
  |  

Abstract

Vegetation indices, such as the Normalised Difference Vegetation Index (NDVI), are common metrics used for measuring traits of interest in crop phenotyping. However, traditional measurements of these indices are often influenced by multiple confounding factors such as canopy cover and reflectance of underlying soil, visible in canopy gaps. Digital cameras mounted to Unmanned Aerial Vehicles offer the spatial resolution to investigate these confounding factors, however incomplete methods for radiometric calibration into reflectance units limits how the data can be applied to phenotyping. In this study, we assess the applicability of very high spatial resolution (1 cm) UAV-based imagery taken with commercial off the shelf (COTS) digital cameras for both deriving calibrated reflectance imagery, and isolating vegetation canopy reflectance from that of the underlying soil. We present new methods for successfully normalising COTS camera imagery for exposure and solar irradiance effects, generating multispectral (RGB-NIR) orthomosaics of our target field-based wheat crop trial. Validation against measurements from a ground spectrometer showed good results for reflectance (R2 ≥ 0.6) and NDVI (R2 ≥ 0.88). Application of imagery collected through the growing season and masked using the Excess Green Red index was used to assess the impact of canopy cover on NDVI measurements. Results showed the impact of canopy cover artificially reducing plot NDVI values in the early season, where canopy development is low. View Full-Text
Keywords: Unmanned Aerial Vehicle; reflectance; radiometric calibration; NDVI; digital cameras; canopy reflectance Unmanned Aerial Vehicle; reflectance; radiometric calibration; NDVI; digital cameras; canopy reflectance
Figures

Graphical abstract

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
SciFeed

Share & Cite This Article

MDPI and ACS Style

Holman, F.H.; Riche, A.B.; Castle, M.; Wooster, M.J.; Hawkesford, M.J. Radiometric Calibration of ‘Commercial off the Shelf’ Cameras for UAV-Based High-Resolution Temporal Crop Phenotyping of Reflectance and NDVI. Remote Sens. 2019, 11, 1657.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Remote Sens. EISSN 2072-4292 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top