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In Situ Calibration of Light Sensors for Long-Term Monitoring of Vegetation

Jin, Hongxiao LU and Eklundh, Lars LU (2015) In IEEE Transactions on Geoscience and Remote Sensing 53(6). p.3405-3416
Abstract
Light sensors are increasingly used to monitor vegetation growing status by measuring reflectance or transmittance in multispectral or photosynthetically active radiation (PAR) bands. The measurements are then used to estimate vegetation indices or the fraction of absorbed PAR (FPAR) in a continuous and long-term manner and to serve as inputs to environmental monitoring and calibration/validation data for satellite remote sensing. However, light-sensor calibration is often overlooked or not properly attended to, which leads to difficulties when comparing the measurement results across sites and through time. In this paper, we investigate a practical and accurate user-level in situ calibration method in daylight. The calibration of a sensor... (More)
Light sensors are increasingly used to monitor vegetation growing status by measuring reflectance or transmittance in multispectral or photosynthetically active radiation (PAR) bands. The measurements are then used to estimate vegetation indices or the fraction of absorbed PAR (FPAR) in a continuous and long-term manner and to serve as inputs to environmental monitoring and calibration/validation data for satellite remote sensing. However, light-sensor calibration is often overlooked or not properly attended to, which leads to difficulties when comparing the measurement results across sites and through time. In this paper, we investigate a practical and accurate user-level in situ calibration method in daylight. The calibration of a sensor pair is made for measuring either bihemispherical reflectance or hemispherical-conical reflectance, which are the two most common ground-based spectral measurements. Procedures and considerations are suggested for user calibration. We also provide a method for calibrating and measuring a single-sensor reflectance-derived Normalized Difference Vegetation Index (NDVI) from red and near-infrared bands. The calibration error propagation is analyzed, and the induced uncertainties in vegetation reflectance and in the NDVI are evaluated. The analysis and field measurements show that the NDVI estimated from a user calibration factor can be as accurate as, or even more accurate than, the manufacturer's calibration. The in situ calibration described here remedies the situation where reflectance for large field-of-view sensors cannot be always estimated from the manufacturer's calibration. The method developed in this paper may help improve the reliability of long-term field spectral measurements and contributes to the near-surface remote sensing of vegetation. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Calibration, error propagation, fraction of absorbed photosynthetically, active radiation (FPAR), light sensor, near-surface remote sensing, Normalized Difference Vegetation Index (NDVI), reflectance, uncertainty, vegetation monitoring
in
IEEE Transactions on Geoscience and Remote Sensing
volume
53
issue
6
pages
3405 - 3416
publisher
IEEE--Institute of Electrical and Electronics Engineers Inc.
external identifiers
  • wos:000351063800030
  • scopus:84923082807
  • scopus:85027921484
ISSN
0196-2892
DOI
10.1109/TGRS.2014.2375381
project
MERGE
BECC
language
English
LU publication?
yes
id
5fc9e3ba-3d88-4003-8e9f-360e1e2bd87c (old id 5281715)
date added to LUP
2015-04-24 11:53:03
date last changed
2017-09-25 11:57:47
@article{5fc9e3ba-3d88-4003-8e9f-360e1e2bd87c,
  abstract     = {Light sensors are increasingly used to monitor vegetation growing status by measuring reflectance or transmittance in multispectral or photosynthetically active radiation (PAR) bands. The measurements are then used to estimate vegetation indices or the fraction of absorbed PAR (FPAR) in a continuous and long-term manner and to serve as inputs to environmental monitoring and calibration/validation data for satellite remote sensing. However, light-sensor calibration is often overlooked or not properly attended to, which leads to difficulties when comparing the measurement results across sites and through time. In this paper, we investigate a practical and accurate user-level in situ calibration method in daylight. The calibration of a sensor pair is made for measuring either bihemispherical reflectance or hemispherical-conical reflectance, which are the two most common ground-based spectral measurements. Procedures and considerations are suggested for user calibration. We also provide a method for calibrating and measuring a single-sensor reflectance-derived Normalized Difference Vegetation Index (NDVI) from red and near-infrared bands. The calibration error propagation is analyzed, and the induced uncertainties in vegetation reflectance and in the NDVI are evaluated. The analysis and field measurements show that the NDVI estimated from a user calibration factor can be as accurate as, or even more accurate than, the manufacturer's calibration. The in situ calibration described here remedies the situation where reflectance for large field-of-view sensors cannot be always estimated from the manufacturer's calibration. The method developed in this paper may help improve the reliability of long-term field spectral measurements and contributes to the near-surface remote sensing of vegetation.},
  author       = {Jin, Hongxiao and Eklundh, Lars},
  issn         = {0196-2892},
  keyword      = {Calibration,error propagation,fraction of absorbed photosynthetically,active radiation (FPAR),light sensor,near-surface remote sensing,Normalized Difference Vegetation Index (NDVI),reflectance,uncertainty,vegetation monitoring},
  language     = {eng},
  number       = {6},
  pages        = {3405--3416},
  publisher    = {IEEE--Institute of Electrical and Electronics Engineers Inc.},
  series       = {IEEE Transactions on Geoscience and Remote Sensing},
  title        = {In Situ Calibration of Light Sensors for Long-Term Monitoring of Vegetation},
  url          = {http://dx.doi.org/10.1109/TGRS.2014.2375381},
  volume       = {53},
  year         = {2015},
}