Consideration of Correlations in Radiometric Measurements of the Environment.
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| Title: | Consideration of Correlations in Radiometric Measurements of the Environment. |
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| Authors: | Brown, Steven W.1 (AUTHOR) swbrown@nist.gov, Litorja, Maritoni A.1 (AUTHOR), Marrs, Julia K.1 (AUTHOR), Allen, David W.1 (AUTHOR) |
| Source: | Remote Sensing. May2026, Vol. 18 Issue 9, p1286. 13p. |
| Subjects: | Reflectance measurement, Calibration, Statistical measurement, Radio measurements, Remote sensing devices, Environmental monitoring, Measurement errors, Spectrographs |
| Abstract: | Highlights: What are the main findings? We introduce a multiple-input, fiber-coupled spectrograph that enables multiple measurements from disparate targets to be acquired simultaneously. Using this instrument, a metric toward furthering understanding of covariance timescales of two environmental measurements is developed. Acquiring the reflectance of a target by two instruments simultaneously may reduce the Type A contribution to the uncertainty budget by a factor of 2 to 3 over measurements taken several minutes apart. What are the implications of the main findings? Results presented in this work may positively influence data acquisition protocols for teams that map the reflectance of vicarious calibrations sites prior to a satellite sensor overpass. Reducing the uncertainty in environmental measurements may reduce the uncertainty in the vicarious calibration of a satellite sensor. Vicarious calibration is a technique that makes use of radiometrically stable targets such as dry lakebeds, desert sites, and open grasslands for the post-launch calibration of a satellite sensor. Top-of-the-atmosphere radiances or reflectances are provided from those sites for the calibration of a sensor. The reflectance of a remote sensing vicarious calibration site is measured by ratioing the signal from a ground target to the signal from a reference target, often a white panel made of PTFE whose reflectance is known. When physically mapping a vicarious calibration site prior to a satellite sensor overflight, there can be elapsed times between the two measurements as great as 10 min. The solar illumination can vary on time scales relevant to the time between measurements of a ground target and a reference panel, impacting the variance in the measured reflectance. In this work, we explore the impact of a temporal delay between two measurements taken outdoors on the Type A uncertainties in their ratios. A factor of 3 reduction in the Coefficient of Variation of the ratio taken simultaneously versus sequentially with delays on the order of 10 min was realized. Implications for protocols employed to measure the surface reflectance at sites used for the vicarious calibration of aircraft and satellite sensors are discussed. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Highlights: What are the main findings? We introduce a multiple-input, fiber-coupled spectrograph that enables multiple measurements from disparate targets to be acquired simultaneously. Using this instrument, a metric toward furthering understanding of covariance timescales of two environmental measurements is developed. Acquiring the reflectance of a target by two instruments simultaneously may reduce the Type A contribution to the uncertainty budget by a factor of 2 to 3 over measurements taken several minutes apart. What are the implications of the main findings? Results presented in this work may positively influence data acquisition protocols for teams that map the reflectance of vicarious calibrations sites prior to a satellite sensor overpass. Reducing the uncertainty in environmental measurements may reduce the uncertainty in the vicarious calibration of a satellite sensor. Vicarious calibration is a technique that makes use of radiometrically stable targets such as dry lakebeds, desert sites, and open grasslands for the post-launch calibration of a satellite sensor. Top-of-the-atmosphere radiances or reflectances are provided from those sites for the calibration of a sensor. The reflectance of a remote sensing vicarious calibration site is measured by ratioing the signal from a ground target to the signal from a reference target, often a white panel made of PTFE whose reflectance is known. When physically mapping a vicarious calibration site prior to a satellite sensor overflight, there can be elapsed times between the two measurements as great as 10 min. The solar illumination can vary on time scales relevant to the time between measurements of a ground target and a reference panel, impacting the variance in the measured reflectance. In this work, we explore the impact of a temporal delay between two measurements taken outdoors on the Type A uncertainties in their ratios. A factor of 3 reduction in the Coefficient of Variation of the ratio taken simultaneously versus sequentially with delays on the order of 10 min was realized. Implications for protocols employed to measure the surface reflectance at sites used for the vicarious calibration of aircraft and satellite sensors are discussed. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 20724292 |
| DOI: | 10.3390/rs18091286 |
