Atmospheric correction of thermal-infrared imagery of the 3-D urban environment acquired in oblique viewing geometry

Meier, Fred; Richters, J.; Christen, Andreas

doi:10.5194/amt-4-909-2011

Cited by 45 publications

(48 citation statements)

References 33 publications

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“…Eos Photomodeler (Version 6.2, Eos Systems, Vancouver, BC, Canada) was used to reconstruct vector building models from digital SLR images. Eos Photomodeler has been used previously for modelling of urban form with good performance (Nikiforiadis and Pitts, 2003). The street canyon was broken down into its component features, with each house being modelled individually, and then integrated together in 3-D Studio Max (Version 8, Autodesk, San Raphael, CA, USA) to form a complete canyon 3-D model.…”

Section: Geometric Informationmentioning

confidence: 99%

“…In some applications it is helpful to express measured L h as a hemispherical radiometric temperature T 0,h (Norman and Becker, 1995). T 0,h was calculated in absence of emissivity effects inverting the Stefan-Boltzmann law (T 0,h /σ ) 0.25 (i.e.…”

Section: Hemispherical Radiometric Temperaturementioning

confidence: 99%

“…A set of MOD-TRAN simulations were run for the current camera spectral range following the procedure outlined in Meier et al (2011 …”

Section: Atmospheric Correctionmentioning

confidence: 99%

“…Secondly, the radiance recorded with distant sensors is affected by atmospheric effects, where absorption and reemission of longwave radiation from gases and aerosols between sensor and ground surface will affect measured T B (Meier et al, 2011). Generally, this affects satellite sensors to a larger extent than airborne or ground-operated sensors due to the increased path length between sensor and surface d s .…”

Section: Introductionmentioning

confidence: 99%

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The effect of radiometer placement and view on inferred directional and hemispheric radiometric temperatures of an urban canopy

2015

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Abstract. Any radiometer at a fixed location has a biased view when observing a convoluted, three-dimensional surface such as an urban canopy. The goal of this contribution is to determine the bias of various sensors views observing a simple urban residential neighbourhood (nadir, oblique, hemispherical) over a 24 hour cycle under clear weather conditions. The error in measuring a longwave radiation flux density (L) and/or inferring surface temperatures (T 0 ) is quantified for different times over a diurnal cycle. Panoramic time-sequential thermography (PTST) data were recorded by a thermal camera on a hydraulic mast above a residential canyon in Vancouver, BC. The data set resolved sub-facet temperature variability of all representative urban facets in a 360• swath repetitively over a 24-hour cycle. This data set is used along with computer graphics and vision techniques to project measured fields of L for a given time and pixel onto texture sheets of a three-dimensional urban surface model at a resolution of centimetres. The resulting data set attributes L of each pixel on the texture sheets to different urban facets and associates facet location, azimuth, slope, material, and sky view factor. The texture sheets of L are used to calculate the complete surface temperature (T 0,C ) and to simulate the radiation in the field of view (FOV) of narrow and hemispheric radiometers observing the same urban surface (in absence of emissivity and atmospheric effects). The simulated directional (T 0,d ) and hemispheric (T 0,h ) radiometric temperatures inferred from various biased views are compared to T 0,C . For a range of simulated off-nadir (φ) and azimuth ( ) angles, T 0,d (φ, ) and T 0,C differ between −2.6 and +2.9 K over the course of the day. The effects of effective anisotropy are highest in the daytime, particularly around sunrise and sunset when different views can lead to differences in T 0,d (φ, ) that are as high as 3.5 K. For a sensor with a narrow FOV in the nadir of the urban surface, T 0,d (φ = 0) differs from T 0,C by +1.9 K (day) and by −1.6 K (night).Simulations of the FOV of hemispherical, downwardfacing pyrgeometers at 270 positions show considerable variations in the measured L and inferred hemispherical radiometeric temperature T 0,h as a function of both horizontal placement and height. The root mean squared error (RMSE) between different horizontal positions in retrieving outgoing longwave emittance L ↑ decreased exponentially with height, and was 11.2, 6.3 and 2.0 W m −2 at 2, 3, and 5 times the mean building height z b . Generally, above 3.5 z b the horizontal positional error is less than the typical accuracy of common pyrgeometers. The average T 0,h over 24 h determined from the hemispherical radiometer sufficiently above an urban surface is in close agreement with the average T 0,C . However, over the course of the day, the difference between T 0,h and T 0,C shows an RMSE of 1.7 K (9.4 W m −2 ) because the relative contributions of facets within the projected FOV of a pyrgeometer do not co...

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Section: Geometric Informationmentioning

confidence: 99%

Section: Hemispherical Radiometric Temperaturementioning

confidence: 99%

“…A set of MOD-TRAN simulations were run for the current camera spectral range following the procedure outlined in Meier et al (2011 …”

Section: Atmospheric Correctionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effect of radiometer placement and view on inferred directional and hemispheric radiometric temperatures of an urban canopy

2015

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“…Atmospheric correction routines for satellite retrieved TIR radiation, therefore, assume uniform or single-LOS geometry because the TIR signal passes through a relatively constant volume of atmosphere over the projected sensor FOV, regardless of surface geometry. Several multi-LOS correction routines have been developed to remove atmospheric effects on near-ground remote sensed TIR radiation: Meier et al [17] describes a correction method for oblique angled thermal imagery of urban terrain. In the method, spatially distributed LOS geometries were calculated by linking each image pixel to the corresponding three-dimensional coordinates of its viewpoint on a digital building model (DBM).…”

Section: Atmospheric Correction Of Near-ground Tir Radiation Measuredmentioning

confidence: 99%

Time-Continuous Hemispherical Urban Surface Temperatures

2017

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Abstract:Traditional methods for remote sensing of urban surface temperatures (T surf ) are subject to a suite of temporal and geometric biases. The effect of these biases on our ability to characterize the true geometric and temporal nature of urban T surf is currently unknown, but is certainly nontrivial. To quantify and overcome these biases, we present a method to retrieve time-continuous hemispherical radiometric urban T surf (T hem, r ) from broadband upwelling longwave radiation measured via pyrgeometer. By sampling the surface hemispherically, this measure is postulated to be more representative of the complex, three-dimensional structure of the urban surface than those from traditional remote sensors that usually have a narrow nadir or oblique viewing angle. The method uses a sensor view model in conjunction with a radiative transfer code to correct for atmospheric effects in three-dimensions using in situ profiles of air temperature and humidity along with information about surface structure. A practical parameterization is also included. Using the method, an eight-month climatology of T hem, r is retrieved for Basel, Switzerland. Results show the importance of a robust, geometrically representative atmospheric correction routine to remove confounding atmospheric effects and to foster inter-site, inter-method, and inter-instrument comparison. In addition, over a month-long summertime intensive observation period, T hem, r was compared to T surf retrieved from nadir (T plan ) and complete (T comp ) perspectives of the surface. Large differences were observed between T comp , T hem, r , and T plan , with differences between T plan and T comp of up to 8 K under clear-sky viewing conditions, which are the cases when satellite-based observations are available. In general, T hem, r provides a better approximation to T comp than T plan , particularly under clear-sky conditions. The magnitude of differences in remote sensed T surf based on sensor-surface-sun geometry varies significantly based on time of day and synoptic conditions and prompts further investigation of methodological and instrument bias in remote sensed urban surface temperature records.

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Unmanned aerial vehicles (UAVs)‐based thermal infrared (TIR) mapping, a novel approach to assess groundwater discharge into the coastal zone

Lee

Yoon

Hyun

et al. 2016

Limnol. Oceanogr. Methods

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Submarine groundwater discharge (SGD) is a widely recognized process that carries considerable amounts of groundwater and dissolved chemicals to the coastal ocean. Despite its importance, a lack of suitable tools to assess SGD's spatial and temporal variability has hampered a complete understanding of the process. Here we report, for the first time, use of an unmanned aerial vehicle (UAV or "drone") to assess SGD variations. An octocopter UAV platform equipped with a thermal infrared (TIR) system was flown along a coastline on Jeju Island, Korea. The UAV clearly captured thermal signatures of SGD plumes and their dynamic temporal fluctuations modulated by tidal variations. Based on a plume area-SGD flux relation we developed by combining aerial and field data, we estimated that the SGD flux of the study site ranged from 33,000 to 54,000 m 3 d 21. The drone approach enabled acquisition of time series plume imagery with easy control of spatial resolution, flexible field operations, and remote sensing of SGD at low cost compared to conventional aerial surveys. Combining the UAV-TIR images with on-site sampling enables one to determine fluxes of nutrients and other dissolved species. UAV-TIR mapping can thus serve as a powerful tool for study of SGD and other coastal processes.

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Atmospheric correction of thermal-infrared imagery of the 3-D urban environment acquired in oblique viewing geometry

Cited by 45 publications

References 33 publications

The effect of radiometer placement and view on inferred directional and hemispheric radiometric temperatures of an urban canopy

The effect of radiometer placement and view on inferred directional and hemispheric radiometric temperatures of an urban canopy

Time-Continuous Hemispherical Urban Surface Temperatures

Unmanned aerial vehicles (UAVs)‐based thermal infrared (TIR) mapping, a novel approach to assess groundwater discharge into the coastal zone

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