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Li, X., Li, X., Li, D., He, X., & Jendryke, M. (2019). A preliminary investigation of Luojia-1 night-time light imagery. Remote Sensing Letters, 10(6), 526–535.
Abstract: Launched on 2 June 2018, Luojia-1 satellite records night-time light imagery at 130 m resolution, which is higher than most of the existing night-time light images to date. This study evaluated radiometric and spatial properties of the Luojia-1 satellite imagery for cities of Los Angeles, Wuhan and Rome as well as the change detection capability for Zunyi city. For the radiometric property, the analysis shows that the Luojia-1 images correlate well with the radiance of the Visible Infrared Imaging Radiometer Suite (VIIRS)’s Day and Night Band (DNB), and that the Luojia-1 images have a wider range of radiance values, as well as higher radiance values (e.g., 40%–90% higher) than the VIIRS DNB images. Using wavelet decomposition and change detection analysis to evaluate spatial property and change detection capability, it was found that the Luojia-1 images provide abundant spatial detail information, with about 20%–54% energy of wavelet component of the images stored in 100–400 m resolutions, and they can help to track the electrification of new roads and buildings at a fine resolution. This study shows that the Luojia-1 images are an effective data source for analysing spatiotemporal distribution of night-time light and its associated socioeconomic attributes.
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Li, X., Li, D., Xu, H., & Wu, C. (2017). Intercalibration between DMSP/OLS and VIIRS night-time light images to evaluate city light dynamics of Syria’s major human settlement during Syrian Civil War. International Journal of Remote Sensing, 38(21), 5934–5951.
Abstract: Monthly composites of night-time light acquired from the Meteorological Satellite Program’s Operational Linescan System (DMSP/OLS) had been used to evaluate socio-economic dynamics and human rights during the Syrian Civil War, which started in March 2011. However, DMSP/OLS monthly composites are not available subsequent to February 2014, and the only available night-time light composites for that period were acquired from the Suomi National Polar-orbiting Partnership satellite’s Visible Infrared Imaging Radiometer Suite (Suomi NPP/VIIRS). This article proposes an intercalibration model to simulate DMSP/OLS composites from the VIIRS day-and-night band (DNB) composites, by using a power function for radiometric degradation and a Gaussian low pass filter for spatial degradation. The DMSP/OLS data and the simulated DMSP/OLS data were combined to estimate the city light dynamics in Syria’s major human settlement between March 2011 and January 2017. Our analysis shows that Syria’s major human settlement lost about 79% of its city light by January 2017, with Aleppo, Daraa, Deir ez-Zor, and Idlib provinces losing 89%, 90%, 96%, and 99% of their light, respectively, indicating that these four provinces were most affected by the war. We also found that the city light in Syria and 12 provinces rebounded from early 2016 to January 2017, possibly as a result of the peace negotiation signed in Geneva.
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Chen, H., Xiong, X., Geng, X., & Twedt, K. (2019). Stray-light correction and prediction for Suomi National Polar-orbiting Partnership visible infrared imaging radiometer suite day-night band. J. Appl. Rem. Sens., 13(02), 1.
Abstract: The Suomi National Polar-orbiting Partnership visible infrared imaging radiometer suite instrument has successfully operated since its launch in October 2011. Stray-light contamination is much larger than prelaunch expectations, and it causes a major decrease in quality of the day-night band night imagery when the spacecraft is crossing the Northern or Southern day-night terminators. The stray light can be operationally estimated using Earth-view data that are measured over dark surfaces during the new moon each month. More than 7 years of nighttime images have demonstrated that the stray-light contamination mainly depends on the Earth–Sun–spacecraft geometry, so its intensity is generally estimated as a function of the satellite zenith angle. In practice, stray-light contamination is also detector- and scan-angle-dependent. Previous methods of stray-light prediction generally rely on using the known stray light level from the same month in the previous year, when the Earth–Sun–spacecraft geometries had been similar. We propose a new method to predict stray-light contamination. The Kullback–Leibler similarity metric is used as a method to combine data from multiple years with appropriate adjustments for degradation and geometry drifts in order to calculate a fused stray-light contamination correction. The new method provides an improved prediction of stray-light contamination compared to the existing methods and may be considered for future use in the real-time NASA Level-1B products.
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Ngadiman, N. F., Shariff, N. N. M., & Hamidi, Z. S. (2020). Sensor Technology for Night Sky Brightness Measurements in Malaysia. International Journal of Recent Technology and Engineering (IJRTE), 8(6).
Abstract: Artificial light at night is apparently showing to be a major contributor to the increase of sky brightness at night. The natural darkness in large regions of the world including Malaysia currently is at risk. Hence, some Night Sky Brightness (NSB) measurements in Malaysia were conducted by using several types of light sensors in order to serve quantitative data and spread awareness on this issue. This paper aims to analyze the sensor technology that have been used in night sky brightness measurement in Malaysia as well as to identify recent or significant advances and discoveries in this field of study. In this paper, the author adopted qualitative method through literature review from numerous conducted studies by other researchers in order to perceive better understanding on the use of dedicated light sensor in NSB related research. Starting from 2005 until now, it is noticeable that most of the light sensor used in the NSB studies in Malaysia was Sky Quality Meter (SQM) photometer, equipped with TSL237 sensor which has high irradiance responsivity 2.3kHz/(µW/cm2) @ λp = 524nm and 5 Milion:1 input dynamic range as well as able to sense down to 0.00002 Lux and has typical dark frequency down to 0.1 Hz. The result indicates the relative frequency of the SQM usage in NSB studies was 76% compared to PBM, APC, PMT and CDD of only 4% respectively. SQM has always been the choice of researchers in Malaysia to carry out their sky brightness measurements due to user-friendly implementation besides its reliable data obtained from TSL237 sensor which capable to convert the light directly to frequency without an amplifier or data converter. Thus, the nonlinearities and voltage offsets in the data can be circumvented. A fairly good development of sensor that have been utilized in NSB studies can be discerned patently besides NSB studies will always look forward for a better sensor to further enhance the efforts to map sky brightness for preserving the potential dark sky areas for the sake of astronomy.
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Burggraaff, O., Schmidt, N., Zamorano, J., Pauly, K., Pascual, S., Tapia, C., Spyrakos, E., & Snik, F. (2019). Standardized spectral and radiometric calibration of consumer cameras. Optical Express, 27(14), 19075–19101.
Abstract: Consumer cameras, particularly onboard smartphones and UAVs, are now commonly used as scientific instruments. However, their data processing pipelines are not optimized for quantitative radiometry and their calibration is more complex than that of scientific cameras. The lack of a standardized calibration methodology limits the interoperability between devices and, in the ever-changing market, ultimately the lifespan of projects using them. We present a standardized methodology and database (SPECTACLE) for spectral and radiometric calibrations of consumer cameras, including linearity, bias variations, read-out noise, dark current, ISO speed and gain, flat-field, and RGB spectral response. This includes golden standard ground-truth methods and do-it-yourself methods suitable for non-experts. Applying this methodology to seven popular cameras, we found high linearity in RAW but not JPEG data, inter-pixel gain variations >400% correlated with large-scale bias and read-out noise patterns, non-trivial ISO speed normalization functions, flat-field correction factors varying by up to 2.79 over the field of view, and both similarities and differences in spectral response. Moreover, these results differed wildly between camera models, highlighting the importance of standardization and a centralized database.
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