Exploring the Use of PlanetScope Data for Particulate Matter Air Quality Research

Planet, a commercial company, has achieved a key milestone by launching a large fleet of small satellites (smallsats) that provide high spatial resolution imagery of the entire Earth’s surface on a daily basis with its PlanetScope sensors. Given the potential utility of these data, this study explores the use for fine particulate matter (PM2.5) air quality applications. However, before these data can be utilized for air quality applications, key features of the data, including geolocation accuracy, calibration quality, and consistency in spectral signatures, need to be addressed. In this study, selected Dove-Classic PlanetScope data is screened for geolocation consistency. The spectral response of the Dove-Classic PlanetScope data is then compared to Moderate Resolution Imaging Spectroradiometer (MODIS) data over different land cover types, and under varying PM2.5 and mid visible aerosol optical depth (AOD) conditions. The data selected for this study was found to fall within Planet’s reported geolocation accuracy of 10 m (between 3–4 pixels). In a comparison of top of atmosphere (TOA) reflectance over a sample of different land cover types, the difference in reflectance between PlanetScope and MODIS ranged from near-zero (0.0014) to 0.117, with a mean difference in reflectance of 0.046 ± 0.031 across all bands. The reflectance values from PlanetScope were higher than MODIS 78% of the time, although no significant relationship was found between surface PM2.5 or AOD and TOA reflectance for the cases that were studied. The results indicate that commercial satellite data have the potential to address Earth-environmental issues.

CIME: Context-aware geolocation of emergency-related posts

Information extracted from social media has proven to be very useful in the domain of emergency management. An important task in emergency management is rapid crisis mapping, which aims to produce timely and reliable maps of affected areas. During an emergency, the volume of emergency-related posts is typically large, but only a small fraction is relevant and help rapid mapping effectively. Furthermore, posts are not useful for mapping purposes unless they are correctly geolocated and, on average, less than 2% of posts are natively georeferenced. This paper presents an algorithm, called CIME, that aims to identify and geolocate emergency-related posts that are relevant for mapping purposes. While native geocoordinates are most often missing, many posts contain geographical references in their metadata, such as texts or links that can be used by CIME to filter and geolocate information. In addition, social media creates a social network and each post can be enhanced with indirect information from the post’s network of relationships with other posts (for example, a retweet can be associated with other geographical references which are useful to geolocate the original tweet). To exploit all this information, CIME uses the concept of context, defined as the information characterizing a post both directly (the post’s metadata) and indirectly (the post’s network of relationships). The algorithm was evaluated on a recent major emergency event demonstrating better performance with respect to the state of the art in terms of total number of geolocated posts, geolocation accuracy and relevance for rapid mapping.

ANALYSIS OF GEOMETRIC AND ORTHOGONAL CORRECTION ACCURACY FOR CAS-500 SATELLITE IMAGES

This paper reports on geolocation accuracy of image products generated from Precision Image Processing (PIP) system developed for CAS-500 Satellite images. CAS-500, launched on 22 March, 2021, will be used mainly for land monitoring and 1:5000 scale mapping over the Korean Peninsula. For this purpose, ground control points (GCPs) and a Digital Terrain Model (DTM) have been collected over the Peninsula and integrated into the PIP for the generation of precision image product in an automated manner. The goal of this paper is to analyze the geolocation accuracy of image products generated from the PIP. Target geolocation accuracy of the PIP was set as 2 pixel RMSE using the internal GCP DB and DTM. Since CAS-500 images were not distributed yet, the analysis was performed using 13 KOMPSAT-3A satellite images, having similar specifications to CAS-500. The result showed that the accuracy of precise sensor models were about 1.797 pixels in South Korea and 1.907 pixels in North Korea. The accuracy of orthoimages were about 1.24 meters in South Korea and 1.59 meters in North Korea. Overall, the geolocation over North Korea was not as good as that over South Korea. It was judged that the quality of GCPs and DTM over North Korea affected the geolocation accuracy and, however, the accuracy gap was not too severe. The PIP system should produce image products within the targeted geolocation accuracy when CAS-500 delivers high resolution images over the Korean Peninsula.

Shared Operation of a Barrage Jammer and Reference Signal Sources for Determining Ground-Based Radio Transmitters Operating via Geostationary Relay Satellites

Introduction. There are incidences of jamming the users of satellite communication systems, who apply e.g. geostationary relay satellites, and the illegal use of such satellite resources. These actions can be both intentional and unintentional, and, among other things, be caused by non-compliance with electromagnetic compatibility standards on part of other users of satellite communication systems. For a prompt and high -quality response of radio monitoring services and satellite operators to these illegal actions, it seems urgent to develop methods for accurate determination of the geolocation of radio emission sources.Aim. To develop a method for improving the accuracy of determining the coordinates of ground-based radio emission sources operating via geostationary relay satellites based on shared operation of a barrage jammer and reference signal sources.Materials and methods. The research was conducted using the statistical theory of radio engineering systems, the theory of digital signal processing and the method of simulation.Results. A method was developed for improving the geolocation accuracy of ground-based radio emission sources operating via geostationary relay satellites based on shared operation of a barrage jammer and reference signal sources. A method for resolving ambiguity regarding the true correlation peak of a reference source signal using a signal from a barrage jammer was described. An expression was obtained for the probability of a correct solution when resolving such ambiguity. As a result, the estimates of geolocation accuracy obtained using the developed method were compared with those obtained by a conventional method relying on the usage of 3 different reference stations.Conclusions. The method proposed in this paper makes it possible to achieve a relatively high accuracy when determining the geolocation of ground-based radio emission sources in the Earth’s regions of interest, at the same time as involving no organizational and financial costs for the installation of a large number of reference stations.

New Orthophoto Generation Strategies from UAV and Ground Remote Sensing Platforms for High-Throughput Phenotyping

Remote sensing platforms have become an effective data acquisition tool for digital agriculture. Imaging sensors onboard unmanned aerial vehicles (UAVs) and tractors are providing unprecedented high-geometric-resolution data for several crop phenotyping activities (e.g., canopy cover estimation, plant localization, and flowering date identification). Among potential products, orthophotos play an important role in agricultural management. Traditional orthophoto generation strategies suffer from several artifacts (e.g., double mapping, excessive pixilation, and seamline distortions). The above problems are more pronounced when dealing with mid- to late-season imagery, which is often used for establishing flowering date (e.g., tassel and panicle detection for maize and sorghum crops, respectively). In response to these challenges, this paper introduces new strategies for generating orthophotos that are conducive to the straightforward detection of tassels and panicles. The orthophoto generation strategies are valid for both frame and push-broom imaging systems. The target function of these strategies is striking a balance between the improved visual appearance of tassels/panicles and their geolocation accuracy. The new strategies are based on generating a smooth digital surface model (DSM) that maintains the geolocation quality along the plant rows while reducing double mapping and pixilation artifacts. Moreover, seamline control strategies are applied to avoid having seamline distortions at locations where the tassels and panicles are expected. The quality of generated orthophotos is evaluated through visual inspection as well as quantitative assessment of the degree of similarity between the generated orthophotos and original images. Several experimental results from both UAV and ground platforms show that the proposed strategies do improve the visual quality of derived orthophotos while maintaining the geolocation accuracy at tassel/panicle locations.

Studies of FY-3 Observations over the Past 10 Years: A Review

With the rapid advances and abundant observations from Chinese Fengyun-3 (FY-3) meteorological satellites, it is of great interest to summarize a decade of quality assessments of FY-3 observations. The topics covered are noise characterization, bias estimation, striping noise detection and mitigation of striping noise, radio frequency interference detection, geolocation accuracy estimation and improvement, data assimilation cloud detection and quality control for observations from the MicroWave Temperature Sounder (MWTS), the MicroWave Humidity Sounder (MWHS), the MicroWave Radiation Imager (MWRI) and the Hyperspectral Infrared Atmospheric Sounder (HIRAS) instruments on board FY-3A/B/C/D. Whether and how much FY-3 data assimilation could improve the numerical weather forecast skill strongly depends on how well the FY-3 data characteristics and errors listed above are known. This review article shall contribute to promoting internal and national usages of FY-3 observations for weather and climate studies.

A New Combined Adjustment Model for Geolocation Accuracy Improvement of Multiple Sources Optical and SAR Imagery

Numerous earth observation data obtained from different platforms have been widely used in various fields, and geometric calibration is a fundamental step for these applications. Traditional calibration methods are developed based on the rational function model (RFM), which is produced by image vendors as a substitution of the rigorous sensor model (RSM). Generally, the fitting accuracy of the RFM is much higher than 1 pixel, whereas the result decreases to several pixels in mountainous areas, especially for Synthetic Aperture Radar (SAR) imagery. Therefore, this paper proposes a new combined adjustment for geolocation accuracy improvement of multiple sources satellite SAR and optical imagery. Tie points are extracted based on a robust image matching algorithm, and relationships between the parameters of the range-doppler (RD) model and the RFM are developed by transformed into the same Geodetic Coordinate systems. At the same time, a heterogeneous weight strategy is designed for better convergence. Experimental results indicate that our proposed model can achieve much higher geolocation accuracy with approximately 2.60 pixels in the X direction and 3.50 pixels in the Y direction. Compared with traditional methods developed based on RFM, our proposed model provides a new way for synergistic use of multiple sources remote sensing data.

A Street-Level IP Geolocation Method Based on Delay-Distance Correlation and Multilayered Common Routers

The geographical locations of smart devices can help in providing authentication information between multimedia content providers and users in 5G networks. The IP geolocation methods can help in estimating the geographical location of these smart devices. The two key assumptions of existing IP geolocation methods are as follows: (1) the smallest relative delay comes from the nearest host; (2) the distance between hosts which share the closest common routers is smaller than others. However, the two assumptions are not always true in weakly connected networks, which may affect accuracy. We propose a novel street-level IP geolocation algorithm (Corr-SLG), which is based on the delay-distance correlation and multilayered common routers. The first key idea of Corr-SLG is to divide landmarks into different groups based on relative-delay-distance correlation. Different from previous methods, Corr-SLG geolocates the host based on the largest relative delay for the strongly negatively correlated groups. The second key idea is to introduce the landmarks which share multilayered common routers into the geolocation process, instead of only relying on the closest common routers. Besides, to increase the number of landmarks, a new street-level landmark collection method called WiFi landmark is also presented in this paper. The experiments in one province capital city of China, Zhengzhou, show that Corr-SLG can improve the geolocation accuracy remarkably in a real-world network.

SIVIM Deciduous Forests – Database of deciduous forests from the Iberian Peninsula

“SIVIM Deciduous Forests” is a thematic database established in 2015, focused on forest vegetation from the Iberian Peninsula and southern France. It was registered in the Global Index of Vegetation Databases (GIVD ID: EU-00-023) in January 2016. All types of temperate and submediterranean non-riparian deciduous forests of the phytosociological classes Carpino-Fagetea sylvaticae, Quercetea pubescentis and Quercetea robori-petraeae (formerly combined in the class Querco-Fagetea) are represented in the database. Currently, it contains 6,642 published vegetation plots of beech, birch, ash, lime and other deciduous mixed forests, as well as forests dominated by different species of deciduous and marcescent oaks, 100% of them classified at association level. Data are stored in TURBOVEG format, and are available upon request from the international vegetation-plot databases EVA and sPlot in semi-restricted regime. The relevés have also been included in SIVIM database, and thus they are freely available online. However, in SIVIM Deciduous Forests geolocation accuracy has been improved and the taxonomy and syntaxonomy unified. Plot size is available for 73% of the relevés, of which 82% are between 100 and 400 m2. Plant taxonomy is standardized to Flora iberica. During the last four years, data of SIVIM Deciduous Forests were requested via EVA and sPlot for different projects, and have been used for several studies with various objectives, from floristic, vegetation and habitat-related topics to macroecological studies, and from local to global scales. Abbreviations: EVA = European Vegetation Archive; GIVD = Global Index of Vegetation-Plot Databases; SIVIM = Iberian and Macaronesian Vegetation Information System.