Finnish Geospatial Research Institute FGI


Finnish Geospatial Research Institute FGI

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Herranen J.,University of Helsinki | Markkanen J.,University of Helsinki | Muinonen K.,Finnish Geospatial Research Institute FGI
2016 URSI International Symposium on Electromagnetic Theory, EMTS 2016 | Year: 2016

We establish a theoretical framework for solving the equations of motion for an arbitrarily shaped, isotropic, and homogeneous dust particle in the presence of radiation pressure. The scattering problem involved is solved by a surface integral equation method, and a rudimentary sketch of the numerical implementation is introduced with preliminary results agreeing with predictions. © 2016 IEEE.

Moreno-Ibanez M.,Institute of Space science IEEC CSIC | Moreno-Ibanez M.,Finnish Geospatial Research Institute FGI | Gritsevich M.,Finnish Geospatial Research Institute FGI | Gritsevich M.,University of Helsinki | And 2 more authors.
Astrophysics and Space Science Proceedings | Year: 2017

The extent of penetration into the Earth’s atmosphere of a meteoroid is defined by the point where its kinetic energy is no longer sufficient to produce luminosity. For most of the cases this is the point where the meteoroid disintegrates in the atmosphere due to ablation process and dynamic pressure during flight. However, some of these bodies have particular physical properties (bigger size, higher bulk strength, etc.) or favorable flight conditions (lower entry velocity or/and a convenient trajectory slope, etc.) that allow them to become a meteoritedropper and reach the ground. In both cases, we define the end of the luminous path of the trajectory as the terminal height or end height. Thus, the end point shows the amount of deceleration till the final braking. We thus assume that the ability of a fireball to produce meteorites is directly related to its terminal height. Previous studies have discussed the likely relationship between fireball atmospheric flight properties and the terminal height. Most of these studies require the knowledge of a set of properties and physical variables which cannot be determined with sufficient accuracy from ground-based observations. The recently validated dimensionless methodology offers a new approach to this problem. All the unknowns can be reduced to only two parameters which are easily derived from observations. Despite the calculation of the analytic solution of the equations of motion is not trivial, some simplifications are admitted. Here, we describe the best performance range and the errors associated with these simplifications. We discuss how terminal heights depend on two or three variables that are easily retrieved from the recordings, provided at least three trajectory (h, v) points. Additionally, we review the importance of terminal heights, and the way they have been estimated in previous studies. Finally we discuss a new approach for calculating terminal heights. © Springer International Publishing Switzerland 2017.

Trigo-Rodriguez J.M.,Institute of Space science IEEC CSIC | Palme H.,Forschungsinstitut und Naturmuseum Senckenberg | Gritsevich M.,Finnish Geospatial Research Institute FGI | Gritsevich M.,RAS Dorodnicyn Computing Center
Astrophysics and Space Science Proceedings | Year: 2017

The general context in which was organized the Barcelona Asteroid Day 2015 workshop is introduced, together with a brief description of the contributions to this proceedings book. To promote the study of asteroids, comets and meteorites was one of the goals of the Barcelona event, an initiative born as part of the international Asteroid Day movement that tries to popularize the Tunguska event (on June 30th, 1908), the most energetic contemporary impact detected so far. This book compiles the contributions presented to this research workshop organized by the Institute of Space Sciences (IEEC-CSIC) at the UAB campus in Bellaterra, together with an outreach event led by astronaut Pedro Duque that conveyed the main issues to the general public. This workshop was coordinated with other initiatives around the world and intended to offer to the general public, and astronomy enthusiasts an environment for public awareness and open discussion. The event was intended to present the most recent science, to promote international cooperation and to raise the scientific interest of studying asteroids to the general public and the media. © Springer International Publishing Switzerland 2017.

Muinonen K.,University of Helsinki | Muinonen K.,Finnish Geospatial Research Institute FGI | Lumme K.,University of Helsinki
Astronomy and Astrophysics | Year: 2015

Context. The scattering of light by an asteroid's surface depends on the properties of its particles, volume density, and roughness. It is described by the reflection coefficient which, upon integration over the illuminated and observed part of the surface, yields the disk-integrated photometric brightness of the asteroid. The Lommel-Seeliger reflection coefficient is applicable to dark, low-albedo C-class asteroids, with prospects for moderate-albedo S-class and M-class asteroids. Aims. We calculate the disk-integrated brightness for an ellipsoidal asteroid with a Lommel-Seeliger reflection coefficient (LS ellipsoid). Furthermore, we calculate the photocenter for the LS ellipsoid, that is, the distance of the center of light from the barycenter. Methods. Because of their analytical nature, the closed-form expressions can be readily utilized in numerical simulations. Results. We show lightcurves and photocenter variations for realistic examples of ellipsoidal shapes for a number of pole orientations. The results highlight the reciprocity principle of the radiative-transfer theory and suggest a nontrivial dependence of the photocenter on the pole orientation and viewing geometry. Conclusions. Finally, we outline a number of applications and future prospects. © ESO, 2015.

Moreno-Ibanez M.,Institute of Space science CSIC IEEC | Gritsevich M.,Finnish Geospatial Research Institute FGI | Gritsevich M.,Moscow State University of Geodesy and Cartography | Trigo-Rodriguez J.M.,Institute of Space science CSIC IEEC
Icarus | Year: 2015

Despite ablation and drag processes associated with atmospheric entry of meteoroids were a subject of intensive study over the last century, little attention was devoted to interpret the observed fireball terminal height. This is a key parameter because it not only depends on the initial mass, but also on the bulk physical properties of the meteoroids and hence on their ability to ablate in the atmosphere. In this work we have developed a new approach that is tested using the fireball terminal heights observed by the Meteorite Observation and Recovery Project operated in Canada between 1970 and 1985 (hereafter referred as MORP). We then compare them to the calculation made. Our results clearly show that the new methodology is able to forecast the degree of deepening of meteoroids in the Earth's atmosphere. Then, this approach has important applications in predicting the impact hazard from cm- to meter-sized bodies that are represented, in part, in the MORP bolide list. © 2015 Elsevier Inc..

Hakala T.,Finnish Geospatial Research Institute FGI | Nevalainen O.,Finnish Geospatial Research Institute FGI | Kaasalainen S.,Finnish Geospatial Research Institute FGI | Makipaa R.,Finnish Forest Research Institute
Biogeosciences | Year: 2015

We present an empirical application of multispectral laser scanning for monitoring the seasonal and spatial changes in pine chlorophyll (a + b) content and upscaling the accurate leaf-level chlorophyll measurements into branch and tree level. The results show the capability of the new instrument for monitoring the changes in the shape and physiology of tree canopy: the spectral indices retrieved from the multispectral point cloud agree with laboratory measurements of the chlorophyll a and b content. The approach opens new prospects for replacing destructive and labour-intensive manual sampling with remote observations of tree physiology. © Author(s) 2015.

Matikainen L.,Finnish Geospatial Research Institute FGI | Hyyppa J.,Finnish Geospatial Research Institute FGI | Litkey P.,Finnish Geospatial Research Institute FGI
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2016

During the last 20 years, airborne laser scanning (ALS), often combined with multispectral information from aerial images, has shown its high feasibility for automated mapping processes. Recently, the first multispectral airborne laser scanners have been launched, and multispectral information is for the first time directly available for 3D ALS point clouds. This article discusses the potential of this new single-sensor technology in map updating, especially in automated object detection and change detection. For our study, Optech Titan multispectral ALS data over a suburban area in Finland were acquired. Results from a random forests analysis suggest that the multispectral intensity information is useful for land cover classification, also when considering ground surface objects and classes, such as roads. An out-of-bag estimate for classification error was about 3% for separating classes asphalt, gravel, rocky areas and low vegetation from each other. For buildings and trees, it was under 1%. According to feature importance analyses, multispectral features based on several channels were more useful that those based on one channel. Automatic change detection utilizing the new multispectral ALS data, an old digital surface model (DSM) and old building vectors was also demonstrated. Overall, our first analyses suggest that the new data are very promising for further increasing the automation level in mapping. The multispectral ALS technology is independent of external illumination conditions, and intensity images produced from the data do not include shadows. These are significant advantages when the development of automated classification and change detection procedures is considered.

de Oliveira R.A.,São Paulo State University | Tommaselli A.M.G.,São Paulo State University | Honkavaara E.,Finnish Geospatial Research Institute FGI
Photogrammetric Record | Year: 2016

Recently, miniaturised hyperspectral sensors operable from small unmanned airborne vehicle platforms have entered the market. The emerging hyperspectral imaging technologies, based on frame cameras and tuneable filters, are attractive alternatives to hyperspectral pushbroom sensors. This paper addresses the geometric calibration process of a hyperspectral frame camera based on a Fabry–Pérot interferometer. However, the addition of more optical elements in front of the image sensor can affect the parameters related to the internal geometry of the camera, and a deficiency in knowledge regarding these parameters can have a critical effect on the accuracy of 3D measurements in photogrammetric applications. The experiments focused on assessing the self-calibrating bundle adjustment to verify the behaviour of the interior parameters, considering different spectral bands. The results indicated that the applied self-calibration method can accurately characterise the interior parameters of this camera and that one set of parameters is required for each internal sensor. © 2016 The Authors. The Photogrammetric Record © 2016 The Remote Sensing and Photogrammetry Society and John Wiley & Sons Ltd

Hietanen E.,Finnish Geospatial Research Institute FGI | Lehto L.,Finnish Geospatial Research Institute FGI | Latvala P.,Finnish Geospatial Research Institute FGI
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2016

In this study, a prototype service to provide data from Web Feature Service (WFS) as linked data is implemented. At first, persistent and unique Uniform Resource Identifiers (URI) are created to all spatial objects in the dataset. The objects are available from those URIs in Resource Description Framework (RDF) data format. Next, a Web Ontology Language (OWL) ontology is created to describe the dataset information content using the Open Geospatial Consortium's (OGC) GeoSPARQL vocabulary. The existing data model is modified in order to take into account the linked data principles. The implemented service produces an HTTP response dynamically. The data for the response is first fetched from existing WFS. Then the Geographic Markup Language (GML) format output of the WFS is transformed on-the-fly to the RDF format. Content Negotiation is used to serve the data in different RDF serialization formats. This solution facilitates the use of a dataset in different applications without replicating the whole dataset. In addition, individual spatial objects in the dataset can be referred with URIs. Furthermore, the needed information content of the objects can be easily extracted from the RDF serializations available from those URIs. A solution for linking data objects to the dataset URI is also introduced by using the Vocabulary of Interlinked Datasets (VoID). The dataset is divided to the subsets and each subset is given its persistent and unique URI. This enables the whole dataset to be explored with a web browser and all individual objects to be indexed by search engines.

Gritsevich M.,Finnish Geospatial Research Institute FGI | Gritsevich M.,Moscow State University of Geodesy and Cartography
Planetary and Space Science | Year: 2016

This paper examines the effects of the atmospheric density, more specifically, the effects that the changes of isobaric altitude have on the accuracy of a fireball's analysis. During winter, especially over high latitude regions like Finland, the true isobaric level may be more than three kilometers below the heights predicted by the US Standard Atmosphere 1976 model. It can differ even more when compared with the heights predicted by the simplified exponential scaled height model. Thus, the true mass of a fireball may differ significantly from those obtained by using either the isobaric altitudes derived from the Standard Atmosphere or the exponential atmospheric model, i.e. without taking into account the corrections for true atmospheric conditions. Likewise, the solutions for the ablation coefficient derived by the generalized models will be less accurate than those that do consider the true atmospheric conditions. This becomes especially crucial for potential meteorite droppers, i.e. low velocity fireballs, with small ablation rates and consequently, high terminal-to-initial mass ratio. We propose an atmospheric height correction method that utilizes real atmospheric data to analysis of the fireball. We demonstrate the proposed method by analyzing the data of three fireballs that were recently recorded by the Finnish Fireball Network and finally, we compare our results against those derived by using the US Standard Atmosphere 1976 model and the exponential atmosphere model. © 2015 Elsevier Ltd. All rights reserved.

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