Maanmittauslaitos

Maanmittauslaitoksessa tuotetaan tietoa, palvelua ja tutkimusta Maasta. Teemme maanmittaustoimituksia, ylläpidämme kiinteistöjen tietoja, tuotamme paikkatieto- ja kartta-aineistoja, huolehdimme lainhuudoista ja kiinnityksistä, kehitämme tietojärjestelmiä sekä edistämme paikkatietojen tutkimusta ja soveltamista.

Paikkatietokeskus (FGI) on Maanmittauslaitoksen tutkimus- ja asiantuntijayksikkö, joka tekee paikkatietoalan tutkimus- ja asiantuntijatyötä. Arvostettu kansainvälinen tutkimusyksikkö tarjoaa luotettavaa tietoa yhteiskunnan hyväksi. Lisää tietoa: www.fgi.fi

Kokoelmat

Uusimmat julkaisut

  • Rantanen, Jesperi; Ruotsalainen, Laura; Kirkko-Jaakkola, Martti; Mäkelä, Maija (2018)
    IEEE Transactions on Instrumentation and Measurement
  • Rantanen, Jesperi; Mäkelä, Maija; Ruotsalainen, Laura; Kirkko-Jaakkola, Martti (2018)
    2018 International Conference on Indoor Positioning and Indoor Navigation (IPIN)
  • Mäkelä, Maija; Kirkko-Jaakkola, Martti; Rantanen, Jesperi; Ruotsalainen, Laura (2018)
    Proceedings of the International Conference on Information Fusion
    In this paper we discuss the effect of cooperation in foot-mounted pedestrian indoor navigation. We study methods to use Ultra-Wide Band (UWB) range measurements between two pedestrians, as well as sharing location information between them. Our aim is to handle the heading offset between two separate pedestrian inertial navigation solutions and to represent the collaborators in a common coordinate frame. Furthermore, we study the effect of the proposed method also on height estimation. Our approach fuses measurements from several sensors, such as Inertial Measurement Units, UWB radios and a barometer using Bayesian filtering. First results from tests done in a realistic scenario show that the method can work in tactical operations.
  • Mäkelä, Maija; Rantanen, Jesperi; Kirkko-Jaakkola, Martti; Ruotsalainen, Laura (IEEE Sensors Council, 2018)
    IEEE Sensors Journal
    In this paper, we study machine learning methods for recognizing the motion context of a user of an infrastructure-free navigation system. Motion context is information about whether the user is running, crawling, or lying down, for instance. This can be valuable information for the command and control of a tactical or rescue operation, and it can also be used to adapt the positioning algorithm accordingly in order to improve the positioning result. We test our approach in collaboration with the Finnish Defence Forces. With only about 5 min of training data, we are able to detect the users motion context over 93% of the time using a random forest classifier. However, our tests show that the performance of the classifier is highly dependent on the user of the system. For this reason, we experiment with different classification algorithms in order to find a user-independent classifier providing a good compromise between accuracy and computational complexity. With a naïve Bayesian classifier, we achieve 85% detection rate in case when the training data is not produced by the user. In addition, we demonstrate how the motion recognition can be used to adjust the zero velocity update threshold in order to improve the performance of a foot-mounted inertial navigation algorithm.
  • Mäkinen, Kirsi (2018)
    Positio - paikkatiedon erikoislehti
  • Vaniala, Riitta (2018)
    Positio - paikkatiedon erikoislehti
  • Markkanen, Johannes; Agarwal, Jessica; Väisänen, Timo; Penttilä, Antti; Muinonen, Karri (IOP Publishing, 2018)
    The Astrophysical Journal Letters
    We show that the scattering phase functions of the coma and the nucleus of the comet 67P/Churyumov–Gerasimenko measured by the Rosetta/Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) instrument can be reproduced by a particle model involving clustered, densely packed submicrometer-sized grains composed of organic material and larger micrometer-sized silicate grains. The simulated and measured coma phase functions suggest that near the nucleus scattering is dominated by large particles, and the size distribution of dust particles varies with time and/or local coma environment. Further, we show that the measured nucleus phase function is consistent with the coma phase function by modeling a nucleus-sized object consisting of the same particles that explain the coma phase functions.
  • Mattila, Kalevi; Haas, Martin; Haikala, Lauri; Jo, Y.-S.; Lehtinen, Kimmo; Leinert, Christoph; Väisänen, Petri (EDP Sciences, 2018)
    Astronomy & Astrophysics
    Context. Dark nebulae display a surface brightness because dust grains scatter light of the general interstellar radiation field (ISRF). High-galactic-latitudes dark nebulae are seen as bright nebulae when surrounded by transparent areas which have less scattered light from the general galactic dust layer. Aims. Photometry of the bright dark nebulae LDN 1780, LDN 1642, and LBN 406 shall be used to derive scattering properties of dust and to investigate the presence of UV fluorescence emission by molecular hydrogen and the extended red emission (ERE). Methods. We used multi-wavelength optical photometry and imaging at ground-based telescopes and archival imaging and spectroscopic UV data from the spaceborn GALEX and SPEAR/FIMS instruments. In the analysis we used Monte Carlo RT and both observational data and synthetic models for the ISRF in the solar neighbourhood. The line-of-sight extinctions through the clouds have been determined using near infrared excesses of background stars and the 200/250 μm far infrared emission by dust as measured using the ISO and Herschel space observatories. Results. The optical surface brightness of the three target clouds can be explained in terms of scattered light. The dust albedo ranges from ~0.58 at 3500 Å to ~0.72 at 7500 Å. The spectral energy distribution of LDN 1780 is explained in terms of optical depth and background scattered light effects instead of the original published suggestion in terms of ERE. The far-ultraviolet surface brightness of LDN 1780 cannot be explained by scattered light only. In LDN 1780, H2 fluorescent emission in the wavelength range 1400–1700 Å has been detected and analysed. Conclusions. Our albedo values are in good agreement with the predictions of the dust model of Weingartner and Draine and with the THEMIS CMM model for evolved core-mantle grains. The distribution of H2 fluorescent emission in LDN 1780 shows a pronounced dichotomy with a strong preference for its southern side where enhanced illumination is impinging from the Sco OB2 association and the O star ζ Oph. A good correlation is found between the H2 fluorescence and a previously mapped 21-cm excess emission. The H2 fluorescence emission in LDN 1780 has been modelled using a PDR code; the resulting values for H2 column density and the total gas density are consistent with the estimates derived from CO observations and optical extinction along the line of sight.
  • Harju, Jorma; Lehtinen, Kimmo; Romney, Jonathan; Petrov, Leonid; Granvik, Mikael; Muinonen, Karri; Bach, Uwe; Poutanen, Markku (IOP Publishing, 2018)
    The occultation of the radio galaxy 0141+268 by the asteroid (372) Palma on 2017 May 15 was observed using six antennas of the Very Long Baseline Array (VLBA). The shadow of Palma crossed the VLBA station at Brewster, Washington. Owing to the wavelength used, and the size and the distance of the asteroid, a diffraction pattern in the Fraunhofer regime was observed. The measurement retrieves both the amplitude and the phase of the diffracted electromagnetic wave. This is the first astronomical measurement of the phase shift caused by diffraction. The maximum phase shift is sensitive to the effective diameter of the asteroid. The bright spot at the shadow's center, the so called Arago-Poisson spot, is clearly detected in the amplitude time-series, and its strength is a good indicator of the closest angular distance between the center of the asteroid and the radio source. A sample of random shapes constructed using a Markov chain Monte Carlo algorithm suggests that the silhouette of Palma deviates from a perfect circle by 26 +/- 13%. The best-fitting random shapes resemble each other, and we suggest their average approximates the shape of the silhouette at the time of the occultation. The effective diameter obtained for Palma, 192.1 +/- 4.8 km, is in excellent agreement with recent estimates from thermal modeling of mid-infrared photometry. Finally, our computations show that because of the high positional accuracy, a single radio interferometric occultation measurement can reduce the long-term ephemeris uncertainty by an order of magnitude.
  • Kirkko-Jaakkola, Martti; Thombre, Sarang; Honkala, Salomon; Söderholm, Stefan; Kaasalainen, Sanna; Kuusniemi, Heidi; Zelle, Hein; Veerman, Henk; Wallin, Anders (Institute of Electrical and Electronics Engineers, 2017)
    Proceedings of the European Navigation Conference
    This paper proposes a set of Key Performance Indicators (KPIs) for European GNSS (EGNSS)-based timing services that are relevant from the user perspective; these KPIs quantify the accuracy, integrity, and stability of the services. Furthermore, the instrumentation and procedures required for reproducing the threats and evaluating the proposed KPIs are described. The proposed test setup makes use of a precise time/frequency reference distributing a Coordinated Universal Time (UTC) realization and is intended for post-processing. The test results provide an indication of the performance of the envisioned Galileo and EGNOS timing services in terms of the proposed KPIs when the receiver is subject to various abnormal conditions.
  • Kirkko-Jaakkola, Martti; Thombre, Sarang; Honkala, Salomon; Söderholm, Stefan; Kaasalainen, Sanna; Kuusniemi, Heidi; Zelle, Hein; Veerman, Henk; Wallin, Anders; Aarmo, Kjell Arne; Boyero, Juan Pablo (Institute of Navigation, 2017)
    Proceedings of ION GNSS+
    GNSS-based time transfer is utilized in various critical infrastructures as it provides important advantages which are being increasingly exploited. In this paper, we present the various implementation options for robust timing service concepts based on European GNSS (EGNSS), i.e., Galileo and EGNOS, that are expected to further foster the use of EGNSS timing; this concept can make use of the redundancy of measurements and of available GNSS constellations. The stability properties of the local oscillator, which are known to the designer, are also exploited. The algorithms are developed to account for cases where several measurement faults occur simultaneously, which is a possible scenario in land-based reception conditions. Furthermore, we derive time protection level equations to quantify the integrity of the GNSS time solution as a function of the false alarm and missed detection probabilities as well as the maximum number of simultaneous outliers to be accounted for. Some of the considered fault scenarios can only be detected but not rectified by the algorithms: in such case, holdover, i.e. processing based on the local oscillator alone, is triggered. Thus, the performance in these scenarios is dependent on the stability of the local oscillator; in this paper, the analysis is based on a low-cost temperature-compensated crystal oscillator. The effect of the robustness concepts is illustrated with a set of experiments which show that when implemented in a timing GNSS receiver, the algorithms presented can deal with failures that affect individual satellites or even an entire constellation. Local disturbances affecting the receiver can also be effectively detected. Specifying EGNSS timing as proper services along with well-defined procedures for testing receiver compliance paves the road for standardizing and certifying robust EGNSS timing receivers, which would be beneficial for many applications and in particular in safety or liability critical use cases.
  • Markelin, Lauri; Suomalainen, Juha; Hakala, Teemu; Alves de Oliveira, Raquel; Viljanen, Niko; Näsi, Roope; Scott, Barry; Theocharous, Theo; Greenwell, Claire; Fox, Nigel; Honkavaara, Eija (ISPRS Council, 2018)
    The International Archives fo the Photogrammetry, Remote Sensing and Spatial Information Sciences
    We study and analyse performance of a system for direct reflectance measurements from a drone. Key instruments of the system are upwards looking irradiance sensor and downwards looking imaging spectrometer. Requirement for both instruments is that they are radiometrically calibrated, the irradiance sensor has to be horizontally stabilized, and the sensors needs to be accurately synchronized. In our system, irradiance measurements are done with FGI Aerial Image Reference System (FGI AIRS), which uses novel optical levelling methodology and can compensate sensor tilting up to 15°. We performed SI-traceable spectral and radiance calibration of FPI hyperspectral camera at the National Physical Laboratory NPL (Teddington, UK). After the calibration, the radiance accuracy of different channels was between ±4% when evaluated with independent test data. Sensors response to radiance proved to be highly linear and was on average 0.9994 for all channels. The spectral response calibration showed side peaks on several channels that were due to the multiple orders of interference of the FPI and highlighted the importance of accurate calibration. The drone-based direct reflectance measurement system showed promising results with imagery collected over Jokioinen agricultural grass test site, Finland. AIRS-based image- and band wise image adjustment provided homogenous and seamless image mosaics even under varying illumination conditions and under clouds.
  • Ferrara, Nunzia Giorgia; Bhuiyan, Mohammad Zahidul H.; Söderholm, Stefan; Ruotsalainen, Laura; Kuusniemi, Heidi (John Wiley & Sons, 2018)
    GPS Solutions
    Due to the very low power of satellite signals when reaching the earth’s surface, global navigation satellite system receivers are vulnerable to various types of radio frequency interference, and, therefore, countermeasures are necessary. In the case of a narrowband interference (NBI), the adaptive notch filtering technique has been extensively investigated. However, the research on the topic has focused on the adaptation of the notch frequen-cy, but not of the notch width. We present a fully adaptive solution to counter NBI. The technique is capable of de-tecting and characterizing any number of narrow inter-fered bands, and then optimizing the mitigation process based on such characterization, namely the estimates of both interference frequency and width. Its full adaptive-ness makes it suitable to cope with the unpredictable and diverse nature of unintentional interfering events. In addi-tion to a thorough performance evaluation of the pro-posed method, which shows its benefits in terms of sig-nal quality improvement, an analysis of the impact of different NBI profiles on GPS L1 C/A and Galileo E1 is also conducted.
  • Cristodaro, Calogero; Ruotsalainen, Laura; Dovis, Fabio (MDPI, 2018)
    Sensors
    Global navigation satellite systems play a significant role in the development of intelligent transport systems, where the estimation of the vehicle’s position is a key element. How-ever, in strongly constrained environments such as city centers, the definition of quality metrics and the assessment of positioning performances are challenges to be addressed. Due to the variability of different urban scenarios, the model-ing of the dynamics as well as the architecture of the posi-tioning platform, which might embed other sensors and aid-ing means to the GNSS unit, make it hard to define unam-biguous positioning metrics. Performance assessment through analytical models and simulators can be ineffective in terms of cost, complexity, and general validity and scala-bility of the results. This paper shows how a record and replay approach can be an efficient solution to grant fidelity to a realistic scenario. This work discusses advantages and disadvantages with emphasis on the case study of harsh scenarios. Such an approach requires proper data collec-tions that allow the replay phase to test the GNSS-based positioning terminals. This paper presents the results ob-tained on a set of field tests related to different scenarios, selected as representative for the key performance indica-tors assessment.
  • Grau Galofre, Anna; Jellinek, Mark; Osinski, Gordon, R.; Zanetti, Michael; Kukko, Antero (Copernicus Publications, 2018)
    The Cryosphere
    Subglacial meltwater channels (N-channels) are attributed to erosion by meltwater in subglacial conduits. They exert a major control on meltwater accumulation at the base of ice sheets, serving as drainage pathways and modifying ice flow rates. The study of exposed relict subglacial channels offers a unique opportunity to characterize the geomorphologic fingerprint of subglacial erosion as well as study the structure and characteristics of ice sheet drainage systems. In this study we present detailed field and remote sensing observations of exposed subglacial meltwater channels in excellent preservation state on Devon Island (Canadian Arctic Archipelago). We characterize channel cross section, longitudinal profiles, and network morphologies and establish the spatial extent and distinctive characteristics of subglacial drainage systems. We use field-based GPS measurements of subglacial channel longitudinal profiles, along with stereo imagery-derived digital surface models (DSMs), and novel kinematic portable lidar data to establish a detailed characterization of subglacial channels in our field study area, including their distinction from rivers and other meltwater drainage systems. Subglacial channels typically cluster in groups of ˜ 10 channels and are oriented perpendicular to active or former ice margins. Although their overall direction generally follows topographic gradients, channels can be oblique to topographic gradients and have undulating longitudinal profiles. We also observe that the width of first-order tributaries is 1 to 2 orders of magnitude larger than in Devon Island river systems and approximately constant. Furthermore, our findings are consistent with theoretical expectations drawn from analyses of flow driven by gradients in effective water pressure related to variations in ice thickness. Our field and remote sensing observations represent the first high-resolution study of the subglacial geomorphology of the high Arctic, and provide quantitative and qualitative descriptions of subglacial channels that revisit well-established field identification guidelines. Distinguishing subglacial channels in topographic data is critical for understanding the emergence, geometry, and extent of channelized meltwater systems and their role in ice sheet drainage. The final aim of this study is to facilitate the identification of subglacial channel networks throughout the globe by using remote sensing techniques, which will improve the detection of these systems and help to build understanding of the underlying mechanics of subglacial channelized drainage.
  • Pyörälä, Jiri; Liang, Xinlian; Vastaranta, Mikko; Saarinen, Ninni; Kankare, Ville; Wang, Yunsheng; Holopainen, Markus; Hyyppä, Juha (IEEE, 2018)
    IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
    State-of-the-art technology available at sawmills enables measurements of whorl numbers and the maximum branch diameter for individual logs, but such information is currently unavailable at the wood procurement planning phase. The first step toward more detailed evaluation of standing timber is to introduce a method that produces similar wood quality indicators in standing forests as those currently used in sawmills. Our aim was to develop a quantitative method to detect and model branches from terrestrial laser scanning (TLS) point clouds data of trees in a forest environment. The test data were obtained from 158 Scots pines (Pinus sylvestris L.) in six mature forest stands. The method was evaluated for the accuracy of the following branch parameters: Number of whorls per tree and for every whorl, the maximum branch diameter and the branch insertion angle associated with it. The analysis concentrated on log-sections (stem diameter>15 cm) where the branches most affect wood’s value added. The quantitative whorl detection method had an accuracy of 69.9% and a 1.9% false positive rate. The estimates of the maximum branch diame-ters and the corresponding insertion angles for each whorl were underestimated by 0.34 cm (11.1%) and 0.67° (1.0%), with a root-mean-squared error of 1.42 cm (46.0%) and 17.2° (26.3%), respectively. Distance from the scanner, occlusion, and wind were the main external factors that affect the method’s functionality. Thus, the completeness and point density of the data should be addressed when applying TLS point cloud based tree models to assess branch parameters.
  • Lehto, Lassi; Kähkönen, Jaakko; Oksanen, Juha; Sarjakoski, Tapani (IARIA, 2018)
    International Conference on Advanced Geographic Information Systems, Applications, and Services
    Providers of geospatial data are facing the challenge of di-verse user needs when delivering their products to different user groups. Academic researchers represent a user group with quite specific requirements, like good support for anal-ysis and high-performance computing. A national infrastruc-ture providing both geospatial data and powerful geocompu-ting facilities for research use is being developed in Finland. The part of the infrastructure described in this paper focuses on the management, storage and efficient delivery of raster-formatted geospatial data by applying the concept of datacube.
  • Lehto, Lassi; Kähkönen, Jaakko; Oksanen, Juha; Sarjakoski, Tapani (ISPRS Council, 2018)
    The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
    An initiative has been started in Finland to build a harmo-nized raster geodata repository, called GeoCubes Finland, to help academic users in carrying out geospatial analysis operations in research projects of diverse disciplines. The aim of the initiative is to expand the adoption of GI methods and tools to new sectors of academic research. GeoCubes Finland is being built in the context of a large-scale program developing national geodata infrastructure for academic studies. The main building blocks of the GeoCubes Finland initiative are: a harmonized, multi-resolution raster geodata storage, a set of standardized mechanisms for accessing the raster contents of the storage, and support facilities for cloud-based geocomputing to help users carry out spatial analysis with the contained datasets.
  • Hakala, Teemu; Markelin, Lauri; Honkavaara, Eija; Scott, Barry; Theocharous, Theo; Nevalainen, Olli; Näsi, Roope; Suomalainen, Juha; Viljanen, Niko; Greenwell, Claire; Fox, Nigel (MDPI, 2018)
    Sensors
    Drone-based remote sensing has evolved rapidly in recent years. Miniaturized hyperspectral imaging sensors are becoming more common as they provide more abundant information of the object compared to traditional cameras. Reflectance is a physically defined object property and therefore often preferred output of the remote sensing data capture to be used in the further processes. Absolute calibration of the sensor provides a possibility for physical modelling of the imaging process and enables efficient procedures for reflectance correction. Our objective is to develop a method for direct reflectance measurements for drone-based remote sensing. It is based on an imaging spectrometer and irradiance spectrometer. This approach is highly attractive for many practical applications as it does not require in situ reflectance panels for converting the sensor radiance to ground reflectance factors. We performed SI-traceable spectral and radiance calibration of a tuneable Fabry-Pérot Interferometer -based (FPI) hyperspectral camera at the National Physical Laboratory NPL (Teddington, UK). The camera represents novel technology by collecting 2D format hyperspectral image cubes using time sequential spectral scanning principle. The radiance accuracy of different channels varied between ±4% when evaluated using independent test data, and linearity of the camera response was on average 0.9994. The spectral response calibration showed side peaks on several channels that were due to the multiple orders of interference of the FPI. The drone-based direct reflectance measurement system showed promising results with imagery collected over Wytham Forest (Oxford, UK).
  • Junttila, Samuli; Sugano, Junko; Vastaranta, Mikko; Linnakoski, Riikka; Kaartinen, Harri; Kukko, Antero; Holopainen, Markus; Hyyppä, Hannu; Hyyppä, Juha (Frontiers Reseach Foundation, 2018)
    Frontiers in Plant Science
    Changing climate is increasing the amount and intensity of forest stress agents, such as drought, pest insects, and pathogens. Leaf water content, measured here in terms of equivalent water thickness (EWT), is an early indicator of tree stress that provides timely information about the health status of forests. Multispectral terrestrial laser scanning (MS-TLS) measures target geometry and reflectance simultaneously, providing spatially explicit reflectance information at several wavelengths. EWT and leaf internal structure affect leaf reflectance in the shortwave infrared region that can be used to predict EWT with MS-TLS. A second wavelength that is sensitive to leaf internal structure but not affected by EWT can be used to normalize leaf internal effects on the shortwave infrared region and improve the prediction of EWT. Here we investigated the relationship between EWT and laser intensity features using multisensor MS-TLS at 690, 905, and 1,550 nm wavelengths with both drought-treated and Endoconidiophora polonica inoculated Norway spruce seedlings to better understand how MS-TLS measurements can explain variation in EWT. In our study, a normalized ratio of two wavelengths at 905 and 1,550 nm and length of seedling explained 91% of the variation (R2) in EWT as the respective prediction accuracy for EWT was 0.003 g/cm2 in greenhouse conditions. The relation between EWT and the normalized ratio of 905 and 1,550 nm wavelengths did not seem sensitive to a decreased point density of the MS-TLS data. Based on our results, different EWTs in Norway spruce seedlings show different spectral responses when measured using MS-TLS. These results can be further used when developing EWT monitoring for improving forest health assessments.

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