Refereed publications

 

Peer-reviewed scientific articles such as journal articles, book sections, chapters in research books, or peer-reviewed articles in conference proceedings.

Recent Submissions

  • Peltonen-Sainio, Pirjo; Jauhiainen, Lauri; Laurila, Heikki; Sorvali, Jaana; Honkavaara, Eija; Wittke, Samantha; Karjalainen, Mika; Puttonen, Eetu (Elsevier, 2019)
    Land Use Policy
    Recent studies assessing agricultural policies, including the EU’s Agri-Environment Scheme, have shown that these have been successful in attaining some environmental goals. In Finland, however, the economic situation of farms has dramatically fallen and hence, the actions do not result in social acceptability. Sustainable intensification is a means to combine the three dimensions of sustainability: environmental, economic and social. Here we introduce a novel land use optimization and planning tool for the sustainable intensification of high-latitude agricultural systems. The main rationale for the development of the tool was to achieve a systematic and comprehensive conception for land allocation across Finland, where field parcels vary substantially in their conditions. The developed tool has a three-step scoring system based on seven physical characteristics (parcel size, shape, slope, distance to the farm center and waterways, soil type and logistic advantages) and the productivity of field parcels. The productivity estimates are based on vegetation indices derived from optical satellite data. The tool allocates virtually all >1 million field parcels in Finland either to sustainable intensification, extensification or afforestation. The tool is dynamic in the sense that its boundary values for land allocation can be fixed according to changes in social targets and supporting policies. Additionally, it can be applied year after year by acknowledging new available data, e.g., on vegetation indices and field parcel rearrangements between farms. Furthermore, it can be applied to all farm types and across Finland. It is a tool for land use planning, implementation and monitoring, but its thorough implementation calls for further development of policy instruments, which are currently more supportive towards land sharing than land sparing activities.
  • Latvala, Pekka; Lehto, Lassi; Kytö, Samuli (Stichting AGILE, 2019)
    Cascading download services combine various background services together so that their contents can be queried via a single service. A common problem with cascading services in a multinational setting is that the features coming from the services of different countries often do not match across border areas. Usually, edge-matching is executed iteratively as an off-line process between the neighbouring countries where adjustments and tests can be made during the matching process. On-the-fly edge-matching process is carried out during the service request and it leaves no room for modifications or negotiations. We present in this paper a method for performing on-the-fly edge-matching for linear features in a multinational cascading service environment. The proposed algorithm uses a country boundary lines data set and a connecting feature points data set that contains pre-determined locations on the boundary lines where the features should be matched. The results show that the proposed approach is suitable for most edge-matching situations where the connecting feature points are available. Problematic cases include situations, where the features are alternating across the border and cases where the features don’t reach near enough to the border line. In the proposed approach, the edge-matching is executed simply by moving selected line end points to the locations of connecting feature points. In future, the process could be improved by adopting conflation methods that produce visually smoother results and extending the edge-matching functionality to cover also polygonal features.
  • Mäkinen, Ville; Oksanen, Juha; Sarjakoski, Tapani (Stichting AGILE, 2019)
    The digital elevation model (DEM) is an invaluable product in numerous geospatial applications from orthorectification of aerial photographs to hydrological modelling and advanced 3D visualisation. With the current aerial laser scanning methods, superior quality digital elevation models can be produced over land areas, but surfaces over water bodies are visually problematic, especially for streams in 3D. We present a method to generate smooth, monotonically decreasing elevation surfaces over water bodies in DEMs. The method requires the point cloud data and the polygons delineating the water bodies as input data. We show how DEM visualisations improve by applying the presented method.
  • Linty, Nicola; Dovis, Fabio (MDPI, 2019)
    Applied Sciences
    The quality of positioning services based on Global Navigation Satellite Systems (GNSS) is improving at a fast pace, driven by the strict requirements of a plethora of new applications on accuracy, precision and reliability of the services. Nevertheless, ionospheric errors still bound the achievable performance and better mitigation techniques must be devised. In particular, the harmful effect due to non-uniform distribution of the electron density that causes amplitude and phase variation of the GNSS signal, usually named as scintillation effects. For many high-accuracy applications, this is a threat to accuracy and reliability, and the presence of scintillation effect needs to be constantly monitored. To this purpose, traditional receivers employ closed-loop tracking architectures. In this paper, we investigate an alternative architecture and a related metric based on the statistical processing of the received signal, after a code-wipe off and a noise reduction phase. The new metric is based on the analysis of the statistical features of the conditioned signal, and it brings the same information of the S4 index, normally estimated by means of closed-loop receivers. This new metric can be obtained at a higher rate as well as in the case of strong scintillations when a closed-loop receiver would fail the tracking of the GNSS signals.
  • Bhuiyan, M. Zahidul. H.; Ferrara, Nunzia Giorgia; Thombre, Sarang; Hashemi, Amin; Pattinson, M.; Dumville, M.; Alexandersson, M.; Axell, E.; Eliardsson, P.; Pölöskey, M.; Manikundalam, V.; Lee, S.; Reyes Gonzalez, J. (European Microwave Association, 2019)
    Proceedings of European Microwave Conference in Central Europe
    The H2020 project STRIKE3 contributes enormously for lifting EU industry and institutions to the premier position in the global market for GNSS interference monitoring, detection, reporting, receiver standardization, applica-tions and services. This has been achieved over the last three years through the deployment and operation of an international GNSS interference monitoring network to capture the scale and state of the problem, and through work with international GNSS partners to develop, nego-tiate, promote and implement standards for GNSS threat reporting and GNSS receiver testing. The achievements of STRIKE3 are based on the following cornerstones: i. STRIKE3 global interference monitoring network, ii. A draft interference reporting standard, iii. A draft receiver testing standard against interference, and iv. Internation-al knowledge sharing and awareness building against interference among key GNSS stakeholders across pub-lic and private sectors. All these aspects will be present-ed herein with greater details.
  • Lehto, Lassi; Kähkönen, Jaakko; Oksanen, Juha; Sarjakoski, Tapani (IARIA, 2019)
    International Conference on Advanced Geographic Information Systems, Applications, and Services
    A viable approach for tackling the challenges of integration and analysis of geospatial raster data is to pre-process datasets into a common framework and store them into a cloud repository, accessible through a set of well-defined access protocols. This paper describes an initiative called GeoCubes Finland, where the aim is to provide a number of country-wide raster geodatasets in a common schema. In addition to more traditional access methods, a custom Application Programming Interface (API) has been designed for supporting the various tasks related to retrieval, use, visualisation and analysis of the contained raster datasets.
  • Kettunen, Pyry; Oksanen, Juha (Taylor & Francis, 2019)
    Cartography and Geographic Information Science
    Animations have become a frequently utilized illustration technique on maps but changes in their graphical loading remain understudied in empirical geovisualization and cartographic research. Animated streamlets have gained attention as an illustrative animation technique and have become popular on widely viewed maps. We conducted an experiment to investigate how altering four major animation parameters of animated streamlets affects people’s reading performance of field maxima on vector fields. The study involved 73 participants who performed reaction-time tasks on pointing maxima on vector field stimuli. Reaction times and correctness of answers changed surprisingly little between visually different animations, with only a few occasional statistical significances. The results suggest that motion of animated streamlets is such a strong visual cue that altering graphical parameters makes only little difference when searching for the maxima. This leads to the conclusion that, for this kind of a task, animated streamlets on maps can be designed relatively freely in graphical terms and their style fitted to other contents of the map. In the broader visual and geovisual analytics context, the results can lead to more generally hypothesizing that graphical loading of animations with continuous motion flux could be altered without severely affecting their communicative power.
  • Puttonen, Eetu; Lehtomäki, Matti; Litkey, Paula; Näsi, Roope; Feng, Ziyi; Liang, Xinlian; Wittke, Samantha; Pandzic, Milos; Hakala, Teemu; Karjalainen, Mika; Pfeifer, Norbert (Frontiers Reseach Foundation, 2019)
    Frontiers in Plant Science
    Terrestrial Laser Scanning (TLS) can be used to monitor plant dynamics with a frequency of several times per hour and with sub-centimeter accuracy, regardless of external lighting conditions. TLS point cloud time series measured at short intervals produce large quantities of data requiring fast processing techniques. These must be robust to the noise inherent in point clouds. This study presents a general framework for monitoring circadian rhythm in plant movements from TLS time series. Framework performance was evaluated using TLS time series collected from two Norway maples (Acer platanoides) and a control target, a lamppost. The results showed that the processing framework presented can capture a plant's circadian rhythm in crown and branches down to a spatial resolution of 1 cm. The largest movements in both Norway maples were observed before sunrise and at their crowns' outer edges. The individual cluster movements were up to 0.17 m (99th percentile) for the taller Norway maple and up to 0.11 m (99th percentile) for the smaller tree from their initial positions before sunset.
  • Peltonen-Sainio, Pirjo; Jauhiainen, Lauri; Honkavaara, Eija; Wittke, Samantha; Karjalainen, Mika; Puttonen, Eetu (Frontiers Reseach Foundation, 2019)
    Frontiers in Plant Science
    Monocultural land use challenges sustainability of agriculture. Pre-crop value indicates the benefits of a previous crop for a subsequent crop in crop sequencing and facilitates diversifi-cation of agricultural systems. Traditional field experiments are resource intensive and evaluate pre-crop values only for a limited number of previous and subsequent crops. We deve-loped a dynamic method based on Sentinel-2 derived Norma-lized Difference Vegetation Index (NDVI) values to estimate pre-crop values on a field parcel scale. The NDVI-values were compared to the region specific 90th percentile of each crop and year and thereby, an NDVI-gap was determined. The NDVI-gaps for each subsequent crop in the case of mo-nocultural crop sequencing were compared to that for other previous crops in rotation and thereby, pre-crop values for a high number of previous and subsequent crop combinations were estimated. The pre-crop values ranged from +16% to -16%. Especially grain legumes and rapeseed were valuable as pre-crops, which is well in line with results from field expe-riments. Such data on pre-crop values can be updated and expanded every year. For the first time, a high number of previous and following crop combinations, originating from farmer’s fields, is available to support diversification of cur-rently monocultural crop sequencing patterns in agriculture.
  • Bhuiyan, Mohammad Zahidul H.; Ferrara, Nunzia Giorgia; Hashemi, Amin; Thombre, Sarang; Pattinson, Michael; Dumville, Mark (MDPI, 2019)
    Sensors
    GNSS-based applications are susceptible to different threats, including radio frequency interference. Ensuring that the new applications can be validated against the latest threats supports the wider adoption and success of GNSS in higher value markets. Therefore, the availability of standardized GNSS receiver testing procedures is central to developing the next generation of receiver technologies. The EU Horizon2020 research project STRIKE3 (Standardization of GNSS Threat reporting and Receiver testing through International Knowledge Exchange, Experimentation and Exploitation) proposed standardized test procedures to validate different categories of receivers against real-world interferences, detected at different monitoring sites. This paper describes the recorded interference signatures, their use in standardized test procedures, and analyzes the result for two categories of receivers, namely mass-market and professional grade. The result analysis in terms of well-defined receiver key performance indicators showed that performance of both receiver categories was degraded by the selected interference threats, although there was considerable difference in degree and nature of their impact.
  • Olsson, Per-Anders; Breili, Kristian; Ophaug, Vegard; Steffen, Holger; Bilker-Koivula, Mirjam; Nielsen, Emil; Oja, Tõnis; Timmen, Ludger (Oxford University Press, 2019)
    Geophysical Journal International
    For the first time, we present a complete, processed compilation of all repeated absolute gravity (AG) observations in the Fennoscandian postglacial land uplift area and assess their ability to accurately describe the secular gravity change, induced by Glacial Isostatic Adjustment (GIA). The dataset spans over more than three decades and consists of 688 separate observations at 59 stations. Ten different organisations have contributed with measurements using 14 different instruments. The work was coordinated by the Nordic Geodetic Commisson (NKG). Representatives from each country collected and processed data from their country, respectively, and all data were then merged to one dataset. Instrumental biases are considered and presented in terms of results from international comparisons of absolute gravimeters. From this dataset, gravity rates of change (g_dot) are estimated for all stations with more than two observations and a timespan larger than two years. The observed rates are compared to predicted rates from a global GIA model as well as the state of the art semi-empirical land uplift model for Fennoscandia, NKG2016LU. Linear relations between observed g_dot and the land uplift, h_dot (NKG2016LU), are estimated from the absolute gravity observations by means of weighted least squares adjustment (WLSA) as well as weighted orthogonal distance regression (WODR). The empirical relations are not significantly different from the modelled, geophysical relation g_dot = 0:03 - 0:163(+-0.016)h_dot. We also present a g_dot -model for the whole Fennoscandian land uplift region. At many stations, the observational estimates of g_dot still suffer from few observations and/or unmodelled environmental effects (e.g. local hydrology). We therefore argue that, at present, the best predictions of GIA-induced gravity rate of change in Fennoscandia are achieved by means of the NKG2016LU land uplift model, together with the geophysical relation between g_dot and h_dot.
  • Karila, Kirsi; Matikainen, Leena; Litkey, Paula; Hyyppä, Juha; Puttonen, Eetu (Taylor & Francis, 2018)
    International Journal of Remote Sensing
    Multispectral airborne laser scanning (MS-ALS) sensors are a new promising source of data for auto-mated mapping methods. Finding an optimal time for data acquisition is important in all mapping applica-tions based on remotely sensed datasets. In this study, three MS-ALS datasets acquired at different times of the growing season were compared for automated land cover mapping and road detection in a suburban area. In addition, changes in the intensity were studied. An object-based random forest classi-fication was carried out using reference points. The overall accuracy of the land cover classification was 93.9% (May dataset), 96.4% (June) and 95.9% (August). The use of the May dataset acquired under leafless conditions resulted in more complete roads than the other datasets acquired when trees were in leaf. It was concluded that all datasets used in the study are applicable for suburban land cover map-ping, however small differences in accuracies between land cover classes exist.
  • Karila, Kirsi; Yu, Xiaowei; Vastaranta, Mikko; Karjalainen, Mika; Puttonen, Eetu; Hyyppä, Juha (Elsevier, 2019)
    ISPRS Journal of Photogrammetry and Remote Sensing
    Satellite images provide spatially explicit information on forest change covering wide areas. In this study, bistatic TanDEM-X (TDX) synthetic aperture radar (SAR) satellite data were used to derive digital surface models (DSMs) of forest areas using SAR interferometry (InSAR). The capability of change features derived from bi-temporal InSAR DSMs to detect forest height (90th percen-tile of canopy height distribution, H90) and density variations was investigated. Moreover, changes in the forest above-ground bio-mass (AGB) were estimated from height changes between two In-SAR DSMs. Bi-temporal airborne laser scanning (ALS) data, aerial orthoimages and an ALS-based AGB change map from a study area in Southern Finland were used as references. The results indicate that the InSAR height change of a forested area correlates more with vegetation density change than with height change. The corre-lation between the InSAR mean height change and the height change feature from ALS was 0.76 at stand level. Correspondingly, the correlation between the InSAR mean height change and the ALS penetration rate change was 0.89. The AGB changes predicted based on InSAR height change agreed well with the reference data; the root-mean-square error (RMSE) was 20.7 Mg/ha (18.5% of the mean biomass in 2012) at stand level and 27.4 Mg/ha (27.0%) for 16 × 16 m grid cells. The results show that TDX DSMs can be used to detect biomass changes of different orders of magnitude, e.g. due to logging and thinning.
  • Mäkinen, Ville; Oksanen, Juha; Sarjakoski, Tapani (Taylor & Francis, 2019)
    International Journal of Geographical Information Science
    Determining stream networks automatically from digital elevation models is an issue that is actively being studied. The quality of elevation models has increased over time, but many hydrologically critical features, such as culverts, are often missing from the elevation data. To analyze the surficial water flow, one must either prepare a special elevation model or post-process an already-existing model. This study builds on the traditional, well-established method of determining the stream network from digital elevation models. We have extended the traditional method by locating culverts automatically, using road network data as an input. We show, by comparison to the reference data, that the culverts being most relevant for the stream network can be found with good accuracy. We demonstrate that by including the automatically located culverts in the automatic stream network determination, the quality of the generated network can be noticeably improved.
  • 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.
  • 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.

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