Maanmittauslaitos: Recent submissions

Now showing items 1-20 of 436
  • Koivula, Hannu (Aalto University, Department of Built Environment, 2019)
    FGI Publications 159
  • Jakobsson, Antti; Lehto, Lassi (2021)
    Positio
  • Kukko, Antero; Kaartinen, Harri; Hyyppä, Hannu (2021)
    Positio
  • Ouattara, Issouf; Hyyti, Heikki; Visala, Arto (Elsevier, 2020)
    IFAC-PapersOnLine, Proceedings of the 21th IFAC World Congress, Berlin, Germany, 12-17 July 2020
    We propose a novel method to locate spruces in a young stand with a low cost unmanned aerial vehicle. The method has three stages: 1) the forest area is mapped and a digital surface model and terrain models are generated, 2) the locations of trees are found from a canopy height model using local maximum and watershed algorithms, and 3) these locations are used in a convolution neural network architecture to detect young spruces. Our result for detecting young spruce trees among other vegetation using only color images from a single RGB camera were promising. The proposed method is able to achieve a detection accuracy of more than 91%. As low cost unmanned aerial vehicles with color cameras are versatile today, the proposed work is enabling low cost forest inventory for automating forest management.
  • Sandru, Andrei; Hyyti, Heikki; Visala, Arto; Kujala, Pentti (Elsevier, 2020)
    IFAC-PapersOnLine, Proceedings of the 21th IFAC World Congress, Berlin, Germany, 12-17 July 2020
    A sensor instrumentation and an automated process are proposed for sea-ice field analysis using ship mounted machine vision cameras with the help of inertial and satellite positioning sensors. The proposed process enables automated acquisition of sea-ice concentration, floes size and distribution. The process contains pre-processing steps such as sensor calibration, distortion removal, orthorectification of image data, and data extraction steps such as sea-ice floe clustering, detection, and analysis. In addition, we improve the state of the art of floe clustering and detection, by using an enhanced version of the k-means algorithm and the blue colour channel for increased contrast in ice detection. Comparing to manual visual observations, the proposed method gives significantly more detailed and frequent data about the size and distribution of individual floes. Through our initial experiments in pack ice conditions, the proposed system has proved to be able to segment most of the individual floes and estimate their size and area.
  • Bilker-Koivula, Mirjam (Unigrafia Oy, 2021)
    FGI Publications
    Positioning using Global Navigation Satellite Systems (GNSS) is widely used nowadays and it is getting more and more accurate. This requires also better geoid models for the transformation between heights measured with GNSS and heights in the national height system. In Finland heights are continuously changing due to the Fennoscandian postglacial rebound. Land uplift models are developed for the Fennoscandian land uplift area, not only for the vertical velocities, but also for the gravity change related to postglacial rebound. In this dissertation geoid studies were carried out in search of the geoid model that is most suitable for the conversion of GNSS heights in the EUREF-FIN coordinate system to heights in the Finnish height system N2000 on land as well as on sea. In order to determine the relationship between gravity change rates and vertical velocities, time series of absolute gravity measurements were analysed. Methods were tested for fitting a geoid model to GNSS-levelling data. The best method for Finland was found to be least-squares collocation in combination with cross-validation. The result was the height conversion surface FIN2005N00, the official model for Finland. Then, high-resolution global gravity field models were tested in geoid modelling for Finland. The resulting geoid models were better than the earlier geoid models for Finland. After correcting for an offset and tilt, the differences with other models disappeared. Also, a method was developed to validate geoid models at sea using GNSS measurements collected on a vessel. The method was successful and key elements were identified for the process of reducing the GNSS observations from the height of observation down to the geoid surface. Possible offsets between different types of absolute gravimeters were investigated by looking at the results of international comparisons, bi-lateral comparisons and of trend calculations. The trend calculations revealed significant offsets of 31.4 ± 10.9 μGal, 32.6 ± 7.4 μGal and 6.8 ± 0.8 μGal for the IMGC, GABL and JILAg-5 instruments. The time series of absolute gravity measurements at 12 stations in Finland were analysed. At seven stations reliable trends could be determined. Ratios between -0.206 ± 0.017 and -0.227 ± 0.024 μGal/mm and axis intercept values between 0.248 ± 0.089 and 0.335 ± 0.136 μGal/yr were found for the relationship between gravity change rates and vertical velocities. These values are larger than expected based on results of others. The knowledge obtained in the geoid studies will be of benefit in the determination of the next generation geoid models and height conversion surfaces for Finland. Before clear conclusions can be drawn from the absolute gravity results, more studies related to glacial isostatic adjustment, and longer high-quality time series from more stations in Finland, as well as the whole of the uplift area and its boundaries, are needed.
  • Kakkuri, Juhani (Maanmittauslaitos, 2021)
    FGI Publications
  • Koski, Christian; Rönneberg, Mikko; Kettunen, Pyry; Eliasen, Søren; Hansen, Henning Sten; Oksanen, Juha (John Wiley & Sons, 2021)
    Transactions in GIS
    Maritime spatial planning (MSP) needs tools to facilitate discussions and manage spatial data in collaborative workshops that involve actors with various backgrounds and expertise. However, the reported use of spatial tools in real‐world MSP is sparse. A better understanding is needed of how geographic information systems (GIS) can effectively support collaboration in MSP. We studied the utility of GIS tools for collaborative MSP in five steps: first, identifying shortcomings in available GIS for supporting collaborative MSP; second, defining requirements for an effective collaborative GIS (CGIS) for MSP; third, designing and developing a prototype CGIS, Baltic Explorer; fourth, demonstrating the system; and fifth, evaluating the system. In a real‐world MSP workshop, we demonstrated that the functionalities of Baltic Explorer can support and facilitate discussions in collaborative work. We also found that more research is needed about the use of spatial data in collaborative MSP and integration of model‐based geospatial analysis into CGIS.
  • Saari, Timo; Bilker-Koivula, Mirjam; Koivula, Hannu; Nordman, Maaria; Häkli, Pasi; Lahtinen, Sonja (Taylor & Francis, 2021)
    Marine Geodesy
    Traditionally, geoid models have been validated using GNSS-levelling benchmarks on land only. As such benchmarks cannot be established offshore, marine areas of geoid models must be evaluated in a different way. In this research, we present a marine GNSS/gravity campaign where existing geoid models were validated at sea areas by GNSS measurements in combination with sea surface models. Additionally, a new geoid model, calculated using the newly collected marine gravity data, was validated. The campaign was carried out with the marine geology research catamaran Geomari (operated by the Geological Survey of Finland), which sailed back and forth the eastern part of the Finnish territorial waters of the Gulf of Finland during the early summer of 2018. From the GNSS and sea surface data we were able to obtain geoid heights at sea areas with an accuracy of a few centimetres. When the GNSS derived geoid heights are compared with geoid heights from the geoid models differences between the respective models are seen in the most eastern and southern parts of the campaign area. The new gravity data changed the geoid model heights by up to 15 cm in areas of sparse/non-existing gravity data.
  • Adekola, Oluwafemi; Krigsholm, Pauliina; Riekkinen, Kirsikka (Elsevier, 2021)
    Land Use Policy
    Land laws provide a legal basis for addressing a country’s land-related strategies and are the central land policy instruments through which governments realise land policy objectives. Considering their vital role, it is imperative that land laws be evaluated to ensure that policy objectives are followed and that the laws are not ineffective or counterproductive. The extant literature, however, provides only a fragmentary basis for evaluation. The present study addresses this gap and constructs a novel framework to support the holistic evaluation of land law performance in the context of sub-Saharan Africa (SSA). The framework was developed through a review of systematically selected literature on land laws in SSA. Four key evaluation perspectives emerged: land access; land tenure; land use and development; and land administration institutions. The framework was then used to assess the overall performance of Rwanda’s Organic Land Law (OLL) 2005 through a content analysis of secondary data on the land reform outcomes. The OLL application suggests that the framework may provide stakeholders with insights into the overall effects of land law and potential areas of improvement. However, the framework must be further explored in various cases of SSA countries to validate its functionality.
  • Bilker-Koivula, Mirjam; Mäkinen, Jaakko; Ruotsalainen, Hannu; Näränen, Jyri; Saari, Timo (Springer, 2021)
    Journal of Geodesy
    Postglacial rebound in Fennoscandia causes striking trends in gravity measurements of the area. We present time series of absolute gravity data collected between 1976 and 2019 on 12 stations in Finland with different types of instruments. First, we determine the trends at each station and analyse the effect of the instrument types. We estimate, for example, an offset of 6.8 μgal for the JILAg-5 instrument with respect to the FG5-type instruments. Applying the offsets in the trend analysis strengthens the trends being in good agreement with the NKG2016LU_gdot model of gravity change. Trends of seven stations were found robust and were used to analyse the stabilization of the trends in time and to determine the relationship between gravity change rates and land uplift rates as measured with global navigation satellite systems (GNSS) as well as from the NKG2016LU_abs land uplift model. Trends calculated from combined and offset-corrected measurements of JILAg-5- and FG5-type instruments stabilized in 15 to 20 years and at some stations even faster. The trends of FG5-type instrument data alone stabilized generally within 10 years. The ratio between gravity change rates and vertical rates from different data sets yields values between − 0.206 ± 0.017 and − 0.227 ± 0.024 µGal/mm and axis intercept values between 0.248 ± 0.089 and 0.335 ± 0.136 µGal/yr. These values are larger than previous estimates for Fennoscandia.
  • Saaranen, Veikko; Lehmuskoski, Pekka; Takalo, Mikko; Rouhiainen, Paavo (National Land Survey of Finland, 2021)
    FGI Publications
    The Third Precise Levelling of Finland was performed in 1978–2006 by The Finnish Geodetic Institute (FGI). The levelling network consisted 9158 km of levelled lines including 29 closed loops, 13 side lines to the tide gauges and 21 connections to the neighbouring countries. The mean standard error of the Third Levelling, calculated from the closing errors of the levelling loops, is ±0.86 mm/ √km. In this publication, measuring methods, equipment, computation of the observations, and the adjustments are presented. In the appendices, yearly progress of the measuring work, the rod corrections, and the observations are presented. The new height system N2000 is a realization of a European Vertical Reference System (EVRS). It is a normal height system, where the permanent tidal deformation is in a zero tidal system. The observations were reduced to the epoch 2000.0 using the Nordic land uplift model NKG2005LU. The Normaal Amsterdams Peil (NAP) is a datum of the N2000 height system. The fundamental benchmark PP2000 for the adjustment of the Finnish observations is located in Metsähovi and its height is 54.4233 m. This height was determined by using the Finnish version of the Baltic Levelling Ring adjustment. The N2000 adjustment contained the measurements of the Third Levelling of Finland and some observations of Sweden and Norway near the Finnish border in order to ensure the compatibility of the new height systems between the neighbouring countries.
  • Junttila, Samuli; Hölttä, Teemu; Puttonen, Eetu; Katoh, Masato; Vastaranta, Mikko; Kaartinen, Harri; Holopainen, Markus; Hyyppä, Hannu (Elsevier, 2021)
    Remote Sensing of Environment
    During the past decades, extreme events have become more prevalent and last longer, and as a result drought-induced plant mortality has increased globally. Timely in-formation on plant water dynamics is essential for under-standing and anticipating drought-induced plant mortality. Leaf water potential (ΨL), which is usually measured de-structively, is the most common metric that has been used for decades for measuring water stress. Remote sensing methods have been developed to obtain information on water dynamics from trees and forested landscapes. However, the spatial and temporal resolutions of the existing methods have limited our understanding of the water dynamics and diurnal variation of ΨL within single trees. Thus, we investi-gated the capability of terrestrial laser scanning (TLS) in-tensity in observing diurnal variation in ΨL during a 50-h monitoring period. We aimed to improve the understanding on how large a part of the diurnal variation in ΨL can be captured using TLS intensity observations. We found that TLS intensity at the 905 nm wavelength measured from a static position was able to explain 77% of the variation in ΨL for three trees of two tree species with a root mean square error of 0.141 MPa. Based on our experiment with three trees, a time series of TLS intensity measurements can be used in detecting changes in ΨL, and thus it is worthwhile to expand the investigations to cover a wider range of tree species and forests and further increase our understanding of plant water dynamics at wider spatial and temporal scales.
  • Campos, Mariana Batista; Litkey, Paula; Wang, Yunsheng; Chen, Yuwei; Hyyti, Heikki; Hyyppä, Juha; Puttonen, Eetu (Frontiers Research Foundation, 2021)
    Frontiers in Plant Science
    The terrestrial laser scanner (TLS) has become standard technology for vegetation dynamics monitoring. TLS time series have significant underlying application in investigating structural development and dynamics on a daily and seasonal scale. However, the high potential of TLS for the monitoring of long-term temporal phenomena in fully grown trees with high spatial and temporal resolution has not yet been fully explored. Automated TLS platforms for long-term data collection and monitoring of forest dynamics are rare; and long-term TLS time series data is not yet readily available to potential end-user, such as forestry researchers and plant biologists. This work presents an automated and permanent TLS measurement station that collects high frequency and high spatial resolution TLS time series, aiming to monitor short- and long-term phenological changes at a boreal forestry field station (0.006◦ angular resolution, one scan per hour). The measurement station is the first of its kind considering the scope, accuracy, and length of the time series it produces. The TLS measurement station provides a unique dataset to monitor the 3D physical structure of a boreal forest, enabling new insights into forest dynamics. For instance, the information collected by the TLS station can be used to accurately detect structural changes in tree crowns surrounding the station. These changes and their timing can be linked with the phenological state of plants, such as the start of leaf-out during spring growing season. As the first results of this novel station, we present time series data products collected with the station and what detailed information it provides about the phenological changes in the test site during the leaf sprout in spring.
  • Herrero-Huerta, Mónica; Bucksch, Alexander; Puttonen, Eetu; Rainey, Katy Martin (American Association for the Advancement of Science (AAAS), 2020)
    Plant Phenomics
    Cost-effective phenotyping methods are urgently needed to advance crop genetics in order to meet the food, fuel, and fiber demands of the coming decades. Concretely, charac-terizing plot level traits in fields is of particular interest. Re-cent developments in high resolution imaging sensors for UAS (unmanned aerial systems) focused on collecting de-tailed phenotypic measurements are a potential solution. We introduce canopy roughness as a new plant plot-level trait. We tested its usability with soybean by optical data collect-ed from UAS to estimate biomass. We validate canopy roughness on a panel of 108 soybean [Glycine max (L.) Merr.] recombinant inbred lines in a multienvironment trial during the R2 growth stage. A senseFly eBee UAS platform obtained aerial images with a senseFly S.O.D.A. compact digital camera. Using a structure from motion (SfM) tech-nique, we reconstructed 3D point clouds of the soybean experiment. A novel pipeline for feature extraction was de-veloped to compute canopy roughness from point clouds. We used regression analysis to correlate canopy roughness with field-measured aboveground biomass (AGB) with a leave-one-out cross-validation. Overall, our models achieved a coefficient of determination (R2) greater than 0.5 in all trials. Moreover, we found that canopy roughness has the ability to discern AGB variations among different geno-types. Our test trials demonstrate the potential of canopy roughness as a reliable trait for high-throughput phenotyping to estimate AGB. As such, canopy roughness provides practical information to breeders in order to select pheno-types on the basis of UAS data.
  • Rahkonen, Jukka (2020)
    Positio
  • Jakobsson, Antti (2020)
    Positio
  • Lahtinen, Sonja; Saaranen, Veikko (2020)
    Positio
  • Kivekäs, Riikka (2020)
    Positio