Multisource Point Clouds, Point Simplification and Surface Reconstruction

As data acquisition technology continues to advance, the improvement and upgrade of the algorithms for surface reconstruction are required. In this paper, we utilized multiple terrestrial Light Detection And Ranging (Lidar) systems to acquire point clouds with different levels of complexity, namely dynamic and rigid targets for surface reconstruction. We propose a robust and effective method to obtain simplified and uniform resample points for surface reconstruction. The method was evaluated. A point reduction of up to 99.371% with a standard deviation of 0.2 cm was achieved. In addition, well-known surface reconstruction methods, i.e., Alpha shapes, Screened Poisson reconstruction (SPR), the Crust, and Algebraic point set surfaces (APSS Marching Cubes), were utilized for object reconstruction. We evaluated the benefits in exploiting simplified and uniform points, as well as different density points, for surface reconstruction. These reconstruction methods and their capacities in handling data imperfections were analyzed and discussed. The findings are that (i) the capacity of surface reconstruction in dealing with diverse objects needs to be improved; (ii) when the number of points reaches the level of millions (e.g., approximately five million points in our data), point simplification is necessary, as otherwise, the reconstruction methods might fail; (iii) for some reconstruction methods, the number of input points is proportional to the number of output meshes; but a few methods are in the opposite; (iv) all reconstruction methods are beneficial from the reduction of running time; and (v) a balance between the geometric details and the level of smoothing is needed. Some methods produce detailed and accurate geometry, but their capacity to deal with data imperfection is poor, while some other methods exhibit the opposite characteristics

Feasibility of Mobile Laser Scanning towards Operational Accurate Road Rut Depth Measurements

This paper studied the applicability of the Roamer-R4DW mobile laser scanning (MLS) system for road rut depth measurement. The MLS system was developed by the Finnish Geospatial Research Institute (FGI), and consists of two mobile laser scanners and a Global Navigation Satellite System (GNSS)-inertial measurement unit (IMU) positioning system. In the study, a fully automatic algorithm was developed to calculate and analyze the rut depths, and verified in 64 reference pavement plots (1.0 m x 3.5 m). We showed that terrestrial laser scanning (TLS) data is an adequate reference for MLS-based rutting studies. The MLS-derived rut depths based on 64 plots resulted in 1.4 mm random error, which can be considered adequate precision for operational rutting depth measurements. Such data, also covering the area outside the pavement, would be ideal for multiple road environment applications since the same data can also be used in applications, from high-definition maps to autonomous car navigation and digitalization of street environments over time and in space

Multisource Point Clouds, Point Simplification and Surface Reconstruction

As data acquisition technology continues to advance, the improvement and upgrade of the algorithms for surface reconstruction are required. In this paper, we utilized multiple terrestrial Light Detection And Ranging (Lidar) systems to acquire point clouds with different levels of complexity, namely dynamic and rigid targets for surface reconstruction. We propose a robust and effective method to obtain simplified and uniform resample points for surface reconstruction. The method was evaluated. A point reduction of up to 99.371% with a standard deviation of 0.2 cm was achieved. In addition, well-known surface reconstruction methods, i.e., Alpha shapes, Screened Poisson reconstruction (SPR), the Crust, and Algebraic point set surfaces (APSS Marching Cubes), were utilized for object reconstruction. We evaluated the benefits in exploiting simplified and uniform points, as well as different density points, for surface reconstruction. These reconstruction methods and their capacities in handling data imperfections were analyzed and discussed. The findings are that (i) the capacity of surface reconstruction in dealing with diverse objects needs to be improved; (ii) when the number of points reaches the level of millions (e.g., approximately five million points in our data), point simplification is necessary, as otherwise, the reconstruction methods might fail; (iii) for some reconstruction methods, the number of input points is proportional to the number of output meshes; but a few methods are in the opposite; (iv) all reconstruction methods are beneficial from the reduction of running time; and (v) a balance between the geometric details and the level of smoothing is needed. Some methods produce detailed and accurate geometry, but their capacity to deal with data imperfection is poor, while some other methods exhibit the opposite characteristics

Soranoton vaikutus pohjaveteen. Raportti V: Soranotto ja pohjaveden suojelu

Tutkimukseen liittyvät tutkimusraportit I, II, III ja IV (VYH:n monistesarja) sekä Raportti VI: Pohjavesi ja soranotto (Tutkimusraportti 1 / 1993. Ympäristöministeriö, kaavoitus- ja rakennusosasto

Sense of presence and sense of place in perceiving a 3D geovisualization for communication in urban planning – Differences introduced by prior familiarity with the place

Technological development towards increased visual quality and accessibility has made photorealistic 3D geovisualizations an interesting tool for communication in urban planning. Particularly the ability to support perception is important in assessing 3D geovisualizations’ effectiveness for communication. We applied both the concept of sense of presence, i.e. effectiveness of the medium, and sense of place, i.e. meanings and affordances, in a user study conducted through a web-based 3D geovisualization. The study addressed a shopping mall in Helsinki, Finland. We collected a sample of adolescent respondents (n = 122), both familiar and unfamiliar with the geovisualized place in question. Adolescents responded to a survey addressing their perceptions of the mall after the virtual visit. The results indicate that prior familiarity with the place affects the results with the sense of presence, sense of place and preferred urban planning outcome. Familiar respondents were more likely to prefer preservation of the mall. The results show how sense of presence and sense of place work in interplay in the perception of a photorealistic 3D geovisualization. Perception is not only dependent on the realism the 3D geovisualization is able to transmit but also on the individual knowledge and experiences of the audience. According to the results, 3D geovisualizations are best used as supportive tools in communication for urban planning and secondary to a real visit.</p

Auditing an urban park deck with 3D geovisualization—A comparison of in-situ and VR walk-along interviews

Virtual reality-based urban audit methods are gaining increasing attention; however, most virtual urban audit studies have focused on panoramic views. The 3D city model-based geovisualizations have remained until now rather unexplored in user studies for urban audits and for communicative urban planning. We explored the feasibility of a 3D geovisualization-based urban audit in virtual reality (VR) for assessing the perceived quality of an urban park deck in Helsinki, Finland. For this purpose, we created a photorealistic and geometrically accurate 3D model (Bryga 3D) based on photogrammetric and laser scanning data. Bryga 3D was implemented on a game engine to be viewed with a head-mounted VR display. Bryga 3D's ability to convey information in a subjective urban audit, that is, subjectively perceived affordances of a park deck, was tested in a walk-along interview study comparing auditing in situ and via the VR method. A comparison of the results with in-situ (n = 13) and VR interviews (n = 21) show that the perception of several tangible elements, such as spatial division, landforms, paths, and chairs when using Bryga VR was similar to when performed in situ. Perception of vegetation was weaker in VR in terms of its detailed quality, which somewhat affected the presented development ideas and assessment of the seasonal context. Also, weaker perception of the surroundings and city context affected the results in VR. However, considering that Bryga 3D presents an example of a highly automated 3D city modeling process conducted with minimal manual work, its results are encouraging for future attempts to advance such realizations for the purposes of communicative urban planning. 3D geovisualization-based virtual audits could be used when urban green space audits are not possible or when they are demanding to implement in situ.</p

Under-canopy UAV laser scanning for accurate forest field measurements

Surveying and robotic technologies are converging, offering great potential for robotic-assisted data collection and support for labour intensive surveying activities. From a forest monitoring perspective, there are several technological and operational aspects to address concerning under-canopy flying unmanned airborne vehicles (UAV). To demonstrate this emerging technology, we investigated tree detection and stem curve estimation using laser scanning data obtained with an under-canopy flying UAV. To this end, we mounted a Kaarta Stencil-1 laser scanner with an integrated simultaneous localization and mapping (SLAM) system on board an UAV that was manually piloted with the help of video goggles receiving a live video feed from the onboard camera of the UAV. Using the under-canopy flying UAV, we collected SLAM-corrected point cloud data in a boreal forest on two 32 m  32 m test sites that were characterized as sparse ( = 42 trees) and obstructed ( = 43 trees), respectively. Novel data processing algorithms were applied for the point clouds in order to detect the stems of individual trees and to extract their stem curves and diameters at breast height (DBH). The estimated tree attributes were compared against highly accurate field reference data that was acquired semi-manually with a multi-scan terrestrial laser scanner (TLS). The proposed method succeeded in detecting 93% of the stems in the sparse plot and 84% of the stems in the obstructed plot. In the sparse plot, the DBH and stem curve estimates had a root-mean-squared error (RMSE) of 0.60 cm (2.2%) and 1.2 cm (5.0%), respectively, whereas the corresponding values for the obstructed plot were 0.92 cm (3.1%) and 1.4 cm (5.2%). By combining the stem curves extracted from the under-canopy UAV laser scanning data with tree heights derived from above-canopy UAV laser scanning data, we computed stem volumes for the detected trees with a relative RMSE of 10.1% in both plots. Thus, the combination of under-canopy and above-canopy UAV laser scanning allowed us to extract the stem volumes with an accuracy comparable to the past best studies based on TLS in boreal forest conditions. Since the stems of several spruces located on the test sites suffered from severe occlusion and could not be detected with the stem-based method, we developed a separate work flow capable of detecting trees with occluded stems. The proposed work flow enabled us to detect 98% of trees in the sparse plot and 93% of the trees in the obstructed plot with a 100% correction level in both plots. A key benefit provided by the under-canopy UAV laser scanner is the short period of time required for data collection, currently demonstrated to be much faster than the time required for field measurements and TLS. The quality of the measurements acquired with the under-canopy flying UAV combined with the demonstrated efficiency indicates operational potential for supporting fast and accurate forest resource inventories.</p

An International Comparison of Individual Tree Detection and Extraction using Airborne Laser Scanning

The objective of the “Tree Extraction” project organized by EuroSDR (European Spatial data Research) and ISPRS (International Society of Photogrammetry and Remote Sensing) was to evaluate the quality, accuracy, and feasibility of automatic tree extraction methods mainly based on laser scanner data. In the final report of the project, Kaartinen and Hyyppä (2008) reported a high variation in the quality of the published methods under boreal forest conditions and with varying laser point densities. This paper summarizes the findings beyond the final report after analyzing the results obtained in different tree height classes. Omission / Commission statistics as well as neighborhood relations are taken into account. Additionally four automatic tree detection and extraction techniques were added to the test. Several methods in this experiment were superior to manual processing in the dominant, co-dominant and suppressed tree storeys. In general, as expected, the taller the tree, the better the location accuracy. The accuracy of tree height, after removing gross errors, was better than 0.5m in all tree height classes with the best methods investigated in this experiment. For forest inventory, minimum curvature-based tree detection accompanied by point cloud -based cluster detection for suppressed trees is a solution that deserves attention in the future.Peer reviewe

3D-mittaukseen perustuva karjan tarkkailu

Maatiloille on jo tarjolla digitaalisia ratkaisuja, mutta uusia digitalisaatiota ja älyteknologiaa hyödyntäviä innovaatioita tarvitaan lisää. Peltojen täsmäviljelyn lisäksi yksi selkeä kokonaisuus uuden teknologian hyödyntämisessä on tuotantoeläinten seuranta maatiloilla. "3D-mittaukseen perustuva karjantarkkailu" on esiselvityshanke, jonka tavoitteena on tutkia fotogrammetrian eli kuvilta mittaamisen soveltuvuutta naudan rakenteen mittaamiseen.Eläinten 3D-mittaukseen liittyy huomioon otettavia erityispiirteitä: 1) Miten määritellään mitattavan eläimen mitat, mikäli eläimellä on niin paksu turkki, että oikeiden mittojen havainnointi koskettamatta on vaikeaa. 2) Mittaus on toteutettava useilla eri mittalaitteilla samanaikaisesti, jotta mallista saadaan lyhyessä ajassa kattava. 3) Mittauksen keston on oltava erittäin lyhyt, koska kohde ei tietoisesti osaa pysytellä liikkumattomana. 4) Eläinten hyvinvointi mittaamisen aikana ei vaarannu. Navettaympäristön haasteita ovat mm. kameran sijoittaminen, mittauksen esteenä olevat rakenteet, eläinten liikkuminen ryhmissä ja valaistus.Esiselvityshankkeessa tutkitaan niitä toimintatapoja, joita tarvitaan eläimen rakenteen mittaukseen maatilalla. Hankkeessa selvitetään tietojen tallentamista sähköisesti järjestelmään, josta tieto olisi luettavissa paikasta ja ajasta riippumatta. 3D-mittausteknologian avulla pyritään saamaan objektiivinen näkemys naudan rakenteesta. Eläimestä eri ajanjaksoina otettuja kuvia vertaamalla voidaan seurata sen kuntoluokan ja kasvun kehitystä. Kuvasarjoista voidaan myös havaita poikkeamia eläimen normaalista kunnosta ja tietoa voidaan hyödyntää sairauksien ehkäisemisessä.Erilaisia fotogrammetriaan perustuvia mittaustekniikoita kokeillaan Seinäjoen Ammattikorkeakoulun Ilmajoen kampuksen tutkimusnavetassa ja eteläpohjalaisilla maitotiloilla. Hankkeeseen osallistuvilta tiloilta voidaan kerätä ainutlaatuista tietoa eläinaineksen ja eläinten hyvinvoinnin kehittämiseen. Samalla selvitetään, soveltuuko valittu teknologia tulevaisuudessa helpottamaan jalostusasiantuntijoiden ja eläinlääkäreiden työtä sekä hyödyttämään maatilayrittäjiä