Solid image extraction from LIDAR point clouds

In laser scanner architectural surveying it is necessary to extract orthogonal projections from the tridimensional model, plans, elevations and cross sections. The paper presents the workflow of architectural drawings production from laser scans, focusing on the orthogonal projection of the point cloud on solid images, in order to avoid the time consuming surface modeling, when it is not strictly necessary. The proposed procedures have been implemented in fortran90 and included in the VELOCE software package, then tested and applied to the case study of the San Pietro church in Porto Venere (SP), integrating the architectural surveying with an existing bathymetric and coastal surveyin

Extensive analysis of IGS REPRO1 coordinate time series

The work describes the analysis conducted on the IGS REPRO1 coordinate time series, in order to detect GNSS permanent stations periodic behavior. Frequency analysis requires cyclostationary time series, while observed coordinates time series are not cyclostationary because of discontinuities of different kind and origin and of long term linear or non linear trend. For this reason time series offsets and trends must be estimated and eliminated, prior to conduct the harmonic analysis. Discontinuities are usually documented by IGS, but undocumented discontinuities also exists and need to be detected. The long term component of the signal is generally modeled as a linear trend, but the linear model is often inadequate to obtain cyclostationary residuals. An alternative model based on a discrete time Markov process will be adopted. The study has been conducted on the up component of the REPRO1 raw coordinates time series. No correction for the atmospheric pressure loading has been applied. Harmonic analysis has been performed using the non linear least square algorithm implemented by F. Mignard in the Frequency Analysis Mapping On Unusual Sampling software (Mignard, FAMOUS, Frequency Analysis Mapping on Unusual Sampling, (OCA Cassiopee), 2003). We obtained a complete statistic on the vertical component period, amplitude and phase. Signals at from 1 to 7 cycle per solar and draconitic year can be observed in most stations as expected, but also other signals have been detected that can be attributed to tidal model errors. Some interpretation will be given referring to recent literature

Extensive analysis of IGS REPRO1 coordinate time series

The work describes the analysis conducted on the IGS REPRO1 coordinate time series, in order to detect GNSS permanent stations periodic behavior. Frequency analysis requires cyclostationary time series, while observed coordinates time series are not cyclostationary because of discontinuities of different kind and origin and of long term linear or non linear trend. For this reason time series offsets and trends must be estimated and eliminated, prior to conduct the harmonic analysis. Discontinuities are usually documented by IGS, but undocumented discontinuities also exists and need to be detected. The long term component of the signal is generally modeled as a linear trend, but the linear model is often inadequate to obtain cyclostationary residuals. An alternative model based on a discrete time Markov process will be adopted. The study has been conducted on the up component of the REPRO1 raw coordinates time series. No correction for the atmospheric pressure loading has been applied. Harmonic analysis has been performed using the non linear least square algorithm implemented by F. Mignard in the Frequency Analysis Mapping On Unusual Sampling software (Mignard, FAMOUS, Frequency Analysis Mapping on Unusual Sampling, (OCA Cassiopee), 2003). We obtained a complete statistic on the vertical component period, amplitude and phase. Signals at from 1 to 7 cycle per solar and draconitic year can be observed in most stations as expected, but also other signals have been detected that can be attributed to tidal model errors. Some interpretation will be given referring to recent literature

Quality Assessment of DJI Zenmuse L1 and P1 LiDAR and Photogrammetric Systems: Metric and Statistics Analysis with the Integration of Trimble SX10 Data

This manuscript focuses on a quality assessment of DJI’s new sensors: the Zenmuse L1 and P1, which are LiDAR and photographic payload sensors, respectively, for UAVs/UASs. In particular, metric and statistical analyses aim to evaluate the data obtained from different 3D survey instruments. Furthermore, we compared these sensors with TLS data derived from a Trimble SX10 scanning station. The integration of LiDAR and photogrammetric data was then performed and tested inside a complex architectural context, the medieval Frinco Castle (AT-Italy). Point clouds obtained from aerial and terrestrial instruments were analysed and compared using specific tools to calculate variance/distance between points and cloud alignment (via the ICP algorithm), as well as to perform qualitative estimations (especially roughness analysis). The medieval castle proved crucial for the purpose of analysing different metric data of an extremely complex architecture and achieving more accurate results. The collected dataset and performed analyses are now essential information for the consolidation and restoration programme

State of the art in digitization of historical maps and analysis of their metric content

The present work discuss the digitization and georeferencing of the cartographic heritage preserved in the public archives, with special attention to image quality, support deformation analysis and metric content verification. The use of the photogrammetric techniques is suggested, with some applications to the Sabaudian cadastre

Impiego di aerei ultraleggeri e camere di medio formato per la fotogrammetria aerea a grande scala

Nella fotogrammetria a grande e grandissima scala l'acquisizione dei dati primari, immagini metriche e parametri di orientamento, può essere convenientemente effettuata anche con mezzi di basso o medio costo alla portata di piccole aziende. Tale possibilità è dovuta particolarmente all'attuale disponibilità di piattaforme aeree a basso costo, con o senza pilota, largamente sperimentate in questi ultimi anni nel campo del rilievo dell'archeologia e del monitoraggio delle emergenze ambientali. Qui si è voluto valutare l'impiego sperimentale di aerei ultraleggeri, piuttosto diffuso all'estero, in unione con camere digitali di buona risoluzione, ma di costo relativamente contenuto. In particolare si è valutata la possibilità di realizzare la cartografia a grande scala di piccoli centri abitati in zona collinare, realizzando una carta dei tetti in scala 1:1000 di una borgata piemontese. Al costo molto contenuto dell'aereo ultraleggero e della camera digitale fa purtroppo contrasto la normativa vigente che ne impedisce l'impiego a fini produttiv

Comparison of ITRF2014 station coordinate input time series of DORIS, VLBI and GNSS

In this paper station coordinate time series from three space geodesy techniques that have contributed to the realization of the International Terrestrial Reference Frame 2014 (ITRF2014) are compared. In particular the height component time series extracted from official combined intra-technique solutions submitted for ITRF2014 by DORIS, VLBI and GNSS Combination Centers have been investigated. The main goal of this study is to assess the level of agreement among these three space geodetic techniques. A novel analytic method, modeling time series as discrete-time Markov processes, is presented and applied to the compared time series. The analysis method has proven to be particularly suited to obtain quasi-cyclostationary residuals which are an important property to carry out a reliable harmonic analysis. We looked for common signatures among the three techniques. Frequencies and amplitudes of the detected signals have been reported along with their percentage of incidence. Our comparison shows that two of the estimated signals, having one-year and 14 days periods, are common to all the techniques. Different hypotheses on the nature of the signal having a period of 14 days are presented. As a final check we have compared the estimated velocities and their standard deviations (STD) for the sites that co-located the VLBI, GNSS and DORIS stations, obtaining a good agreement among the three techniques both in the horizontal (1.0 mm/yr mean STD) and in the vertical (0.7 mm/yr mean STD) component, although some sites show larger STDs, mainly due to lack of data, different data spans or noisy observations

Stakeholder Analysis for Sharing Agro-environment Issues Towards Concerted Action: A Case Study on Diffuse Nitrate Pollution

There is increasing need for participatory approaches to support the development of sustainable farming systems, based on the active involvement of stakeholders in the definition of research objectives and priorities. This paper reports the experience of a team of agronomy researchers involved in the SLIM project (http://slim.open.ac.uk), around a case study of nitrate pollution. The agro-ecosystem analysis included biophysical processes at microcatchment scale and the stakeholders' perceptions, interests and practices related to the nitrate issue (stakeholders analysis). The conceptual SLIM framework model supported new interactions among stakeholders, that were facilitated by researchers, using dialogical tools to enable them to use scientific data and to integrate their own knowledge on the farming system. The agro-environment policies, based on compulsory prescriptions, revealed weak assumptions and insufficient integration of scientific knowledge. The stakeholder analysis contributed to the identification of priorities both for scientific research and agro-environment policies. Researchers provided the site-specific scientific knowledge, in a way that enabled stakeholders to identify the relationships between agricultural practices, landscape values and the nitrate pollution issue and to elaborate shared strategies to develop concerted actions. New spaces for interaction between researchers and stakeholders should be created to face complex agro-environment issues at catchment scale, such as the nitrate pollution of groundwater. The implication for agronomy research is that the experiments should be designed to produce suitable results to facilitate participatory sessions and that it is worthwhile to invest in specific skills of communication science and group dynamics management within the agronomy researchers' community, in order to integrate agronomy knowledge into high quality participatory processes

A review on non iterative closed form configuration matching and rotations estimation

Orthonormal matrices, Procrustes and quaternion analysis are closed form solutions of the configuration matching problem, common in geodesy as in the datum transformation problem. Literature reports more Procrustes based geodetic applications than Quaternions, which are more used in other application fields, such as aerospace navigation, robotics and computer vision. The large popularity of Procrustes in geodesy is mainly due to its capability to take into account a priori observation weighting in a simple wa