Search results for "levelling"
showing 8 items of 8 documents
PolyACO+: a multi-level polygon-based ant colony optimisation classifier
2017
Ant Colony Optimisation for classification has mostly been limited to rule based approaches where artificial ants walk on datasets in order to extract rules from the trends in the data, and hybrid approaches which attempt to boost the performance of existing classifiers through guided feature reductions or parameter optimisations. A recent notable example that is distinct from the mainstream approaches is PolyACO, which is a proof of concept polygon-based classifier that resorts to ant colony optimisation as a technique to create multi-edged polygons as class separators. Despite possessing some promise, PolyACO has some significant limitations, most notably, the fact of supporting classific…
CHANGING THE NATIONAL HEIGHT SYSTEM AND GEOID MODEL IN LATVIA
2016
According to the decision of IAG Reference Frame Sub-commission for Europe (EUREF) the EVRF2007 solution as the vertical reference has to be deployed in EU countries.The new height system LAS-2000,5 had been enacted as the European Vertical Reference System‘s EVRF2007 realization in Latvia and the new geoid model LV‘14 had been introduced by Latvian authority Latvian Geospatial Information Agency. However, the appreciation of the quality of quasi-geoid model LV‘14 is rather contradictious among the users in Latvia. The independent estimate and comparison of the two Latvian geoid models developed till now has been performed by the Institute of Geodesy and Geoinformatics. Previous geoid model…
REDESIGN OF AN AUTO-LEVELLING BASE FOR SUBMARINE SEISMIC SENSOR
2011
The OBS (acronym of Ocean Bottom Seismometer) is a system to monitor the submarine seismic activity. To properly work, an OBS system needs a suitable auto-levelling base to maintain a fixed (horizontal) position during the measurement phases. In this work a new auto-levelling base for submarine seismic sensors has been designed. During the redesign process a preliminary phase of analysis of the state of art has been made. Afterwards, the technological solutions chosen by different manufactures have been critically analysed, and a full description of their functionalities, working principles and system performances has been carried out. Later, some innovative concepts have been proposed. Amo…
Development of the One Centimeter Accuracy Geoid Model of Latvia for GNSS Measurements
2015
There is an urgent necessity for a highly accurate and reliable geoid model to enable prompt determination of normal height with the use of GNSS coordinate determination due to the high precision requirements in geodesy, building and high precision road construction development. Additionally, the Latvian height system is in the process of transition from BAS- 77 (Baltic Height System) to EVRS2007 system. The accuracy of the geoid model must approach the precision of about ~1 cm looking forward to the Baltic Rail and other big projects. The use of all the available and verified data sources is planned, including the use of enlarged set of GNSS/levelling data, gravimetric measurement data and…
Levelling Of I-Umlaut in Classical and Post-Classical Old Frisian Nouns
2022
The paper discusses and evaluates the extent of i-umlaut levelling in classical (ca. 1300–1400) and post-classical (ca.1400–1550) Old Frisian nouns. In terms of the methodology, the main goal of the analysis is to identify the quantitative relation between the incidence of i-umlauted and umlautless root vowels in the nominal declension paradigms. In order to understand and assess the process of levelling of i-umlaut in Old Frisian, three aspects that may have had an impact on the presence or absence of i-mutated vowels are taken into account, namely: the presence of the i-mutation trigger *-ī and *-j and *-i, the establishment of whether i-mutation is noticeable in the entire paradigm or it…
Coastal Development of Daugavgrîva Island, Located Near the Gulf of Riga / Rîgas Lîèa Piekrastes Krasta Attîstîba Daugavgrîvas Salâ
2015
Abstract Natural as well as anthropogenic processes impact greatly sensitive coastal areas all over the world. The spectrum of natural processes involved can be classified as meteorological, geological, marine, and lithodynamic. The Baltic Sea with its Gulf of Riga is an area in which combined sea erosion and accumulation processes, as well as alluvial processes, play significant roles in the coastal development. Major anthropogenic processes include impacts from ports and coastal protection structures, such as Riga Port hydraulic structures, fairway channels and coastal defence items. During summer also additional pressure of recreational activities has increased the effect on the coastal …
DFHRS-based computation of quasi-geoid of Latvia
2013
In geodesy, civil engineering and related fields high accuracy coordinate determination is needed, for that reason GNSS technologies plays important role. Transformation from GNSS derived ellipsoidal heights to orthometric or normal heights requires a high accuracy geoid or quasi-geoid model, respectively the accuracy of the currently used Latvian gravimetric quasi-geoid model LV'98 is 6–8 cm. The objective of this work was to calculate an improved quasi-geoid (QGeoid) for Latvia. The computation was performed by applying the DFHRS software. This paper discusses obtained geoid height reference surface, its comparisons to other geoid models, fitting point statistics and quality control based…
Monitoring displacements of an earthen dam using GNSS and remote sensing
2014
This paper shows the results of a scientific research in which a GNSS continuous monitoring system for earth-dam deformations has been developed, then, deformations have been related with reservoir water surface and level. The experiment was conducted near Bivona (Sicily, Italy), on the Castello dam (Magazzolo Lake). On the top of the dam three control points were placed and three GNSS permanent stations were installed. The three stations continuously transmitted data to the control centre of the University of Palermo. The former has been determined using freely available satellite data (specifically Landsat 7 SLC-Off) collected during the whole study period (DOYs 101 to 348 2011). Issues r…