EURO-ECO 2010 Hanover 2 - 3 Dezember 2010	Environmental, Engineering - Economic and Legal Aspects for Sustainable Living
	European Academy of Natural Sciences, Hanover European Scientific Society, Hanover University of Bremen, Bremen

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The behaviour of the planet Earth has been continuously studied by geodesists using various techniques and methods on the ground, air and space. These studies reflect the global and local environmental changes caused by both the natural sources and the influence of mankind and its industrial activities. The Institute of Geodesy and Geoinformation of the University of Latvia (LU GGI) applies the space related technologies for the environmental studies in Latvia. The paper presents the techniques and methods developed and used at the Institute of Geodesy and Geoinformation for the ongoing environmental studies.

The small size modern satellite laser ranging system (SLR) and it’s control software has been developed at the Institute recently. It will be used for the regular observations of low Earth orbiters (LAGEOS, GOCE, GRACE, ERS2, ENVISAT, CRYOSAT, etc.) within the framework of ILRS. The test observations have proved the results of high quality. The developed SLR could be used as a mobile SLR as well for the transportation to the sites where and when the proper interest arises.

Application of Global Navigation Satellite Systems (GNSS) in geodesy discovers a powerful tool for the verification and validation of the historically long time ago established geodetic levelling benchmarks. The differential GNSS and RTK methods appear very useful to identify the vertical displacement of landscape by means of inspection of the deformation of levelling networks. Within the framework of ground based GNSS European positioning augmentation system EUPOS^® the local EUPOS^®-Riga continuously operating geodetic reference system has been developed in cooperation with a Rigas GeoMetrs land surveying company. The system consists of 5 GNSS base station network. The system has been properly investigated and controlled. The GNSS observation RTCM corrections produced by the EUPOS^®-Riga can be used for high precision position determination in various navigation and land surveying applications.

Recently we have applied the real time kinematics (RTK) measurements for the studies of the earth vertical movement which is to some extent reflected by the state of levelling network. The deformation of Riga levelling network may be caused by the vertical movement of local earth surface. The tectonic continental and intercontinental movement of the earth core is available as well. There are several effects of vertical movement in urban environment. Development of the new building construction, increase of traffic intensities and both the geologic and hydrogeologic conditions in upper layers of ground are additional sources of the up or down movement of earth surface. The vertical movement could be controlled by height determination of levelling benchmarks. The criteria of Mean Sea Level not always is highly useful. The mean Baltic Sea level has risen by 26 cm during 100 years according the records of Riga tide gauge station. It is placed near the Daugava river estuary where the water level changes depending of the work regime at the Riga hydroelectric power station placed on the Daugava river at a distance of about 20 km. Therefore it is rather difficult to fix the real value of mean sea level. It is influenced by the artificially changing water level of river Daugava.

Additional tool for the independent height determination is the application of both the GNSS applied positioning and Satellite Laser Ranging System (SLR) observations.

The high precision geoid model is essential for the normal height determination when the GNSS positioning methods are used. In order to improve the Latvian geoid model quality and accuracy we are taking part in ESA performed GOCE mission. Additionally, we have commenced the development of mobile zenith telescope for determination of vertical deflection. It will serve for the studies of anomalies of regional gravitation field.

At the LU GGI there is a skilled personnel of developers of the geographic information system 2D and 3D data bases for Riga city and for entire Latvia.

All the developments carried out at the Institute of Geodesy and Geoinformation serve for the studies and for monitoring of the environmental changes. The ongoing process is accelerated in cooperation with a Riga Technical University (RTU). The staff of Institute taking part in education of Geomatics bachelor, master and PhD students in RTU and LU. The students of RTU and LU taking part in research of LU GGI.

 

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