Geodetic Infrastructure Research Articles

Data communication for real-time positioning and navigation in global navigation satellite systems (GNSS)/continuously operating reference stations (CORS) networks

Today, global navigation satellite systems (GNSS), real time differential correction techniques, CORS networks, GNSS user equipments, wireless communications and networking (WCN) systems, cellular systems, mobile navigation and Internet GPS are the systems used for different purposes in scientific, commercial and daily life areas. The latest innovations and developments in these systems play vital role in human life. Especially real-time positioning and navigation applications, mainly in terms of spatial-based applications, networking and telecommunication technologies usage integrated GNSS/CORS networks are increasing in every area. In this paper, we present the classification of GNSS, past and present of GNSS/CORS networks, spatial geodetic infrastructure works in the world, real-time positioning techniques, and communication systems used for them. Key words: Global navigation satellite systems (GNSS), continuously operating reference station (CORS), GNSS/CORS networks, communication technology, real-time applications, positioning, navigation, data transmitting.

USING AN OFFICIAL UNDULATION MODEL FOR ORTHOMETRIC HEIGHT ACQUISITION BY GNSS

Since the beginning of 2006 the vertical control system in Israel has been ellipsoidal. The Survey of Israel constructs and maintains the ellipsoidal vertical control system based on permanent Global Navigation Satellite System (GNSS) stations. Nowadays, the vertical control system's objective of providing a framework upon which topographers and engineers can base and adjust their heights is achieved more easily by GNSS measurements. Despite this, the vertical orthometric control system is still in use since many height data users prefer the orthometric system. However, the characteristics of the orthometric control system are localized.The Geoid Undulation Model is one of the foundations of the geodetic infrastructure. It is used to connect ellipsoidal and orthometric heights. Intensive utilization of GNSS for geodetic, surveying and engineering applications necessitates the rapid development of an undulation model. Today, the efforts to develop a geoid undulation model with an accuracy level of one centimetre over an entire country demand multiple resources. This paper suggests a method for developing an orthometric control system with a reasonable accuracy level on a nationwide basis by means of GNSS measurements, ellipsoidal vertical control and an official geoid undulation model. The best available geoid undulation model can be used as the official geoid undulation model, regardless of its accuracy level.Research was conducted in Israel in order to test the feasibility of the idea of using an official geoid undulation model. Two kinds of official models were tested, the world wide geopotential model GPM98B and a local countrywide model computed by the Survey of Israel. We compared the orthometric height differences obtained by GPS measurements using the undulation model with the known orthometric differences. This paper presents the results of these experiments. It verifies the capability of the suggested technique to define seamless orthometric vertical control, adequate for most geodetic and surveying purposes, via a low-cost and fast procedure.

Geodetic control on Barbados, West Indies

Complete redevelopment of the traditional geodetic infrastructure on the island of Barbados, West Indies, took place in 1968/9 when both angles and distances were observed to provide horizontal control of high order. Observations made in 2007 at selected stations with thirteen GPS operating simultaneously to measure 377 baselines shows that integrity of the network has been retained. Seven transformation parameters are now available to convert between the local datum and WGS84 to an accuracy of 0.15 m. Accuracy of a three parameter transformation is reduced to 0.5m due to a difference of 12" in azimuth between the local datum and WGS84. In the vertical component, height data from traditional control is used with that from the GPS observations and the CARIB97 geoidal model for the region, to refine a height correction model. This is capable of reducing heights from WGS84 to the local land survey datum to an accuracy of 3 cm. Contrary to previous reports, no significant change in sea level with respect to the land survey datum is found. Analysis of data sets used previously suggests that there is more likely a misunderstanding of the reference level adopted for sea level observations. With both horizontal and vertical components of the relationship between WGS84 and the local datum now realised, the survey community can better integrate data from different sources. While some surveyors have made the transition to new technology, the density of existing control points together with the geologically stable conditions, that have preserved integrity, and clear visibility across the island imply that conditions are still suited to traditional surveying methods.

New geodetic infrastructure for Australia

In November 2006, the Australian Federal Government announced $15.8M in funding for geospatial research infrastructure through the National Collaborative Research Infrastructure Strategy (NCRIS). NCRIS is an initiative under the Australian Government's Backing Australia's Ability package with a number of key principles, including maximising the contributions of the R&D system to economic development, national security, social wellbeing and environmental sustainability. Here we outline why particular components of geospatial infrastructure are required in Australia to advance (equip) geospatial research over the next 20 years. We describe some of the scientific objectives that required an upgrade and densification of Australia's geospatial infrastructure. This paper is the perspective from a subset of University researchers involved in the AuScope Geospatial component, and so does not necessarily encompass the opinions of all those involved in AuScope Geospatial.

Geodetic infrastructure - A cooperative future

The Victorian geodetic network is being augmented with dual frequency Global Positioning System base stations, in cooperation with industry, as a part of a state geodetic strategy which anticipates reducing reliance on ground marks. The base station infrastructure development reflects worldwide trends and is in response to changing user needs.

The contribution of GLONASS measurements to regional and continental scale geodetic monitoring regimes

Throughout late 1998 and early 1999, the International GLONASS Experiment (IGEX) has delivered the first comprehensive inter-continental dual frequency GLONASS data set. This experiment represents the first opportunity to assess how a second global satellite positioning system could complement existing GPS geodetic infrastructure. Based on analysis of a three station network of IGEX stations from Southern Hemisphere IGEX stations, this paper discusses the internal and external precision of long baseline GPS, GLONASS and combined GPS/GLONASS solutions, and the possible contribution of GLONASS to future regional-scale geodetic work.

Status of the Australian Geocentric Datum

Abstract Australia is moving towards the introduction of a Geocentric datum as a basis for the national geodetic infrastructure and for mapping to meet international navigation requirements. The Australian Fiducial Network and the Australian National Network of precise GPS points will provide the fixed framework of coordinates on the geocentric system. The current status of the preparation for the change to a Geocentric datum is described