Fitting gravimetric geoid models to vertical deflections

Regional gravimetric geoid and quasigeoid models are now commonly fitted to GPS-levelling data, which simultaneously absorbs levelling, GPS and quasi/geoid errors due to their inseparability. We propose that independent vertical deflections are used instead, which are not affected by this inseparability problem. The formulation is set out for geoid slopes and changes in slopes. Application to 1080 astrogeodetic deflections over Australia for the AUSGeoid98 model shows that it is feasible, but the poor quality of the historical astrogeodetic deflections led to some unrealistic values

On the geodetic datums in Sri Lanka

The geodetic datums in Sri Lanka (formerly Ceylon) for latitude and longitude, height and gravity are described and discussed, because this information is not available in the open literature. It is recommended that most of these datums require some upgrading

Recent Uses of Electron Microscopy in the Study of Physico-Chemical Processes Affecting the Reactivity of Synthetic and Biological Apatites

Studies which used scanning electron microscopy (SEM) to investigate subsurface demineralization of dental enamel have recently been well reviewed. The purpose of the present paper was to review several studies, carried out in our laboratories, which have used electron microscopy to examine physicochemical properties of synthetic and biological apatites, to relate these results to previous studies, and to present new data. Aspects of the ultrastructure of hydroxyapatite and carbonated-apatites have been observed by high resolution transmission electron microscopy, and related to shape and growth of these crystals. Surface morphologies of discs prepared from precipitated carbonated-apatites and from ceramic carbonated-apatites were examined by SEM and the information was used in the interpretation of apatite dissolution studies relevant to dental caries. Improvements in the technique of backscattered electron imaging of demineralized enamel have enabled better interpretation of enamel caries experiments. SEM examination of enamel and dentin treated by low energy lasers of specific wavelengths have shown that lasing conditions can be chosen that produce surface fusion of the apatite which inhibits caries-like lesion progression. SEM examination of crystals formed on and in enamel during high concentration fluoride treatments implies that calcium fluoride-like crystals are formed and they may act as a slow-release fluoride reservoir in the mouth

Targeted messages on TV screens in remote Indigenous communities

This paper describes a research project to enhance the viability of remote Indigenous communities through culturally-appropriate use of information and communications technologies (ICT). The project investigated the use of community rebroadcast TV infrastructure for new low cost communications services. A key part of the project was establishment of trusting relationships with the Ngaanyatjaara Lands communities of Irrunytju and Kanpa. Community members,administrative staff, and external service providers were involved in investigations into current communication problems and potential solutions. A working prototype of a messaging system using satellite broadcasting infrastructure to send multimedia messages to TV sets within remote communities was developed and evaluated. Such a system could be used by government agencies or remote communities themselves to deliver messages about visitors to the community (e.g.health workers), emergencies (e.g. bushfire); cultural business, sporting events, etc. The expected outcomes of such a system are increased social capital within the region, developed through more efficient and effective communication, leading to enhanced viability and sustainability of remote communities

Predicting sea level variations with artificial neural networks at Hillarys Boat Harbour, Western Australia

In the present study, the artificial intelligence meshless methodology of neural networks was used to predict hourly sea level variations for the following 24 hours, as well as for half-daily, daily, 5-daily and 10-daily mean sea levels. The methodology is site specific; therefore, as an example, the measurements from a single tide gauge at Hillarys Boat Harbour, Western Australia, for the period December 1991-December 2002 were used to train and to validate the employed neural networks. The results obtained show the feasibility of the neural sea level forecasts in terms of the correlation coefficient (0.7-0.9), root mean square error (about 10% of tidal range) and scatter index (0.1-0.2)

Transformation between Australian datums using a modified transverse Mercator projection

The introduction of the Geocentric Datum of Australia (GDA94) in the year 2000 will undoubtedly require the transformation of a large amount of coordinate data in Australia. This paper presents a modified transverse Mercator (MTM) map-projection such that the latitude and longitude on one datum are projected so that they closely agree with the transverse Mercator easting and northing on another datum. This approach will allow the introduction of the GDA94 whilst preserving Australian Map Grid (AMG) coordinates. Conversely, the MTM projection can be used to transform coordinates directly from the Australian Geodetic Datum (AGD) to the new Map Grid of Australia (MGA94). In order to test these two approaches, MTM parameters have been computed from 82 co-located GDA94/MGA94 and AGD98/AMG84 coordinates that comprise the Western Australian STATEFIX geodetic network. When using the national seven- and three-parameter datum transformations, the maximum differences between observed and transformed coordinates are 2.04m and 2.21m, respectively. When using the transformation by MTM projection, the projected coordinates agree with the observed coordinates to less than 2.04m