Narrow Results

Precision and accuracy estimation is an important index used to reflect the measurement performance and quality of a measurement system. To reveal the significance and connotations of the precision and accuracy estimation index of a close-range photogrammetry system, several common precision and accuracy estimation methods are proposed. They are explained from a theoretical perspective, and the mechanism of the internal coincidence precision estimation and the external coincidence accuracy estimation are deduced, respectively. Through detailed experimental design and testing, the validity and reliability of the proposed precision and accuracy estimation methods are verified, which provides strong evidence for the quality control, optimization and evaluation of the measurement results from a close-range photogrammetry system. At the same time, it has significance for the further development of precision and accuracy estimation analysis of close-range photogrammetry systems.

Concerns of Pacific island nations regarding the widely publicised issue of sea level rise associated with global warming are being addressed through a monitoring array of high resolution sea level stations established in eleven countries of the South Pacific Forum. While these stations accurately measure sea level, it is vital that the stability of the adjacent land mass be monitored to the same degree of accuracy.

To this end the stations are supported by networks of deep bench marks established at coastal and inland sites where possible. Repeat high precision levelling and Global Positioning System (GPS) connections are undertaken to monitor the stability of the sea level sensor. Surveyors use techniques capable of matching the size of the expected sea level rise in the order of 1.5mm/year.

Currently the geodetic monitoring program enables sea level change to be determined relative to the adjacent land. While this is of prime importance to the communities, the program needs to be enhanced to enable the monitoring of absolute sea level rise by separating eustatic sea level change from tectonic movement of the islands.

This paper describes the rationale behind the Pacific program, the essential geodetic survey support, technology transfer in high precision measurement and results of the monitoring to date.

A similar array of sea level stations has been established around Australia and in the Cocos (Keeling) Islands in the Indian Ocean. Geodetic survey support is provided by the Australian Commonwealth and State surveying agencies, coordinated through the Intergovernmental Committee on Surveying and Mapping. Although the Australian mainland is theoretically more stable than the Pacific islands, the same level of geodetic control is required to monitor the stability of the monitoring stations themselves.