John G. Fryer

Estimator for the random error in subpixel target location and its use in the bundle adjustment

A CCD camera and frame store provide image data that are affected by a number of imperfect processes. However, most of these can be quantified or estimated. For instance, the quantization process of allocating integer values from 0 to 255 for the intensity level of each pixel has well-known statistical properties. This paper discusses how these can lead to an estimate of the precision of location of target image centroids. Two centroid algorithms are analyzed. The theory is tested against experimental and simulated data.

Non-metric photogrammetry and surveyors

Abstract The costs and benefits of using terrestrial photogrammetry to gather field information is examined. A study of the results obtained with different types of cameras on a survey for dam deformation measurements is presented so that the range of accuracies that may be expected in practice can be compared. The paper explains in simple terms the differences between “metric” and “non-metric” cameras and various photogrammetric adjustment techniques. It discusses the main problem areas to be overcome including the high cost of analytical stereoplotters or precise image co-ordinate measuring machines which are essential if the full potential of analytical photogrammetry is to be realised.

Cadastral Surveyors in New South Wales—How many?

Abstract For the last decade, the number of surveyors registered in New South Wales with the Board of Surveyors has remained close to 1,530. A suspicion has existed that this relatively large number did not actually reflect the “real” situation of how may surveyors are actively using the added qualification of a cadastral license to generate their income. An examination of all survey plans lodged in the eight month period from September 1991 until April 1992 has shed some light onto this question. The implications of this study for questions regarding the number of new registrations required per annum in New South Wales are assessed, as are quotas for Bachelor of Surveying students at the Universities of New South Wales and Newcastle.

An underwater trilateration

Abstract A description is presented of an underwater trilateration that was carried out to provide control points for a block adjustment of 360 overlapping photographs of a section of a coral reef.

The age profile of registered surveyors in NSW

Abstract In late 1994, the Board of Surveyors of NSW commissioned a study on the age profile of registered surveyors. The findings are reported. In the next 12 years, it is likely that around 40% of surveyors currently registered will retire or scale down their surveying activities. If numbers are to be maintained, registrations will need to exceed current levels. Other implications are discussed.

Electronic lodgement of plans

Abstract Procedures available for electronic lodgement of plans are reviewed. Differences between engineering and cadastral surveying plans are highlighted. The results of a questionnaire supplied to over 800 registered surveyors in New South Wales are presented and discussed. The diversity of opinions held by members of the profession at this time is explored and a tentative proposal for a style of electronic lodgement is suggested.

Photogrammetric Monitoring of Deformation Caused by Mine Subsidence

Abstract A photogrammetric survey was carried out in the Lithgow area of New South Wales, approximately 150 km west of Sydney, to monitor the movement of rock masses under the influence of longwall mining. The task was to determine three dimensional coordinates of a number of target points on the subject rock masses with respect to time, such that the rock movements could be modelled as the longwall face passed below. The exercise was carried out as a student project and was supervised by university academic staff. In the area of interest, it was anticipated that both subsidence and lateral movements would be in the order of one metre. Accuracy requirement was in the order of 0.1 metres. The photography was undertaken from 14–23 December, 1993 inclusive, hourly from 8 a.m. to 6 p.m. with a further session on January 20, 1994. Both 35 mm (Canon AE-1) and 70 mm (semi-metric Hasselblad 500 ELM) cameras were used. A comparison was made between the results achieved from both photographic formats.

A snapshot of the surveying profession, 1988

Abstract In September 1988 the Institution of Surveyors NSW Incorporated prepared a questionnaire which was sent to all members in New South Wales. The questionnaire was extensive. A part from personal information such as tertiary qualifications, salaries and work activities, the opinions of members of the profession were solicited on a range of topics of wider interest to the Institution and other bodies such as the Board of Surveyors.

Underwater 35 mm photogrammetry

Abstract A photogrammetric technique is being developed by the Department of Civil Engineering at the University of Newcastle for the stereoscopic monitoring and measuring of the marine environment near ocean outfall sewers. A pollution monitoring program is already being undertaken in the Newcastle Region using an underwater camera to take a single exposure of marine organisms at several test sites. The new technique aims to provide quantitative data for this program.

Photogrammetric monitoring of cliffs

Abstract Two photogrammetric projects which involved the monitoring and detailing of the topographical features of cliff faces in Newcastle were undertaken by staff from the Department of Civil Engineering and Surveying, University of Newcastle, during the past year. Small format 70mm photographs coupled with analytical stereoplotter techniques were used to provide cost effective solutions to surveying tasks which would have been time consuming, costly, and even dangerous by more conventional surveying techniques.