Geodesy and Geomatics Engineering Technical Reports

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An empirical usability evaluation of a web-based public participation geographic information system and discussion forum
An empirical usability evaluation of a web-based public participation geographic information system and discussion forum
The study of Public Participation Geographic Information Systems (PPGIS) focuses on the use of GIS by non-experts and regular citizens, which requires that such systems be accessible and easy to use. Review of PPGIS literature reveals, however, a lack of documented research about how non-expert users and the general public are using PPGIS tools. Building on earlier PPGIS research, a GIS-enabled Online Discussion Forum prototype named GeoDF has been implemented and evaluated. In this thesis, Human-Computer Interaction (HCI) principles are drawn upon and a rigorous set of usability evaluation procedures are designed to empirically evaluate the usability and user acceptance of the GeoDF software. Evaluation results confirm that the GeoDF is not only an effective communication platform, but also a useful participatory tool that encourages participants to be more involved in land use planning procedures. Results also show that by enhancing usability, lowering the cost of entry, and providing effective communication channels would result in greater user acceptance of the PPGIS technology. A two-sample t-test analysis proves the research results to be statistically significant.
An evaluation of three techniques for the prediction of gravity anomalies in Canada
An evaluation of three techniques for the prediction of gravity anomalies in Canada
Recent studies have shown that the Canadian height control network, which was defined on the basis of normal gravity, suffers from the influence of gravity anomalies that can introduce significant systematic regional distortions. Proposals have been made for a new definition of heights for Canada which would be based on observed gravity values. Since, observed gravity is not now available at all points along levelling paths, (as required by the new definition), techniques suitable for the prediction of point gravity values at bench marks, say, are, therefore, required. The performances of three prediction techniques – least-squares surface fit, least-squares collocation, and weighted mean methods – in three terrain situations in Canada were evaluated. The terrain situations considered correspond to the flat, gently rolling, and mountainous terrain types. Test points were selected randomly from each terrain type considered, and the nine samples generated by using each technique to predict for point gravity anomalies at the selected points were vigorously tested statistically. The method of weighted means performed well in the three different types of terrain. It was the fastest of the three techniques, and the most economical in terms of computer time. The other two techniques gave good results in the flat, and rolling terrains, but did not perform so well in the mountainous terrain.
An examination of alternative compensation methods for the removal of the ridging effect from digital terrain model data files
An examination of alternative compensation methods for the removal of the ridging effect from digital terrain model data files
The province of New Brunswick began a systematic program of province-wide Digital Terrain Model (DTM) coverage in the late-1980's. Using 1:35,000-scale aearial photography, the DTMs were collected photogrammetrically as a series of profiles spaced 70 metres apart. No regard was given to breaklines along roads or water bodies. The DTMs have gone through a series of stringent quality control checks to eliminate blunders and ensure the elevations of data points are blunder-free and all fall within specified accuracy tolerances. However, users of these DTM's have continued to express concern over perceived data quality based on the evidence of a regular "ridging" effect within many of the DTM files when viewed under certain conditions. Aware of similar phenomena found in DTMs produced by other organizations, Service New Brunswick (SNB) commissioned researchers in the department of Geodesy and Geomatics Engineering at the University of New Brunswick to investigate the respective requirements and alternatives for batch processing of the DTMs to remove this ridging effect. This report presents research examining specific technical issues and compensation approaches associated with the quantification and removal of the ridging phenomena found in SNB's Enhanced Topographic Database digital terrain data. Further, the issues of ridging will be investigated from points of view ranging from a data limitation issue to a visualization issues. Finally, up to five specific solutions will be examined and compared.
An improved approach for soil moisture estimation by employing illumination-corrected data in a modified Ts-VI method
An improved approach for soil moisture estimation by employing illumination-corrected data in a modified Ts-VI method
There are a great number of publications that apply different methods to estimate soil moisture from optical satellite imagery. However, none of the proposed methods have considered correcting solar illumination error that is caused by variation in topography before estimating soil moisture. In this research, an integrated approach is developed to improve the estimation of soil moisture. The integration is represented by removing the solar-illumination error from the data. Several modifications were made in the Ts-VI space based on the Universal Triangle Relationship. The data used in the research are obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. The research results show that the surface-illumination error, which is caused by variation in topography, misleads the estimation of soil moisture index. Based on statistical and visual analysis, the results are improved with removing error. The method is further enhanced with the application of enhanced vegetation index (EVI) to the Ts-VI relationship.
An investigation into acceleration determination for airborne gravimetry using the Global Positioning System
An investigation into acceleration determination for airborne gravimetry using the Global Positioning System
This thesis investigates the determination of acceleration using the NAVSTAR Global Positioning System (GPS) for airborne gravimetric applications. Particular attention is placed on the development and implementation of an observing model which will accurately measure accelerations using the second time derivative of the GPS carrier phase. This development follows from the work performed by Kleusberg et al [1989] and Kleusberg [1989]. The position and velocity requirements for airborne gravimetry have been met using GPS observing and processing techniques. However, the separation of the airborne acceleration due to air pockets, wind gusts, etc., from the observed gravity still remains to be resolved to the 1 to 2 mGal accuracy requirements. As a means towards determining accelerations to this accuracy level, this thesis develops a model in which the accelerations are obtained by utilizing the second time derivative of the GPS carrier phase. Carrier phase data was collected from pairs of GPS receivers located at fixed points. Three different types of GPS receivers available to the market today were used for data analysis. Spectral analysis techniques in determining acquired acceleration accuracy were applied to computed accelerations from these data sets. Low-pass filters were applied to the acceleration data in order to separate the high frequency receiver measurement noise from the low frequency acceleration data. The implications and handling of GPS data contaminated by selective availability is addressed. Results show that for carrier phase observations over a fixed baseline of less than 100 metres differential techniques can give accelerations which meet the 1 to 2 mGal accuracy requirements. Recommendations for the continuation of this research are given as well.
An investigation on the use of GPS for deformation monitoring in open pit mines
An investigation on the use of GPS for deformation monitoring in open pit mines
In order to implement GPS for deformation monitoring purposes, subcentimetre displacements must be detected in all three directional components. These results must be attained with such frequency as to provide sufficient warning of impending danger. In applications such as open pit mining where unfavourable conditions exist for GPS, this requirement is particularly challenging to meet. This research determines what accuracy can be expected in an unfavourable GPS environment. GPS data which have been collected in a large open pit mine are analyzed using optimal software settings determined from a nearly ideal scenario. It is shown that GPS can be used to augment the current robotic total station deformation monitoring system used at this mine site to obtain subcentimetre accuracy displacement values at 95%. The potential of improving these results through processing strategies and new technology is also investigated.
Analysis and procedures of multibeam data cleaning for bathymetric charting
Analysis and procedures of multibeam data cleaning for bathymetric charting
Multibeam echosounding (MBES) bathymetric surveying is a new hydrographic methodology. Criteria for the most appropriate ways of using MBES systems in hydrography must be established. This report addresses two questions concerning the “cleaning” of MBES bathymetric data: 1. What rules should the hydrographer follow in MBES data cleaning for bathymetric charting, in order to uniformly achieve the most reliable data cleaning results? 2. What features in multibeam acoustic backscatter data can be used to help identify bathymetric anomalies? MBES bathymetric data contains blunders. These errors need to be identified and the corresponding soundings rejected. This is the goal of data cleaning task. Currently, one of the major obstacles of using MBES in hydrography is the data cleaning. Frequently this is because the sequence of data cleaning steps is not always the most logical and uniform. This report summarizes the background information required for the analysis and cleaning of MBES data. Several data cleaning methods are reviewed. For two commercial methods. HDCS (a module from the Hydrographic Information Processing System. Universal Systems Ltd.) and BINSTAT (a module from Neptine. Simrad Norge AS). A logical sequence of steps for their use is proposed; as well suggestions for standardization of processing are made. As there is a correlation between seafloor bathymetric features and side scan targets, this report assesses, for two case studies, how acoustic seabed backscatter information provided by many MBES systems, can be useful as a potential coadjutant of data cleaning. The results obtained show that bathymetric features such as wrecks are highlighted by a decrease of the backscatter strength, and boulders are highlighted by an increase of the backscatter strength. It is concluded that the bottom detection parameter (amplitude or phase) is an important data cleaning factor for making decisions about blunders and real features, whereas the acoustic imagery provides a mean to define areas where either automatic or interactive data cleaning should be used.
Analysis of deformation surveys
Analysis of deformation surveys
A generalized approach to deformation analysis has been developed and successfully applied to five examples of monitoring networks within the activity of the “ad hoc” committee on the analysis of deformation surveys of the International Federation of Surveyors (FIG). The approach is applicable to any type of geometrical analysis, both in space and in time domain, including detection of unstable points in reference networks, and determination of strain components and relative rigid body motion within relative networks. It allows utilization of not only geodetic observations, but also physical mechanical measurements. Functional relations between deformation parameters and various types of observables have been developed. The approach is capable of handling any datum defects and configuration defects in monitoring networks. The problem of datum defects has been approached through the projection theory in the parameter space. The generalized approach consists of three basic processes: preliminary identification of deformation models, estimation of the deformation parameters and diagnostic checking of the models. The MINQUE principle has been adopted for the assessment of multi-epoch observations prior to the final adjustment of monitoring networks. A method of iterative weighted projection in the parameter space has been created or the identification of the deformation models in space domain. Formulation and computation strategies for the estimation of the deformation parameters are provided in detail. The statistic for testing linear hypotheses in the General Gauss-Markoff Model has been formulated using the theory of vector spaces and, from this statistic, all the hypothesis tests used in the different phases of deformation analysis were derived. Compared with other methods, the generalized approach permits a systematic step-by-step analysis of deformations. During the development of the generalized approach some problems encountered by other authors have been rectified. Examples of the problems and their solution are also given in the thesis.
Analysis of multi-frequency carrier phase linear combinations for GNSS
Analysis of multi-frequency carrier phase linear combinations for GNSS
With the modernization of GPS and the deployment of Galileo expected soon, there will be an increase in the number of precise or carrier phase signals arriving from space which are at our disposal. One method of utilizing these signals is to form carrier phase linear combinations which: 1) reduce ionospheric delay; 2) reduce receiver noise; 3) increase the wavelength of the observable. This means improved position capability and more reliability for these space based systems. This report focuses its investigation on those combinations which mitigate ionospheric delay, reduce receiver noise and perform best under typical survey conditions. The derivation of the characteristics for the linear combinations is performed including the second and third order ionosphereic delay amplification factors. A number of conclusions are reached. It is possible to more effectively reduce the effect of the ionosphere by using three frequencies rather than two frequencies. Care must be taken in understanding the effects of the linear combinations on the higher order terms especially for very precise applications. Concerning receiver noise, it was shown theoretically that although the triple frequency narrow-lane combination does improve the precision of the measurement it is more effective to use the three frequencies independently to improve the precision in the position domain. Finally it was shown through the use of simulated modernized GPS observations that linear combinations can be very effective in reducing the errors present in satellite positioning.

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