Geodesy and Geomatics Engineering Technical Reports

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Assessing alternative technologies for use of volunteered geographic information in authoritative databases
Assessing alternative technologies for use of volunteered geographic information in authoritative databases
Volunteered Geographic Information (VGI) has been enabled by advances in positioning, Web mapping, cellular communications and wiki technologies. These technological advances have allowed ordinary citizens to become producers as well as users of geographic information. Predictions have been made that VGI could be used to fill gaps in existing spatial databases, for example, complementing Spatial Data Infrastructure (SDI) datasets. However there are critical issues surrounding its production and possible integration which need to be addressed before considering it for use in complementing SDI datasets. This thesis presents research which investigated the extent to which VGI enabling technologies affect its accuracy and ensures accuracy compliant with Canadian Geospatial Data Infrastructure (CGDI) accuracy standards. The research examines the suitability of VGI as a resource for augmenting authoritative datasets, like CGDI datasets, by assessing its positional accuracy and other data quality factors. Factors influencing the accuracy hence quality of VGI, e.g. Location Based Service (LBS) positioning techniques, are analyzed and a framework for integrating VGI into suitable authoritative CGDI datasets is developed. The framework is designed to provide a platform for validation and integration of VGI into authoritative databases. The framework‘s limitations and strengths are also analyzed.
Assessment of atmospheric pressure loading on the international GNSS REPRO1 solutions periodic signatures
Assessment of atmospheric pressure loading on the international GNSS REPRO1 solutions periodic signatures
Unambiguous, consistent and homogeneous GPS station coordinates are the fundamental requirement in the appropriate determination of geodetic velocities that are often used to derive geodetic and geophysical models for different applications. As for that, there have been significant efforts in the past decade to improve the modeling and parameterization of GPS solutions. Recently, the International GNSS Service (IGNSS) has generated REPRO1 solutions by reprocessing the historical GPS data from 1994 to March, 2010. REPRO1 solutions adopted the new absolute antenna phase center variations models along with most of the recent model parameters available by then and they are the first solutions to be consistently represented in one reference frame, IGS05. Based on the availability of REPRO1 solutions, this research has two objectives. The primary objective is to identify the remaining periodic signatures in the International GNSS REPRO1 solutions. These signatures are the impacts of short and long term mismodeled and unmodeled effects from both known and unknown phenomena. As a parallel activity, this research will try to explain the signatures by correlating them with different effects that have either not been modeled or modeled differently with a specific attention to the atmospheric pressure loading (APL). The secondary objective of this study is to perform the harmonic analysis investigation of weekly time series in position and residual domain of REPRO1 solution using Least Squares Spectral Analysis (LSSA) and Least Squares Coherent Analysis (LSCA) with and without APL corrections. Based on the resulting least squares spectra, the impact (benefits) of APL corrections in the present solutions have been assessed as a basis of formulating recommendations in future similar reprocessing campaigns. In order to accomplish the research objectives, a set of twenty nine (29) stations (part of the present IGNSS network) were selected in a manner which would portray the global overview. Thereafter, the selected stations analyzed using Least Squares Spectral Analysis (LSSA) and Least Squares Coherent Analysis (LSCA) frequency domain multiplications with and without the impact of APL from GGFC model. The investigations were carried out at both REPRO1 positions and residuals domains. Based on the LS spectra results, it is evident that periodic signatures are still present in the REPRO1 solutions for most of the stations under study and they appear as spectral peaks. Furthermore, the observed signatures appear to be consistent around the first to fourth draconitic harmonics with respective periods of 351.2, 175.6, 117.1 and 87.8 days, within a range of ± 14 days (±0.04 CPY). It was also observed that, there is a slight improvement to spectral peaks that may result into slight improvement of coordinate repeatability if APL were included in the processing. However, the pattern was neither clear nor consistent at different harmonic levels of the same station as well as from one station to another. Furthermore, it was also observed that, the APL does not cause any significant reduction in spectral peaks that are still present in the REPRO1 solutions. This suggest that most of the remaining signatures could be attributed to other un-modeled displacements such as non tidal loading displacement, high order ionosphere terms and mismodeling effect in GPS attitude models. To ascertain the findings, independent solutions for YELL and NRC1 were generated (1995-2010) using Bernese v5.0 software in a baseline mode, in conjunction with latest IERS models. The computed solutions were verified to be compatible with present solutions within a range of ±2.5 cm. Thereafter the computed solutions were analyzed with and without the impact of APL using LSSA and LSCA as a basis of recommendations and future work.
Assessment of tropospheric slant factor models
Assessment of tropospheric slant factor models
The tropospheric delay still remains a limiting factor to the accuracy of space based positioning techniques. If this effect is not properly modeled it can adversely effect the accuracy and precision of station coordinates derived from these techniques. Particulary susceptible to errors in the delay, is the station height parameter which is important for geophysical studies such as studying sea level rise and isostatic adjustment and for the realization of a stable reference frame. Ray-tracing through numerical weather models has been shown to be very beneficial for the development of mapping functions which model the elevation angle dependence of the tropospheric delay. Typically, due to computational constraints, only the vertical profile above the site is utilized, and the atmosphere is assumed to be spherically symmetric, therefore ignoring the azimuth-dependence of the delay. Instead of only using the vertical profile, it is possible to make no assumptions about the nature of the atmosphere and use the full information provided by the numerical weather model. Ray-tracing through the 3D state of the numerical weather model, generally referred to as 3D ray-tracing, makes it possible to model both the elevation angle- and azimuth-dependence of the tropospheric delay. This contribution is divided into two parts, first an assessment of current mapping functions and functional formulations for describing both the elevation angle- and azimuthdependence of the tropospheric delay is performed using the three dimensional ray-tracing as truth data. The results of this experiment indicate that currently, the Vienna Mapping Function 1 (VMF1) should be used for all geodetic applications, and if necessary, the Global Mapping Function (GMF) can serve as an acceptable replacement without introducing a significant bias into the station position. Secondly, the Marini expression, truncated at three coefficients, is capable of modeling 3D ray-traced delays down to the 3° elevation angle with sub-millimeter accuracy and therefore it’s use as the basis of current mapping functions is supported. In terms of modeling the asymmetry of the tropospheric delay with respect to azimuth, the Chen & Herring linear horizontal gradient formulation was found to be the best candidate when estimating the gradient parameters from space geodetic observations, although some tuning of the elevation dependent term may still be possible. The benefit of the higher order functional formulations was somewhat dependent on the nature of the asymmetric delay, although in general, the second degree spherical harmonics were better able to model the asymmetry of the delay at low elevation angles. In terms of estimating the unknown coefficients using the space geodetic observations, these higher order functions may not be practical as they introduce more unknown parameters into the design matrix. However, these formulations may be useful for providing asymmetric delay corrections in a convenient closed-form which can be distributed to end users. The second experiment investigated the use of three dimensional ray-tracing at the observation level for the reduction of space geodetic observations. This consisted of a global precise point positioning (PPP) campaign comparing four strategies to modeling the delay. It was found that the use of three dimensional ray-tracing gave identical performance in the horizontal station repeatability as the current recommended approach of estimating two gradient parameters from the space geodetic observations, while in the vertical domain the estimation of the gradient parameters resulted in a small improvement. Both of these methods performed better than ignoring the asymmetric nature of the tropospheric delay all together. Although the ray-traced zenith delays and the estimated zenith delays using the PPP approach agreed to the 3 mm level, the ray-traced zenith delays could not capture the short term fluctuations which occur, mainly due to the presentee of water vapor in the atmosphere. For this reason, it was still necessary to estimate a residual zenith delay parameter in order to achieve sub-cm repeatability in the vertical component.
Automated dam displacement monitoring using a robotic total station
Automated dam displacement monitoring using a robotic total station
An automated data collection and processing system has been created for geodetic monitoring of point displacements at a large earthfill dam project in southern California. Because of the size of this facility, currently the largest earthfill dam project in the United States, the geodetic monitoring program could not be affordably implemented using traditional survey techniques. Therefore, a system was designed that uses a network of permanently installed robotic total stations (RTS) to carry out the measurements and data processing in a fully automatic fashion, with updated point coordinates delivered to the system operator after each measurement cycle. Implementation of this automated monitoring system required the development of specialized software to carry out data collection and processing. Because the robotic total stations were to be housed in observation shelters with glass windows, it was necessary to employ data processing algorithms that would not be unduly affected by the resulting refraction effects. This was achieved by treating each observing station as a standalone monitoring system, eliminating the need to combine the biased RTS measurements with external data sources while still recognizing that refraction effects will cancel out in the computation of point displacements. The automated monitoring system was first activated in October 2000, and has successfully collected displacement measurements for more than a year. A preliminary evaluation of data collected by the system shows that atmospheric refraction has a significant effect on the accuracy achievable during individual measurement cycles. However, averaging measurements collected at different times of day allows the system to meet its design goal of detecting displacements larger than 10 mm at the 95% level of confidence.
Automated tidal reduction of soundings
Automated tidal reduction of soundings
In Hydrographic Surveying, soundings are reduced to a chart datum established at a reference gauge station from a long period of tidal observations. Unfortunately, due to the variations in tidal characteristics from place to place, soundings can only be reduced to the chart datum within the vicinity of the gauge station. As we move away from the gauge station, it becomes necessary to obtain new information on the tidal characteristics and apply necessary corrections to the chart datum to obtain an appropriate sounding datum for reducing the soundings. To reduce soundings means to subtract the heights of ride, at the sounding locations and at the times of soundings, from the depths sounded to obtain the depths referenced to the chosen datum. Manual reduct6ion of soundings is a tedious aspect of the field hydrographer’s list of chores. There have been some attempts to automate the tidal reductions using digitized cotidal charts. The objective of this work has been to develop alternative approaches to automated tidal reductions, namely, using analytical cotidal models. The range ratio and time lag fields have been approaximated by surfaces described by two dimensional algebraic polynomials (Pn(ɸ, λ)). The observed time series at a reference station has been approximated by one dimensional trigonometric polynomial. With the coefficients of these Polynomials stored in the computer, the range ratio and the time lag at any point (ɸ[subscript i], λ[subscript i]) in the area can readily be predicted and the height of tide at the point and at time I can be predicted from the predicted height of ride at the reference station. Test computation, using data from the ‘Canadian Tides and Current Tables. 1978’ for the Bay of Fundy have been done. It has been shown that the water level (h) at a location (ɸ[subscript i], λ[subscript i]) can be produced with a standard deviation ([superscript 15] h [subscript i]) of 0.5 m or better.
Automatic mid-water target detection using multibeam water column
Automatic mid-water target detection using multibeam water column
A potential new automatic application in multibeam water column is the recognition and precise location of suspended mid-water targets. This is already being applied manually in the ArcticNet program for searching for lost under-ice mooring hardware. The pattern of the scattering field around a suspended point mid-water target is directly related to the multibeam imaging geometry, including pulse length, transmission and reception main lobe beam-widths as well as side lobe spacing and suppression. Knowing this geometry-specific scattering pattern, optimal 3D matched filters can be designed to pick out faint targets from noise. Having picked an object in this manner, its location can be derived with the same positioning uncertainty that we already associate with depth. Equivalent detection of objects can be achieved manually by the trained operator when carefully inspecting all the data, but is a very long and tedious task. An automatic algorithm developed as the main component of this thesis can be used to perform this task more rapidly and reliably, as well as tracking the object’s movement. These new capabilities can be used in oceanographic research, in search and rescue, also for military purposes, and to track geological activity. A specific case study used as an example is the monitoring of suspended targets over seabed markers that are progressively displaced by landslides.
Autonomous mobile robot indoor navigation using multi-sensor integration
Autonomous mobile robot indoor navigation using multi-sensor integration
Currently, most autonomous mobile robot indoor navigation systems are unable to provide absolute state information (e.g., coordinates in a reference frame) and rely on expensive sensors. The goal of this research is to develop a low-cost, high-accuracy, autonomous mobile robot indoor navigation system. The robot starts from an unknown location in a corridor environment and arrives at a selected target point with certain accuracy by following the centre line or virtually any lane of the corridors. The core research of this autonomous navigation system is in the development of reliable indoor orientation and position estimation algorithms. Integrating MEMS inertial and magnetic sensors improves overall performance of orientation estimation. However, challenges exist in dealing with the large gyro sensor errors and the large measurement noises of the accelerometers and magnetometers. A quaternion-based Kalman filter has been developed, which applies tightly-coupled and closed-loop integration strategies. It incorporates an online sensor calibration procedure for modelling time-varying sensor biases of the accelerometers and magnetometers, and a mechanism for adapting the measurement noise in the presence of motion and magnetic disturbances. In static mode, the integration algorithm can provide an estimation accuracy of less than o 1 when there is no magnetic anomaly. Even with the existence of significant magnetic disturbances, the orientation estimation error is reduced from up to o 131.6 to o 4.7 . In kinematic mode, the solutions show as much as 40% error reduction compared to those without applying the integration strategy. A novel indoor positioning system based on radio frequency identification technology has been developed, which can deal with complicated indoor radio signal environments due to multipath, non-line-of-sight, and signal interference. A regularized particle filter has been built by employing a non-parametric, probabilistic observation model. An effective online measurement quality control algorithm has been developed, which can identify and reject non-line-of-sight and/or multipath corrupted measurements. The developed indoor positioning system achieved a mean positioning error of 1.64 m, which is about 49% or more improvement in accuracy compared to other conventional methods. To successfully guide a robot to a target position, a sonic-vision system that can profile the local environment has been developed and two intelligent controllers have been designed. An efficient autonomous navigation algorithm has been developed, which choreographs all sub-system components comprising the orientation estimation module, the positioning module, the sonic-vision, and the intelligent controllers. The results showed that the robot is able to autonomously navigate to a pre-specified target point with a mean offset of 2.38 m. The average cross-track error was about 0.1 m which indicates the controllers’ autonomous capability in tracking and guidance. Overall results have confirmed the significant performance improvements of the developed orientation and position estimation methods, the benefits of applying them for indoor navigation, and the effectiveness of the autonomous navigation algorithm.
Bedform migration and associated sand transport on a banner bank
Bedform migration and associated sand transport on a banner bank
A new integrated method of measuring bedload transport using repetitive multibeam surveys of a sand bank in Mispec Bay, Saint John, NB, has been developed. Migration rate and morphometric parameters, all derived from the bathymetric dataset, are used to calculate net sediment transport that is expressed as migrating bedforms. This bedform associated sediment transport value was tested for validity by combining observed median grain size and observed hydrodynamic data from one of three M2 tidal current measurement cycles, the latter initially conducted to investigate the nature of the current field in Mispec Bay. The maximum bedform associated bedload transport value of 30 kg/m/tide falls in the range predicted by a pre-existing sediment transport model of the area. At the least, the bedform associated bedload transport value is a good lower estimator of bedload transport. This is because of the unknown component of bedload not expressed in bedform migration. A conceptual model for the formation and maintenance of the Cape Spencer sand bodies has been proposed. Comparison of observed hydrodynamic data with pre-existing hydrodynamic and sedimentary models of headland localities reveals that the asymmetric coastline of Cape Spencer has an impact on its local current field and consequently sand bank development. With respect to ebbing currents, the coastline of Cape Spencer has an elliptical aspect ratio greater then the threshold necessary to advect a major tidal eddy in Mispec Bay. Thus, the tidal eddy advected in Mispec Bay locally induces major tidal asymmetry, with a line of net bedload reversal, inferred from hydrodynamic observations, separating the flood dominated and ebb dominated regions. Mispec bank has built up inshore of this line and sediment is continually advected from its tip, where there is an increasing net sediment transport rate; a portion of this sediment ends up being redeposited on the distal end of the bank only to be recirculated around the bank. Given the static nature of the overall bathymetry of Mispec Bank, a steady state recirculation appears to maintain the bank. In contrast, for opposing flood currents the elliptical aspect ratio is less than the eddy advection threshold to the east so a major eddy is not advected on this tidal phase. The lack of an advected tidal eddy dictates less tidal asymmetry on the east side of Cape Spencer and thus the sand bank there occurs as a stretched sand sheet with much lower thickness than the Mispec Bank.
Bottom tracking issues and recognition thereof using SHOAL-300 green laser beam in dense fields of Zostera Marina and Laminaria Sp.
Bottom tracking issues and recognition thereof using SHOAL-300 green laser beam in dense fields of Zostera Marina and Laminaria Sp.
This thesis assesses the ability of the SHOALS-3000 bathymetric lidar to correctly track the bottom in areas of dense aquatic vegetation, and explores a method to recognize improper bottom tracking, as a result of the vegetation, without ground truthing data. To perform the analysis, SHOALS-3000 and overlapping ship-based acoustic data were collected near the shores of Bonaventure and Paspébiac on the Bay de Chaleur, Quebec, in June 2006. EM3002 multibeam bathymetry and water column data, and Knudsen 200 kHz singlebeam water column backscatter were utilized for the SHOALS-3000 bottom tracking assessment. To assure a high level of vertical accuracy and exclude the necessity for real time, or predicted tide values post-processed kinematic (PPK) antenna solutions were allocated to the multibeam transducer face, by which multibeam solutions were matched with ellipsoid-referenced lidar solutions. An algorithm was developed that characterizes green laser waveforms, but excludes those that returned from land, or too shallow or too deep water. The algorithm includes three techniques to adapt as thoroughly as possible to obscure waveform bottom returns from vegetation soundings. A by-product of the characterization method is a term that describes the water clarity. The relative assessment revealed that the SHOALS-3000, compared to the EM3002, could achieve the manufacturer’s and IHO Order 1 accuracy specifications in unvegetated areas. Once aquatic vegetation is present, the bottom tracking of the SHOALS-3000 degrades: manufacturer’s and IHO Order 1 accuracy specifications could not be met. The green laser beam tracks the vegetation, or fails to return a sounding. This last observation is most concerning, implying that lidar datagaps, aside from reducing the effective coverage, are not necessarily due to lidar extinction depths, but potentially due to marine life covered navigational hazards. Waveforms from vegetation soundings have a small bottom return height, when compared to typical unvegetated seabeds, and as no sediment was found with similar reflectance, vegetated seabeds could therefore easily be discriminated from unvegetated seabeds. Vegetation identified with ground truthing data showed good agreement with small bottom return height values once the characterized waveforms were spatially plotted. A ratio describing typical bottom return height values of vegetated and unvegetated seabeds, confirmed the unambiguous reflectance of the laser, despite some day-to-day differences. This unambiguous behavior was incorporated with lidar bathymetry slopes to validate lidar soundings and identify fields of aquatic vegetation. Finally, overlapping keel mounted side scan sonar backscatter provides a potential to identify habitat based vegetation such as Laminaria sp. and Zostera Marina species.
Boundary delineation of wilderness and ecological reserves in Newfoundland
Boundary delineation of wilderness and ecological reserves in Newfoundland
The Government of Newfoundland and Labrador passed the Wilderness and Ecological Reserves (WER) Act on May 28, 1980. Through the establishing of this act, the government formally recognized the need to protect a portion of the province’s wildlands for future enjoyment. This legislation has provided the basis for site selection and reserve protection through a Wilderness and Ecological Reserves Program. The strengths and weaknesses of the WER Program are reviewed in this report with particular emphasis placed on the need for, and use of, information in selecting reserve boundaries. Though a case study, the ABC Resource Survey procedures are applied to site selection and an attempt is made to incorporate Geographical information System (GIS) technology in the process. The results of the case study demonstrated how both the ABC methodology and GIS can be included in the reserve selection procedures, however, the quality of information presently available for applying this procedure is poor.
Bringing GPS into harsh environments for deformation monitoring
Bringing GPS into harsh environments for deformation monitoring
Certain deformation monitoring environments pose severe limitations on the achievable accuracy and precision that can be attained by instrumentation used to monitor deformation behaviour. Large open pit mines are one example. In such environments, it is not uncommon for the degradation in precision of geodetic technologies to be so large that the minimum detectable displacement fails to meet the mine’s requirements for displacement detection. In order to meet these requirements, an innovative approach to deformation monitoring is required. Presented is a technique which capitalizes on the advantages of Global Positioning System (GPS) sensors to provide fully-automated and continuous subcentimetre displacement detection in real time. Software was developed which utilizes triple-differenced carrier phase observations in a Delayed-State Kalman filter to provide continuous, high precision position updates in a fully automated mode. The software was enhanced to include pseudolite processing capabilities. An interdisciplinary approach was then used to predict deformation behaviour to aid in the design of a geodetic deformation monitoring scheme. It was shown that the processing strategy employed helps to mitigate the effects of residual tropospheric delay biases. Additionally, it was illustrated that pseudolites can be used to provide more continuous position updates in harsh environment conditions. An example was also given to demonstrate how deterministic modelling can be used to predict deformation behaviour and how this information can be incorporated into the design of a geodetic deformation monitoring scheme.
Building detection in off-nadir very high resolution satellite images based on stereo 3D information
Building detection in off-nadir very high resolution satellite images based on stereo 3D information
Mapping or updating maps of urban areas is crucial for urban planning and management. Since buildings are the main objects in urban environments, building roof detection is an important task in urban mapping. The ideal geo-spatial data source for mapping building information is very high resolution (VHR) satellite images. On the other hand, because buildings are elevated objects, incorporating their heights in building detection can significantly improve the accuracy of the mapping. The most cost-effective source for extracting the height information is stereo VHR satellite images that can provide two types of stereo 3D information: elevation and disparity. However, most VHR images are acquired off-nadir. This acquisition type causes building leaning in the images and creates major challenges for the incorporation of building height information into roof detection. Thus, this PhD research focuses on finding solutions to mitigate the problems associated with 3D-supported building detection in off-nadir VHR satellite images. It also exploits the potential of extracting disparity information from off-nadir image pairs to support building detection. In the research, several problems associated with building leaning need to be solved, such as building roof offsetting from its footprint, object occlusion, and building façades. Moreover, the variation of the roofs offsets based on the building heights. While the offsets of building roof create difficulties in the co-registration between image and elevation data, the building façades and occlusions create challenges in automatically finding matching points in off-nadir image pairs. Furthermore, due to the variation in building-roof offsets, the mapped roofs extracted from off-nadir images cannot be directly geo-referenced to existing maps for effective information integration.

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