Browsing by Author "Detchev, Ivan Denislavov"
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- ItemOpen AccessAutomatic Registration of Imagery to Mobile LiDAR Maps(2024-02-15) Jones, Kent Douglas; Lichti, Derek D.; Detchev, Ivan Denislavov; Yang, Hongzhou; El-Sheimy, Naser M.; Chapman, Michael AlastairMapping in 3D that records geospatial data from platform-mounted sensors with digital twinning supports maintenance and future planning of civil infrastructure. Three-dimensional mapping is efficiently performed with a Mobile Mapping System (MMS). This research demonstrates camera-only registration of subsequently captured images to an MMS point-cloud for updating MMS datasets. The research resolves key issues with inherent resolution differences between MMS laser scanner point-clouds and camera images by bridging differences between MMS point-clouds and camera images using a synthetic camera image (SCI). SCI are used to determine the approximate pose or coarse register the camera image to the MMS point cloud. The SCI coarse registration precision is maximized by generating surfaces, interpolating intensity values, and reducing noise with a median filter. The SCI is processed with a median filter to remove salt-and-pepper noise from the generation methods while preserving edges. Edgeboxes are adapted to find similar features in both SCIs and camera images. These features are then passed through layers of a convolutional neural network to provide a feature descriptor for coarse registration. Real camera images (RCI) are processed to mitigate resolution differences with the SCIs. The RCI is downsampled to align with the spatial resolution of the SCIs. Robust features are used to register the RCI to the SCIs. SIFT is used for fine registration between RCIs and SCIs generated from dense point-clouds. Landmark features are used for registration of RCIs to SCIs generated from MMS point-clouds. The edgebox parameters require tuning to detect the same features in two disparate image sets. The fourth layer of AlexNet was found to provide the most ideal feature descriptor for registration between RCIs and SCIs. The approximate location of the RCI using SCIs as interpreters between RCI and MMS point-cloud detect scenes at a precision of 97% when changes are less than 20%, and foliage does not exceed 20% of the camera image. This novel application of landmark features aligns with camera-to-camera place recognition precision. The focal length and IOPs do not influence the precision of the registration because the registration precision does not change when different cameras capture the real images.
- ItemOpen AccessHybrid Land Administration and Street-Level Bureaucracy in Peri-Urban Settlements: A study of Waitiki Farm, Kenya(2022-06-01) Muthama, Dennis Mbugua; Barry, Michael Brendan; Ballantyne, Brian Andrew; Whittal, Jennifer Frances; Detchev, Ivan Denislavov; Chigbu, Uchendu EugeneThe thesis develops hybrid governance and street-level bureaucracy theories, as a set of hypotheses, to explain land administration effectiveness in Waitiki, an in situ regularised peri-urban informal settlement in Mombasa, Kenya. Peri-urban informal settlements in Sub-Saharan Africa are dynamic and complex situations under which conventional land administration systems are likely to be dysfunctional. To improve the effectiveness of land administration systems in peri-urban settlements, the study argues that it is necessary to explore how street-level land administration officials provide services and how the multiple land governance systems relate. In addition, the study draws upon Lipsky’s Street Level bureaucracy theory and Hybrid Governance theory to develop hypotheses to explain street-level land administration officials (SLAOs) service delivery and hybrid governance arrangements inter-relationship. Using these hypotheses and drawing on the aforementioned theories, two theories as sets of hypotheses suited to the Waitiki case were developed. To investigate the research problem a case study strategy of inquiry was adopted. A single case, Waitiki Farm, was used in the study. Waitiki Farm was chosen because it is an informal settlement that was upgraded in situ and hybrid land governance continues to prevail. Both official and unofficial organisations and leadership structures play a role in land tenure administration. In addition, SLAOs are active in Waitiki Farm. Data was collected from multiple sources. The primary data comprised a total of 105 semi-structured interviews involving 148 people. I used 42 key-person interviews and 57 door-to-door interviews with residents. Secondary data included historical documents, national and county government documents, the courts’ law reports and documents, NGO documents, land administration, and demographic documentary, and online data from different government agencies. The fieldwork was undertaken between May and November 2017. To build theory, an interpretive approach was used i.e., interpreting data as the research progresses and building on prior theories as one does not start from a clean slate. Hybrid governance and Street Level bureaucracy theories were developed from the Waitiki data analysis. The hybrid governance theory that emerged explained that the de facto hybrid governance arrangement continues to be dominant and influential in in-situ regularised peri-urban settlements because SLAOs and residents use them for different land tenure administration functions.
- ItemOpen AccessImplementation of a close range photogrammetric system for 3D reconstruction of a scoliotic torso(2010) Detchev, Ivan Denislavov; Habib, Ayman
- ItemOpen AccessIntegration of Multiple Low-Cost Wearable Inertial/Magnetic Sensors and Kinematics of Lower Limbs for Improving Pedestrian Navigation Systems(2019-07-25) Tjhai, Chandra; O'Keefe, Kyle; El-Sheimy, Naser M; Ferber, Reed; Detchev, Ivan Denislavov; Wieser, AndreasThis thesis presents a work in pedestrian navigation that utilizes multiple low-cost wearable inertial/magnetic sensors and kinematics of lower limbs for improving the positioning performance. A multi-wearable sensor system is developed for this research in order to record the walking motion using multiple MPU-6050 and MPU-9250 sensors. The focus of this research is to investigate the feasibility of using multiple low-cost sensors distributed on lower limb segments as a pedestrian navigation system. The proposed method uses seven wearable sensor modules distributed on pelvis, thighs and shanks. A skeletal model consists of five limb segments is used to model the forward kinematics of lower limbs. Different attitude estimator algorithms are tested and compared. The step size and heading are computed using the forward kinematics. To evaluate the proposed navigation method, two experiments are conducted. The first experiment is a treadmill walk to evaluate the accuracy of the estimated segment orientation angles and step sizes. The second experiment involves turning motion where a test subject walks around a rectangular path. The results show that the use of a wearable multi-sensor system can provide a pedestrian navigation solution with error comparable to the solution computed using a single higher-cost sensor.
- ItemOpen AccessInvestigating RTK using Geostationary Satellites and IRNSS(2017) Bhandari, Vimalkumar; O'Keefe, Kyle Patrick Gordon; Detchev, Ivan Denislavov; O'Keefe, Kyle Patrick Gordon; El-Sheimy, Naser M; Gao, Yan; Messier, Geoffrey; Macabiau, ChristopheThe IRNSS and SBAS constellations have geostationary satellites in the space segment. Geostationary satellites provide additional observations and are always visible to a given user. However, due to their small line-of-sight velocities, geostationary satellites have two unique challenges: Doppler collision and observability, both of which can affect their use in an RTK solution. The first phase of this research is aimed at understanding Doppler collision. It is a unique phenomenon in GNSS where tracking errors are introduced in the measurements due to cross-correlation between two or more satellites. Doppler collisions affect geostationary satellites for longer durations and the error resembles code multipath. If not mitigated, Doppler collision could have an impact on the ability to use code measurements of geostationary satellites in RTK positioning. This research describes likely conditions for Doppler collision, derives a Doppler collision error envelope for geostationary pseudorange measurements, and then demonstrates the effect using simulated and live signals. The second phase of this research presents the effect of Doppler collision on an RTK solution using geostationary satellites, with emphasis on ambiguity convergence time. Multiple mitigation techniques such as de-weighting of geostationary observations and use of narrow correlator are proposed to reduce the impact of Doppler collision. iii The third phase talks about the observability of a geostationary satellite. The relatively static nature of geostationary satellites leads to poor observability and has a direct impact on the convergence of ambiguities. The poor observability can limit the use of standalone constellations such as IRNSS in an RTK solution. Finally, an investigation is conducted on both hardware-simulated and live data of IRNSS to understand the impact of Doppler collision and observability. Mitigation methods are applied, and the improvement in the code measurement error and the convergence of ambiguities is presented. Overall, this thesis is aimed at addressing some of the key issues arising from the use of geostationary satellites in an RTK solution so that a multi-constellation RTK solution progresses one step closer to the possibility of an all-constellation RTK solution, including IRNSS.