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Roadway grades have a diverse effect on vehicle speeds, depending on vehicle and roadway characteristics. For example, passenger cars can generally negotiate grades of 5 percent or less without considerable reductions in vehicle speeds, while heavy-duty trucks are affected significantly by grades because of their inferior operating capability. Consequently, due to the potential significant speed differential between automobiles and heavy-duty trucks, these trucks can have a significant impact on the quality of flow, throughput, and safety of a traffic stream. Truck climbing lanes are typically constructed in an attempt to lessen this negative impact. Currently, the American Association of State Highway and Transportation Officials (AASHTO) and Highway Capacity Manual (HCM) represent the state-of-art and state-of-practice procedures for the design of truck climbing lanes. These procedures only consider the tangent vertical profile grades in the design of climbing lanes and do not capture the impact of vertical curvature on truck performance. The dissertation describes the TruckSIM framework for modeling vehicle motion along roadway sections by considering both the longitudinal and lateral forces acting on a vehicle. In doing so, the tool reflects the impact of horizontal and vertical alignment on a vehicle's longitudinal motion. The model is capable of reading Global Positioning System (GPS) (longitude, latitude, and altitude), roadway, and vehicle data. The dissertation demonstrates the validity of the software modeling procedures against field data and the HCM procedures. It is anticipated that by automating the design procedures and considering different vehicle and roadway characteristics on truck motion, the TruckSIM software will be of considerable assistance to traffic engineers in the design of roadways. The Global Positioning System (GPS) was originally built by the U.S. Department of Defense to provide the military with a super-precise form of worldwide positioning. With time, GPS units were introduced into the civilian domain and provided transportation professionals with an opportunity to capitalize on this unique instrumentation. With this GPS capability, this research investigates the feasibility of using inexpensive WAAS-capable units to estimate roadway vertical and horizontal profiles. The profiles that are generated by these inexpensive units (less than $500) are compared to the profiles generated by expensive carrier-phase DGPS units ($30,000 per unit including the base station). The results of this study demonstrate that the use of data smoothing and stacking techniques with the WAAS data provides grade estimates that are accurate within 10% of those generated by the carrier-phase DGPS units and thus offer a cost effective tool for providing input data to the TruckSIM software. Using the TruckSIM software, this research effort investigates truck performance reflective of various truck and road characteristics. These characteristics include vehicle engine power, weight-to-power ratio, pavement type, pavement condition, aerodynamic aid features, engine efficiency, tire type, and percentage mass on tractive axle. The study demonstrates that the vehicle weight-to-power ratio, vehicle engine power, pavement surface condition, tire type, aerodynamic aids, and engine efficiency are critical factors in the design of truck climbing lanes. / Ph. D.

Obtaining accurate and precise position information is critical in precision and autonomous agriculture. Systems accurate to the centimeter-level are available, but may be prohibitively expensive for relatively small farms and tasks that involve multiple vehicles. Optical resection is proposed as a potentially more cost-effective and scalable positioning system for such cases. The proposed system involves the placement of optical beacons at known locations throughout the environment and the use of cameras on the vehicle to detect the apparent angles between beacons. The position of the vehicle can be calculated with resection when three or four beacons are identified. In addition, the system provides precise orientation information, so a separate inertial measurement unit is not required. The system is seen as potentially cost-effective by taking advantage of the precision and low cost of digital image sensors. Whereas the components in other positioning systems tend to be more specialized, the widespread consumer demand for inexpensive and high quality cameras has allowed for billions of dollars of research and development to be spread across billions of image sensors. / Master of Science

A number of tests were conducted to determine the realizable accuracies of the Global Positioning System for natural resource conditions. The effects of terrain, forest canopy, number of consecutive position fixes, and PDOP on accuracy were evaluated. Position accuracies were determined for a total of 27 sites: three replicate sites selected for each of nine distinct conditions: three canopy (deciduous, coniferous, open) and three terrain (ridge, slope, valley) in all possible combinations. Each site was visited ten times over a span of eight months to collect position data, for ten replicates of 60, 100, 200, 300, and 500 position fixes. The mean differentially corrected positional accuracy for all sites was 4.35 meters with 95 percent of the positions estimated within 10.2 meters of the true value. The least accurate differential position data were observed at coniferous sites. Positional accuracy was higher for deciduous sites and the most accurate differential position data was collected at open sites. Accuracy increased with increasing number of position fixes. When the number of position fixes increased from 60 to 500, mean accuracy increased 46.7% at deciduous sites, 32.8% at coniferous sites, and 44.5% at open sites. The average time required by the GPS receiver to lock onto four satellites and begin collecting positions varied from one to two minutes. The most time was spent collecting position fixes at coniferous sites. No correlation was found between accuracy and the receiver's distance from the base-station. Nine replicates of 300 position fixes were averaged for six sites, which ranged from 43 kilometers to 247 kilometers from a Virginia Tech base-station. Mean accuracy ranged from 1.48 meters to 2.43 meters. GPS position data were evaluated for ease of conversion to GIS formats. Conversion was accomplished without problems. / Master of Science

This dissertation describes a novel method of providing position-location from geosynchronous communication satellites. The Global Positioning System (GPS) has become the standard for position-location and navigation in the world. It provides extremely accurate coordinates to military users and slightly less accurate coordinates to "non-authorized" users. Disadvantages of GPS are complexity and high cost. The U.S. Department of Defense (DoD) has spent billions of dollars in developing and fielding the system. Maintenance and GPS satellite replenishment costs will continue to climb. A simpler, lower cost alternative to the GPS system is explored. This study describes a position-location system using transponders on-board geosynchronous communication satellites. The system uses three geosynchronous communication satellites at a time to relay synchronized television signals. The signals provide a timing system to measure the ranges from the satellites to the receiver. The least squares method is used to calculate the location of the receiver. A software model is developed to demonstrate the ability of the system to "track" three geosynchronous satellites and calculate receiver position. A test is conducted to demonstrate the use of television signals to provide timing for the system. The basic model is further refined by adding perturbation forces which act on the satellites. The Intelsat Eleven-Parameter algorithm is incorporated into the systenl model and provided the most precise location of the satellites. The accuracy of the proposed system in determining the position-location of the receiver is estimated based on the results of the simulation and the test. Further research is proposed to build on the concepts discussed in this dissertation. / Ph. D.

Radio signals transmitted by GPS satellites orbiting the Earth are modulated as they propagate through the electrically charged plasmasphere and ionosphere in the near-Earth space environment. Through a linear combination of GPS range and phase measurements observed on two carrier frequencies by terrestrial-based GPS receivers, the ionospheric total electron content (TEC) along oblique GPS signal paths may be quantified. Simultaneous observations of signals transmitted by multiple GPS satellites and observed from a network of South African dual frequency GPS receivers, constitute a spatially dense ionospheric measurement source over the region. A new methodology, based on an adjusted spherical harmonic (ASHA) expansion, was developed to estimate diurnal vertical TEC over the region using GPS observations over the region. The performance of the ASHA methodology to estimate diurnal TEC and satellite and receiver differential clock biases (DCBs) for a single GPS receiver was first tested with simulation data and subsequently applied to observed GPS data. The resulting diurnal TEC profiles estimated from GPS observations compared favourably to measurements from three South African ionosondes and two other GPS-based methodologies for 2006 solstice and equinox dates. The ASHA methodology was applied to calculating diurnal two-dimensional TEC maps from multiple receivers in the South African GPS network. The space physics application of the newly developed methodology was demonstrated by investigating the ionosphere’s behaviour during a severe geomagnetic storm and investigating the long-term ionospheric stability in support of the proposed Square Kilometre Array (SKA) radio astronomy project. The feasibility of employing the newly developed technique in an operational near real-time system for estimating and dissimenating TEC values over Southern Africa using observations from a regional GPS receiver network, was investigated.

M. Tech. (Department of Information Technology, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Tracking involves information gathering, manipulation and proving information on the location of a set item. Many single or hybrid technologies – Global Positioning System (GPS), Radio Frequency (RF), Bluetooth (BLT) or Wireless Fidelity (WiFi) – have been used to provide tracking information of an asset of interest. The use of hybrid technology in tracking assets has proven to be effective if the selection of the technologies used is done correctly. This study used a hybrid of GPS and Radio Frequency technologies to track assets of interest because of their characteristics for use inside and outside a building. In this study GPS geo-fencing was used and time interval was used to receive data from the technology. Heuristic methodology, which enabled us to divide a room into sections, was used, where testing was done in sections in a room with different types of material, such as bricks, wood or metal, and the RF signal degradation, called attenuation, was measured. A straight-line distance and a sum of distances at 30-minute intervals were calculated to determine how far the asset had travelled from the point of origin to the new position. A distance of less than 10 metres was ignored. Geofencing was used to trigger an event since it indicates that the asset has crossed the permitted boundary. An RF reader was placed at the door to identify when the asset left a building and triggered an event. A model was used for searching for a missing item in a room. The results showed that the system was able to produce two distances, one straight-line distance and the other the approximate sum distance travelled by the asset in 30-minute intervals. The RF model was able to find an asset in a room filled with different materials.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper describes the development of a compact mobile telemetry system using commercial-off-the-shelf components. The personal computer-based systems support microwave pulse code modulation and serial spread-spectrum radio modem telemetry. The mobile ground station provides data display and archiving of test activities, air-ground communications between experimenters and the flight test crew, and acts as a flight test Differential Global Positioning System base station. The success of the systems indicates that functional telemetry capabilities can be established for small flight test programs at modest cost.