Search Results (1 - 5 of 5 Results)

Sort By  
Sort Dir
 
Results per page  

Yen, Shih-WeiTwo-Satellite Positioning with a Stable Frequency Reference, Altimeters, and Bistatic Satellite Altimetry
Doctor of Philosophy (PhD), Ohio University, 2017, Electrical Engineering & Computer Science (Engineering and Technology)
This dissertation investigates the feasibility of completing an aircraft precision approach using two GNSS satellites in combination with a Stable Frequency Reference (SFR) and various altimeters. Two different sensor combinations are implemented for altimetry. The first combination uses both barometric and radar altimeters to provide height estimates, which are integrated with Global Navigation Satellite Systems (GNSS) satellites from different constellations with a SFR for positioning. Before the start of the approach, a full GNSS solution is used to calibrate the SFR and the vertical solution relative to the aircraft touchdown point (ATP). The theoretical clock and position error covariance is derived as a function of measurement error, satellite geometry, SFR stability, barometric height and radar altimeter performance. Detailed error models for each of the navigation sensors are developed for a covariance analysis. This is followed by both simulations and evaluations using flight test data to verify the positioning accuracy and the feasibility of completing an aircraft precision approach with only two satellites from different constellations. With respect to Category I precision approach requirements of 16 m (95%) horizontal and 4 m (95%) vertical, the horizontal radial 2-σ positioning performance is approximately 6 m, while the vertical 2-σ positioning performance is approximately 4 m. The second sensor combination uses GPS reflection measurements from a software defined receiver (SDR) for aircraft passive bistatic altimetry, and a SFR to continue navigation when only two GPS satellites are available. The scenario for this combination is focused on flights over water, which provides strong reflected signals while alternate terrestrial radio navigation signals are generally not available. Theoretical clock and position error covariance are derived as a function of measurement error, satellite geometry, SFR stability, and GPS bistatic altimetry performance. This is followed by computer simulations, and evaluations using flight test data to characterize the positioning performance. The positioning performance in east and north are 13.6 m (2-σ) and 9.0 m (2-σ), respectively, and 5.6 m (2-σ) in vertical over 170 seconds of 2-satellite positioning.

Committee:

Frank van Graas (Advisor); Maarten Uijt de Haag (Advisor); Michael Braasch (Committee Member); Douglas Lawrence (Committee Member)

Subjects:

Electrical Engineering

Keywords:

GPS; GLONASS; GNSS; two-satellite positioning; Rubidium oscillator; barometric altimeter; radar altimeter; bistatic satellite altimetry; aircraft navigation; integrated navigation; covariance analysis

Engelis, TheodossiosRadial orbit error reduction and sea surface topography determination using satellite altimetry /
Doctor of Philosophy, The Ohio State University, 1987, Graduate School

Committee:

Not Provided (Other)

Subjects:

Education

Keywords:

Artificial satellites;Sea level;Altimeter

Cheng, Kai-chienAnalysis of water level measurements using GPS
Doctor of Philosophy, The Ohio State University, 2005, Geodetic Science and Surveying
Accurate knowledge about sea level and its change is essential to humanity because a large proportion of the Earth's population lives in coastal regions. This study discusses the existing techniques for sea level measurements, including the use of different types of gauges (e.g., water level gauge or tide gauge, and bottom pressure gauge), as well as GPS and satellite altimetry. The GPS water level measurements from a buoy or a vessel are presented and utilized in this study along with other techniques to collect ellipsoidal, geocentric sea surface height measurements for various studies that help improve our knowledge about sea level and its change. An operational technique of using GPS water level measurement is proposed in this study. The limitation and an upper bound accuracy of the kinematic (epoch-by-epoch) positioning in terms of baseline length are discussed. A set of GPS data in Lake Erie, including buoy data as well as a local GPS network on land, are used to provide the numerical results. Three main applications of using the GPS water level measurements are presented in this study. They are integration of various data sources in the coastal, satellite radar calibration, and GPS hydrology. The objective of these applications is to demonstrate the potential of the GPS technique in collecting water level measurements. The use of GPS measurements is also highlighted in connection with the improvement that they may bring to various techniques such as the use of coastal water level gauge and bottom pressure gauge, and satellite altimetry. This study discusses three applications of using GPS water level measurements. They have shown the capabilities of the GPS technique on buoys or vessels to interact with other techniques for making accurate water level measurements. With the water impacts humanity, such measurements have proven to be valuable for better understanding for the coastal environment.

Committee:

Che Kwan Shum (Advisor)

Subjects:

Geodesy

Keywords:

GPS; GPS water level; tide gauge; satellite altimetry; altimeter calibration; GPS hydrology

Mainville, AndreThe altimetry-gravimetry problem using orthonormal base functions /
Doctor of Philosophy, The Ohio State University, 1987, Graduate School

Committee:

Not Provided (Other)

Subjects:

Education

Keywords:

Gravimeters;Altimeter;Normal forms

Wheelock-Davis, Emily JElevation Changes in Greenland over Two Decades from Cross-Platform LIDAR Analysis
Master of Science, The Ohio State University, 2013, Geodetic Science and Surveying
NASA’s Airborne Topographic Mapper (ATM) and the Land, Vegetation, and Ice Sensor (LVIS) are two airborne Light Detection and Ranging (LIDAR) systems that retrieve information about surface elevation and roughness. Both altimeters have been flown in Greenland to measure changes in ice sheet surface elevation through time. ATM surveys in the region have been conducted nearly every year since 1993, with extended, annual coverage by ATM and LVIS since 2009 during Operation IceBridge (OIB). These recent surveys provided repeat coverage of many older, previously unrepeated, ATM flight lines. Combined, these datasets offer a unique multi-decadal record of ice sheet change. The different beam trajectory technologies on each system require a specific methodology to compare coincident data between the systems. Here, a general slope-fit regression analysis is applied to difference overlapping ATM and LVIS data. This method is validated using overlapping field data over ice-free terrain. Examination is made of the spatial and temporal distribution of ice sheet surface elevation changes since 1993 revealed by cross-platform analysis.

Committee:

Ian Howat (Advisor); Michael Durand (Committee Member)

Subjects:

Climate Change; Earth; Environmental Science; Geography; Physical Geography; Remote Sensing

Keywords:

Greenland; remote sensing; lidar; laser altimeter; ATM; LVIS; Operation IceBridge; elevation change; ice sheets