My areas of interest include:
- Non-gravitational effects on GPS satellite orbits
- Higher-order ionospheric effects on GPS
- GPS reference frames and precise long-term GPS timeseries
- GPS data processing and analysis, particularly in relation to vertical rates of ground motion
- Sea-level change (and climate change more generally)
- Vertical reference surfaces - chart datum.
They came about gradually during the course of my somewhat zig-zag career to date:
PhD
The title of my PhD thesis is "Modelling higher-order ionospheric effects on global GPS solutions" and you can read the abstract here. My supervisors were Matt King and Phil Moore.
I explain higher order ionospheric effects on GPS as follows: as signals travel from the GPS satellites in orbit to the GPS receiver, they pass through the ionosphere. This affects the wave carrying the GPS signal, causing an error. The effect is frequency dependent, so to first order it can be removed by forming a combination of the GPS L1 and L2 frequencies. However, higher order terms are still present, so I investigated different ways of modelling the second order and third order terms by coding them into the GAMIT GPS processing software. I also implemented a model of bending or refraction of the signal and investigated the effect.
If you would like to learn more, have a look at my publications, particularly the review paper.
MSc dissertation
My dissertation for the MSc in Hydrographic Surveying was on "Vertical Offshore Datums - Investigating the creation of a mean sea surface". My supervisors were Jon Iliffe and Marek Ziebart at UCL. To read the abstract follow this link:
MSci dissertation
My MSci dissertation at the University of Cambridge was on "Climate change in the North Atlantic during the last Interglaciation" and was supervised by Mark Chapman, then working at the Godwin Laboratory. It involved using foraminifera (species counts and oxygen and carbon isotope ratios) and ice rafted debris from a sediment core to look at how the climate was changing at that time. During the project I counted and identified ~ 45000 individual microfossils.