  In this paper we apply a Bayesian framework to the problem of geodesic curve
matching. Given a template curve, the geodesic equations provide a mapping from
initial conditions for the conjugate momentum onto topologically equivalent
shapes. Here, we aim to recover the well-defined posterior distribution on the
initial momentum which gives rise to observed points on the target curve; this
is achieved by explicitly including a reparameterisation in the formulation.
Appropriate priors are chosen for the functions which together determine this
field and the positions of the observation points, the initial momentum $p_0$
and the reparameterisation vector field $\nu$, informed by regularity results
about the forward model. Having done this, we illustrate how Maximum Likelihood
Estimators (MLEs) can be used to find regions of high posterior density, but
also how we can apply recently developed \SLC{Markov chain Monte Carlo (MCMC)}
methods on function spaces to characterise the whole of the posterior density.
These illustrative examples also include scenarios where the posterior
distribution is multimodal and irregular, leading us to the conclusion that
knowledge of a state of global maximal posterior density does not always give
us the whole picture, and full posterior sampling can give better
quantification of likely states and the overall uncertainty inherent in the
problem.

Probability;Analysis of PDEs