A robust feature extraction and parameterized fitting algorithm for bottom-side oblique and vertical incidence ionograms

Automatic processing of ionograms to extract ionospheric propagation characteristics and electron density profile parameters is an important enabling step toward constructing real time data-assimilative models of the ionosphere. A robust and reliable feature extraction and fitting algorithm that supports both oblique and vertical incidence ionograms has recently been developed to enhance the regional ionospheric model for Australia's Jindalee Operational Radar Network. The so-called DST-IIP algorithm is an autoscaling technique based on a constrained quasi-parabolic segment profile, which is modified from its climatological estimate to fit a set of key peak, edge, and line features in the ionogram image, representing the E, sporadic-E (Es), and F2 layers. The F2 fitting, in particular, is performed in the ionogram domain, using analytic ray-tracing and homing to produce a synthetic trace that reproduces the image features. Following thorough testing on a large database of midlatitude Australian ionograms, the DST-IIP algorithm now runs routinely on-board DST Group's Digital Oblique Receiving System. This paper provides an overview of the technique, along with sample results and performance statistics.