Ground Wave Radar Research Articles

Remote sensing of icebergs by ground-wave Doppler radar

A software detection model has been developed to predict the returned Doppler spectrum for an iceberg target for ground-wave Doppler radars. This software model is based on proposed new estimates for the backscattered Doppler-dependent iceberg cross section for assumed iceberg models, as well as the backscattered Doppler spectrum from the ocean surface. The model includes estimates for forward and reverse transmission losses, based on classical spherical earth derivations. In addition, the transmission losses account for the effects of surface roughness through a modified surface impedance. Standard estimates for man-made and atmospheric noise have been considered in the detection model. A comparison between the results predicted by the detection model and data acquired during an experiment conducted at Byron Bay, Labrador, Canada has been effected. The hardware used for the experiment was an HF Doppler radar operating at 25.40 MHz. The transmitting antenna was a three-element Yagi array and the receiving antenna a 24-element narrow-beam linear array. By using iceberg ground truthing information the Doppler spectrum for individual icebergs was predicted using the software model. The predicted spectra were compared with the received spectra on a target signal-to-noise power ratio basis. The results of this comparison give a degree of confidence to the detection model and show that ground-wave radars are effective ice hazard remote sensors.

Panel discussion summary [HF radar technology for ocean-surface remote sensing and surveillance

Following the presentation of papers at the IEEE/URSI Special Session on HF Radar at Vancouver, B.C., Canada, an afternoon was devoted to discussion of the status of HF radar technology for ocean-surface remote sensing and surveillance. Participants included previous speakers and authors, as well as members of the audience. The status summary can be grouped into two categories: the capabilities of the various systems, and their accuracies. The present section is formulated from: a) notes of the discussion taken by the two editors; b) notes taken by J.R. Barnum of SRI International and R.A. Williams of NOM, whose assistance is gratefully acknowledged; and c) information gleaned from the manuscripts submitted and published in this Special Issue. Two main classes of HF radar systems are treated separately here: ground-wave and skywave radars.

Evaluation of HF ground-wave radar on the east coast of Canada

HF ground-wave radar runs of roughly ten days duration were carded out in two tidally dominated regions off the Canadian East Coast in conjunction with oceanographic experiments. The surface current deduced from the HF radar observations are here compared with Eulerian velocities from various moored current meters and Lagrangian velocities derived from surface drifters. The agreement with the current meters is generally better than 0.05 m/s. Real current shear in the top 15 m of the water column of up to 0.1 m/s, lasting for up to 12 h, was observed on several occasions, coincident with wind reversals. The agreement between moored instruments and shallow-draft rectangular drifters was good, and with deeper draft cylindrical drifters it was excellent.

Rijkswaterstaat's interest in HF radar

In this paper an explanation is given of Rijkswaterstaat's need for hydrological and meteorological information. The present means to gather this information are described together with their limitations. Future developments in the field of HF narrow-beam groundwave radar systems are indicated and some recommendations are given for the design of an operational HF radar system for Rijkswaterstaat (RWS).

An assessment of a FMICW ground-wave radar system for ocean wave studies

Abstract In February 1982 the first successful trial of a frequency modulated, interrupted, continuous wave (FMICW), monostatic ground-wave radar for sea backscatter studies was carried out. Since then data have been collected in a number of different meteorological conditions over a range of HF frequencies. The data are presented and compared with simulated Doppler spectra obtained by evaluating the integral equation, which relates the sea backscatter spectrum to the ocean wave directional spectrum (Barrick 1972). The dynamic range performance of the system is as good as or better than has been achieved by pulse radars currently in operation. Good agreement with the theoretical formulation is demonstrated

Propagation and scattering in MF/HF groundwave radar

Vertically polarised MF/HF groundwave radar has been used over the frequency range 2-30 MHz for sea-state sensing, surface-current measurement and ship tracking. The paper reviews the propagation factors and noise environment which control the performance of such systems. The various definitions of antenna gain, propagation loss and sea backscattering coefficient are discussed and related to physical concepts. The various first-order and higher-order mechanisms of scattering are reviewed and related to the relevant electromagnetic and hydrodynamic processes involved. These processes, linked with the velocities of the water waves responsible, result in a Doppler spectrum of the radar echoes which may be used to infer the wave height and wave directional spectra on the sea surface. Particular attention is directed towards remaining problems in understanding these processes. In evolving radars for ship tracking, detectability depends on the knowledge of the Doppler spectra of the sea clutter and, in particular, on limitations in directional determination of ship echoes with practical antenna systems located on available coastal sites. In conclusion, experimental measurements of sea echo, ship tracks and antenna-array characterisations are compared with theoretical considerations.

Off-shore wind measurements by HF doppler ground-wave radar

Remote measurements of wind velocity are performed, up to 100 km away from the shore, by using some features of the Doppler spectrum of HF radio waves backscattered by the sea. The variation with radio-frequency of the ratio of the amplitudes of the two Bragg lines in this spectrum shows a discontinuity occurring at a value simply related to the wind velocity. The validity of these measurements is discussed by comparison with meteorological data obtained by conventional methods.