Mal Heron

James Cook university Queensland, Physics Department, Adjunct

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Mal Heron is a trained physicist and qualified engineer with expertise in electromagnetic wave propagation and ocean science. He has broad experience in ocean surface radar and applications. He graduated with a PhD from The University of Auckland in 1971, and is a Fellow of IEEE and of Engineers Australia. He is CEO of Portmap Remote Ocean Sensing Pty Ltd based in Queensland, Australia.

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Papers by Mal Heron

HF Ocean Radars in Ship Navigation

2018 IEEE 27th International Symposium on Industrial Electronics (ISIE), 2018

Phased HF ocean radar technology is being widely used for surface current mapping in coastal wate... more Phased HF ocean radar technology is being widely used for surface current mapping in coastal waters, and the WERA radar produces gridded maps of surface currents and wave heights. These data can be put into existing AIS ship navigation messages to provide Aid to Navigation information to ship's bridges in coastal waters. A case study in the Straits of Malacca shows how this can be achieved within the protocols of the AIS, and demonstrates the way to improved functionality in autonomous shipping.

Water quality in a major port monitored by HF ocean surface radar

'Challenges of Our Changing Global Environment'. Conference Proceedings. OCEANS '95 MTS/IEEE

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A mobile HF impulse source locator

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Performance of a VHF ocean surface radar in the surf zone

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Interpretation of VHF radar echoes from a complex flow field

Bragg lines on spectra from ocean radar systems are broadened when echoes come into the antenna f... more Bragg lines on spectra from ocean radar systems are broadened when echoes come into the antenna from different azimuths. Phased-array systems minimise the effects of this by selecting a small target area on the sea surface by beam-forming and range-gating. While phased array systems are better conditioned for high spatial resolution than direction finding systems, in some cases there may be fine structure in the surface current field within the smallest of target areas. In estuaries or other areas where there are sand banks and low islands there is potential for contamination from side-lobes of phased array antennas to contaminate adjacent pixels. This paper uses data from an area of highly complex flow field in Dingle Bay, Ireland to examine the complex structure of Bragg echoes. A numerical hydrodynamic model is used as an aid in understanding the degree of structure to be expected in the Bragg lines, and an improved analysis is described to extract surface current data from the r...

On the inclusion of Stokes and Ekman surface currents into hydrodynamic models

OCEANS Conference, 2008

Recently published results (Mao and Heron, J. Phys. Oceanog., 2008) comparing sea surface current... more Recently published results (Mao and Heron, J. Phys. Oceanog., 2008) comparing sea surface currents, measured by a 30 MHz ocean radar with wind speed and direction under a range of conditions in Bass Strait, Victoria, Australia indicate that the coupling between wind and surface currents depends on the maturity of the sea wave spectrum. For a mature sea the main

A probabilistic method of paleobiogeographic analysis

Lethaia, 1977

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Line broadening on HF ocean surface radar backscatter spectra

IEEE Journal of Oceanic Engineering, 1985

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HF radar QC on azimuth measurement: Dealing with sea echoes seemingly from the land

OCEANS 2016 MTS/IEEE Monterey, 2016

Echoes that seemingly come from the land occur on both phased array and crossed loop systems. Pas... more Echoes that seemingly come from the land occur on both phased array and crossed loop systems. Past practice has generally been to avoid pointing the phased array beam at land targets, and masking out any land echoes from the radials data file for crossed loop system. In an attempt to avoid this sanitising of data this paper addresses possible causes and evidence-based procedures for dealing with the effect. Phased array radars do get echoes when the beam is pointed towards land and it is shown that the echo power drops significantly when the main beam is swept across the coast from sea to land. This change in amplitude can be used to develop a robust criterion for the elimination of land echoes. For crossed loop direction finding systems the error in determination of the bearing of sea echoes is used to identify a coastal land area in which the echoes are actually from true sea scatter from the adjacent ocean. It is suggested that these echoes should be included in the estimation of sea surface currents.

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Nonintrusive measurement of ionisation in vegetation fire plasma

The European Physical Journal Applied Physics, 2008

Vegetation fires are slightly ionised gaseous medium. Omnipresent alkali metal species in plant's... more Vegetation fires are slightly ionised gaseous medium. Omnipresent alkali metal species in plant's organic structure are the main source of thermally produced electrons in the fires. In the flames, electronneutral particle collisions dominate other modes of particle interaction. The collision regime absorbs some of the incident energy when the fire is illuminated with electromagnetic waves. The rate of electromagnetic wave absorption in the vegetation fires has implications on the safety of fire-fighters. During wildfire suppression, radio communication blackout at vhf/uhf has been experienced. This may be partly due to thermal ionisation in the fire. In the experiment, the extent of ionisation in vegetation fires is measured using a 2-port vector network analyser. X-band microwaves are caused to propagate combustion zones of eucalyptus bark and guinea grass fires with maximum temperatures of 1114 and 1054 K respectively. Alkali content in the vegetation fuel was different. Measurements show maximum ionisation in flames produced from guinea grass, which had almost twice much potassium as that of eucalyptus bark, to be 2.63 × 10 16 m −3 while that produced in eucalyptus bark flame was 1.46 × 10 16 m −3 .

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Design parameters for an HF ocean surface radar installation

Europe Oceans 2005, 2005

A long range HF radar system is being installed in the southern part of the Great Barrier Reef La... more A long range HF radar system is being installed in the southern part of the Great Barrier Reef Lagoon as one component in a monitoring site for coral reef bleaching. The scientific requirements of the wider project are to monitor physical parameters which impact on coral bleaching and is guided by the "Degree Heating Days" product produced by the NOAA Coral Reef Watch group for bleaching event prediction. The relevant physical parameters are currents, waves and insolation. HF radar can provide monitoring solutions for the first two of these parameters. The design parameters for the installation follow from these requirements and we review the HF radar solutions available. The determination of range is common to all systems and is made by time domain measurements. The determination of azimuth from a radar station to the target pixel on the sea surface has traditionally been more difficult. The configuration of antennas is a critical issue for the installation and there are some trade-offs to be made. The phased array solution is technically superior but has a larger space requirement for the antennas on the coast. The crossed-loop plus dipole antenna system has a smaller antenna footprint but has limitations in the quality of the surface current coverage and is restricted to parameters which can be extracted from the first-order part of the Doppler spectrum.

Tsunami Monitoring by HF Ocean Radar: Time and Space Scales

OCEANS 2007 - Europe, 2007

HF coastal ocean radars are ideal instruments for detection of surface currents in coastal waters... more HF coastal ocean radars are ideal instruments for detection of surface currents in coastal waters and have had wide application for monitoring tidal and wind driven surface currents. This paper addresses the questions of spatial and temporal scales for optimal detection of tsunami properties by HF radar at the shelf break and on the continental shelf itself. Two approaches are used in this evaluation. One is a stylized tsunami wave approaching a shelf which has parallel bathymetry contours and a shelf with uniform depth. In this case the non-linear effects at the edge of the shelf are the same at all points along the shelf edge, and the subsequent wave train emerging onto the shelf has parallel wave fronts. The second approach is a case study of a real section of shelf-edge and shelf bathymetry. In this case numerical modelling indicates that there is a complex pattern of surface currents at the shelf break which varies in space and time. The subsequent wave train has a complex wave front which can be considered to be generated from point sources along the shelf edge. These wave fronts are shaped by local shelf bathymetry as well as interference of waves from the originating source points at the shelf edge. In the case of real bathymetry there are complexities in the surface current field which will produce different outcomes for direction-finding and phased array types of HF radar facilities. Because of its ability to resolve spatially complex current patterns, the phased array system is preferred for tsunami observation networks.

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VHF PortMap Sea Surface Radar Observations in a Shipping Channel

OCEANS 2006 - Asia Pacific, 2006

A new sea surface radar system is described, covered an azimuthal range of 120 degrees. The which... more A new sea surface radar system is described, covered an azimuthal range of 120 degrees. The which gives a spatial resolution of 100 m and operating ranges to up to 3 km. The deployment of the dual-radar system at the time for data collection for each radar, and for Lido Entrance to the Venice Lagoon gave current flow data in each antenna position, is about 4.5 minutes. The the channel and provided detail of a complex counter-flow at two radars operate alternately, one being off the end of the channel where it debouches into the Adriatic Sea. This circulating flow near the end of the Channel is while the other is on. We programmed the similar to that observed in wide-mouthed natural channels system to operate in 5-minute time slots so that and is bringing turbid water into the channel. The presence of each station would go through its 4-position the circulation at the end of the channel has some consequences for sediment dynamics at the site. This sequence in 40 minutes. Due to some hardware deployment demonstrates the functionality of the PortMap problems in this first deployment, we carried out radar in a busy shipping channel.

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PortMap- a VHF ocean surface radar for high spatial resolution

Europe Oceans 2005, 2005

... The two case studies shown had small-scale eddy features which would be difficult to visualis... more ... The two case studies shown had small-scale eddy features which would be difficult to visualise and understand without the mapping capability. ... surface current maps from Europe: http://ifmaxp 1 .ifm.uni-hamburg.de/ 7. Williams, J., B.Arens, D.Aubrey, P.Bell, A.Bizzaro, M.Collins ...

Microwave attenuation in forest fuel flames

Combustion and Flame, 2008

The flames of forest fuels form a weakly ionized gas. Assuming a Maxwellian velocity distribution... more The flames of forest fuels form a weakly ionized gas. Assuming a Maxwellian velocity distribution of flame particle and collision frequencies much higher than plasma frequencies, the propagation of microwaves through forest fuel flames is predicted to have attenuation and phase shift. A controlled fire burner was constructed where various natural vegetation materials could be used as fuel. The burner was equipped with thermocouples and used as a cavity for microwaves with a laboratory quality network analyzer to measure phase and attenuation. The controlled fires had temperatures in the range of 500-1000 K and microwave attenuation of 1.0-4.5 dB m −1 was observed across the 0.5 m diameter cavity. Attenuations of this magnitude could affect active remote sensing systems signals at microwave frequencies in forest fire environments where flame depths of up to 50 m are possible. In the experiment, temperature was not the only controlling parameter for the ionisation; type of fuel burnt also influenced it. Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) analysis of the composition of the fuel confirmed that a higher content of alkali (with low ionization potential) lead to higher electron densities. Electron densities in the range of 0.32-3.21 × 10 16 m −3 and collision frequencies of 1.1-4.0 × 10 10 s −1 were observed for flames with temperature in the range of 730-1000 K.

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Ionospheric scintillation to 1 GHz

Short-wave ocean wave slope models for use in remote sensing data analysis

IEEE Transactions on Geoscience and Remote Sensing, 2006

Recent developments in the directionality of sea waves are reviewed and adapted into a working mo... more Recent developments in the directionality of sea waves are reviewed and adapted into a working model for radiometric remote sensing. There is a weight of evidence, both theoretical and observational, that a bimodality exists in the directional wave spectrum for sea surface gravity waves at wavenumbers greater than the value at the peak of the spectrum. We develop a model for the directional splitting which is consistent with observations but which extrapolates in a credible manner to the omnidirectionality observed at wavelengths around 0.3 m. At shorter wavelengths the directional spectrum becomes unimodal and has an approximately constant shape across the gravity-capillary wave regime. A working model is suggested for the directionality of the wave spectrum to improve the analysis of radiometric sea surface data. The model will also be useful for other analyses including active radar techniques which use Bragg scatter.

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$Research paper thumbnail of The Refraction of Satellite Signals$

The Refraction of Satellite Signals

ABSTRACT

Guest Editorial Special Issue on Marine and Maritime Radar Remote Sensing

IEEE Journal of Oceanic Engineering

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Can HF ocean radar provide vertical current profile estimates?

2017 IEEE Underwater Technology (UT), 2017

This paper explores the possibility of using real-time measurements of surface current vectors an... more This paper explores the possibility of using real-time measurements of surface current vectors and U10 wind vectors to estimate the 3D current field. Calibration is required by using an ADCP over a one-month period to find the roughness parameter, z0, for the logarithmic boundary layer. Ekman and Stokes current profiles are derived from the U10 wind vector. This methodology uses some of the assumptions that 3D models normally use, but with its empirical input at the surface from an HF ocean radar, it has the potential to be more accurate in real-time operational tasks than 3D models.

HF Ocean Radars in Ship Navigation

2018 IEEE 27th International Symposium on Industrial Electronics (ISIE), 2018