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The Australian hydrographic service--charting Australia, the continent encircled by sea.

INTRODUCTION

Ensuring safety of life at sea requires the collection and dissemination of hydrographic data. The Australian Hydrographic Service (AHS) collects, manages and disseminates a vast amount of hydrographic information via its published paper charts and Electronic Navigational Charts (ENC) of Australia, its offshore islands and the waters around Papua New Guinea.

Incidents resulting from a lack of accurate data are potentially catastrophic in terms of loss of human life, economic loss, maritime security and degradation of the marine environment. The AHS is also the Australian Defence Force agency responsible for the provision of maritime data and products for military operations, exercises and support roles.

The charts produced by AHS provide information that underpins the 'Blue Economy'. This term refers to the sum of all economic activity associated with the oceans, seas, harbours, ports and coastal zones. Every human activity conducted in, on or under the sea, depends on knowing the depth and the nature of the seafloor, the identification of any hazards and an understanding of the tides, currents and the characteristics of the water column.

The Australian Hydrographic Service is the Commonwealth Government agency responsible for the publication and distribution of nautical charts and publications required for meeting Australia's responsibilities under the Safety of Life at Sea (SOLAS) and the Navigation Act requirements which includes ships navigating in Australian waters. The AHS is also the Australian Defence Force (ADF) agency responsible for the provision of operational surveying support and maritime Military Geographic Information for ADF operations and exercises.

Founded in 1911, the Royal Australian Navy (RAN) assumed responsibility for hydrographic surveys in 1920, and for the publication of charts in 1942. In 1946 Cabinet decided that the Navy would maintain the national responsibility for hydrographic surveying, nautical charting and the provision of hydrographic services. Hydrographic charts and ENCs are legal documents and the AHS is responsible for ensuring they are correct and up to date.

In 1978 the Memorandum of Understanding (MOU) on Hydrographic Arrangements between Department of Transport and Civil Aviation, Papua New Guinea and Department of Defence, Australia gave the AHS charting responsibilities for PNG, that is, to publish and maintain charts of PNG waters.

As the Australian national charting authority, the AHS is responsible for the management of Australia's surveying program and charting area. We are responsible for charting over 30,000 km of coastline and more than one-eighth of the earth's water surface. In 2016 the AHS will be expanding its responsibilities to publish and maintain navigational charting products for the Solomon Islands.

THE BLUE ECONOMY

Hydrographic services are essential enablers for the safe and efficient transport of goods and people within the maritime domain and are integral for the economy, development of effective infrastructure and the future growth of Australia. As an island nation, Australia is dependent on maritime trade more than 90% of our total trade by weight is carried by ship, which is valued at close to $300 billion annually.

Official nautical charts are used to facilitate more than 10,000 international trading voyages each year, including in excess of 25,000 port entries (Fig. 1.). Therefore hydrographic surveying and nautical charting forms a significant part of Australia's national infrastructure providing access to ports from the sea.

Increased maritime trade, larger vessels and more requests for timely product delivery have placed increasing pressure on the sensitive marine environment. Providing mariners with information about shipping routes, environmentally sensitive sea areas, and restricted and protected zones helps ensure that the marine environment remains protected.

Safety of life at sea also plays a major role in hydrography. Incidents due to lack of hydrographic data can be potentially catastrophic in terms of: loss of human life, economic impact, maritime security, degradation of the marine environment and safe navigation.

CHART EVOLUTION

The earliest nautical charts were based upon limited information and were far more superstition than fact. Some charts even said "here be monsters". Up until the 1700s content was built up over time through the acquisition of ad-hoc information and the occasional voyage of discovery.

For Australia, vast sections of the continent were missing or were no more than guess-work, there were gross distortions in shape and scale, and the detection and positioning of underwater hazards was limited to what was visible to the eye.

Technology progressed with the development of celestial navigation methods, time pieces, controlled survey methods and echo sounders. For example, Captain Cook's 1770 chart shows the greater accuracy achievable when using chronometers to determine longitude. The first ship to use this chart was HMS Sirius in 1787.

Charts using imperial units of measurement that were, compiled up to around 1970, were typified by a variety of horizontal and vertical datums. The last of the imperial-unit charts was Aus444 which was replaced in March 2012. All the charts are now metric, following the AHO's multi-million dollar project to metricate and modernise our portfolio to modern standards and convert them to vector ENCs (Fig. 2.).

Creation of ENCs from older charts, has therefore been a significant challenge and, in the Australian experience, has involved returning to the original surveys, re-referencing many of these surveys either against modern land survey networks, against satellite imagery, or by sending survey teams into the field with GPS. The project to convert all paper charts to ENCs was the largest program undertaken by the Australian Hydrographic Service in 60 years.

The development of instruments and systems used to conduct hydrographic surveys and the tools used to compile the resulting navigational charts and related products has changed significantly over time. It has been a journey from lead-line to echo sounder and sonar systems to laser, from sextant to radar and electronic shore based positioning systems to SATNAV and GPS; from pen and ink to geographic information system, all to collect and process hydrographic information and produce charts.

AHS PRODUCTS

The current AHS portfolio consists of 474 paper charts and 849 published Electronic Navigational Charts (ENCs). In the financial year of 2015-2016 the AHS published 1329 Notices to Mariners (NtMs) for paper charts and 1042 updates to ENCs.

AHS also manages the Digital Hydrographic Database (DHDB) which provides a system to store data and produce products, validate and assess all incoming survey data, produce and distribute Australian National Tide Tables (AHP11), the Seafarers Handbook for Australian Waters (AHP20), the Chart & Publication Maintenance Handbook (AHP24) and the Maritime Gazetteer of Australia (MGA).

CHARTING PRIORITIES

The list below provides guidance for prioritising charting, and activities that impact upon charting, in order to concentrate AHS resources to meet customer demands. The priority list specifically relates to the production of published navigational charts (both manuscript and electronic), tides and other nautical publications, and the data assessment and preparation activities associated with producing these products.

Priorities for national chart production are:

* The production of fortnightly Notices to Mariners and maintenance of navigationally significant dangers and changes to all forms of charts as they are discovered.

* A re-scheme of port charts and ENCs--In response to emerging demands from port authorities and in recognition that navigationally constrained areas are those that will benefit most from the availability of better larger-scale ENC coverage.

* A re-scheme of coastal charts and approach coverage on ENCs--only where existing arrangements are hazardous.

* A re-scheme of coastal passage and other shipping routes on ENCs--particularly those with the highest levels of SOLAS traffic.

* International obligations--the need to meet specific charting responsibilities to PNG and the Solomon Islands, and meet international responsibilities under the International Hydrographic Organisation (IHO) International Charting Scheme, including in the Antarctic region.

PRODUCTION TOOLS

These days all our navigation products are made using GIS software. The Production software we use is CARIS, which is a commercial software package customised for AHS purposes. The main components of CARIS utilised within Product Generation include:

* CARIS GIS, used for the registration and manipulation of source data.

* CARIS Editor, used for processing all bathymetric surveys onto a uniform datum. This will eventually be replaced by CARIS Bathy Data Base.

* CARIS HPD Source Editor, used for the compilation of source ENCs.

* CARIS HPD Product Editor, used to produce the published ENC products.

* CARIS Paper Chart Composer (CPCC), used to compile paper charts from the published ENCs.

SOURCE DATA

To compile a chart many areas of expertise is required and subject matter experts provide in-depth knowledge, decisions and guidance to the production process. The cartographer has the responsibility to acquire all the data and then portray the data to its optimum ensuring that the product he is producing is fit for purpose and meets all international standards and specifications.

The first step in creating a new chart, new edition or update is to collect the source data (Fig. 3.). A number of sources are used to create and update the charts such as:

* RAN bathymetric data

* Non-RAN bathymetric data privately captured surveys

* Port/harbour infrastructure

* Topographic information from local, state, and Commonwealth sources

* Satellite imagery

* Navigation aids

* Notices to Mariners

* Maritime boundaries and limits

* Larger scale charts and plans

* Tidal/geodetic data

* Wrecks

* Names

DATA CAPTURE

Hydrographic surveys and fairsheets were historically produced as paper products either by hand or by other means such as stencilling. Since then, all historic fairsheets have been captured electronically. There are many reasons to why they have been converted to digital:

* Take up less space--space efficient.

* Historical data is protected from insects, water damage etc.

* Easier to use--modern cartography is done using computers so it's easier to have the data already in electronic form.

* Files can be altered for processing purposes i.e. geo-referencing.

The fairsheets have all been scanned and saved as tiff images, many of which have also been geo-referenced as geo-tiffs. The geo-referencing is primarily done using CARIS software and often involves the transformation of the data to the WGS84 spheroid. This depends on the knowledge of the datum, ellipsoid and projection used to compile the paper fairsheet and the shifts needed to transform the data. Geo-referencing of old paper products can also be complicated by factors such as paper stretch which can affect the accuracy.

The geo-tiffs are then viewed in a GIS so the soundings printed on the images can be captured digitally as latitude, longitude and depth (x,y,z). Based on charting priorities, many (but not all) of the historical fairsheets have had their sounding information digitised and stored in vector format. The vector format most commonly used by the AHS is HTF (hydro transfer format). However the data is also stored, supplied and transferred in various other vector formats from port authorities and other agencies, these include .xyz, .dwg, .shp, cad, and .000 S-57 standard files.

DATA CAPTURE ISSUES

When attempting to create a seamless dataset including both bathymetric and topographic data, one needs to be very aware of the different vertical datums used, and the sign of the elevation (noting that soundings are positive downward from the Least Astronomical Tide (LAT)).

It is this "white ribbon", surf zone, inter-tidal area, littoral zone--whatever you might call it--that is of significant importance to paper charts and ENCs and is often poorly understood by land-based geospatial analysts and topographic cartographers. To a mariner these areas are to be avoided and the representation is vital for safety to navigation.

There is a requirement in nautical charting for the safest situation to always be shown which means that contours need to be drawn to represent the first occurrence of a particular depth coming from deeper water. This presents a challenge to the automated contouring packages and often contours need to be cartographically displaced to encompass a particular sounding.

It is far quicker to use automated contouring software packages to produce the contours on a chart, however none of these packages can replace the human eye in terms of accuracy, interpretation and presentation for use, as they are not smooth nor do they consider a shoal bias depiction.

Similarly, software limitations can cause challenges when geo-referencing data across the dateline. Most software is configured to think of the earth as four hemispheres: North, South, East and West. North and south latitudes are divided by the equatorial 0[degrees] line, with North having positive values and South having negative values. East and West longitudes are divided by the 0/180[degrees] line, with the East hemisphere being represented by positive values and the West by negative values. When an image is geo-referenced to positions crossing the hemispheres, GIS software will often display the geo-tiff as though it has been cut in half and mirror reversed. This can be overcome by geo-referencing the chart and assuming the earth is divided into 360 degrees of longitude, rather than two sets of 180 degrees each.

The delivery of metadata is a common issue experienced at the AHO as we use data sourced from third-party private companies who use different datums that make it difficult to transform into WGS84 and LAT.

DENSITY AND AVAILABLE SURVEYS FOR PRODUCTION

The sounding selection pattern is often an indication to the mariner of the density and quality of the underlying survey data used to compile the charted area, for example a sparsely surveyed area covered only by track plots (individual lines of soundings) should have a sounding selection pattern that clearly indicates the tracks, and areas not covered by the tracks, to the mariner. This will indicate the possibility of an undiscovered shoal existing outside the tracks. Differing density of the selection pattern may also be utilised to provide the mariner with an indication that areas have been surveyed to different levels of quality.

This quality is also displayed in the Zone of Confidence Diagram (ZOC) on the paper chart or as a M_QUAL feature in an ENC representing the quality of data in the area.

In a paper chart or ENC the quality of data may also be visually identified. If the contour is unreliable, inadequate or unsurveyed it will be illustrated as a dashed line and the soundings will be thin upright values on a paper chart, and on an ENC the soundings will be illustrated with circles around them. If the soundings are reliable they will be a solid italic value on the paper chart, and the soundings will have no circles around them on an ENC. The contours will be a solid black line.

DATA DENSITY ISSUES

One of the biggest challenges facing cartographers at the AHO is the volume and density of sounding information collected with modern survey techniques, and how to represent this on a chart so it is both easy to read and safe for navigation.

Bathymetric survey data is primarily collected using multibeam echo sounders or a Lidar sensor called the Laser Airborne Depth Sounder (LADS), and the data collected by these sensors is extremely dense. A three-month multibeam survey can produce around 800 million soundings.

Typically these techniques can produce anywhere between 1 and 50 gigabytes of data for a LADS survey, and hundreds of gigabytes of data for a multibeam survey.

All of this source data is used to generate the contours on a chart; however, for display purposes, only a selected sample of the soundings make it onto a traditional paper chart. The soundings must be thinned so they are readable, whilst still preserving the shoalest picture, which is safest for navigation.

CONVERTING THE DATUM TO IHO STANDARDS

Vertical Datums

Mean Sea Level (MSL) is an approximation of the geoid based on tidal measurement at individual locations, and is used extensively for topographic and engineering surveying and mapping. For nautical charting, MSL is not a suitable datum. The navigator needs to know what is the least depth that is below his vessel without regard to the particular tidal state.

Hydrographic charts use a low water chart datum which is the level below which the tide rarely falls, and to which soundings on a chart are reduced, and above which tidal predictions are given. The geoid is far from a smooth regular surface. It has significant undulations, up to several hundred metres in places. Heights are also important as the vertical datum must also be recorded in the GIS to assist mariners with position-fixing and distance measurements.

Lowest Astronomical Tide (LAT)

* The chart datum recommended by the IHO. LAT is adopted by the AHS for all our published products.

* Correctly determined by analysis of tidal observations over an 18.6 year period--lowest tide encountered in this period.

* Varies from chart to chart and along the coast because it is based on local tidal observations, and is affected by the tidal regime (macro/meso/micro)

* Can result in a range of sounding adjustments for a single survey.

* Provides the most generous maritime boundaries and is allowed to be used for maritime boundary calculations under the 1982 UN Convention on the Law of the Sea.

Horizontal Datums

Local horizontal datums are based on the geographic position of a fixed object such as a lighthouse or observatory and also a pre-defined ellipsoid. A basic mathematical 'model' (e.g. CLARKE 1858 ellipsoid) was used for simplicity because they predate the use of computers.

National horizontal datums are based on continental scale and relevance--they have a geodetic centre not related to the centre of the earth. The Australian Geodetic Datum 1966 (AGD66)--a best fit of the MSL geoid over the Australian Continent--is still used extensively in oil and gas exploration.

Satellite mapping has vastly improved the accuracy of the earth's geoid. A global datum requires that the reference ellipsoid has its origin related to the centre of the earth and best fit to the geoid. A geocentric datum is one that best fits the ellipsoid to the geoid over the entire earth such as WGS84 and GDA94; both are used with GPS systems.

Some challenges are:

* The IHO has recommended that all charts be converted to WGS84 for consistency with GPS, as GPS is referenced to WGS84.

* The S-57 standard for ENCs states that all ENCs must be referenced to WGS84.

* Converting all data to WGS84--maintaining and checking the accuracy.

* The average difference between AGD66 and WGS84 is approximately 180m. Local datums can vary more than this.

Horizontal datums and maritime boundaries

Internationally, different datums are used for various reasons; but complications arise when countries lodge territorial claims or lease offshore resource exploitation areas based on different datums. In Australia, states use MGA94 for accuracy; this must be converted to WGS84 for charting and database storage.

Historically territorial seas were 3nm from the coast--the cannon-shot rule. Now Territorial Seas, Coastal Waters, Contiguous Zones, Exclusive Economic Zones and Extended Continental Shelf areas are based on the 'territorial base line'.

Projections and boundaries

Under the United Nations Convention on the Laws Of the Sea (UNCLOS), boundary and baseline definitions often use the term 'straight line' such as Territorial Sea Straight Baseline. It must be realized that a straight line on one projection may be curved on another; therefore when defining straight-line limits it is important to specify the type of straight line to be used, such as:

* Geodesic (Great circle)--the shortest distance along an ellipsoid.

* Rhumb line (loxodrome)--the straight line of constant bearing.

Aeroplanes fly along Great Circles (geodesic lines) as these are the shortest distance between two given points. Ships sail along Rhumb lines as they are lines of constant bearing and appear as straight lines on Mercator-projection charts.

The difference between the two types of straight line can be significant, but in some cases they are the same, e.g. the equator as well as all lines of longitude are simultaneously both Rhumb Lines and Great Circles.

Whilst it may appear to be a contradiction that a curved line can represent a shorter distance than a straight line on a chart, due to the increased scale towards the poles, lines closer to the equator represent longer distances. This also affects curved boundaries defined as a distance from a particular point; the particular line used to measure the distance may affect the location of the boundary.

ENC PRODUCTION

An ENC is an official vector electronic chart produced in International Hydrographic Organization (IHO) S63 encrypted format. It is a digital database of all the objects (points, lines, areas, etc.) represented on a chart.

The versatility of the ENC vector chart database and the comprehensive Electronic Chart Display and Information System (ECDIS) display and performance standards allow the mariner to select and display navigational information relevant to the requirements and the situation at any time.

ENC ATTRIBUTES

ENCs contain much more information than a paper chart; each object on an ENC can have several attributes. Some attributes are mandatory while others are optional. Some determine whether an object is in the base display, some objects make no sense without certain attributes, some attributes are necessary to determine which symbol is to be displayed, and some are required for safety of navigation.

All mandatory attributes for an encoded object must be present in an ENC, however if the value of the mandatory value is not known, it must be encoded as an "UNKNOWN" attribute value.

Some objects are seasonal, such as fishing grounds which are only in effect during certain months of the year. This can be encoded as an attribute, whereas on a paper chart these months would be written next to the object.

All features in the ENC have a list of attributes that can be populated, this information is then used by the ECDIS onboard the ship to help ensure safe navigation. This system will respond to the safety depth contour based on the vessel's actual draft, dangers or hazards will be identified automatically by warnings, and alerts and the level of chart detail can be adjusted according to different circumstances for clarity and purpose.

SCAMIN

The Scale Minimum (SCAMIN) value of an object determines the display scale below which the object is no longer displayed. Its purpose is to reduce clutter, to prioritise the display of objects and to improve display speed. In encoding its value, these factors need to be considered, as well as the scale at which the object is no longer likely to be required for navigation.

CONTOURING

In most modern production systems, functionality exists to automatically generate depth contours based on the sounding data stored in the system/database. This contouring must not be considered to be representative of the final charted contours, but may be used as a tool to aid in the selection of charted soundings and as a guide for the interpolation of charted contours. Where automatic contouring is performed, this must be done using the entire sounding data stored in the system, or a complete quality-assured multibeam survey, and must not be performed on only a subset of the data, in order to ensure all depths within a depth range are covered (Fig. 4.).

Soundings and contours must be used to complement each other in giving a reasonable representation of the seafloor, but always illustrating the shoalest depiction in every circumstance. This includes all significant breaks in slope.

The responsibility of the cartographer is, through the use of depth contours and soundings, to provide the mariner with as accurate a representation of the seafloor as possible. Mariners often compare echo sounder readings with charted depths as an aid to position fixing, and if the full range of depths is not indicated, the mariner may be misled into thinking that he is farther offshore than is actually the case.

One of the improvements the AHS is researching and considering is the capturing and adoption of onemetre, or even decimetre, contours in areas of confined navigating, for example through Torres Strait.

SOUNDING SELECTION

Sounding selection is one of the most important tasks performed by the nautical cartographer during the compilation and maintenance of a nautical chart. When a danger to navigation exists, soundings must be selected to represent the situation to the mariner. Soundings must also be selected to show as many routes as possible that may be followed in safety, based on the specific intended usage of the chart. If the chart is to be of any use, emphasis must always be placed on illustrating a shoal bias depiction whilst maintaining clarity of presentation (Fig. 5.).

Modern chart-production platforms, such as the computer programs used at the AHS, contain tools that aid the compiler to perform a sounding selection. This assistance improves production times in ways that were previously unavailable to cartographers that operated in a purely manual production environment. Such tools include database systems that allow for the deconfliction of all survey data in the area of interest into a single, uniform dataset on common datums; automated contouring; depth colour banding; and sounding suppression algorithms to perform an analysis of a sounding dataset and mathematically select a subset of the dataset that is representative of the sounding selection pattern required.

Such automated processes, while considered to be very good tools, must not be considered to replace the human element in the sounding selection process, which must include assessment of all the variables (not just mathematical) inherent in the area to be charted. It has been recognised world-wide that there are currently no automated systems capable of producing an ideal sounding selection for navigation purposes. Additional factors that must be considered when determining a satisfactory sounding pattern for a particular area include:

* The scale of the chart. This gives an indication as to the intended usage of the chart by the mariner.

* The purpose of the chart, e.g. navigation through a specific channel, or general approach to a harbour mouth.

* Seafloor topography: The sounding selection pattern can vary greatly depending on the unevenness of the seafloor. A closer, more irregular sounding selection pattern is normally required in an area of greatly undulating seafloor topography, while a more regular, consistent pattern is sufficient for a relatively flat or evenly sloping seafloor.

* Water depth--in general, soundings can be more widely spaced in deeper water, gradually becoming more closely spaced as depth decreases.

SOUNDING SUPPRESSION VERSUS GRIDDING

Thinning a dense multibeam or Lidar survey is known as sounding suppression and it differs from surface interpolation and gridding techniques because of this preservation of the shoalest picture. Sounding suppression selects soundings using either the Circle of Influence (COFI) or Nearest-neighbour algorithms, depending on the purpose for the chart.

The COFI algorithm preserves soundings that have a shallower value than those surrounding it. The COFI of a sounding is a function of the depth, with a larger radius as sounding values get deeper. The end result is more soundings shown in shallower areas than deep ones.

The Nearest-neighbour algorithm performs sounding selection by removing soundings over flat featureless terrain and preserving them in areas with irregular terrain (such as the continental shelf).

Gridding techniques can produce nice looking coverages, however the surface values have been calculated by the algorithm, they are not actually measured points. Therefore gridding does not preserve the shoalest soundings, so it is generally not well accepted in nautical cartography. In less navigationally-critical applications, gridding is accepted and is used in many instances for maritime military geographic information (MGI) situational awareness and 3D visualisation of the battle space.

FINALISING THE PRODUCT

After drawing coastlines and contours, and selecting soundings, the rest of the data that is product-specific can be added. This includes topographic information, navigational aids, lights, beacons, buoys, port infrastructure, names of features, seafloor quality data, routing measures, maritime boundaries and any other features used for navigation.

ENC quality control consists of checking every object and its attributes encoded in CARIS HPD Source Editor assisted by validation checks, and then rechecking through third-party validation tools, such as 7Cs Analyser and dKart Inspector, to ensure the ENC is encoded correctly. Finally, additional quality control of completed ENC cells is conducted in type-approved ECDIS systems to visually check the presentation of features from a mariner's perspective. All products are assured compliant to international standards and the specifications of the International Hydrographic Organisation (IHO).

The quality control processes of paper charts have evolved greatly, but realistically they have been simplified as the entire original production process of capturing the ENC from the published paper chart has now been reversed. In 2014 the AHO recognised the advantage of improving the compilation process by compiling the ENC first, and using the ENC file to create a paper chart. This initiative was tested on the Notice to Mariners products, and was then adapted to the paper chart products. Since the ENC is compiled first, all the features have been checked and validated in ENC S57 format using CARIS HPD. The ENC is then used as a source file in the CPCC, which has been designed to convert all S57 features into cartographic points, lines and areas illustrating their related paper chart symbology. From all this results the paper chart.

CPCC gives the AHS the ability to customise our symbol library, annotations of features, and presentation, with the use of XML files. From this the cartographer can select what is to be represented at the compilation scale of the paper chart. The selected features are then quality assured for presentation only, which reduces the publication time between the ENC and paper chart to two weeks.

PORT OF GLADSTONE RE-SCHEME PROJECT

The accuracy of chart products relies highly on the quality of data input. The data required for charts includes new and accurate bathymetry to depict intertidal areas, rock and coral reefs, obstructions, and changes to shoal areas that are navigationally critical. The supply of new or updated navigational marks assists mariners with the safe transit of vessels from port to port. As maritime trade continues to prosper, ports and ships are evolving to adapt to future demands. Infrastructure plans supplied by port authorities illustrate Australia's development with deeper dredged areas that extend to more extensive port facilities that accommodate easier berthing for larger vessels. The update and re-scheme of Gladstone Port charting products is one of many charting re-schemes that are expected to be requested.

As mentioned above, the re-scheme of port charts and ENCs is a priority in response to emerging requests from port authorities and in recognition that navigationally constrained areas are those that will benefit most from the availability of larger scale ENC coverage.

Gladstone was nominated as one of 17 Portfolio Budget Statement (PBS) projects for the 2014-2015 financial year due to the vast growth and development of Gladstone's port infrastructure and Liquid Natural Gas (LNG) facilities. The PBS is a federal government document that lists projects, commitments and goals planned to be addressed for the year. It details functions and responsibilities and financial statements. In addition, the AHS drafts a complementary document, Hydro Scheme, that details our charting and product outcomes in a rolling three year plan.

From this initiative the AHS investigated the related products and found the coverage of pilotage was not adequate for safe navigation into the expanding port. The outcome was to re-scheme, i.e. redesign the hierarchy of charts applying to the port area and approaches.

The first stage in the re-scheme was to design the new paper charts and chart limits required to support the expansion. This involved knowing the geographical extent of the development, the data required to be illustrated for navigation, and the scale of the charts needed to cover the port. This process is a twoway decision as it is crucial to include all stakeholders to ensure the published products are fit for purpose. The design also includes the orientation of the paper charts, trying to cover all critical areas without the use of too many charts or too much overlap between them. The re-scheme plots were delivered to the Port Gladstone Port Authority to approve the charts limits and supply any feedback.

At the second stage, we planned the process of compiling the re-schemed chart series. There were some complexities involved as three of the five charts were already published. Aus244 was the chart in the middle of the harbour and it was currently a sheet of plans. This was the greatest challenge as the sheet of plans needed to be divided up geographically and used as source information for three of the new charts designed for the port. Aus244 remained as one of the charts but its geographical coverage was extended dramatically.

A decision requested from the port authority was to compile charts in the area of the new LNG facilities as there was no chart available for the construction and tug ships to navigate by. For safety reasons and customer service we prioritised the compilation of two new charts, Aus271 and Aus272, to cover the northwest of the port from Lairds Point to Gladstone Boat Harbour (Fig. 6.). Another factor that was critical to prioritise these charts was a new dredge area that was constructed for Jacobs Channel. This also included a major re-construction of all the navigational aids along the maintained depth areas.

Some of the area covered on these charts existed on the Aus244 sheet of plans, so the corresponding plans needed to be withdrawn from that chart via a Notice to Mariners. The next chart was the original Aus244. Two of the plans from the old chart were used for the new Aus244 which included South

Trees Point and the southern portion of Entrance to North Channel. The northern portion of Entrance to North Channel was removed from being published at a large scale as it was mainly used by small craft and the re-scheme was to provide larger-scale information in the high-traffic area in the port. The charts mentioned above are compiled at a scale of 1:10,000.

After completing the larger scale charts covering the critical area of the port the plan was to compile the two approach charts Aus245 and Aus246. The main focus on these two charts was to update the changes derived from the larger-scale charts and relevant source information so that they agreed with the real world depiction whilst being generalised for clarity. These two charts remained at their current published scales, but their chart limits were modified to include the new bathymetry, new navigational critical information from the larger scale charts, anchorage areas outside Gatcombe Heads, and the new pilot boarding place east of the dredged area going all the way into the port to Fishermans Landing Wharfs and including Jacobs Channel. The charts were also updated to current international specifications.

Finally, after planning the charts' compilation process, the team was ready to start processing the new data to be used in the charts. This involved designed dredge limits, hydrographic surveys, newly constructed navigational aids, construction plans of all the wharfs, jetties and berthing facilities which were all in vector format, and topographic information from one-metre resolution raster imagery. Due to the nature of the project, while all the new developments and construction continued, the compilation was continuously chasing the changes with imagery which become more and more out-of-date in relation to the vector data provided by port authority surveyors. Eventually all the construction was complete and the team was able to finalise the compilation of the larger-scale charts Aus271, Aus272 and Aus244 to be used as source material for the approach charts Aus245 and Aus246.

The re-scheme also created some planning and decisions that influenced the final depiction of the products. Mariners' feedback gave guidance on how the products were being used, and the need for better large-scale coverage of the maintained depth area. This resulted in a policy change to the way Harbour ENCs will be published. The change to the limits and scale of the ENCs also improved the product to have one compilation scale of 1:8,000 instead of five separate areas that reflected the limits of the old sheet of plans. The addition of a larger compilation scale along the maintained depth routes and high traffic areas made the use of ENCs more user-friendly by removing over-scale bars on the ECDIS and reduced the number of alerts on the bridge of the ship.

The next major change to the ENCs was to remove Aus246 data from the original Coastal ENC usage to the Harbour usage. This allowed the mariner to distinguish the difference between using the ENC for route planning on the Coastal ENC and navigating on the larger scale Harbour ENC in the port. This decision also made it easier to maintain the ENCs for Notices to Mariners because there are more changes and updates to the larger scale ENCs than to the Coastal usage.

It was a great project to be involved in as there seemed to continually be new pieces of data to filled in blank parts of the chart; each change or improvement gave the team motivation, knowing they were one step closer to placing the last piece and completing the 'puzzle'.

FUTURE AHS ENDEAVOURS

The AHS will soon be introducing the CARIS Bathy Data Base (BDB), which is a new efficient tool to process large bathymetric datasets. The AHS has started to investigate the possibility of compiling one-metre, half-metre or even decimetre contours in products that cover constrained navigation areas (Fig. 7.). This has been initiated by feedback from the port authorities, pilots and mariners using ENCs in these areas, and the desire for the advantage of a more accurate safety depth contour capability. BDB is definitely the tool to generate contours at decimetre intervals for such products.

Another development is working with the port authorities to see how the same datasets used for ENCs can be used for Vessel Tracking Systems (VTS) or Under Keel Clearance (UKC) systems like the system used in the Torres Strait.

FINAL POINTS TO CONSIDER

* The AHS relies on third parties to provide data to enhance our products--we do not generally have permission to release third party data (although we can direct interested parties to the data owners). Common data suppliers are state government agencies, resource exploration companies, port authorities, maritime safety authorities, infrastructure development companies, private survey companies, and similar.

* Details of AHS chart products are found on our website--www.hydro.gov.au

The web site illustrates--The Australian Chart Index including a GoogleEarth overlay

* Product distributors

* Product currency and latest edition details

* NtMs including printable block corrections, tracings and e-notices

* Chart Maintenance Handbook

* Hydroscheme

* Australian ENC updates

* To supply data to the AHS, email information to <datacentre@hydro.gov.au>

* To access our data, contact <hydro.licensing@defence.gov.au> and outline your area of interest and general purpose. If we have data available, an application form will need to be submitted, and the data will be supplied under license.

Lewis Pietrini [1]

[1] Mr Lewis Pietrini is a Chart Production Supervisor at the Australian Hydrographic Service, Wollongong, NSW. Email: lewis.pietrini@defence.gov.au

Caption: Figure 1. The black areas illustrate shipping routes around Australia.

Caption: Figure 2. The chart evolution from Imperial charts to Metric charts and then to ENC.

Caption: Figure 3. Source data--The image illustrates various sources data overlayed to compile an ENC or a paper chart.

Caption: Figure 4. The technique of colour banding sounding data allows contours to be captured accurately and efficiently.

Caption: Figure 5. Sounding selection--triangles illustrating a shoal bias depiction captured from a digital sounding dataset from the DHDB. The soundings at the apex of the triangles are the shoalest soundings in each area.

Caption: Figure 6. Port Gladstone Re-scheme--The outlined limits in red illustrate the new larger scale charts compiled at a scale of 1:10,000.

Caption: Figure 7. An example of one metre contouring in Torres Strait.
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Author:Pietrini, Lewis
Publication:The Globe
Article Type:Report
Geographic Code:8AUST
Date:Mar 1, 2017
Words:6567
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