Hydrographic Offices Research Articles

Ship pictures on the municipal seals of medieval seaports: Ship seals show notices to mariners on tokens of municipal identity

Many late-medieval western European seaports showed a ship in the central image of their municipal seal (a ship seal). Municipal seals to identify and authorize documents ranging from important supra-regional charters to local ephemera were widely used at the time, and probably also on trade contracts and (predecessors to) maritime bills of lading. This study of 115 ship seals from 80 seaports between ad 1200 and ad 1450 reveals that the central image of all ship seals contained striking details, strongly reminiscent of semiotic pictorial signals that conveyed information. The supposed signals were assigned a probable meaning by linking them to nautical aspects of the approach to each seaport and to the state of the harbour at the time. The results strongly suggest that the signals provided information about the risks and hazards in the approach to port, the water depth, and the facilities at the port in question. Compelling evidence comes from ports issuing successive ship seals over an extended period of time: updated images with properly adjusted signals were shown on subsequent seals when significant changes in the approach or port facilities had occurred, but the signals remained the same as long as the local situation stayed unchanged. These findings provide a clear explanation for the divergent ship portraits; ship seals served a dual purpose: first, to confirm the identity of the seaport and the authority of the council in its various actions and tasks, and, second, to provide up-to-date insight into the nautical challenges when approaching the port and in the local port facilities, in a manner similar to the current ‘notices to mariners’ from hydrographic offices. The rapidly increasing number of ports using ship seals in the thirteenth century and their continued use for two centuries supports the success of this late-medieval nautical information system. The study results also provide up-to-date impressions of the 80 seaports involved and of various nautical aspects of the hazardous maritime traffic in the thirteenth and fourteenth centuries, about which written archival information is scarce. The results may help to put the rare yield of maritime archaeology of this period into perspective. The ship seals lost their appeal as buoys and beacons made approaches safer, harbours became deeper and better equipped, and written information (‘rutters’) became widely available.

Unlock insights from hydrographic data with GeoAI

Hydrographic offices are collecting hundreds of terabytes of data every day. This information not only comes from bathymetry data sensors, but also from weather stations, radar, ships, satellites, aerial and drone imagery, and other sensors. With all this data pouring in, hydrographic offices need to be able to automate time consuming processes and adopt modern technologies. One such technology is GeoAI, the intersection of spatial data and artificial intelligence. GeoAI can be considered an enabling technology, in that it allows you collect the data once and apply different algorithms to the data for it to be for multiple purposes. Data collected from multibeam echo sounders can be analyzed to update ENCs by finding new obstructions such as rocks and shipwrecks. Using that same point cloud, GeoAI can then be used to understand marine animal habitat by identifying underwater structures and seafloor patterns that lead to increased biodiversity. GeoAI can be used to aid in coastal resilience projects by analyzing aerial imagery from drones captured in multiple seasons and years for change detection, highlight the areas that need the most attention. Machine Learning, a part of the GeoAI portfolio, can additionally use that same imagery data set to run predictive analytics, highlighting areas that are susceptible to erosion, flooding, and landslides. Many of the same GeoAI algorithms can be used to help maximize investments in the blue economy by bringing location intelligence to the decision-making process. Models can predict the best locations to establish aquaculture, Marine Protected Areas, and offshore energy production. In addition to its applications in coastal resilience projects and maximizing investments in the blue economy, GeoAI offers a wide array of benefits in the domain of hydrospatial data management. The integration of GeoAI in hydrographic offices revolutionizes the way hydrographic data is processed and utilized. Traditionally, processing and interpreting vast amounts of hydrospatial data, including bathymetry, weather, radar, and imagery, required extensive human resources and time-consuming manual efforts. However, with GeoAI, these offices can automate complex tasks and streamline data analysis, significantly improving efficiency and accuracy.

Shared waters, same standards – The Baltic Sea e-Nav project: A partnership for the future of marine navigation

In order to deploy the first layers of S-100 based navigation products in the Baltic Sea, and do so in a regionally harmonized manner, the Hydrographic Offices involved are partnering with academia and industry in the Baltic Sea e-Nav project. To unlock the full potential of the S-100 paradigm shift towards e-navigation, there is a need for transnational collaboration to build capacity and ensure seamless, harmonized products. In addition, the project will test S-100 products from an end-user perspective to ensure the most relevant and useable navigation data possible. The recently started project will continue until 2026 and is co-financed by the EU Interreg Baltic Sea Region programme.

Added value of amateur observational network for high-resolution climatological analysis: a case study in the aterno valley, abruzzo, Italy

The ecological transition calls for an increasing need for local climate services. A fine spatial characterization of atmospheric relevant quantities (temperature, precipitation, humidity, wind, solar radiation, etc.) at long-term climatological scales is typically based on observational networks run by public entities such as the European Union (e.g. Copernicus services) and national and regional Agencies (e.g. National Met Office, Hydrographic Offices). The aim of this work is to verify if the density of these networks is adequate to represent the variability over the territory, with particular regard to a complex terrain area such as the Aterno river Valley in Abruzzo, Central Italy. We use a combination of public networks and the available dense amateur network of weather stations. We subject the database to careful data quality check both in terms of temporal and spatial anomalies. We found that the public network is generally adequate to represent the spatial and temporal variability over the area in terms of temperature and precipitation, but this is not the case for wind and relative humidity for the lack of sensors. We suggest that an integration of public and non-institutional observational networks is desirable for a finer climatological characterization of a complex territory and for allowing the description of more phenomena, in order to better inform adaptation measures with respect to climate change.

Geospatial information management between hydrography and the law of the sea: A milestone opportunity for their further integration

These past few years have marked the beginning of a revived surge of interest worldwide for the topic of marine geospatial information management, which is reflected in the work of the International Hydrographic Organization and United Nations relevant bodies. Building on this momentum, this contribution firstly introduces a milestone initiative on marine geospatial data recently launched by the United Nations General Assembly. Secondly, it addresses the significance of marine geospatial data collection, storage, and dissemination for the law of the sea. Finally, the role of hydrographic offices is emphasized in the challenge of moving from local to global in the management of marine geospatial data, focusing on the experience of the Italian Navy Hydrographic Office.

Towards Automated Nautical Chart Compilation and Verification of Output Topology and Safety

Abstract. The compilation of Electronic Navigational Charts (ENCs) requires significant amount of time, labor-intensive efforts, and cost. Despite the advancements in technology and the various research efforts, generalization tasks are still performed manually or semi-manually with expected human errors. The dramatic increase in the amount of data that is collected by modern acquisition systems, in addition to the increasing timeline expected by the end-users, are constantly driving Hydrographic Offices (HOs) toward the investigation and adoption of more advanced and effective ways for automating the generalization tasks to speed up the process, minimize the cost, and improve productivity. Full automation of the nautical chart compilation process has been unreachable due to the strict nautical cartographic constraints (and particularly those of safety and topology) that pose a challenge for most of the available generalization tools, while it remains questionable whether automation can replace human thought processes. In this paper, we discuss a research effort for an Automated Nautical-chart Generalization (ANG) model in the Esri environment. The ANG model builds upon the nautical chart generalization guidelines and practice and utilizes available tools in the Esri environment to perform the generalization of selected ENC features to the target scale. Safety constraints in the marine domain is of utmost importance, however, since most of the readily available tools do not respect safety, the main goal of this effort has been an output with no topological violations. In the current phase of the project, we evaluate safety of soundings and contour for user fixing and while the validation of bathymetry is a well-researched topic, there was the need for an automated process to identify the sections of the generalized contours that have been displaced toward the shallow water side Therefore, this work also presents a safety validation tool that detects the contours’ safety violations in the output. The tool is composed of three main stages that run individually after the ANG model is complete with the aim to highlight the safety violations for fixing by cartographers.

The Hydrographer of the Future - Reflections on an international virtual workshop

The Canadian Hydrographic Service (CHS) expects the skillsets of its multidisciplinary hydrographers to evolve as the field of hydrography undergoes a digital transformation. To characterize these changes, the CHS organized a virtual workshop titled Hydrographer of the Future, in which it heard the perspectives of international colleagues in other Hydrographic offices (HO’s), industry, and academia. Despite some variations, common themes emerged: the changing technological context, people and culture, and the future role of hydrography. The results of this workshop support the CHS’ own internal planning; however, the CHS also hopes to continue learning from its international partners and share its experiences through the International Hydrographic Organization’s (IHO) e-learning center.

Investigating the introduction of e-navigation and S-100 into bridge related operations: the impact over seafarers

The present work is focused on analyzing how e-navigation will affect the daily work of seafarers involved in bridge-related operations. Within e-navigation, the International Hydrographic Organization (IHO) is currently working in the development of the new standard (S-100) whose role is to guarantee a homogeneous management of the maritime domain data. S-100 is called to act as the Common Maritime Data Structure (CMDS), it represents the technical framework required to guarantee a wider and better use of maritime data. The mission of the standard is to create a common foundation that can be used for multiple purposes; meteorologists, physicists, and whoever is interested in developing maritime related products will refer to the same standard. Not having a homogeneous type of data processed with standardized procedures will allow a better combination and processing of maritime data. Considering the perspective of Hydrographic Offices, the objective of the present document is to analyze the impact which e-navigation will have over seafarers. The study is focused on the evaluation of the risks connected to S-100-based products and on the analysis of specific bridge operations. Considering that e-navigation products are still at their design phase, being aware of the consequences for the final users is essential to make S-100-based products more customer oriented and to allow seafarers who are involved in bridge operations to get familiar with this new technology.

Effective Automated Procedures for Hydrographic Data Review

Reviewing hydrographic data for nautical charting is still a predominately manual process, performed by experienced analysts and based on directives developed over the years by the hydrographic office of interest. With the primary intent to increase the effectiveness of the review process, a set of automated procedures has been developed over the past few years, translating a significant portion of the NOAA Office of Coast Survey’s specifications for hydrographic data review into code (i.e., the HydrOffice applications called QC Tools and CA Tools). When applied to a large number of hydrographic surveys, it has been confirmed that such procedures improve both the quality and timeliness of the review process. Increased confidence in the reviewed data, especially by personnel in training, has also been observed. As such, the combined effect of applying these procedures is a novel holistic approach to hydrographic data review. Given the similarities of review procedures among hydrographic offices, the described approach has generated interest in the ocean mapping community.

Depth Contours and Coastline Generalization for Harbour and Approach Nautical Charts

Generalization of nautical charts and electronic nautical charts (ENCs) is a critical process which aims at the safety of navigation and clear cartographic presentation. This paper elaborates on the problem of depth contours and coastline generalization—natural and artificial—for medium-scale charts (harbour and approach) taking into account International Hydrographic Organization (IHO) standards, hydrographic offices’ (HOs) best practices and cartographic literature. Additional factors considered are scale, depth, and seafloor characteristics. The proposed method for depth contour generalization utilizes contours created from high-resolution digital elevation models (DEMs) or those already portrayed on nautical charts. Moreover, it ensures consistency with generalized soundings. Regarding natural coastline generalization, the focus was on managing the resolution, while maintaining the shape, and on the islands. For the provision of a suitable generalization solution for the artificial shoreline, it was preprocessed in order to automatically recognize the shape of each structure as perceived by humans (e.g., a pier that looks like a T). The proposed generalization methodology is implemented with custom-developed routines utilizing standard geo-processing functions available in a geographic information system (GIS) environment and thus can be adopted by hydrographic agencies to support their ENC and nautical chart production. The methodology has been tested in the New York Lower Bay area in the U.S.A. Results have successfully delineated depth contours and coastline at scales 1:10 K, 1:20 K, 1:40 K and 1:80 K.

Generalization of Soundings across Scales: From DTM to Harbour and Approach Nautical Charts

This paper presents an integrated digital methodology for the generalization of soundings. The input for the sounding generalization procedure is a high resolution Digital Terrain Model (DTM) and the output is a sounding data set appropriate for portrayal on harbour and approach Electronic Navigational Charts (ENCs). The sounding generalization procedure follows the “ladder approach” that is a requisite for the portrayal of soundings on nautical charts, i.e., any sounding portrayed on a smaller scale chart should also be depicted on larger scale charts. A rhomboidal fishnet is used as a supportive reference structure based on the cartographic guidance for soundings to display a rhombus pattern on nautical charts. The rhomboidal fishnet cell size is defined by the depth range and the compilation scale of the charted area. Generalization is based on a number of rules and constraints extracted from International Hydrographic Organization (IHO) standards, hydrographic offices’ best practices and the cartographic literature. The sounding generalization procedure can be implemented using basic geoprocessing functions available in the most commonly used Geographic Information System (GIS) environments. A case study was performed in the New York Lower Bay area based on a high resolution National Oceanic and Atmospheric Administration (NOAA) DTM. The method successfully produced generalized soundings for a number of Harbour and Approach nautical charts at 10 K, 20 K, 40 K and 80 K scales.

Evaluation of EURO-CORDEX (Coordinated Regional Climate Downscaling Experiment for the Euro-Mediterranean area) historical simulations by high-quality observational datasets in southern Italy: insights on drought assessment

Abstract. Many recent studies indicate climate change as a phenomenon that significantly alters the water cycle in different regions worldwide, also implying new challenges in water resource management and drought risk assessment. To this end, it is of key importance to ascertain the quality of regional climate models (RCMs), which are commonly used for assessing at proper spatial resolutions future impacts of climate change on hydrological events. In this study, we propose a statistical methodological framework to assess the quality of the EURO-CORDEX RCMs concerning their ability to simulate historic climate (temperature and precipitation, the basic variables that determine meteorological drought). We then specifically focus on drought characteristics (duration, accumulated deficit, intensity, and return period) determined by the theory of runs at seasonal and annual timescales by comparison with high-density and high-quality ground-based observational datasets. In particular, the proposed methodology is applied to the Sicily and Calabria regions (southern Italy), where long historical precipitation and temperature series were recorded by the ground-based monitoring networks operated by the former Regional Hydrographic Offices, whose density is considerably greater than observational gridded datasets available at the European level, such as E-OBS or CRU-TS. Results show that among the more skilful models able to reproduce, overall, precipitation and temperature variability as well as drought characteristics, many are based on the CLM-Community RCM, particularly in combination with the HadGEM2 global circulation model (GCM). Nevertheless, the ranking of the models may slightly change depending on the specific variable analysed as well as the temporal and spatial scale of interest. From this point of view, the proposed methodology highlights the skills and weaknesses of the different configurations and can serve as an aid for selecting the most suitable climate model for assessing climate change impacts on drought processes and the underlying variables.

Charting Newly Created Statehood: A Maritime Survey of the Adriatic by the Joint Forces of the Austro-Hungarian and Italian Hydrographic Offices

ABSTRACT The process of political and territorial unification of the Kingdom of Italy (1860) and Austria-Hungary (1867) highlighted the issues of territoriality both on land and at sea. As a part of that effort, a need of maritime survey of the Adriatic conducted by the joint forces of the Austro-Hungarian and Italian hydrographic offices appeared. The purpose of this endeavour was to enable the production of modern charts based on a comprehensive survey covering the whole sea surface area, from coast to coast. Under the supervision of Commander Tobias Ritter von Oesterreicher and Counter-Admiral Duke Antonio Imbert, the survey started in 1866 and, by the end of 1873, resulted in a general chart of the Adriatic, 4 course charts of the Adriatic Sea, 55 coastal charts as well as number of harbour plans. This paper presents an analysis of the course of the survey, its products as well as its impact on the subsequent cartography of the Adriatic Sea.

The impact of sensors for satellite derived bathymetry within the Canadian Arctic

Canada’s coastline presents challenges for charting. Within Arctic regions, in situ surveying presents risks to surveyors, is time consuming and costly. To better meet its mandate, the Canadian Hydrographic Service (CHS) has been investigating the potential of remote sensing to complement traditional charting techniques. Much of this work has focused on evaluating the effectiveness of empirical satellite derived bathymetry (SDB) techniques within the Canadian context. With greater knowledge of applying SDB techniques within Canadian waters, CHS is now interested in understanding how characteristics of optical sensors can impact SDB results. For example, how does the availability of different optical bands improve or hinder SDB estimates? What is the impact of spatial resolution on SDB accuracy? Do commercial satellites offer advantages over freely available data? Through application of a multiple band modelling technique to WorldView-2, Pléiades, PlanetScope, SPOT, Sentinel-2, and Landsat-8 imagery obtained over Cambridge Bay, Nunavut, this paper provides insight into these questions via comparisons with in situ survey data. Result highlights in the context of these questions include the following: Similarities between sensors: Overall linear error at 90% (LE90) results for each sensor ranged from 0.88 to 1.91 m relative to in situ depths, indicating consistency in the accuracy of SDB estimates from the examined satellites. Most estimates achieved Category of Zone of Confidence level C accuracy, the suggested minimum survey accuracy level for incorporating SDB information into navigational charts. SDB coverage: Between sensors, differences in the area of the sea floor that could be measured by SDB were apparent, as were differences in the ability of each sensor to properly represent spatial bathymetry characteristics. Sensor importance: Though relationships between SDB accuracy and sensor resolution were found, significant advantages or disadvantages for particular sensors were not identified, suggesting that other factors may play a more important role for SDB image selection (e.g., sea floor visibility, sediments, waves). Findings from this work will help inform SBD planning activities for hydrographic offices and SDB researchers alike.

Photogrammetric Bathymetry for the Canadian Arctic

Remote sensing is becoming common in the estimation of bathymetry for navigational charting through a process known as Satellite Derived Bathymetry (SDB). Most SDB techniques currently used by hydrographic offices employ an empirical approach, requiring the use of in-situ data to calibrate a relationship between spectral information and coincident depths. This article reports on a multi-site test of an alternative SDB method which uses photogrammetry to extract depths from stereo WorldView-2 imagery. In areas with heterogeneous seafloors, the empirical approach faces difficulties in establishing the relationship between colour and depth, while the photogrammetric approach uses the contrasting seafloor features for triangulation. Additionally, the photogrammetric method may be applied in areas lacking previous survey data. Five study areas in Nunavut, Canada were selected to test the robustness of the method in different environments and under different imaging conditions. Study areas were (with resulting RMSE/Bias given in metres) Coral Harbour (0.84/−0.47), Cambridge Bay (1.16/−0.15), Queen Maud Gulf (0.97/0.06), Arviat (0.99/−0.009), and Frobisher Bay, where extraction largely failed due to environmental conditions. Accuracies demonstrated here are similar to those seen using the empirical approach, suggesting that these two methods may be used in conjunction, each applied to regions where they are better suited.

From Coast to Coast: The Mapping of the Adriatic Sea by the Joint Forces of the Austro-Hungarian and Italian Hydrographic Offices

Abstract. With the establishment of the second Austrian rule on the eastern Adriatic coast (1815), after several centuries, the Adriatic Sea was divided between two sides – Italian (Papal States and Kingdom of Two Sicilies) which ruled the western Adriatic coast, and the Austrian, which ruled the eastern coast and Lombardy-Venetia. Such division of the Adriatic Sea between the two powers in constant tension adversely affected the dynamics of mapping, and in the mid-19th century, there was a serious setback in mapping. In the 1860s, the strengthening of Italian and Austrian realms (Italy began its unification in 1860, and the Austrian Empire was converted into the Austro-Hungarian Monarchy in 1867) created a need for cooperation between the two empires on the joint mapping of the Adriatic Sea, which was to enable the production of modern charts based on a comprehensive survey covering the whole sea surface area, from coast to coast.For the purposes of the hydrographic survey, both imperial powers established their hydrographic offices as part of their military (naval) forces. The Austrian Empire established its Hydrographic Office in 1860, at first in Trieste and, from 1869 onwards, in the city of Pula (Hydrographisches Amt der k. u. k. Kriegsmarine). Its Italian counterpart, the Istituto idrografico della Marina, was founded in 1872 with its headquarters in Genoa (yet its first administrative act appeared as early as 1867). A systematic survey of the Adriatic Sea was started on its eastern side by the Austrian Hydrographic Office. It was conducted from 1866 to 1870 under the supervision of the experienced mariner and hydrographer Tobias Ritter von Oesterreicher. After land and sea surveys had been carried out on the basis of a dense triangulation network (first-, second-, and third-order triangulation), the first edition of the hydrographic charts of the eastern Adriatic coast was prepared by the Military Geographical Institute in Vienna and published by W. Essmann in Trieste as early as 1870 (and reissued in 1872). The survey resulted in a general chart of the Adriatic at a scale of 1:1 000 000, four course charts of the whole Adriatic Sea at a scale of 1:350 000, thirty-one coastal charts of the eastern Adriatic at scales of 1:40 000 to 1:100 000, and fifty-seven harbour charts at scales of 1:20 000 to 1:30 000. The survey of the Italian side of the Adriatic was conducted under the supervision of Counter-Admiral Duke Antonio Imbert, who earlier assisted Oesterreicher in the survey of the eastern coast. It started in 1867 and, by the end of 1873, conducted by the joint forces of the Austro-Hungarian and Italian hydrographic offices, resulted in a series of twenty-four charts at a scale of 1:100 000. Printed by the Military Geographical Institute in Vienna in 1873, together with a series covering the eastern Adriatic coast, these charts continued to serve as the main base map in the Office’s cartographic production for several decades, but also as a template for maps of Adriatic issued by foreign hydrographic offices, including that of the British Admiralty.The collaboration between the Austrian and Italian hydrographic offices continued, jointly promoting the improvement of quality of nautical charts of the Adriatic and the development of the hydrographic service in general. Apart from producing the first modern charts of the Adriatic, this survey marked the beginning of a state institutions for hydrographic exploration, including first measurements of geomagnetism, salinity, currents, and tides. The 19th-century charting thus played a crucial role in the birth of the official hydrographic services and the development of modern hydrographic exploration of the Adriatic. The proposed paper is based on archival sources.

The GEBCO and NOAA Chart Adequacy Workshop

Abstract. On July 23, NOAA Coast Survey hosted a three-day Chart Adequacy Workshop that included participants from 13 countries. This is the fourth Chart Adequacy Workshop held at National Oceanic and Atmospheric Administration’s (NOAA) Silver Spring, Maryland campus. This was the fourth workshop hosted by NOAA and Nippon Foundation / General Bathymetric Chart of the Oceans (GEBCO) Training Program at the Center for Coastal and Ocean Mapping, UNH. Unlike previous years (2017, 2016, 2015), the focus of this week was on networking and support for the upcoming International Cartographic Association (ICA) Working Group on Marine Cartography meeting held on July 26 and in preparation for next year’s International Cartographic Conference (ICC). The main goal of the workshop is to provide training for professional cartographers and hydrographers on techniques for assessing nautical chart adequacy using publicly-available information, such as satellite images and maritime automatic identification system (AIS) data. . The participants received an overview on Coast Survey datasets, processes, and requirements for nautical charts. They also learned about pre-processing hydrographic data, such as loading charts, uploading imagery, and applying electronic navigation charts (ENCs) and AIS point data. Through a series of lab units, the attendees practiced performing the concepts they learned.The 2018 participants were from Australia, Greece, Ireland, Japan, Latvia, Madagascar, Mexico, Nigeria, Peru, Poland, St. Vincent and the Grenadines, Taiwan, and Trinidad and Tobago. The international nature of the event allows the participants to meet and learn from cartographers from a variety of backgrounds and expertises. Thee individuals include Nippon Foundation / GEBCO training program students and those nominated by their home hydrographic offices and their travel was sponsored through funds secured by the workshop organizers. The workshop was developed in part too address the need to improve the collection, quality, and availability of hydrographic data world-wide, and increase the standardization of chart adequacy evaluations across the globe. Coast Survey is currently working with the International Hydrographic Organization (IHO) to recommend participants for next year’s workshop towards the end of July, 2019.

Precise Bathymetry as a Step Towards Producing Bathymetric Electronic Navigational Charts for Comparative (Terrain Reference) Navigation

Bathymetric Electronic Navigational Charts (bENCs) contain only bathymetry data and can be used in applications such as underwater positioning, dredging and piloting. According to International Hydrographic Organization (IHO) standard S-57, Electronic Navigational Charts (ENCs) contain depth information with pure density of depth contours. Typical depth contours encoded by Hydrographic Offices are limited to 2, 5, 10 and 20 m. Availability of more depth contours in bENCs would allow the visualisation of a safety contour which is closer to users' specific needs, especially in restricted waters such as ports, lakes and rivers. Another problem is non – Global Navigation Satellite System (GNSS) Unmanned Underwater Vehicle (UUV) navigation. bENCs could be used as reference data for UUV comparative navigation. This is called terrain reference navigation. This article presents the results from bathymetric data processing that was performed to convert data contained in bENCs into a reference for underwater comparative navigation. We use data obtained using a multibeam echo sounder to produce depth data with a horizontal spacing of 0·10 m that is suitable for use in restricted waters. The experimental data was collected in and around the Port of Gdansk, Poland.

Consideration of Level of Confidence within Multi-Approach Satellite-Derived Bathymetry

The Canadian Hydrographic Service (CHS) publishes nautical charts covering all Canadian waters. Through projects with the Canadian Space Agency, CHS has been investigating remote sensing techniques to support hydrographic applications. One challenge CHS has encountered relates to quantifying its confidence in remote sensing products. This is particularly challenging with Satellite-Derived Bathymetry (SDB) where minimal in situ data may be present for validation. This paper proposes a level of confidence approach where a minimum number of SDB techniques are required to agree within a defined level to allow SDB estimates to be retained. The approach was applied to a Canadian Arctic site, incorporating four techniques: empirical, classification and photogrammetric (automatic and manual). Based on International Hydrographic Organization (IHO) guidelines, each individual approach provided results meeting the CATegory of Zones Of Confidence (CATZOC) level C requirement. By applying the level of confidence approach, where technique combinations agreed within 1 m (e.g., all agree, three agree, two agree) large portions of the extracted bathymetry could now meet the CATZOC A2/B requirement. Areas where at least three approaches agreed have an accuracy of 1.2 m and represent 81% of the total surface. The proposed technique not only increases overall accuracy but also removes some of the uncertainty associated with SDB, particularly for locations where in situ validation data is not available. This approach could provide an option for hydrographic offices to increase their confidence in SDB, potentially allowing for increased SDB use within hydrographic products.

Magenta and alternative red colour spectroscopy on nautical charts in the visible and near-infrared electromagnetic spectrum

The International Hydrographic Organization (IHO) publishes Regulations and Technical specifications for the official nautical charts in order to standardize the use of colours to all hydrographic offices of IHO Member States. The use of magenta is reserved for highlighting, drawing attention and to distinguish information to elements of a chart of maritime importance and it is necessary to ensure its visibility.So far, there is no information on the spectrographic composition of colours intended to highlight specific content. For the first time, spectroscopy of magenta and alternative red colour is performed on the charts of hydrographic offices that have officially published colour compositions. Spectroscopy extends beyond the visible area to the near-infrared part of the electromagnetic spectrum. The article presents the absorption curves of magenta and red colour that contain information on the spectrographic composition of these colours in the visible and near-infrared spectrum. The purpose of the study is to show what proportion of black colour added to magenta or red can give positive response or positive absorption properties in the near-infrared part of the spectrum. The results are also part of preparatory research aimed at introducing colour twins, a system of hidden graphical elements designed to protect nautical charts from forgery and to expand their information content.