Raster Charts… the comeback [Update]

[Update 26 August 2018]

I was for many years a strong advocate for vector maps. compact, a low numerical weight, easy to update, they are ideal for use on our mobile devices.

According to the good old adage that only fools don't change opinion, recent technical developments hardware and software, added to maritime events of recent years, led me to reflect on the accuracy of my opinion. Trained in the old school of safety in Glénans Sailing School, the only bias I have to authorize me to express is the safeguarding of human life at sea. This may cause a little "old goatee" for some, but I assume. Hang in there, This is gonna be long.

Marine events

Since the beginning of this decade the press recounted of spectacular sea groundings related to navigation errors. For the most recent examples : on April Marion Dufresne II in Crozet archipelago (2012), The’USS Guardian in Philippines (2013), Customs patrol boat Arafenua in Tuamotu archipelago (2014), and highly publicized VOR65 Team Vestas Wind during the 2nd leg of the Volvo Ocean Race. In all these groundings (except for the last) human error investigation reports have also implicated electronic mapping and / or its interpretation, highlighting the lack of elementary prudence of boaters using inaccurate charts, or by nature, either their scale, either the seniority of the recorded surveys.

To consider only the two most recent groundings, It is clear that human errors concern the lack of discernment in relation to electronic charting whose vagueness ought to encourage boaters to more cautious in their approach to the dangers. Beyond the reports which I invite you to the rewarding reading (²), Let's look only at charting available on the crash scene.

• Patrol boat Arafenua, 1June St 2014, 4h00 Local.

On the night of Saturday 31 May to June 1 2014, the Customs patrol boat Couach 32 meters DF48 'Arafenua' ran aground on the reef of atoll of Tikei, up to 300 MN northeast from Tahiti by 14 ° 56',504S and 144 ° 32',436W on the North coast of Tikei

Provided with the application MaxSea on PC, an ECS equipment type, and not ECDIS (³), the watch crew uses a SHOM marine chart 6689 until 1:595.000, is a so-called ' landing' chart in the official nomenclature of paper charts. Unusable for a coastal approach, especially at night and in heavy rain falls. The position of Tikei island in the Tuamotu archipelago, North of which the customs patrol boat ran aground, is incorrect on the SHOM chart 6689. Excerpt from the report :

[ The most accurate paper map is " 6689 -Tuamotu Islands (Western part) ”, that used for approach. It is, view across (1/595 000), unusable for direct vicinity navigation Tikei. It was established according to the bathymetric information collected by SHOM until 1977. His last updated date 2010. The datum does not appear on this card. On such a chart 1 mm represents 595 meters, the thickness of the pencil (0,3 mm) represent 178,5 meters ] … [ The flat chart 6689 (ladder 1/595.000), published 1978, was determined from the map 6057 (1/510000), it replaced. Chart 6057, published 1952, operates a topography minute also produced by the geodesic mission 1948. the position of the island on the topographical minute is 1 mile south likely due to a clerical error in the preparation of this document. This shift affected the card 6057 then the current chart 6689, and the ENC FR266890 electronic navigational chart which were developed from the same paper map.]

Excessively zooming the MaxSea PC a chart on such a scale, whose the most recent surveys are up to 1977, the greatest caution and a consequent uncertainty margin is needed. However the route drawn on the chart came 1 mm, thus 600 meters high, from the island. Most of our electronic charts display the same lag in latitude with the reference satellite location :

SHOM, After this accident, has published a correction to the chart 6689 for the position of Tikei island, but this does not solve the problem of scaling, too much small to address these parts safely at night. Only allow it a lookout of day associated with a cautious approach at low speed.

• VOR65 Team Vestas Wind, 29 November 2014, 19H10 Local.

Shortly after the sunset, the Danish VOR65 ran aground South of the Cargados Carajos Islands in the Indian Ocean. Team Vestas Wind is provided with Expedition " Expedition is simply the best tactical and navigation software available ” (sic) and vector charting C-Map charts. After the grounding, the skipper Chris Nicholson spoke about a conversation he had with the Navigator Wouter Verbraak after noticing shoals on the charts :

"Wouter replied that the depth ranged from 3000 m to 40 m", "currents were not significant and the need to monitor the state of the sea in approaching this area."

This response confirms the theory that men have not seen the reefs on the charts. Wouter Verbraak :

"With hindsight, We should zoom in on this area on electronic charts. It was a mistake on my part not to have done."

In turn, Yann Riou, Reporter aboard the VOR65 Dongfeng Race Team says :

"This archipelago Charles (Caudrelier) had spotted it a few days ago, but we must recognize that it is not obvious to find. In fact to see it appear on our e-charts need to zoom at the top. "But how and why zoom when you do not know it is there."

Actually, on some vector charts and at certain zoom levels the dangers do not appear. And yet, SHOM chart 6884 until 1:10.000.000 (Indian Ocean West) represents all the dangers, islands and shoals, including the conspicuous Cargados. Furthermore these dangers are perfectly identified by the official publishers of charting (UKHO, NHO, NGA) (⁴). And many publishers use these resources, as vector chart Navionics 30XG at virtually all levels of zoom, where the Cargados appear at scales greater than 1:8.000.000 (either a diagonal of 1.800 MN on a screen 10″) :

It seems hard to believe that we can not see so extended reefs on electronic charts, unless the C-Map charts used are particularly deficient (⁵).

In this connection, un fil de discussion fort instructif sur le forum Hisse et Oh fait état de nombreuses approximations relevées sur les cartes vectorielles, including Navionics, in some regions of the globe. The conclusion that is drawn, ultimately, by one of the posters (I salute by the way) is quite radical but of common sense :

"There is a lesson for us : This isn't electronic navigation which is involved, It is the exclusive use of vector charts (³). With electronic Raster charts (³) at small scale, this accident would not have occurred. These small-scale charts (as 1:3.500.000) have been developed by generations of Hydrographers for sailors. These charts are almost caricatures, because they show very clearly in open seas small and large islets or even simple rocks."

Why an exclusive use of vector electronic charts ? This did however not always so. The oldest of our french software, MaxSea, has developed its own Raster MapMedia cartography based on data from official hydrographic services, starting with SHOM. And it is always the case. "Tile" display technology, developed by this company, allows overlapping levels of scale as the zoom in /. Combined with the power of graphics cards these computers fluid display gives different scales available, that is called a seamless display, seamless display in English. In addition, exponential capacity of hard drives offers widely enough room to store the large files of digitized charts. So, What has changed ?

Technical and software developments

• Vector mapping

Vector charts appeared in two totally different ways. To make it short, computer tracing techniques, developed for industrial software, as AutoCad for automobile, helped to transform the whole of the content of the charts extremely compact database, offering ease of update : coast shorelines, boyage, bathymetry, texts, that can be modified independently. The first private publishers, Navionics charts, C-Map charts, took this technique in the years 90 s to provide the first charts to the GPS becoming chart plotters. vector charts stored on cards (SD-Card, CF-Card) perfectly meet these new devices with limited memory capacity and rudimentary graphics processor, which is the delight of ship chandlers.

In parallel, The’IHO (International Hydrographic Organization) preparing the foundations of ECDIS (³), secured navigation systems based on the use of standard vector charts, developed by global hydrographic services around the world, and complying with the rules of the international convention SOLAS (³) imposed on merchant ships, transport of passengers and large fishing. These standard charts, now accessible to boating, are called ENC S-57, S-63 and S-100 (³). They are the only one allowed in place of the official hydrographic services paper charts.

At the same time, the evolution of boating chartplotters to more powerful devices, the MFDs (Multi Functional Displays) translated by "traceurs" in French., and the gradual arrival of the laptops aboard leasure boats, have prompted the private cartography publishers to produce vector charts from S-57 official data , but do not meet the requirements of ECDIS. These charts, called Private ENC, feed the so-called navigation devices ECS (³), as opposed to the ECDIS. These ECS are those we all own (or almost) aboard our cruising and regatta boats.

Everything would be for best in the best of worlds if the ENC corresponded to the needs of the recreational boating. Alas, it is not. Their acquisition is tedious, requires a device or software with a user permit (⁶), they are distributed in the form of numerous cells which the addition becomes quickly expensive, and more cover only major shipping routes. So not at all suited to recreational boating. That is why we saw multiply private publishers of electronic charts, In addition to veterans MapMedia, C-Map and Navionics, We now find Garmin, Transas, Imray charts, NV Chart, Solteknik. and so on.

• Raster charting

Faced with the increase of vector charts, Raster charts have lost their attractiveness. Publishers such as SoftChart and the American MapTech who each had a global catalog of Raster charts have disappeared. Have hardly survived MapMedia, "stainless" in its management of Raster charts, with TimeZero technology allowing a 3D display added to the most beautiful effect satellite imagery, the UKHO with its ARCS catalog (³), and NOAA, US administration which still distributes free RNCs charts (³) for the whole coasts of the USA. A geographic coverage, Raster charts need ten times more space in storage, and are almost unusable with applications not able to process seamless display, because all the items in a scanned chart increase by zooming-in, or decrease in zooming-out, which is totally inappropriate for a good charts reading.

And yet, a new phenomenon will revive this technology…

Mobile devices

For almost ten years appeared in science fiction devices : smartphones and tablets. In a few years millions of mobile devices was sold, and it did not take longer time that developers design applications (no more say software) for navigation. This blog is one of the most ardent proponents. Charting publishers rushed : Navionics charts, C-Map charts, Garmin, Imray charts, Transas, and also developers of navigation applications, independent of cartographers (iNavX, SEAiq).

Vector charting meeting these small devices : little graphics power, low storage, poor memory, the dream ! You can store all of the global catalog Navionics in less of 5 GB of storage, there where 50 GB is not sufficient to MapMedia. So voilà : Now these hyper-popular gems are going around the world aboard pleasure boats, and become real ECS. And mariners around the world discover that vector charting flawed. Based on official data, but not always up to date (see above), the restatements and transformations by publishers can also add human transcription errors. Some publishers do not always transcribe the details they have (¹), either they forget them as Easter Island that recently disappeared from Navionics charts, and few application proceeds the overzoom (excessive expansion bringing no more detail than the initial scale) (⁷). In addition, the cartographic generalization of information according to levels of zoom display corresponds to arbitrary algorithms whose results are sometimes disturbing (total disappearance of the texts with Transas, in example). All this makes mess, and it applies to maritime safety. Of course, It must temper the words. To my knowledge and that of many users of the application iNavX, Navionics still remains today the vectorial cartography covering the better the globe, better update, the more detailed, Although it is not perfect.

Raster charts coming back

Facing the vector charts available for leasure boating, Raster charts have multiple disabilities : no detailed world coverage, large size of files, slow display and lack of connection between the different scales. But if we can fix these objectives shortcomings, they have considerable advantages : manual chart design by professional hydrographers, richness of the graphic interpretation of reliefs, coasts contours, rockfill and objects which often stem from a true artistic creation, textual information related intimately to each scale level, no computer reprocessing a posteriori generator of errors, as for example a dotted isobath (meaning of uncertain soundings) turning into continuous isobath on the private vector charts. Short, the great come back to Dady's paper chart. But how ?

MaxSea initiated the first simmering of the come back of Raster charts in June 2013 by launching its application for Apple iOS TimeZero. MapMedia charts boarded on iPad, with a very successful interface complies with the basic Windows version. Alas ! The development was put on hold in November 2013, and apart from the support of the AIS and Radar Furuno in WiFi 2015, little progress was made in this application.

Weather4D hit hard by presenting at the Paris Boat 2014 on April navigation module his now famous weather application in the version under Android. In 2015 the iOS version has been completely re-developed to integrate the navigation module for weather-routing Weather4D Pro Version, under the name Weather4D 2.0. A key feature is to rely on a raster map catalog, directly from official hydrographic services : SHOM, UKHO, BSH, NOAA, CHS, etc,, served in the form of tiles by the French platform Geogarage.

The developer has solved the problem of the display by the technique of these maps tiles to a fluid sequence of different measurement scale levels of zoom in / out. No more buy charting, one subscribes yearly to the full chart catalog of an editor (SHOM = 60 €/year). You can load as many memory cards available space, tiling enabling a compression ratio that significantly reduces the weight of the cards.

The highest mentioned technical disabilities are therefore solved, remains still incomplete global coverage. The availability of the cards is performed by the server Geogarage, who buys, stores and keep available the international catalogues. GeoGarage continues to negotiate with global hydrographic services provision from their catalogues of charts on its server. The subscription can be used on multiple devices.

These two major players of tablets navigation application will therefore devote the comeback of Raster charting, to the delight of a majority of us, and cartographers who will see their work recognized at its fair value.

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(¹) Comparative mapping, mixed results
(²) Investigation reports :
Report BEAmer Marion Dufresne.
Report BEAmer Arafenua
L’organisateur de la VOR a commandé un rapport d’enquête indépendant rendu public le 9 March 2015.
(³) See Glossary for the definition of these terms.
(⁴) See article by Geogarage Questions asked about volvo Ocean Race
(⁵) Voir l’analyse sévère de Olivier Chapuis sur its built-in Blog.
(⁶) ENC user permit, what is ?
(⁷) Electronic charts : scales and overscale [Update]
(⁸) The stakeholders of electronic charting

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