lect 16 - electronic charts and ecdis-n
TRANSCRIPT
Electronic Chart Display and Information
Systems
Objectives:
1. Become familiar with the principal types of electronic charts.
2. Understand the difference between an ECDIS and an ECS.
3. Understand the different Electronic Chart formats and their advantages and disadvantages.
Objectives:4. Become familiar with the display characteristics of
an ECDIS System.
5. Understand the limits of an ECDIS based on the performance limits of sensors.
6. Understand the US Navy policy and plan on ECDIS Systems.
7. Understand the risk of over reliance on an ECDIS System.
Background Electronic databases, operating systems, computer technology and the widespread deployment of Digital technology has made it possible to employ electronic charts at sea.In addition, the advent of continuous and automated positioning systems (such as GPS), have made it possible to take maximum advantage of electronic charting.
The benefits of the integrated system GPS and chart data in digital format
include:
- Real time position .- Automated plotting of the navigation. - Reduce Manning - Minimizing Human error .- Alert to navigation dangers. - Dramatically increase awareness in low visibility.
Electronic Charting Systems
Advances in technology have made it possible to replace the traditional paper charts with Electronic Charting Systems.
All electronic charting systems fall into two categories. The two categories are:
• ECDIS (Electronic Charting and Display System) • ECS (Electronic Charting System).
Electronic Chart Display & Information System (ECDIS)
“means a navigation information system which, with adequate back-up arrangements, can be accepted as complying with the up-to-date chart requirements by regulation V/20 of the 1974 SOLAS Convention, by displaying selected information from a system navigational chart (SENC) with positional information from navigation sensors to assist the mariner in route planning and route monitoring, and by displaying additional navigation-related information if required.”
Sec. 2.1 IMO PS
And that means???? The short explanation is an ECDIS is a
system that is able to display electronic chart information with:
- automatic position updates
- built in redundancy
- that will assist the mariner in all aspects of Navigation.
It is the legal equivalent of a paper chart.
It is Not an ECDIS if…..
Equipment is not legally approved. Does not have adequate electronic chart
coverage. Does not have chart updating capability.Even though an ECS may perform many of
the same functions as an ECDIS, it is not the legal equivalent of an ECDIS. It may only be used for “situational awareness”.
What makes up an ECDIS or ECS?
1. Position inputs (GPS, DGPS, LORAN, Radar, gyro, fathometer, etc.)
2. Electronic Navigation Charts (ENC)
3. System Electronic Navigation Charts (SENC)
Color Display
Computer AISGyrocompass
ENCDepthsounder Currents
Updates
Radar/ARPA(GPS, LORAN)Nav Sensors
Water level
Ice info
ECDIS COMPONENTS
SENC
XTD
SPD
CSE
Electronic Navigational Chart (ENC)
“means the database, standardized as to content, structure and format, issued for use with ECDIS on the authority of government-authorized hydrographic offices. The ENC contains all the chart information necessary for safe navigation, and may contain supplementary information in addition to that contained in the paper chart (e.g., sailing directions) which may be considered necessary for safe navigation.”
Sec. 2.2, IMO PS
So What?
An ENC is a database, not a chart as you think of it. As such, there are:
• different types of ENC data
• various formats
• differences in the level of content
System ENC (SENC)
“means the database resulting from the transformation of the ENC by ECDIS for appropriate use, updates to the ENC by appropriate means, and other data added by the mariner. It is this database that is actually accessed by ECDIS for the display generation and other navigational functions, and is the equivalent of an up-to-date paper chart. The SENC may also contain information from other sources.”
Sec. 2.3, IMO PS
ENCENC
Data
Updates
#1
#2
#3
SENC
#1
#3
#2
+
+
+
SENC
SENC
SENC
1
2
3
IHO S-57 Performed in ECDIS
Software
IHO S-52 Colors & Symbols
Display
System Electronic Navigational Chart (SENC)
NextNext
Not all charts are equal….
• Many different formats exist for electronic charts.• The two major types are vector based and raster
charts.• Raster charts are scanned paper charts.• Most vector charts are digitized paper charts,
thereby inheriting any errors (and possibly introducing some!)
• Countries are producing unique digital charts based on their interpretation of IHO standards.
ENC
DNC® BSB
ARCS
C-MAP
Navionics
Transas
The Types of EC Formats are:Raster and Vector
NIMADigital Nautical Chart (DNC®)
IHO S-57Electronic
Navigational Chart(ENC)
NOAARaster Nautical
Chart (RNC)
Digital Chart Formats
The Basic Difference
• Raster charts are simply bitmap images created by scanning a paper chart
• Vector charts portray charted features as points, lines, or areas with amplifying information (attributes) found in an associated database
Raster Charts
• A set of colored pixels representing chart information as a picture on computer screen
• Simply an array of pixels arranged in rows and columns
• Pixels are color coded, but do not represent features explicitly
The Appeal of Raster
• Looks like a paper chart (appeals to traditionalists)
• Cheap and easy to produce (scan existing paper chart)
• Runs easily on PC
• World-wide availability
Vector Charts: More detail
• A set of accurately positioned lines (vectors), points and areas, with associated attributes (e.g. “shoreline”, “buoy - red”) organized in a database accessed by clicking on displayed symbol
Paradigm Shift
• Looks “different” from a paper chart
• Underlying database allows queries and layer selection
• Zooming reveals detail• Complex, expensive, and
time-consuming to produce• Needs more powerful
computer and expensive display to meet IHO/DoD requirements
USN Approach is to use NIMA’s Digital Nautical Chart (DNC), a vector based format.
DNC with Base data only showing (Less clutter)
Standard Display with Depth Contours
The user defines what features are necessary!!!
Standard Display with Spot Soundings
DNC with User defined Color
All Features
Which is better?
• Depends on your point of view….
• Raster is easier and cheaper to produce, but vector provides much more information to the navigator
• DoD standard is Vector Product Format --DNC®
• NOAA BSB charts cover US waters
The Advantages of Vector Charts
• Information on Chart can be linked to specific points. (Click on light and you can retrieve more info, like a picture of the light)
• Allows the user to display the information that is necessary for the ship’s current mission.
Raster Concerns
• High scan resolution required for detailed chart….lot’s of CPU memory required and slower refresh rates.
• Zooming degrades quality.
• Mixed pixels—is it water or land?
Raster Model
Land
Shoreline
Water
Vector Shoreline
US Navy Policy• The Chief of naval Operation ( CNO) issued a directive in march 1998 establishing minimum ECDIS standards (ECDIS-N) and calling for a transition of the entire Navy fleet from paper based charts to electronic digital Chart by FY 2007. This has recently changed to 2004, with the first ECDIS-N certified battlegroup deploying in FY01.• Until then, ships may use an ECS for enhanced situational awareness, but the paper chart must be maintained as well.
USN ECDIS-N Requirements
•Navy standard, automated and continuous positioning systems
•Display of radar, visual and celestial navigation fix information
•Ability to read and display National Imagery and Mapping Agency (NIMA) Digital Nautical Charts (DNCs)
• System-to-system interoperability
The US Navy Approach
• Several Different Programs including NAVSSI (USN), NAVSSI-Lite, and VMS/IBS.
• All programs will use NIMA’s Digital Nautical Charts.
• Most systems will also be able to read raster charts.
ECDIS-N Platforms
169 combatants scheduled for NAVSSI/NAVSSI Lite, including NIMITZ class aircraft carriers, ARLEIGH BURKE class destroyers, TICONDEROGA class cruisers, WASP class amphibious assault ships and Perry class frigates.
Virginia class SSN will employ ECDIS-N software for its Navigation Data Distribution and Display (ND3) system.
13 FAMOUS class cutters. There is potential for installation on other cutters.
Visual Bearing LOP Fix
Radar Range LOP Fix
Piloting Guidance
Automatically calculates:• cross-track error• recommended course to
steer accounting for set/drift
• nearest hazard • next navigation aid• depth • distance and time to turn
Military standard navigation report
Tabular turnpoint solution data
Tide and Current Information
Displayed on the chart…
…and graphically in pop-up windows.
The Risks of ECDIS
• ECDIS is only a tool that helps a mariner safely and effectively navigate a ship.
• It is not the end-all be-all to ship navigation.
• One of the biggest risks with the transition to ECDIS is an over reliance in the information provided
Some things to consider…• Poor GPS performance• DGPS used/not used• ECDIS malfunction• installation setup• ENC compilation errors (e.g., datums)• chart (errors, omissions, out-dated)• survey errors• human error
Any Questions?