Industry stakeholders have discussed a lot about the pros and cons of paperless navigation concluding that ECDIS does have an edge over the traditional paper chart navigation. However, the question for the navigating officers remains the same. Can they steer the vessel, following a pre scheduled passage plan, within the safety margins that they set, from berth to berth, avoiding grounding? At this point, it is worth to mention the passage plan’s main purpose which is to use the available ‘navigational waters’ for the indented voyage so that the vessel could safely conduct the voyage.
- The ‘navigational waters’ can be mainly affected by the water depth, which is indicated both on paper charts and ENCs.
- Specifically, the depth measurement, as indicated, is the result of a relevant depth survey which varies in age and quality depending on the measurement techniques and the available technology.
Because priority for surveying is given to the major shipping routes, each navigator sailing into unfamiliar waters away from these routes should be able to interpret the various quality indicators that are, or should be, indicated on every chart. This is why many guides are available with best practices of navigation for commercial vessels and cruising yachts that help mariners to decide on how much confidence they should show on the marked depths.
- However, a mariner should be always wary of any chart that does not feature these indicators, irrespective of whether it is a traditional paper chart, or an ENC.
- ECDIS dispay vs traditional paper charts On the traditional paper charts, the Reliability Diagram (old charts) or Zone of Confidence diagram (new charts) indicate the depth accuracy based on surveys.
Navigators should carefully check the areas that they have chosen to sail, find the relevant indication on diagram and apply additional measures or safety features to protect the vessel from grounding. On ENCs the same policy is followed with the exception of the indication of accuracy which is well spread and marked on the chart with CATZOCs (Categories of zone of confidence). which indicates the accuracy of depth. This indication is subject to ON or OFF selection by the navigator, therefore, for an unfamiliar user the risk is increasing. In particular, there is risk of not displaying and checking the depth accuracy, resulting in unpleasant situations for the passage planning, thus, vessels to reach the depth limits (in accordance with calculated UKC) and finally to run aground because the depth result was not as accurate as the navigators expected to be.
Shallow Contour: Indicates the depth below a vessel could run aground and it is equal to vessel’s maximum static draft.Safety Depth = Maximum Draft(static) + UKC (Company’s Policy) + Squat(Maximum) – Height of TideSafety Contour: Is calculated same as per Safety depth AND activates ALARM when depth is lessDeep Contour: Indicates the limit of sea area where shallow water effects occur that can affect a vessel. It should be estimated twice or four times the draught of vessel (depending on the depth of water available)
Image 1: Areas of Navigational Waters ECDIS safe settings Although color code may vary in different ECDIS system displays, the generic idea remains the same. Another key issue to consider is to include the chart depth accuracy into UKC calculation or make a comparison between the CATZOC with the UKC (Under Keel Clearance) which is more common.
- The UKC sets the minimum level of distance between the deepest point of a vessel and sea bottom.
- In particular, it is a company-specific measurement, therefore, it is company’s responsibility to specify this distance and Masters must consider it during passage planning (especially in shallow waters).
Again, the depth accuracy emerges as an important issue for UKC calculations. For example, if a vessel has set the UKC to 0.5m but the chart accuracy has +/- 1 m, this may cause problem and the navigating officers are advised to take this issue into consideration.
Table 1 shows UKC correction due to the different Zone of Confidence of ENCs. The Category D is worse than Category C; it cannot be trusted and large anomalies in the depth can be expected. Also, the Category U is the unassessed category; the quality of the bathymetric data is not yet assessed. In conclusion, Electronic charts and ECDIS are necessary tools for navigators in order to plan the route and monitor the position easier and faster.
Considering that these electronic means are based on human surveys and measurements, the possibility of false information regarding depths, heights etc cannot be excluded. This is an additional factor to be considered during e-navigation and therefore all mariners (navigators, OOW and Masters) are advised to be always alerted and stay focused when they use these means of navigation. Table 1: Recommended table of UKC correction due to different Zone of Confidence of ENCs.
- 0.1 What is safety depth and safety contour in ECDIS?
- 0.2 What is the meaning of safety depth?
- 0.3 What is the safety contour?
- 1 What is the contour depth?
- 2 What is CatZoc in ECDIS?
- 3 What is the color of the safety contour on ECDIS?
- 4 How do you calculate contour?
- 5 What are the errors in ECDIS?
- 6 How is ship depth measured?
What is safety depth and safety contour in ECDIS?
Assumptions – The following assumptions were made in creating the scenarios described in these slides.1.ECDIS allows the mariner to set the Safety Depth and the Safety Contour Depth independently.2.The mariner sets the Safety Contour Depth equal to the “Vessel Safety Draft,” which is calculated as: Vessel Safety Draft = Vessel Draft + Dynamic Squat + Safety Margin 3.Depths are considered “safe” if they are equal to or deeper than the Safety Contour Depth.4.Depths shoaler than the Safety Contour Depth are considered “unsafe.”
What is the meaning of safety depth?
Safety Depth setting – So far we have only been talking about contours. We have not said anything about the actual safe depth. Safety depth is the only depth setting on ECDIS. Safety depth is the depth of the water we can safely navigate upon. And it might sound repetitive but it is the depth that satisfies the UKC policy of the company.
In ECDIS we need to enter this minimum depth. It is same what we calculated as a simple example in safety contour setting. And as I said in that section, we need to follow the UKC calculation form of the company which may account for number of factors to calculate the safety depth required. But the question is why do we need safety depth settings when we can navigate in waters above the safety contours ? This is because of two straight forward reasons i) The depth above safety contour may not always be navigable.
This is in case of a shallow depth at one point in the navigable waters. Although we might be navigating in area above safety contour, this isolated depth pose a danger. Safety depth highlights this danger. ii) The depths below safety contour may not always be non-navigable.
We can understand this If you allow me to again go through the safety contour value we entered. We entered the value of 11 meters and when we enter this value the ECDIS will take next available contour. This will be 15 meter contour. Now the depths between 11 and 15 meters are navigable for us but it will show below the safety contour.
So in the area between shallow contour and safety contour, safety depth will show the depth on which we can navigate. Let us say we set the safety depth to 16 meters. On the ECDIS, all depths below 16 metes will be shown more prominently (in Black compared to others in grey color).
What is the safety contour?
ECDIS has become the essential tool for watchkeeping officers on ships. Navigating a ship with an ECDIS is fundamentally different from navigating with paper charts. It is important that the Masters, navigating officers, and ship-owners are aware of the benefits of managing the chart display, safety settings, and alarm system of ECDIS.
ECDIS equipped vessels have been involved in a number of groundings which may have been avoided had it not been for failures in the setup and use of ECDIS safety settings and alarm systems. Inappropriate settings are likely to render the safety contour alarms meaningless. The use of ECDIS safety settings has often been overlooked by navigating officers due to either ignorance or insufficient knowledge.
Deck officers may be unfamiliar with the setup and use of ECDIS alarms thereby increasing the risk of grounding in shallow waters and causing other unwanted situations. Related Read: Real Life Accident: Improper Use Of ECDIS Leads To Vessel Grounding Appropriate safety settings are of paramount importance for ECDIS display.
These settings control how the ECDIS presents depth information, making it easier to visualize areas of water that are safe for the vessel to navigate in from those which are not. This article will help to understand the best practice for handling safety settings on ECDIS which includes the Safety contour, safety depth, shallow contour, and deep water contour.
The model of ECDIS used for illustrations is Furuno. Related Read: Pros and Cons of ECDIS Or Paperless Navigation Of Ships These values can be entered in Furuno ECDIS by following the steps mentioned below:
Go to the main menu and select Chart display Select the Main Tab to display it.
Safety Contour: The safety contour is the most important parameter of all the safety settings for the display of unsafe water areas, detecting isolated dangers and triggering anti-grounding alarms. The safety contour is basically an outline which marks the division between safe and unsafe waters.
Related Read: Ship Stability – Understanding Intact Stability of Ships The colour blue is used to indicate the unsafe areas while white or grey for safe areas. The default safety contour if not specified by the mariner is set to 30m. The blue colour in a traditional paper chart does not provide a vivid picture of shallow water, i.e the depths mentioned in the blue part of a paper chart may be shallower for a deep draft vessel while safe for a vessel with a smaller draft.
Unlike paper charts ECDIS allows the officer to set safety parameters according to the ship’s static or dynamic particulars. The safety contour can be calculated as follows: SAFETY CONTOUR = SHIP’S DRAFT + SQUAT + UKC – HEIGHT OF TIDE Let us check an example. Let us consider that as per company policy UKC requirement is 10%. Please note that UKC calculation takes into account various factors such as sea conditions, density or increase in the draft due to rolling. It should be calculated as per company UKC calculation sheet.
UKC = 1.0m Consider SQUAT AT MAX SPEED = 1 m Height of tide = 1 m Safety contour value would, therefore, be equal to 11 m. Contours are present in the values of 5, 10, 15, 20, and 30 and so on. If the value set by the mariner is not available among the available depth contours, ECDIS selects the next deepest available contour in the ENC.
Related Read: What are the Methods To Update Navigation Charts On Board Ships? If within a specified time set by the user, the ship is about to cross the safety contour, an alarm will sound. Based on the value of safety contour, ECDIS displays the isolated danger symbol for underwater features and obstructions which may pose a danger to navigation. Safety Depth Setting: The sole purpose of the safety depth is to portray spot soundings either in gray for deeper depths or black for shallower depths compared to the safety depth value entered by the navigating officer thereby highlighting the potentially safe and unsafe areas.
The safety depth value has no effect on alarms or any other aspect of ECDIS. Safety depth is normally the ship’s draft + squat. Related Read: How Squat, Bank and Bank Cushion Effects Influence Ships? Now the question is why do we need to mention safety depth when safety contour can demarcate between safe and unsafe waters? It is also logically to select Safety Depth equal to Safety Contour.
Some soundings on the shoaler side of the safety contour will be gray because they are deeper than the safety depth set by the mariner, although shoaler than the safety contour selected by ECDIS. The depths below safety contour may not always be non-navigable,
- Suppose for example if safety depth and safety contour are set to 11 m, the ECDIS will emphasize the depth contour equal or deeper than the selected contour which say is 20m, whichever is available in the ENC.
- Related Read: How ECDIS Can Be Further Improved – A 2nd Officer’s Perspective Thus we can see that water areas with depths between 11m to 20 m are navigable but are below the safety contour.
This provides the mariner with additional information about where the ship could most safely pass if crossing the safety contour is required (an alarm will still sound). This could provide additional maneuvering room in narrow passages where safe depths exist. In the picture above, safety depth value is 14m. You can see that depths equal to and below safety depth value are highlighted in bold. Zone Of Confidence Catzoc: In calculating safety depth it is also important to consider CATZOC features OR ZONE OF CONFIDENCE, Let us consider an example. Ship’s draft = 7.7m Squat = 1m Effective draft = 8.7m Required company UKC is 10% of the deepest draft which is 0.87 approximately 0.9m. Thus we see that the total safety depth required complying with company UKC policy is 9.6m.
Safety depth value can be set as 10m. However, we haven’t yet considered the depth accuracy as per ZOC. Let us consider that Catzoc in this area is category B which implies there can be an error of 1m + 2% of depth = 1.2m. Therefore if catzoc error is allowed, the minimum depth required would be 10m + 1.2m = 11.2m.
As safety depth cannot be entered in decimals in ECDIS, we can enter 12 m as safety depth. During passage planning, it is essential that CATZOC is displayed and noted for all stages of the voyage. Catzoc Category B Shallow Contour: The shallow contour highlights the gradient of the seabed. It is considered to be the grounding depth i.e this is the depth below which the ship will definitely go aground. This value can be set equal to the ship’s draft, Therefore if ship’s draft is 7.7m, shallow contour value can be set as 8m.
The ECDIS will then display the next depth contour available in the ENC. All of the areas between the 0m depth and the shallow contour is therefore not navigable at all and appears hatched. As I have already mentioned earlier that the division between safe and unsafe water is highlighted by chart colouring, with blue colour for indicating unsafe area while white or grey for safe areas.
The unsafe area is further defined with the selection of shallow contour showing dark blue in the shallow water and light blue between the shallow water and the safety contour when 4 shade display is selected.2 shade and 4 shade display is further explained below. ECDIS also gives the option of simple two colour shading. In this situation light blue and deep blue will merge into a single blue colour and grey and white will merge to a single white colour. If the value of the safety contour is changed, the boundary between two depth shades changes accordingly. The picture above shows that the four shade depth option is not selected. The pictures below show a comparison between two shade and four shade depth in daytime and night time. Day Time Night Time Watch Vector/Anti Grounding Function: The look ahead or watch vector actually compares the safety settings that have been entered by the navigating officer with the depth information contained in the ENC, and generates an indication or warning where the safety settings will be contravened.
It provides advance warning of dangers/cautions, primarily intended to prevent grounding. It acts as a final layer of safety should a navigational danger be missed by the visual check or route scan. The scanned area is sometimes displayed as a cone or column on screen and should be set to a distance appropriate to the amount of navigable water ahead of the vessel.
This value should be determined for each stage of the voyage and noted in the passage plan. Many officers fail to realize the significance of the safety contour and do not make proper use of the look-ahead vector. This is how you can activate own ship check-in Furuno ECDIS.
Go to Chart menu and select Initial Settings
Open the menu displayed at the left and choose Chart Alert Parameters
Click the Check area tab. Set Ahead Time or Ahead distance The Around field allows the officer to set fixed areas.
Note that the chart alert always uses the largest scale chart available, which may not be the visualized chart. Note that the ‘Chart Alert’ feature should be highlighted so as to trigger the audible alarm whenever safety contour is breached. It is required to amend the alarm parameters from their previous settings when beginning a new voyage. The alarm parameters need adjustments throughout the voyage to ensure they are optimized for the prevailing circumstances and conditions.
ECDIS is a valuable asset in assisting navigators and providing them with more detailed situational awareness. However, until used accurately and properly, ECDIS may contribute to accidents rather than preventing them. Related Read: How to Order Electronic Navigation Charts and Keep Them Updated On Ships? Increased training and practical use will help to develop and create a better ECDIS mindset.
Trainee officers should be encouraged to understand the benefits that Ecdis provide and make the optimum use of the same. During route planning, a chart alert calculation should be done to detect any dangerous situation and the same should be modified as necessary.
- A better understanding of ECDIS safety settings and their proper use can act as a potential barrier to the grounding of ships and any untoward situation.
- Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight.
- Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority.
The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader. Paromita has completed graduation in Nautical Science and is presently preparing for 2nd mate exams. Besides sailing, she loves to read books and travel. She has also won many awards in music.
What is the contour depth?
Numbers on a nautical chart are depth measurements, – Soundings, or water depth measurements, are represented by numbers on nautical charts. Water depths are measured by soundings usually acquired by hydrographic surveys, The depths may be in either feet or fathoms (the chart will indicate which). A fathom is a nautical unit of measurement and is equal to six feet,
On a chart, water depths may be connected with a line known as a depth contour, similar to the topographic lines or surface features that you see on a map. Depth contours present a picture of the bottom to the mariner. In addition to showing water depths, a nautical chart also tells mariners about dangers to navigation, aids to navigation, anchorages, and other features.U.S.
Chart No.1 explains all the numbers and symbols found on both paper and electronic nautical charts.
What is depth on ECDIS?
ECDIS enables mariners to set their own-ship ‘safety depth.’ If no depth is set, ECDIS sets the value to 30m. Soundings equal to or shoaler than the safety depth are shown in black; deeper soundings are displayed in a less conspicuous gray.
What is CatZoc in ECDIS?
The oceans account for approximately 70% of the planet Earth, where about 50,000 ships ply every day. But how is it secured that they ply in safe areas? The seabed is a complex surface that is likely to differ in depth at all points across the ship hull.
- How has such a large area been measured and mapped accurately to make sure that the water depth is adequate? S hips’ navigation for the transport of goods has been present for thousands of years, with Britannica recording the first indications of waterborne vessels as early as 4000 BCE.
- Measuring the ocean depths is not a task that took place in one day and certainly remains a key task of the world’s hydrographic offices in each state.
Measuring the oceans’ depth In the past, the measuring of water level was carried out manually with ropes and acoustic signals. A more recent method included a wire being towed by two or more ships with weights sunk at a fixed depth. Any obstruction in the area the wire was being dragged would be detected by the wire being stretched.
With the technological advancements of today, the method of conducting these hydrographic surveys has changed. The modern approach for recording the oceans’ depth is using SONAR ( SO und N avigation A nd R anging). The SONAR technique is using sound propagation, to measure distances or detect objects underwater.
The data collected through SONAR are then processed in combination with other data, such as tide, to make the depth measurement as accurate as possible. However, the data shown on nautical charts and ENCs may have errors depending on how these data were measured and when they were measured.
- The older the data are, the less accurate they will be, due to the limited technology equipment used in each time.
- A case study The Captain and the second officer are reviewing the passage plan.
- At some point, they realize that the under keel clearance – the vertical distance between the bottom of the ship and the seabed- is 1.5 meters which is more than enough under the company’s SMS.
But how trustworthy is this estimation? What if the depth is lower? Looking at it a bit further, they realize that the measurement provided for this point of the passage plan was made over a century ago. And while navigating on this route would be alright under the company’s procedures, it could prove catastrophic in practice.
- So how much of a range should the crew expect regarding the water depth? This is what CatZoc addresses.
- CatZoc and its importance for safe navigation As there are several parts of the water that were mapped years ago, with different technological means, it is expected to not trust all the measurements.
The main possible errors may concern the actual depth measurement, as well as the position at which the depth measurement is depicted. At the same time, the potential errors of these two variables are not constant. In this respect, a CATZOC (also known as Zone of Confidence) is a deviation that helps make sure which of these variables are accurate and to what extent errors are expected.
|A1||5 meters||0.5 meters + 1% of depth|
|A2||20 meters||1.0 meters + 2% of depth|
|B||50 meters||1.0 meters + 2% of depth|
|C||500 meters||2.0 meters + 5% of depth|
|D||Over 500 meters||Over 2.0 meters + 5% of depth|
The zones of confidence above provide the maximum errors per depth and position. As such, CatZoc (Categories of Zone Of Confidence) is a rather simple aspect of understanding ECDIS and electronic nautical charts (ENCs). On ECDIS, the CatZocs are symbolized by a number of stars.
the location of depths marked on this chart may be inaccurate by approximately 50 meters; orthe possible error of the depth is 1 meter + 2% of the depth, e.g., if the mapped depth shows 20 meters, the error in that could be 1.4 meters (1 meter + 2% of 20 meters).
Did you know? The effects of shallow water on ships’ navigation can be not only disrupting but also dangerous. For example, a very big cruise ship, e.g., the size of the Costa Concordia, is unable to float if the water is less than 26ft deep. Usually, when a ship is navigating in shallow waters, maneuvering becomes more sluggish and the speed of the ship over water reduces.
What is the safety contour setting on ECDIS?
What are setting on ECDIS ? There are following safety settings: –
Safety Contour Setting Shallow contour settings Deep contour setting Safety Depth setting
Safety Contour Setting – Safety contour is the contour line above which we can navigate without any water depth concern. It includes the Vessel’s static Draught + UKC + Squat.
Safety contour may be set equal to but not lower than the safety depth setting. The area beyond safety contour is termed as NO GO. Shallow contour setting – Shallow contour value need to be used to tell ECDIS what is the value of shallow waters for our draft.
- This is the value of depth below which it is definite for the vessel to get aground.
- The shallow contour value need to be equal to or more than the draft of the vessel.
- Let us say the vessel’s draft is 9 meters and we enter the shallow contour value of 9 meter,
- The ECDIS will display 10-meter contour line as the shallow contour.
If 10-meter contour is not available, it will take next contour as the shallow contour for the vessel. : What are setting on ECDIS ?
What is the color of the safety contour on ECDIS?
Traditional method of passage planning on paper chart: Using a draft of 14 mtr and applying a 2 mtr safety margin, the second mate would mark off areas with depth 16 mtrs and less, on the navigational chart. These areas would then be highlighted, using a pencil, as a NO GO area and the passage would be planned keeping well clear of this area. Correspondingly on ECDIS When the safety contour value is set as 7 mtrs. ⦁ Safety contour is emphasized (bolder) than other contours. ⦁ If the safety contour specified by the mariner is not in the displayed SENC, the safety contour shown defaults to the next deeper contour. ⦁ ECDIS will give an alarm if, within a specified time set by the mariner, own ship crosses the safety contour. ⦁ Areas with depths lesser than the set safety contour is coloured blue and deeper depth area is coloured white. ⦁ Enabling the “shallow pattern” provides a cross hatch pattern to further emphasis the NO GO area as was done on paper charts. Hence like the traditional NoGo areas on a paper charts, on an ECDIS, ⦁ Blue area denotes NO GO areas ⦁ White area denotes the navigable area. If the entire planned passage upto the pilot station is through the “white” and the “Grey” areas, followed by a channel/river transit to the berth: Then at no point in the voyage, the vessel’s planned track is expected to cross into the blue areas. In this case ⦁ By setting safety contour setting ⦁ And enabling the shallow contour pattern, The No Go area is automatically marked by the ECDIS. There is, generally, no need to additionally mark NoGo areas using mariner info overlay. What should the OOW do an obtaining a safety contour alarm? OOW should call the master immediately and alter course back into grey/white zone if you are about to violate the NO-Go area. By just feeding in the safety contour setting, the ECDIS ENC display is sub-divided into blue (no-go) and white (navigable) zones. Changing over from 2 color mode to 4 color mode and by entering appropriate values for shallow contour setting and deep contour setting, we find that: ⦁ The blue area gets subdivided into dark blue and light blue areas. ⦁ The white area gets subdivided into grey and white. What does the colour indicates DARK BLUE ZONE: On inputting the shallow contour setting, areas on the ENC with depth value <= Shallow contour setting is displayed as dark blue zone. Example:- Assuming vessel static draft of 7.80 mtr With shallow contour setting at 5.00 mtrs Dark blue zone denotes grounding depths. LIGHT BLUE ZONE: On inputting the safety contour setting, areas of the ENC with depth value lesser<= Safety contour setting is displayed as light blue zone. Example:- Safety contour setting = (Static draft + all allowances + Minimum net UKC requirement for that area – Height of tide) Vessel is in congested waters, Height of tide as 1.5 mtrs, we take 0.50 mtrs as the minimum net UKC requirement. Giving us Safety contour setting = 7.8+3.0+0.5-1.3 = 10.0 meters With safety contour setting at 10.0 mtrs Light blue zone denotes an area where you are in non-compliance with the Minimum Net UKC policy of the company. GREY ZONE On inputting the deep contour setting, areas of the ENC with depth value <= Deep contour setting is displayed as Grey zone. Grey zone denotes an area of potential shallow water effects White zone is relatively safe waters No Go Area :- Dark Blue Zone and Light Blue Zone IMO "standard" display setting is the minimum ECDIS layers considered essential by IMO for safe navigation. The "standard" display des not include the sounding layer as the four colours shown on the ECDIS display provide sufficient data for anti-grounding purposes. Example:- The pilot station is situated within the light blue zone (No go area) of the ENC. We will use a vessel with draft of 12 mtrs. Dynamic Draft= 12+1.9 (all allowances ie. Squat, heel correction, density correction and others) = 13.9 m Safety Contour Settings = 13.9+0.5-0.4 = 14.0 m Safety depth = 14.0 m Shallow contour = 10.0 m Vessel has to pass the safety contour area to enter channel When the vessel first crosses the safety contour, the safety contour alarm will be generated to alert the navigator to a potential violation of the NO GO area. However no further Anti-grounding warnings will be generated, if for any reason, the vessel deviates off her planned route. Why ECDIS has this issue The ECDIS ENCs like the earlier paper charts, have sounding contour layers of 5/10/15 or 05/10/20 / 30 or 100/200/300 etc. Hence, when we set the safety contour setting as 14 mtrs, the ECDIS defaults to the next available contour which is 20 mtrs. So though the light blue area is a No-GO area as per the ECDIS display, technically we can navigate in waters with depths> the safety contour setting of 14 mtrs (highlighted as NAVIGABLE ) Depths <=14 mtrs (highlighted as NO GO and cross hatched with red lines ) are still No-Go depths as the vessel will likely be violating the UKC policy of the company. The risk associated with navigation in these safer areas within the light blue zones are: ⦁ Availaible sea room inside light blue area is generally confined or restricted for safe navigation ⦁ Soundings are not easily visible, more so in the night mode ⦁ No more alarms are generated once the vessel crosses the safety contour Configuring the ECDIS for crossing the safety contour As per above the safety depth setting is set at 14m, so all depths <=14 m will appear bold. Spot soundings with depth <= safety depth will appear bold. Note These are not required to generate any alarms as per the IMO performance standards Lets make some modification on ECDIS for more safe passage planning Using user maps (mariner info overlays), demark the no-go areas within the light blue zone. (only usermap lines with danger attribute will generate alarms when interrogated by the safety cone) Use warning lines to follow the virtual 14 mtrs (safety depth setting) contour indicated by the darker safety depths. Note: These warning lines will generate an alarm when interrogated by the vessel's look ahead (danger detection) cone Navigate within the light blue zone with the vessel look ahead (danger detection) cone activate. (Ensure that look ahead cone time or distance setting is carefully set to meet the particular circumstances. Note: If set too long it will create numerous alerts that may distract the navigator. Obstructions (dangerous to navigation) All obstructions (dangerous to navigation) with an attribute equal to or lesser than the safety contour setting will be highlighted with a Magenta Cross Head Symbol. Any obstructions (dangerous to navigation) with an attribute more than the safety contour setting will not be highlighted with a Magenta cross head symbol.
What are the three types of contour?
Download 1m Contours of the UK for CAD software here – Diagrams provided by Encyclopaedia Britannica Contour lines are critical to understanding the elevation profile of your terrain or a particular land formation. This information can be helpful when selecting a hiking route. In addition to backpacking and hiking, countless other professions use them – land surveyors, architects foresters, engineers, miners, geologists, hunters and more.
- Topography is the study of the geographical features of a landscape.
- A map with contour lines on it is called a topographic map.
- Topographic maps use a combination of colors, shading and contour lines to represent changes in elevation and terrain shape.
- Specifically, a topographic map represents the three-dimensional landscape of the Earth within the two-dimensional space of a map.
The first known maps to include geographical features were found in Ancient Rome. It would be thousands of years before cartographers could chart large areas of terrain with any real accuracy. The contour lines we are using today came into popular use in the mid-1800s along with the rise of resource extraction industries like mining and logging. Shallow slope (the contours are spaced apart) Steep slope (the contours are close together) Diagrams provided by https://getoutside.ordnancesurvey.co.uk There are 3 kinds of contour lines you’ll see on a map: intermediate, index, and supplementary.
Index lines are the thickest contour lines and are usually labeled with a number at one point along the line. This tells you the elevation above sea level. Intermediate lines are the thinner, more common, lines between the index lines. They usually don’t have a number label. Typically one index line occurs for every five intermediate lines. Supplementary lines appear as dotted lines, indicating flatter terrain.
How do you calculate contour?
1. How to find contour interval? To find the contour interval divide the difference in elevation between the index lines by the number of contour lines from one index line to the next. For example, if the distance of 200 is divided by the number of lines, where the number of lines is 5.
What are the errors in ECDIS?
Through a root cause analysis, the potential errors for using ECDIS are identified on three categories: human error, equipment error, and operation or management error.
How is ship depth measured?
shipbuilding measurements –
In ship: Naval architecture The depth is measured at the middle of the length, from the top of the keel to the top of the deck beam at the side of the uppermost continuous deck. Draft is measured from the keel to the waterline, while freeboard is measured from the
What are the safety parameters of ECDIS?
Main features of shipborne ECDIS – North up/heads capability of ECDIS: In the normal north up mode, the ship moves across the static chart until it approaches the edge of the screen when a new section of the chart is automatically displayed. In heads up, the vessel remains in the center of the display while the chart moves underneath.
- The vessel always appears up on display with the image automatically rotated to the correct orientation, thereby matching the scene outside the window.
- Radar overlay A navigation system which superimposes live radar video output over ECDIS.
- It provides a scan-converted output for display, automatically scaled to suit the displayed chart.
The transparency can be adjusted so that the chart can be seen through the radar image. The overlay and its controls conform to the ECDIS standard for combining radar with the ECDIS chart display. Electronic navigational chart (ENC), also vectorised chart Vector charts made up of layers which can be displayed selectively.
Each point on the chart is digitally mapped, allowing information to be used in a more particular way, such as clicking on a feature to display its information. Vector charts have the advantage of being “interactive.” For instance, the operator can pre-set the vessel draught and a mile exclusion zone.
When the vessel is within mile of an area of shallow water, an alarm activates. Chart data can be shared with other equipment such as ARPA and radar. There are various chart formats. Hydrographic offices are responsible for the production and accuracy of the ENC material.
Related Information ECDIS warning procedure Although many vessels have fitted Electronic Chart Display and Information Systems (ECDIS) on a voluntary basis, its use will significantly increase once passenger vessels, tankers and dry cargo ships begin to comply with mandatory SOLAS requirements for ECDIS.
ECDIS alarm parameters Safety Contour: Is to be set to the maximum dynamic draft, plus 10% of static draft. Note that ECDIS will select the next deepest contour contained as an object within ENC. Passage planning guideline on ECDIS The principles of voyage planning are the same with ECDIS as with paper based navigation.
ECDIS warning procedure Although many vessels have fitted Electronic Chart Display and Information Systems (ECDIS) on a voluntary basis, its use will significantly increase once passenger vessels, tankers and dry cargo ships begin to comply with mandatory SOLAS requirements for ECDIS. Admiralty Chart correction procedure There are currently two methods of carrying out electronic chart corrections, either via Weekly Updates, CD or downloaded weekly from a recognised electronic chart suppliers data.
The preferred method will be decided by the Management Office depending on the communications equipment onboard the vessel but in the majority of cases the lack of internet access will determine the update CD as the best option. Requirement of ECDIS training and implementation guideline To ensure compliance with the ECDIS requirement, to ensure that the transition is smooth, equipment installed and Master and Bridge watch keepers are all provided generic and ship-specific ECDIS equipment training before the implementation dates of various type vessel:,
What are the safe navigational procedure for the officer of the watch ?, The officer of the watch (OOW) shall comply with masters standing orders (including any supplementary instructions) to carry out the navigational watch. He must always bear in mind that he is the Masters representative and has primary responsibility at all times for the safe navigation of the ship and for fully complying with the latest COLREGS,
Guidance on ECDIS- data presentation and performance check standards Type approval is the certification process that ECDIS equipment must undergo before it can be considered as complying with the IMO Performance Standards for ECDIS. The process is conducted by type approval organisations and marine Classification Societies. Other info pages ! Ships Charterparties Related terms & guideline Stevedores injury How to prevent injury onboard Environmental issues How to prevent marine pollution Cargo & Ballast Handling Safety Guideline Reefer cargo handling Troubleshoot and countermeasures DG cargo handling Procedures & Guidelines Safety in engine room Standard procedures Questions from user and feedback Read our knowledgebase Home page ShipsBusiness.com is merely an informational site about various aspects of ships operation,maintenance procedure, prevention of pollution and many safety guideline. The procedures explained here are only indicative, not exhaustive in nature and one must always be guided by practices of good seamanship.
What is the difference of guard zone and safety frame?
The guard zone (also known as Safety Frame) provides the user with an advance warning of dangers/cautions. The user sets the dimensions of this guard zone which must be altered according to the prevailing circumstances to prevent unnecessary alarms or to give adequate warning.