0 - OpenCPN - Feature Requests

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FS#224 - ALARM Depth - Warn when route crosses area shallower than shallow or safety depth

Attached to Project: 0 - OpenCPN - Feature Requests
Opened by Fabbian Dufoe (fgd3) - Monday, 08 November 2010, 06:26 GMT-7
Last edited by sean d'epagnier (seandepagnier) - Saturday, 31 May 2014, 21:20 GMT-7
Task Type Feature Request
Category Backend / Core
Status Accepted
Assigned To No-one
Operating System All
Severity Low
Priority High
Reported Version future version
Due in Version Undecided
Due Date Undecided
Percent Complete 0%
Votes 10
Private No


One of the justifications for replacing raster charts with vector charts is vector chart plotters can be cognizant of depth, allowing the program to warn the mariner when a proposed route crosses an area less than the vessel's draft. There would be a big safety advantage to warning a mariner who is focused on getting from point A to point B that there are intermediate obstacles he must avoid.

Here's how I think I would approach adding such a feature to OpenCPN.

Add a field in which the user could enter the draft of his vessel. Leave it to the user to decide if he is going to enter the draft with boards and rudders raised or lowered or actual depth of keel or depth some distance below the keel. The idea is the draft he enters will be the depth he is comfortable sailing over.

When creating or editing a route on a vector chart--if the vessel's draft is other than zero--check each leg of the route to see if there is any area whose depth is less than the vessel's draft. If there is, mark that leg number with an asterisk in the Route Properties dialog box. Add a note at the bottom of the dialog box saying "*WARNING: Leg is shallower than vessel draft." Once a leg is flagged as shallow the asterisk would continue to be displayed in the Route Properties dialog box no matter what type of chart was in use. It would also be useful if the offending leg were displayed in a different color than the rest of the route.

If the user wanted to eliminate the warning by editing the route he would have to use a vector chart to edit the route, avoiding the shoal area. Ideally routes edited when raster charts were in use would be rechecked any time the user switched to vector charts, but I don't see how that could be accomplished without ruining the program's performance. You might, though, add a "Check Depths" button to the Route Properties dialog box when vector charts were in use (and vessel depth was greater than 0). The user could click on that button to recheck the depths along the route. That would correct any route that might have been edited with a raster chart and had left-over, now invalid, shallow depth flags set.

Nothing should prevent the user from creating a shallow route. He may know he is going to traverse it at high tide, when there will be adequate depth. Still, a reminder that the depth at low water is insufficient could prevent grounding.

The "shallow" flag would have to be preserved when routes were saved or exported. The GPX format allows an extensions type that I think could handle the shallow flag. It's important that the flag be preserved in exported routes since selectively importing and exporting routes is the method for keeping the charts free of "route clutter".

As you can see, I'm making this up as I go. It needs more discussion but I think it would be a useful feature.

This task depends upon

Comment by Markus (membercare) - Saturday, 19 May 2012, 17:09 GMT-7
This is related to: "Add Grounding and Radar Alarms" (ID 242) (Detection of objects by route checking)
There are standards how this has to happen in IOH (ioh.int) and SOLAS .... Has to be implemented and tested in ECDIS (legal replacement of paper charts)
Would be great to have this feature in openCPN

Comment by Fabbian Dufoe (fgd3) - Friday, 15 March 2013, 07:45 GMT-7
Any chance of getting this moved to a higher priority? It has been languishing for over two years and it seems to me a pretty important feature for an ECDIS.

Comment by Rick Gleason (rgleason) - Thursday, 22 August 2013, 14:19 GMT-7
I am going to assume it should be under pi_Route and should be assigned higher priority.
Excuse me, it should be with Route Manager RM perhaps.
Comment by Rick Gleason (rgleason) - Saturday, 15 February 2014, 09:53 GMT-7
I believe Sean's WatchDog plugin could implement a depth feature that alarms at a set depth using an instrument. (he has a place for it), however he'd like a depth instrument to test it. This is slightly different that looking at the chart depths themselves....almost better because BSB charts won't work.

Note that the above idea flags SHALLOW areas on a route, using the ENC charts depth, which would be usefel.

The plugin has many other useful alarms too. Talk to Sean about this feature perhaps.
Comment by Serge (AISEAG) - Sunday, 16 February 2014, 05:38 GMT-7
  • Field changed: Attached to Project (0 - OpenCPN - Feature Requests → pi - Watchdog / Watchman)
  • Task reassigned to Anonymous Submitter
Hi Sean,

Another one for Watchdog

Comment by Fabbian Dufoe (fgd3) - Sunday, 06 April 2014, 19:29 GMT-7
A shallow water alarm isn't what I am looking for. I want a planning tool that will warn me that a planned route passes through a shoal area. There's nothing wrong with an alarm that sounds when the depth sounder reports a depth less than a set threshold, but it isn't what was requested and is of little value to me.

Comment by sean d'epagnier (seandepagnier) - Tuesday, 08 April 2014, 19:28 GMT-7
It should be possible to determine if on the current course the boat will run aground giving parameters for how far ahead to search (distance and/or time and depth) taking tides into account if possible, otherwise falling back to low water. This is a bit more advanced than the current landfall alarm. It could also have a button to check current routes as well.

I don't think it's possible to implement all of this without extending the plugin api.
Comment by Fabbian Dufoe (fgd3) - Tuesday, 08 April 2014, 20:33 GMT-7
I don't think you should be working on this task, Sean. The request was for a warning to appear when a proposed route crosses a shoal area. I think it's a good idea to offer warning of shoals ahead and your plugin might be partial solution to FS242, "Add Grounding and Radar Alarms". I just don't think the Watchdog plugin is the right place to tackle warning of shoal areas in a proposed route.

The more I think about it, the more I think it was a mistake to put grounding and radar alarms in the same request. It's pretty clear those affect different parts of the program. You can detect shoals ahead without the radar plugin, but you can't provide a radar alarm without the radar plugin, can you? Should I amend FS242 to remove the radar alarm part of the request and create a new request for a radar alarm?

Comment by sean d'epagnier (seandepagnier) - Saturday, 31 May 2014, 21:18 GMT-7
I think the request is to warn if a route crosses an area of shallow water, where the watchdog would only be warning if the boat may pass over shallow water in the future, and is not tied to routes. I will for this reason move this to feature requests.