Ocpc_draw 'open' polyline option

[GroteStern]

Hi, I like to use ocpn_draw to draw polylines (not closed) to mark e.g. a dam or a advised sailing route. Similar to the route option of OpenCPN itself but without arrows etc. Now I can only achieve this by getting back on the same line and so draw a polypoint area with no with. Not convenient. And not easy adjustable later. I can draw a straight line (from point A to B), but I like from A to B to C etc. Merging as discribed in the manual doesn't work (v. 1.8.44). As this could be a (timeconsuming) workaround. So, maybe it is possible to add a polyline option. With regards, Michiel Firet, the Netherlands

[jongough]

OD does not really do single lines apart from EBL's which are not what I think you are after. There is the DR section, but this is just to help workout where you may be in a set time. It is not designed to draw polylines except as a part of a boundary (inclusion, exclusion or just a closed line). I use small routes created from tracks I have generated in the past for getting into and out of reef lagoons, harbours, safe anchorages etc. They show on the chart, just they don't have to be activated, unless I need assistance from the autopilot.

Is there a use case where you cannot reasonably use the current feature set of OCPN and a combination of the current plugins to do what you want to? If not, I will have a think about it, but....

[GroteStern]

Hi, want to use polyline to draw preferred sailing tracks in the shallow (Dutch) Waddensea. These tracks changes over time due to hydromorfology, so points must be adjustable in time. I can draw OpenCPN routes, export them to gpx, convert them to tracks-gpx and import again. But then points are not adjustable anymore. And additional information is limited. So yes, it is a workaround, but a polyline feature would be nice ;-).

[kay-o]

+1 for open polylines - this same feature would be useful for a variety of boundary lines distinguishing 'seaward' and 'shoreward' requirements e.g. the line used to determine a part of the sea service qualifications for US Coast Guard licensing

[jongough]

Why wouldn't you use an exclusion boundary for this purpose with the 'safe' side following all the points and the 'unsafe side' having a few points on land or obvious places? Then you can use the watchdog plugin to tell you when you enter (cross) the boundary line. It then not only represents the line you would draw on the chart but has utility as there is a good side and a bad side. If you need curved lines you can use exclusion boundary points as well to achieve this.

[kay-o]

Thanks for the recommendation, @jongough - I'll give that a try. Sounds especially useful if the watchdog plugin can (be adapted to?) log the event as part of autogenerating a sea time report.

[jongough]

The watchdog plugin uses the OD binary API to workout if you are entering an exclusion boundary and will provide an onscreen prompt. I have not checked if that gets logged into the OCPN log, but it may.