2019-03-27, 05:22 PM
You might also ask on the opencpn forum because this is something more suited to a plugin there rather than specifically for openplotter.
So far I do not know of anyone who has done it. It has been a goal for me for a long time now but I am completely sidetracked from making my own depth sounder which needs to happen before I can do this.
It is not an easy problem for a lot of reasons. How do you intend to measure depth? A typical sonar depth sounder works well for knowing approximate depth and if it will become too shallow, but for a survey it can be a problem. This is because the speed of sound travels at different speeds depending on the water temperature. It is impossible to know the water temperature at different depths without dropping a probe and then you might as well use a lead line. This is more of an issue in deeper water, so it is not actually that bad.
To get a really accurate survey I think you either need to use lead line to measure depth, or repeat the survey many many times in different weather.
Another issue is tide compensation. This can be mostly compensated for with lunar tide harmonics, but it is very difficult to compensate for other effects like wind-driven tides, and storm surges. This is a big problem of navionics and many of their user-produced sonar charts also caused the next user to run aground. It's difficult to know or trust the accuracy of whatever sounder is used by whatever user.
So again, multiple surveys of the same area are likely needed if using a depth sounder.
It might be useful for fishing and to get a more detailed contour, but absolute accuracy for transiting areas where you will nearly (but not) touch the bottom is going to be difficult to produce.
So far I do not know of anyone who has done it. It has been a goal for me for a long time now but I am completely sidetracked from making my own depth sounder which needs to happen before I can do this.
It is not an easy problem for a lot of reasons. How do you intend to measure depth? A typical sonar depth sounder works well for knowing approximate depth and if it will become too shallow, but for a survey it can be a problem. This is because the speed of sound travels at different speeds depending on the water temperature. It is impossible to know the water temperature at different depths without dropping a probe and then you might as well use a lead line. This is more of an issue in deeper water, so it is not actually that bad.
To get a really accurate survey I think you either need to use lead line to measure depth, or repeat the survey many many times in different weather.
Another issue is tide compensation. This can be mostly compensated for with lunar tide harmonics, but it is very difficult to compensate for other effects like wind-driven tides, and storm surges. This is a big problem of navionics and many of their user-produced sonar charts also caused the next user to run aground. It's difficult to know or trust the accuracy of whatever sounder is used by whatever user.
So again, multiple surveys of the same area are likely needed if using a depth sounder.
It might be useful for fishing and to get a more detailed contour, but absolute accuracy for transiting areas where you will nearly (but not) touch the bottom is going to be difficult to produce.