Hello Vector Charters....
So, I got to thinking:
"Why are rocks and wrecks coded by IHO in Category "Other", when any reasonable navigator would say that the locations of rocks and wrecks are critical to safe navigation
, and should be in Category "Standard", i.e. the minimum safe navigation set? What were they thinking?
Researched this, and found the following:
1. Don't know why the default category is "Other". However, there is in the standard conditional display algorithms the possibility of moving the objects dynamically to Category "Base", so that they always display and cannot be disabled. They will be moved if their depth
is less than the surrounding depth
, and that depth is within the Safe Navigation area as set by the "Safety Depth". I'll say it another way: If the water
near the rock is deeper than your set Safety
Depth, and the rock is less than that depth, then the rock MUST be shown. Sensible.
However, if the rock is in a water
area shallower than your Safety
Depth, then it is NOT shown, to reduce clutter. I guess the theory here was that you won't be navigating outside of your Safety Depth generally, so you don't care about rocks in that area.
2. So, we look at OCPN in this light, and, mirabile dictu, we find a bug.
O did not properly move the rock to Category "Base". Fix that bug and O does the right thing according to the spec. In "Standard" category, rocks are shown or not depending on the setting of Safety Depth.
3. Comes another complication...
We are working with a very old specification of S52 PLIB. The modern spec costs $$$. However, we can get some hints of modern thought by scanning the public minutes of the IHO meetings.
Someone in IHO has noticed that the the objects displayed in category "Standard" depend on the setting of the Safety Depth. This is not good, since category "Standard" is meant to be the one-touch default that will always produce safe, usable information, regardless of other settings. Sounds like some of our discussion in this thread, doesn't it?
So, there is a proposal to dynamically move all rocks and wrecks to at least category "Standard", and possibly to category "Base" depending on the Safety Depth. Under this proposal, dated just this year, category "Standard" will display all rocks and wrecks, and symbolize them as "dangerous" if their least depth is less than the safety depth.
Here's a link:
Who knows if the proposal will be adopted. Regardless, I suggest that we adopt this logic. It is sensible, and solves some of the concerns of this thread. Rocks and Wrecks will be shown in Category "Standard", our default.
Whew....Specs make my eyes cross.