A shortcoming of maritime charts and chartplotters is that the base data is often very old. Official charts from NOAA (in the case of US waters) are marked with the effective date of the soundings (depths). But, this information is not reflected on most (if any) chartplotters. So, it's not easy to believe that your chartplotter correctly reflects where your boat can and cannot go.
When relying on data that may be several years old. sandbars, particularly near harbors, and the mouth of rivers can be very different.
We intend to use a version of crowdsourcing to address this problem. In crowdsourcing, depth soundings and GPS coordinates of different boats are uploaded to the internet, then downloaded to all participating boats. Essentially, depth soundings on your electronic charts will show what other boaters before you have found. The idea behind this is to keep depth sounding data current. The only problem is that you are relying on other people and their equipment. There is no telling who may, or may not have older equipment, and whether it is correctly installed or calibrated.
Our plan is to use the crowdsourcing mechanism, but we will only rely on data from our own source, the tender. Our tender with be setup with a sonar and chartplotter that is compatible with Fir's chartplotter. When we near questionable waters the tender will be deployed to map the area, and transfer data back to Fir. This will be significant for getting Fir to the shipping channel from where she is currently moored.
This is our plan. Check back to see if it works.