The association I'm a member
of is thinking of producing some chart-lets/mud-maps of say 30 anchorages
. They need to have enough detail to show key features and approximate depths. They will refer to the appropriate chart for navigational detail and accuracy and will have carefully worded disclaimers, we also have to respect chart producers Copywrite etc. Ė this will be checked by legal
people. (Thus we cannot just take a screen
snapshot of electronic charts
- or can we??). We would collect text of key features using local knowledge.
They will be made available to cruisers at virtually cost price
(ie not for profit).
Once upon a time one might have traced the shoreline off the chart, rowed a boat around with a lead line and recorded depth
and time against a (GPS) fix. Each depth
reading would then have been reduced from the predicated datum at that time, possibly using a simple cosine curve rather than site by site predictions. (Donít forget that errors in depth measurement and failure to correct for pressure differences etc are likely to produce greater inaccuracies). We don't have the funds to buy a lot of software
- but some would be OK.
What are the options today?
Many thanks, Andrew