I spend sevral days testing (OpenCPN versus MaxSea
and Tsunamis99). I tested charts on several locations where I once was such as Ducie (Pitcairn Group), Conway Reef and Minerva Reefs) and found a bug which can be reproduced as mentioned below:
Minerva Reef (south of Tonga) 23 39 S 178 55 W
On Google Earth
clearly visible (I spent several days at these reefs
In Tsunamis99 charts OK, reefs
are visible at all scales
CM93 2010 very detailed ONLY when zoomed in correctly (OpenCPN version 2.1.0 build 514)
Before zooming in there is no indication whatsoever of a danger
Charts of the reefs only show from True Scale 357300 (True scale 44600 gives the whole chart of the northern reef)
ALSO the detail charts at true scale 357300 ONLY shows up when the cursor is ON the exact position of the reef when zooming in.
Just zooming in does NOT result in showing up the detailed chart
I checked the same chart set with MaxSea
MaxSea has the similar display problems as OpenCPN which suggest that it may be a problem of the chart set.
However the following test shows a small but significant difference:
With the cursor exactly ON the detail chart zoom in/out and you get or lose the details.
With the smaller scale (= big area chart) you have no indication of the fact that a shoal or reef is there.
Put the cursor (AFTER zooming in) just slightly off the detail chart and zoom in/out again and you will see that the detail chart does NOT show up again (in OpenCPN 2.1.0 build 514)
With MaxSea you can zoom in/out without the cursor being in the right spot and still get the detail charts to show up.
The MaxSea is therefore a little bit safer with navigation
, but this may be a repairable bug in OpenCPN.
However, for far greater safety
it is necessary for the smaller scale charts (= big area map) to indicate by way of showing availabillity and location of larger scale detailed maps that dangers could be ahead.
The indication of the availabillity of largers scale details should show up on ALL levels of smaller scale instead of just showing up on SOME smaller scale
charts. At present it seems as if the detail map areas show up (in the purple outlined rectangles) only with scales appraoching the scale of the detail chart.
It would greatly enhance the safety
of using OpenCPN if smaller scale charts ALWAYS indicate the location of available larger scale detail.