Originally Posted by tonydix
I have just managed to get OpenCPN
working and have been given a disk with I suspect very old CM93 charts which open correctly. My question is how can I find out the date of these files and whether or not a more up-to date series of charts is available. Thanks for any help, Tony
Hi Tony - Welcome to Cruisers Forum!
To find the date of your CM93 charts in Windows, Open Windows Explorer (not IE) & navigate to wherever you stored the charts, usually C:\CM93. In that folder will be a bunch of other folders that are just numbers - open any folder. In there you will find a bunch of folders that are just letters - open a C folder. In there will be the actual chart files. Set your view to Details so you can see the dates of the files. Click on the "Date Modified" to sort on the date. The newest files will be the effective date of your CM93 chart database. You can check some other files in other folders to double check this. It does not work to just check the dates of the folders, as those will be the date that you created the folder (ie, when you installed the charts) but the files themselves usually keep their dates when they're copied.
We've seen CM93 charts dated 2000, 2002, 2005, 2006, 2008, 2009, & 2010. No doubt there are others that we haven't seen. The charts are surprisingly good, but have strange errors. All of Sri Lanka seemed to be spot on, EXCEPT the one port you could go into (Galle) which was out by 1/4nm until 2009! Tonga
was ALL out by 1/4nm when we were there in 2004. Apparently the Philippines
have errors of up to 2nm in places.
The charts are usually correct within themselves - their errors are that they're displaced from where they should be. OpenCPN has a lovely feature to correct this manually but you have to remember to turn that correction OFF when you leave that area.
When approaching a new area, it's always a question: How accurate are my charts? If your radar
is tied into your GPS
, there's a couple of ways to test this. Turn on your radar
& find a prominent headland or point that's not too far away. Put your cursor on that point to read off the Lat/Lon & compare that to your charts. This gives a good comparison between reality (GPS/Radar) & your charts.