You may think (hope) that your just "updated" Navionics or C-MAP charts are now "up-to-date". This is not necessarily the case (applies to both app and card-based updates).
Recently, checking "Notices to Mariners" (NOTMAR: https://www.notmar.gc.ca/monthly-mensuel-en.php) by Canadian Hydrographic Services (CHS), I noticed the February version indicated newly discovered rocks/shallows in the general area near Discovery Islands and Desolation Sound.
Below are images from official CHS Raster charts from May 2020 and June 2021:
The updated CHS charts (June, 2021) show the two new drying rocks in Manson Passage (top, right) and the 0.3m shallows in Plunger Pass (bottom, right). Both are dangerous to most boats (especially the shallow area in Plunger Pass, which we passed through last summer).
What about Navionics and C-MAP? As of June 7, 2021, neither show these updates. This includes the C-MAP App and C-Map SD card (card purchased in May, 2021) as well as the Navionics App (as well as the online viewer).
|Manson Passage: Navionics (June, 2021, not accurate)|
|Plunger Passage: Navionics (June, 2021, not accurate)|
|Manson Passage: C-MAP (June, 2021, not accurate)|
|Plunger Passage: C-MAP (June, 2021, not accurate)|
At least 3 months after CHS issued a NOTMAR about these rocks/shallows, yet they are still not shown on "updated" Navionics or C-MAP charts.
O-Charts (https://www.o-charts.org/) makes CHS ENC Vector charts available for OpenCPN at a very reasonable annual price (20 Euros for Pacific Coast of Canada). These charts can be updated monthly, and are supposed to be the same as CHS ENC charts.
(OpenCPN is an excellent free/near-free chartplotter software for Windows, Mac, Linux and Android.)
By March, 2021, the O-Charts for Manson and Plunger Passages included the February update:
|Manson Passage: O-Charts (March, 2021 -- accurate!)|
|Plunger Passage: O-Charts (March, 2021 -- accurate!)|
Update: just checked earlier NOTMAR editions: current Navionics and C-MAP missing more rocks/shallows in other areas of BC! (O-charts, however, are correctly updated.)
CONCLUSION: Commercial charts such as Navionics or C-MAP may NOT be up-to-date (even though you just "updated" them). "New" rocks and shallows shown on up-to-date official charts may be missing on Navionics and/or C-MAP!
On Pelagia, we ensure our CHS charts are up-to-date. Though we also have Navionics and C-MAP, we but put much greater trust on the CHS raster charts (we are still getting used to the O-charts -- so far, so good.)