Sunday, 20 March 2016

What year are your CM93 electronic charts? Make sure they are the "latest"!

UPDATE/COMMENT: This post concerning "CM93" charts is proving to be very popular. It must be noted that CM93 Version 2 charts are often not the most up-to-date charts available, so users of these charts must be cautious. In some cases, Jeppesen C-MAP or Navionics electronic charts (which are fairly inexpensive on Android and IOS platforms) may be more accurate. However, as we have noted in other posts, Navionics or CMAP charts may also not be fully up-to-date.

CM93 vector electronic charts, covering the whole world, are shared widely among cruisers; they are also available from some sites on the web. Technically, these charts are "pirated", so user beware....

[Note: By "latest", we mean the most recent CM93 available which works in OPENCPN]

CM93 "version 2" charts are easily used in the open-source, freely available, OPENCPN navigation program (CM93 "version 3" charts do not work in OPENCPN).

When we were planning to sail to Mexico, a cruising friend gave us a copy of the CM93 charts. We were impressed that they covered the globe; we were less impressed when we saw their lack of detail. This was especially the case when we left the highly accurate (and free) raster charts of the USA and entered Mexico. In Mexico, we quickly learned (i) our CM93 charts were nearly useless, (ii) our updated CMAP charts (on our chartplotter) were much better, and (iii) in many (most?) places, even our up-to-date CMAP charts provided insufficient detail.* As we note in our earlier blog posts about charts and guides (as well as comparing official Mexican SEMAR charts with CMAP charts), we did not feel confident navigating close to shore until we reached Cabo San Lucas where we could finally use the excellent Blue Latitude Press cruising guides, with their excellent, detailed chartlets and accurate waypoints.

[*Our experience with Navionics charts in Mexico indicates they suffer similar problems as CMAP charts; indeed, we note areas where CMAP has important detailed updates not found in the Navionics. See our blog posts concerning CMAP, Navionics and SEMAR charts.]

It turns out, we were using a very out-dated version of  the CM93 vector charts, dated mostly before the year 2000. Since returning home, we have found CM93 version 2 charts dating as late as 2012. The differences (improvements) over the years are substantial.

To help other cruisers, the examples below show the improvements in the CM93 charts for the years "2000", "2007" and "2012" (dates are approximate).

Turtle Bay/Bahia Tortugas (Baja California Sur)
Our first real experience with CM93 charts coming in to an unfamiliar bay. Our circa-2000 CM93 chart was useless: no details, no depths, and the datum way off (on the other hand, the CMAP turned out to be pretty good).

The circa-2007 CM93 has much more detail and correct datum, although lights were not correct.  

The circa-2012 CM93 chart for Turtle Bay is quite accurate (determined using GE2KAP and Google Earth (see this blog post) -- we wished we'd had it back in 2013!

La Paz, Baja California Sur
Both our circa-2000 CM93 charts and our CMAP chart showed few details and were inaccurate for the section from (and including) Bahia Los Frailes, to Ensenada de Los Muertos, the Cerralvo Channel, and finally, the San Lorenzo Channel entering Bahia de La Paz (they still are...). The Blue Latitude Press Sea of Cortez cruising guide was a godsend.

We entered the narrow, dogleg channel entering La Paz harbour just as the sun began to rise (we had left Los Frailes in the morning and done an overnight trip from Los Muertos in order to beat a Northerly, accurately predicted to come fiercely the next day). The circa-2000 CM93 chart showed NO details; fortunately, the CMAP chart showed good detail which turned out to be very accurate (though we did not know/trust this at the time).

Again, we wished we had the 2012 CM93 charts as confirmation of the CMAP (and Blue Latitude Press) information.

Punta Sabalo/Estero de Sabalo/Marina Mazatlan

In late April 2014, it was time to sail across the Sea of Cortez to Marina Mazatlan in the Estero de Sabalo, where we planned to keep Pelagia for the 2014 hurricane season. Again, our circa-2000 CM93 charts were useless. Our CMAP chart was also incomplete, although it had much more and better information than CM93 (the June 2014 CMAP update provided much more information for this area).


The circa-2012, CM93 chart shows an outline of the Marinas in the Sabalo Estero, but with few details. Fortunately, the combination of our CMAP charts and the Blue Latitude Press Pacific Mexico guide gave us the information we needed.

CM93 charts in Canada?

After seeing these large changes (improvements) in the various versions of the CM93 charts, we wondered how the CM93 charts would look in our home waters in British Columbia.#

The circa-2000 CM93 charts are terrible for BC waters, even on the south coast of BC (even though most areas in 2000 were exquisitely charted by the Canadia Hydrographic Service (CHS) as well as preceding (mostly British) cartographers). However, by 2012, the CM93 charts are quite good.

Further north in British Columbia, there remain "pockets" of unsurveyed (or poorly surveyed) coastline -- almost all well away from typical routes. One area is "Lady Trutch Passage" on the Central Coast near Bella Bella. This passage always looked inviting, but was choked with narrow passages and no chart was available. However, in 2011, the CHS produced a new chart including Lady Trutch Passage. Interestingly, the circa-2012 CM93 chart includes this detailed information; the circa-2007 CM93 chart as a subset of this new charting; and predictably, the circa-2000 CM93 "chart" is hopeless for this area, even for the relatively well-traveled (and well-charted for years) "Perceval Narrows".

Up-to-date, detailed CM93 "2012" chart for Lady Trutch Passage area

Circa-2000 CM93 "chart" for Lady Trutch Passage area: useless

(# Legally, in Canada, vessels must carry up-to-date CHS charts, so technically, circa-2012 CM93 charts are not sufficient; neither, legally, are CMAP or Navionics charts.)

Before we sailed down to Mexico, we wish we had been aware of the substantial changes in the CM93 electronic charts. We should have been... but we were probably too wrapped-up in too many things as we prepared to sail to Mexico, and as were were on our way down the coast.

Hopefully, some cruisers heading offshore will find this blog post helpful!

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