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Author Topic:   Great Lakes Charts: ENC Chart Coordination between Canada and USA
jimh posted 09-10-2014 09:03 AM ET (US)   Profile for jimh   Send Email to jimh  
This news is a year old, but I just came across it. The charting agencies of Canada (Canadian Hydrographic Service or CHS) and the USA (NOAA) have worked out an agreement to coordinate the publication of electronic navigation charts (ENCs) to eliminate overlapping coverage at their borders.

The underlying cause or motivation for this agreement seems to be an attempt to comply with international recommendations about ENC overlaps. Apparently some ship electronic chart display and information system (ECDIS) units could be affected if more than one ENC were available for a particular area. This problem tended to occur at border regions, where ENCs were being produced by two countries, and overrlapping ENCs could affect safety of navigation.

The Great Lakes are a region where the borders of Canada and the USA meet, and both CHS and NOAA were publishing ENCs with coverage that overlapped at the border regions. An agreement was reached in which the responsibility for publishing ENCs was split as follows:

For Lake Ontario and Lake Erie, CHS will retain responsibility for the ENCs. For Lake Huron and Lake Superior, NOAA will retain responsibility for the ENCs.

The policy of the USA with regard to ENC publication is to freely distribute the electronic charts. The policy of CHS with regard to ENC publication is to charge for the electronic charts. This means that ENC charts for Lake Superior and Lake Huron will be free and ENC charts for Lake Erie and Lake Ontario must be purchased. (Note that CHS does not sell charts directly, but has many authorized sales agencies.)

The changes to the ENCs are summarized in


The region of Georgian Bay, although part of Lake Huron, is entirely in Canada. As a result, responsibility for ENCs for Georgian Bay is with Canada.


Since most USA boaters probably had not purchased any CHS ENCs and were likely using only the free NOAA ENCs, there were not likely to be any problems in operation of their recreational-grade chart plotters due to overlap of ENCs. With the new coordination policy, some NOAA ENCs for the Great Lakes have been eliminated or their coverage area reduced. For example, the ENC for Lake Huron


used to cover Georgian Bay. It has now been modified to remove coverage of Georgian Bay. ENC coverage of Georgian Bay is now provided with CHS ENC


There are similar instances in Lake Erie in the vicinity of Put-in-Bay, Ohio. I guess if recreational boaters want to maintain ENC coverage of these areas, they will have to purchase the applicable ENC from CHS through its retail agents.

jimh posted 09-10-2014 09:24 AM ET (US)     Profile for jimh  Send Email to jimh     
Note that NOAA continues to publish free ENC charts for areas of Lake Erie and Lake Ontario that do not contain any Canadian waters. However, the small scale (wider area) charts that NOAA used to publish that included these areas, which also contained coverage of Canadian water, have generally been withdrawn or modified. As a result, one may see some odd omissions in NOAA ENC coverage at certain scales or zoom-settings for Lake Erie and Lake Ontario if one does not have the CHS chart that now provides coverage at the particular scale or zoom-setting.

Also, for ENCs from NOAA that have been withdrawn, if your ENC inventory retains the old ENC, it can still be used, although with the understanding that the chart has not been updated since 2013 or older.

jimh posted 09-10-2014 11:51 AM ET (US)     Profile for jimh  Send Email to jimh     
Electronic navigation charts (ENCs) are produced in six distinct ranges of chart scale, and these divisions referred to as bands. The six bands are typically referred to by both number and name designators:

1 = Overview, scale band smaller than 1:1,500,000
2 = General, scale band from 1:600,001 – 1:1,500,000
3 = Coastal, scale band from 1:150,001 – 1:600,000
4 = Approach, scale band from 1:50,001 – 1:150,000
5 = Harbour, scale band from 1:5,000 – 1:50,000
6 = Berthing, scale band of larger than 1:5,000

There is also a naming convention for ENCs that uses the scale band number as part of the file name of the ENC. The file name of an ENC typically begins with two letters that indicate the country, thus US for the United States of American, followed by the numerical designator for the scale band. ENCs from NOAA have eight-character identifiers. For example the previously mentioned chart


can be interpreted by its eight-character name as follows:

US = country code of chart producer; USA

3 = navigational purpose, by scale band; Coastal, scale from 1:150,001 – 1:600,000

MI = state, territory, or region abbreviation; Michigan

06 = an arbitrary number to identify the chart; 06

M = chart's unit of measurement; Metric


jimh posted 09-10-2014 01:49 PM ET (US)     Profile for jimh  Send Email to jimh     
ASIDE: a chart scale is indicated by the ratio of its dimension to the actual area. This ratio is used to express the scale. The comparison between chart scales is made by evaluating the scale as if it were a number. For example, consider two charts with scales of




The chart at 1:40,000 is said to be larger scale than the chart with 1:400,000 because 1/40,000 is a larger number than 1/400,000.

Many people confuse this and apply exactly the opposite comparison, in error.

Hoosier posted 09-20-2014 09:35 AM ET (US)     Profile for Hoosier  Send Email to Hoosier     
It seems that the US-Canada agreement for the Great Lakes still ends at the border, the NOAA interactive catalog doesn't show any detailed coverage north of the border.

jimh posted 09-23-2014 01:18 AM ET (US)     Profile for jimh  Send Email to jimh     
David--The website you have mentioned shows precisely what the cooperative agreement has set out: there are NOAA ENCs that cover the Canadian side of the border for Lake Superior (US2MI79M) and Lake Huron (US2MI60M), but not for Lake Erie and Lake Ontario.
Hoosier posted 09-23-2014 08:46 AM ET (US)     Profile for Hoosier  Send Email to Hoosier     
Yeah, I misread what they said.
jimh posted 09-23-2014 09:13 AM ET (US)     Profile for jimh  Send Email to jimh     
By the way, it seems that NOAA previously had some charts with larger scale, such as charts with the band number 3, for parts of Lake Superior in Canadian water, but they have withdrawn them. Only the "general" or band number "2" chart remains.

I have the older charts with band 3scales in my ENC inventory. Since I don't plan on spending $600 per Lake with CHS to get their ENC charts, I am going to keep using the old NOAA ones.

jimh posted 09-24-2014 12:50 AM ET (US)     Profile for jimh  Send Email to jimh     
Another artifact of this agreement about no overlap of ENC's between NOAA and CHS is seen in Lake Erie. NOAA coverage of Lake Erie on ENC's in some regions was only on band 2 or 3 level charts. NOAA withdrew those because the agreement calls for using the CHS charts. This has left blank regions in NOAA ENC coverage of some USA water in Lake Erie at certain zoom levels. It is only a cosmetic problem. If a user of an ECDIS just zooms in to a band level 4 or higher chart coverage, the missing region fills in.

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