This is from the Lewis's website for the Explorer Charts...
Explorer Charts – Electronic Format
We are often asked which electronic charts include Explorer Charts for the Bahamas. Until recently the answer has been Nobeltec
charts for PC’s, Garmin Chartplotters, and chartplotters using C-Map
cartridges. The Bahamas content of Nobeltec and C-Map products changed in 2011, and now Explorer Charts have been amended and blended with data from other sources in some areas. We have recently studied some of these products and have found a number of inaccuracies in the Bahamas data from other sources that has now supplemented and/or replaced Explorer data. Our findings of the current
with preloaded maps for all U.S. coastal areas, including Alaska
, plus Explorer Charts for the Bahamas, have all of the Explorer Bahamas data, but
this data is covered over in some areas by NGA charts. The NGA charts are produced by the National Geospatial-Intelligence Agency and the coverage is for waters outside of the US. Where a NGA chart is available in areas at a larger scale than the Explorer Chart, the NGA is seen covering the Explorer Chart. In the affected areas the NGA data is usually older than Explorer data and sometimes omits important features shown on Explorer Charts. Some of the NGA charts in the Bahamas are based on surveys over 100 years old. We have advised Garmin of this problem and hope that changes will be made in future product releases. Most areas of the Bahamas are pure Explorer data on the Garmin products.
Chartplotters using C-Map cartridges
(C-Map 4D, MAX’11, and NT+), and C-Map by Jeppesen programs for PC navigation
(MAX Pro, MAX/PC, and NT+/PC) in the spring-summer 2011 release have the Explorer Charts for the Bahamas, but
areas the Explorer Charts are covered up by chart data from other sources when zooming in to obtain a larger scale view. After studying the chart data from the other sources, we have found many inaccuracies that are correctly shown on the Explorer Charts being covered. We believe the other-source soundings in many areas show the water
to be deeper than it actually is and correctly shown on the Explorer Charts. In some cases hazards shown correctly on Explorer Charts are omitted on the larger scale charts from the other source.
Jeppesen furnished us with a newer release of its electronic Bahamas Chart package for our review. This version, C-Map NT Max, September 2011 (M-NA-M022-14) was reported to have fixed the problem of two data sources in the same chart area showing different detail. As we were advised, no
Explorer Chart data has been used in the Abaco, Grand Bahama, Little Bahama Bank area, and in the area east of the Crooked Island Passage, and the Turks and Caicos.
These areas contain only chart data from another source. The remaining areas of the Bahamas are covered mostly by Explorer Chart data. After reviewing the C-Map product we agree with Jeppesen that this release corrects the problem of commingled data from two sources on a given chart area. It now segregates the data into two areas–Explorer and other source data. However, we find many inaccuracies
in many areas not showing Explorer chart data.
The entire Little Bahama Bank area including Grand Bahama Island, Great and Little Abaco
, and the Abaco
Cays are void of any Explorer Chart data. We found a number of known hazards to navigation shown on Explorer Charts and on previous C-Map versions missing on the new C-Map product. We found courses drawn over shoal areas with no depths shown and depths shown in shallow narrow channels deeper than we have found to exist. The typical pattern of the data from another source is a jumble of closely spaced strings of soundings in some areas and other important areas empty of useful data. In a number of shallow areas, depths are shown generally deeper than we have measured. No Explorer Chart data is shown east of the Crooked Island Passage
In a few locations in the areas that are covered by Explorer Charts, US NGA and UK (British Admiralty) charts are shown instead. These charts mostly are based on old surveys. An example is the New Providence and Nassau
area where these outdated government
charts fail to show the Albany Marina and its approaches and also the current
dredged ship channel, buoys, and pier configurations in Nassau
Harbour. Some coral
heads and reefs
that are hazards are not shown and some are shown that do not exist.
The few hours of reviewing this product leave us very disappointed with the Jeppesen’s decisions to eliminate Explorer data in favor of less accurate and less up-to-date material. We recommend the charts in the Explorer Chartbooks
be used as the primary navigation reference
in the Bahamas and particularly in the areas covered by data from other sources.
In addition to the chartplotter
and PC products, C-Map by Jeppesen has recently released Jeppesen Marine Plan2Nav
4. This app is downloaded free and East Coast
and Bahamas may be purchased for $29.95 from i-Tunes. The app charts are similar to the other C-Map by Jeppensen products, but when metric units are used only the even
meters rounded off to the lowest meter are seen. The app needs wireless or cellular service
to work for navigation, but as the charts remain on the device after being downloaded, it may be used for planning.
Nobeltec PC products
(Time Zero Trident, Admiral, and Visual Navigation Suite, Maxsea
Time Zero Navigator C-map by Jeppesen, and Furuno NavNet
3D chartplotters with MM3-R01-P00 cartridges) now contain the same Bahamas chart data as the C-Map by Jeppesen products and will presumably will be the same with new releases.
After reviewing the above listed products we believe the Garmin Chartplotters have the best Explorer Bahamas chart data in the vector format. The raster Explorer Charts show the most accurate Bahamas data on the other C-Map by Jeppesen, Nobeltec, MaxSea, and Furuno
products. Currently all of the electronic Explorer chart data is up to date only in the Exumas and Ragged Island area with the Sixth Edition. The various electronic versions use the Near Bahamas Fifth Edition and the Far Bahamas Fourth Edition both outdated now. All of the Explorer Charts for the Bahamas are currently converted to electronic format by Jeppesen, a division of Boeing. We will continue to work with Jeppesen to make Explorer Charts available in the future in products that are not corrupted by other source data.
No Explorer Chart data for the Turks and Caicos
is available in any of the above products, and no
Explorer Chart data is available in any Navionics
products. Given the current shortcomings of the current electronic Bahamas chart products, it is important to use the latest Explorer Chartbooks for the primary source of navigational information in the Bahamas.
The Explorer Team