![]() ![]() Most of the weekly corrections to the NOAA charts are for changing ATON positions or new ATONs. ![]() The algorithms used by Navionics to create their SonarCharts are not shared so I do not know how they do it, or the weights they may give to different inputs, I can only see the results in the examples that will follow.ĪTON is short for Aids TO Navigation and are maintained by the US Coast Guard (USCG). Be ready for huge updates, usually in the 300 to 700 MB, which can be even higher if you let the updates go longer than a couple of weeks. Updates are provided upon clicking (or tapping) on the “Update All” button in their app. Navionics takes the uploads and constructs their SonarChart product with 1 ft depth contours. They receive inputs from boaters using chart plotters they partner with that upload soundings to Navionics as they navigate. In a league by itself are the SonarCharts from Navionics. The changes lag behind NOAA but can be close if all the changes are caught during the manual corrections, which is not always the case. Navionics depends upon manual updates to their Navionics+ charts based on changes to the NOAA charts and, in some cases, from other inputs. In contrast, there is no delay with iNavX or SEAiq, which use the NOAA format directly.Īqua Map reports that they rebuild their charts directly from the NOAA source every three months and the rebuild is directly from the NOAA standard. As a result, the frequency of updating is not always the same day that the updated NOAA charts are released. With the formatting and additional icons added, the cost for the provider is in the additional processing required. Also added to the charts in some cases are Waterway Guide icons, as well as tide and current markers and other crowdsourced data. Their starting point is also the NOAA database, but their charts are formatted into a seamless whole (quilted) so when you zoom or pan, there’s no hesitation in the screen display as new charts load. Other navigation apps employ a different approach. Aqua Map, iNavX and SEAiq also add Waterway Guide icons on top of the charts, which can be tapped to bring up additional information about alerts, marinas, anchorages and other information. Charts other than NOAA are available for an additional price from each app. Both apps read the raw NOAA chart catalog and, after an update (press a button), your charts will show the same data as NOAA. Likewise, SEAiq displays either format for free once the app is bought. iNavX displays the RNC charts for free once you buy their app. Either Raster Navigational Charts (RNC) that look like their paper counterparts or Electronic Navigational Charts (ENC). Some navigation apps use the raw charts from NOAA. ![]() How those updated charts find their way into navigation programs and apps also varies between the providers. Even then, the changes usually affect only small areas of the updated chart. NOAA updates its charts once every seven days, but not every chart is updated, only the ones with changes, perhaps 10% to 15%. The sources for coastal charts in the US are those provided for free by the National Oceanic and Atmospheric Administration (NOAA). The choices can be bewildering, there are so many.įor this article my definitions are as follows: A chart can be on a chart plotter, a tablet (e.g., iPad) or on paper, it doesn’t matter as far as accuracy if they are all up to date and viewed at the proper zoom levels. There are also many guidebooks, including my own 2018 ICW Cruising Guide that addresses trouble spots. Then there are the crowd-sourced data from Waterway Guide and other sources. The surveys from USACE are also popular to follow. Still others have favorites like SonarChart from Navionics. Others say pay more attention to the chart. Some say, just follow the Aids to Navigation (ATONs). When it comes to bestowing our trust in sources of critical navigational information we must make our way through a sea of advice, opinions and options. There’s no simple answer for all situations, but here are his personal observations. He has collected a list of examples, so you can decide for yourself who to rely on. Sherer is a paid on-the-water Cruising Editor for Waterway Guide and also publishes a guidebook. He is currently on his ninth trip down the AICW to Key West. Bob423, and his wife Ann have made the round trip from New York to Key West on my 42 ft sailboat eight times. Source: Bob Sherer, Waterway Guide ContributorĮditor’s Note: Robert Sherer, aka. ![]()
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