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Old 09-02-2019, 14:28   #16
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Re: Garmin to Discontinue Bahamas Explorer Data

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Originally Posted by Suijin View Post
Iím fairly certain Navionics scrubs the data through an algorithm that compares your data against known good data. They may, for example only use data between known good readings (in case you change settings or move it to a new boat). There are a lot of things they can do programmatically to validate and adjust data. What they actually do, who knows.
Pretty tough to come up with an algorthim that operates effectively like this. There isn't a range of known good depths in a given spot, there is only one depth. If you have known good depth then you don't need added unverified data.
I'd really like to see a writeup on how they are evaluating and treating the raw data and what transformations they make on it.
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Old 10-02-2019, 08:19   #17
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Re: Garmin to Discontinue Bahamas Explorer Data

Too bad they are dropping Explorer data. I use the Garmin Blue iPad app last year throughout the Bahamas and it was excellent. We draw 4.5 feet and love to gunkhole. Never touched bottom once - no lie. I found the Navionics Charts to be great on the ICW but terrible in the Bahamas.
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Old 10-02-2019, 08:36   #18
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Re: Garmin to Discontinue Bahamas Explorer Data

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Pretty tough to come up with an algorthim that operates effectively like this. There isn't a range of known good depths in a given spot, there is only one depth. If you have known good depth then you don't need added unverified data.
I'd really like to see a writeup on how they are evaluating and treating the raw data and what transformations they make on it.
Well that was my point. If at a specific lat/long there is a known good depth of 10', and a crowd sourced sonar log shows 10' at that spot for a commensurate tide, then the sounder could be considered verified. It's the only way I can think of for validating user data. That said, I suspect it would make the majority of logs unusable although I have no idea how much data they are getting back.

And yes, some info on how they are using the data would be incredibly helpful to those of us using the charts as it would given us some parameters for using them more effectively or confidently, or not.
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Old 10-02-2019, 14:34   #19
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Re: Garmin to Discontinue Bahamas Explorer Data

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Well that was my point. If at a specific lat/long there is a known good depth of 10', and a crowd sourced sonar log shows 10' at that spot for a commensurate tide, then the sounder could be considered verified. It's the only way I can think of for validating user data. That said, I suspect it would make the majority of logs unusable although I have no idea how much data they are getting back.

And yes, some info on how they are using the data would be incredibly helpful to those of us using the charts as it would given us some parameters for using them more effectively or confidently, or not.
I just see no advantage to adding user sourced data that is the same as existing hydrographic data. It adds nothing to the chart.
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Old 10-02-2019, 15:24   #20
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Re: Garmin to Discontinue Bahamas Explorer Data

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I would think that Navionics would over time surpass Explorer charts in accuracy by virtue of the crowd sourced bathymetric sonar data, anywhere they are available. Iím assuming this is Garminís rationale for dropping them.

Personally I canít stand C-map charts. The presentation layer gives me a headache.
The day that Navionics (or any chart supplier) puts "crowd sourced" data on their navigation charts is the day I throw them in the trash.

Anyone who uses the crowd sourced layer of the Navionics charts for serious navigation... deserves what they get. Get for finding a fishing hole, or a dive spot. TERRIBLE for life-safety navigation.
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Old 10-02-2019, 15:45   #21
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Re: Garmin to Discontinue Bahamas Explorer Data

With the ActiveCaptain mess, the Bluechart App getting axed, now you have to scramble to get the better charts... It was nice knowing you, Garmin.
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Old 10-02-2019, 18:00   #22
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Re: Garmin to Discontinue Bahamas Explorer Data

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The day that Navionics (or any chart supplier) puts "crowd sourced" data on their navigation charts is the day I throw them in the trash.

Anyone who uses the crowd sourced layer of the Navionics charts for serious navigation... deserves what they get. Get for finding a fishing hole, or a dive spot. TERRIBLE for life-safety navigation.

Crowd sourced data is often more accurate and granular -- it's good to have another set of data points beyond the official charts (which are generally based on very old surveys and aren't updated until after hazards are reported or government funding every decade or four). I generally take a conservative approach and if one source shows a shallow spot or hazard -- I take action to avoid it.

I often switch chart views between the Navionics official charts, the Navionics SonarCharts, and the Government NOAA charts. The NOAA ENC charts are the least accurate with less granular info, and the Navionics official charts are the best among that selection. I like government raster charts but they tend to be decades old. The Navionics SonarCharts are the ones you want to look at when crossing bars or rivers -- areas with shifting sands.
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Old 10-02-2019, 20:59   #23
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Re: Garmin to Discontinue Bahamas Explorer Data

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Originally Posted by Vasco View Post
User data for charts is unreliable. I prefer charts that are made by hydrographers. Not to say that I have never used sketch charts but they are used with caution and from sources that I am familiar with and trust (to a degree ).


Lots of people run aground and hit stuff using data from trusted professional sources.
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Old 10-02-2019, 21:03   #24
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Re: Garmin to Discontinue Bahamas Explorer Data

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I have my depth finder offset so that it displays depth under the keel, others true depth.
How could Navionics determine which is which?

By comparing the track to known benchmark points. They compensate for tides and variable lake and river levels the same way.


[crossposted]
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Old 10-02-2019, 21:06   #25
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Re: Garmin to Discontinue Bahamas Explorer Data

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User data for charts is unreliable. I prefer charts that are made by hydrographers. Not to say that I have never used sketch charts but they are used with caution and from sources that I am familiar with and trust (to a degree ).

All charts are out of date. Charts made by formal hydographic surveys rather than crowdsourced data are more out of date.


It's like Wikipedia. You trade off one potential source of error for another.
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Old 10-02-2019, 21:50   #26
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Re: Garmin to Discontinue Bahamas Explorer Data

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By comparing the track to known benchmark points. They compensate for tides and variable lake and river levels the same way.


[crossposted]
Is the method of doing this specifiex at all on the Navionics website? I'm not seeing any mention of how they validate and age data.
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Old 11-02-2019, 09:53   #27
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Re: Garmin to Discontinue Bahamas Explorer Data

Planning our first trip to the Bahamas (Abacos/Spanish Wells/Exumas/Berrys);
Just purchased a new Garmin chart plotter (1042xsv);
just learned the Explorer charts can't be used on it any longer. Suggestions???????
I have Navionics as a backup on my iPad.
I am not very computer savvy, simple English would be appreciated...
Thanks
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Old 11-02-2019, 18:13   #28
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Re: Garmin to Discontinue Bahamas Explorer Data

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Originally Posted by sailorman7225 View Post
Planning our first trip to the Bahamas (Abacos/Spanish Wells/Exumas/Berrys);
Just purchased a new Garmin chart plotter (1042xsv);
just learned the Explorer charts can't be used on it any longer. Suggestions???????
I have Navionics as a backup on my iPad.
I am not very computer savvy, simple English would be appreciated...
Thanks
You could just buy a used G2 card on ebay, I don't see why that wouldn't work in your new plotter.
https://www.ebay.com/itm/Garmin-Blue...FsEV:rk:1:pf:0
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Old 16-02-2019, 12:30   #29
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Re: Garmin to Discontinue Bahamas Explorer Data

I’ve been getting a message from AquaMap that they are now going to be able to provide Explorer data for the Bahamas.

It’s a near application, good support.

I don’t know if there is an extra cost involved, I presume so. I’ve already got Explorer raster charts using iNavex so I haven’t followed up.
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Old 08-04-2019, 06:36   #30
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Re: Garmin to Discontinue Bahamas Explorer Data

I have a 2014 vintage Garmin 1040xs chart plotter. I recently downloaded an update online because Iíve never updated it since purchasing it and figured it would be a good idea before going to the Bahamas this May. Should I not do this update?

Two years ago in the Abacos I used this Garmin plotter and my IPad with Garmin Blue Chart and it seemed to work well. Will it not work well this time?
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