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Old 21-01-2020, 13:20   #1
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Navionics question

I have a question about the pictures below. The pictures are of the same area. One is a screen shot from my PC and the other is a picture from my phone. If you look at the soundings the PC is what I believe to be correct and the phone has numbers that are high. If you touch a spot on the phone app then hit the "?" to show more info the soundings match what the PC shows. Why is the phone app showing these strange sounding numbers (or are they not soundings?)

Thanks for any useful explanation.
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Old 21-01-2020, 13:26   #2
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Re: Navionics question

Check the scale on both displays and check the units for depth on both. I think that your pc is showing fathoms or meters.
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Old 21-01-2020, 14:10   #3
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Re: Navionics question

Good thought. I have the same one at first and did check for that. They both are set to feet.

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Old 21-01-2020, 15:05   #4
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Re: Navionics question

Below is the raster chart straight from NOAA with soundings in feet. Seems like a question for the phone app developers.

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And the ENC (curiously the ENC shows zero feet but 0.3 meters where the RNC shows 1 foot - must be a rounding thing):
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Old 21-01-2020, 15:21   #5
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Re: Navionics question

While we are on this subject. I have a bundled Navionics+ set of charts for north America on my new Axiom. Looking at Lahaina harbor on Maui, I find that this shows a depth of 0.4 meters. My other sources (C-Map and MaxSEA) both how that there should be 2.7 meters.

Querying Navionics support - they say I need to download a Sonar Map to get the real depths.

Am I just an idiot? I thought that Navionics plus was a true navigations map - not a kids toy.

Since I will be sailing fr several more years - should I purchase Navionics Platinum to get a real chart? I seriously don't like the sonar chart which I downloaded
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Old 21-01-2020, 15:27   #6
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Re: Navionics question

Maybe the two charts are using a different tide level as base zero. In Navionics there is a ‘water level’ setting ( found under ‘menu’ then ‘map options’). Maybe your Navionics is set differently than NOAA.
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Old 21-01-2020, 16:20   #7
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Re: Navionics question

The Navionics may be accounting for the current tide level where you are. That's why it's showing the correct number when you are clicking on the detailed info in the app.

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Old 21-01-2020, 17:09   #8
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Re: Navionics question

Quote:
Originally Posted by Dsanduril View Post
Below is the raster chart straight from NOAA with soundings in feet. Seems like a question for the phone app developers.
...
And the ENC (curiously the ENC shows zero feet but 0.3 meters where the RNC shows 1 foot - must be a rounding thing):
...
Your app is likely just rounding; I see 0.9 feet and 0.3 m on mine. More importantly, the survey was done in the 1870s. I wouldn't get too caught up on the precise numbers; you're in Category D territory:

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Old 21-01-2020, 17:27   #9
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Re: Navionics question

Quote:
Originally Posted by carstenb View Post
While we are on this subject. I have a bundled Navionics+ set of charts for north America on my new Axiom. Looking at Lahaina harbor on Maui, I find that this shows a depth of 0.4 meters. My other sources (C-Map and MaxSEA) both how that there should be 2.7 meters.

Querying Navionics support - they say I need to download a Sonar Map to get the real depths.

Am I just an idiot? I thought that Navionics plus was a true navigations map - not a kids toy.

Since I will be sailing fr several more years - should I purchase Navionics Platinum to get a real chart? I seriously don't like the sonar chart which I downloaded
The sonar charts are extremely accurate if you live in an area that has a lot of small fishing boats. The ICW east coast is nearly perfect in sonar charts so I guess it depends on where you cruise. I think that expecting one chart source to provide perfect data is expecting too much, even the official NOAA charts issue NTM.
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Old 22-01-2020, 03:16   #10
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Re: Navionics question

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The sonar charts are extremely accurate if you live in an area that has a lot of small fishing boats. The ICW east coast is nearly perfect in sonar charts so I guess it depends on where you cruise. I think that expecting one chart source to provide perfect data is expecting too much, even the official NOAA charts issue NTM.
Did you try the new USACE (US Army Corps of Engineers ) in Aqua Map? This feature is so useful, I strongly recommend it.
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Old 22-01-2020, 05:13   #11
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Re: Navionics question

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Originally Posted by flee27 View Post
Good thought. I have the same one at first and did check for that. They both are set to feet.

The PC application and the phone app ate both Navionics?

Send those pics to Navionics and ask the same question?

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Old 22-01-2020, 05:38   #12
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Re: Navionics question

ranger42c, yes the PC and phone app are both navionics. That is why the differences are odd to me.

Seagirt is the winner. On the phone app there is a "water level" setting under map options. With this you can reset zero plus or minus whatever you would like. On my app this was not set to zero (it was +13 feet) so it was adding 13 to all the depths.

Thanks for all the input.

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