Jump to content

Which electronic charts?


Recommended Posts

Here's us stopped in a nice little bay not far from Cape Brett. had a swim and lunch then noticed this.

611595929_OfftheChart.thumb.jpg.1128debbff5d16b653054eeba5f1a4fb.jpg

Up to date chart, 2019 I think, on Garmin Plotter, not sure which chart set and have sold it since then. The Yellow is the land supposedly.

Was using Pickmeres at the time and exploring a bit. GPS chart probably 50m off.

Link to post
Share on other sites

Hmm, BOIG, that is also a zoom function. You can zoom in past the accuracy of the chart data. If you do this on Opencpn, it warns your with an "overzoom" display. Most MFD's (maybe all) don't...

Using a small scale chart zoomed right in is dangerous.

 

Link to post
Share on other sites

I zoomed in for the photo, what your saying is right but that's the point, the chart is not accurate at that location.

First time I've seen it though, usually spot on every where else I've been. 

 

Link to post
Share on other sites
1 hour ago, BOIGuy said:

I zoomed in for the photo, what your saying is right but that's the point, the chart is not accurate at that location.

First time I've seen it though, usually spot on every where else I've been. 

 

It's the charts, not your GPS. There's a 'green fluffy' area defined as 'dries out at low tide' it's on the paper charts, so it's transferred to all the electronic charts.

It's in most places around NZ, cartographers don't have enough accuracy at very close proximity.  So safer to say it dries out.... 

We saw exactly the same at the hen and chicks South Cove. Tucked in close, 20m of depth, 10m from the physical shore, and the boat was in the green fluffy area on the chart plotter. Overlaying the Satellite image we were in the right place, ie the water not the land :) :)

 

 

Screenshot_20210820-163434_New Zealand Maps.jpg

Screenshot_20210820-163343_Boating.jpg

Screenshot_20210820-163033_New Zealand Maps.jpg

Link to post
Share on other sites
2 hours ago, chariot said:

I have a new Garmin [ well 12 months old] and it puts me in the corret marina berth every time.

If there is a large scale chart of the area, the data will be good enough to put you in a marina berth. If you only have a small scale chart (because there is not a better one, or you dont have it) then the data close in will not be good enough. Paper charts have the same issue. To illustrate, then take a paper chart of say the north island - try to Gulf Harbour - not even there; 

Yes this is an extreme example - just trying to make it clear it is important to use a properly scaled chart when navigating close to dangers. This chart is a current chart, and overzoomed. The boat is in Gulf Harbour...

Gulf Harbour.jpg

Oh, and that is the latest Raster chart from Linz - same as the paper chart NZ2101

 

Link to post
Share on other sites

I have the latest update of the Garmin charts and the entrance of Caroline Bay at the Mercs is a bit vague, compared to Navionics, we managed to hit a shallow rocky area on the Nortern side of the entrance - not good! Open CP showed a better image also! 

Link to post
Share on other sites
3 minutes ago, Black Panther said:

Who uses a gps to get into a marina berth?

Launch drivers

Who looks out the windows now days, that’s so last century 

  • Haha 1
Link to post
Share on other sites
1 hour ago, Island Time said:

Do you mean Coralie Bay?

 

Coralie Bay.jpg

Yes, IT, see that reef structure on the northern side in the narrow entrance which looks quite obvious in this image, is actually very solid and not that obvious in the Garmin map, I entered at hign tide and with calm conditions and found it, the reefs to the south made me stay away from there!

Next time no problem and I had been there plenty of times, I will take a photo after lockdown.

 

Link to post
Share on other sites
23 minutes ago, ballystick said:

Yes, IT, see that reef structure on the northern side in the narrow entrance which looks quite obvious in this image, is actually very solid and not that obvious in the Garmin map, I entered at hign tide and with calm conditions and found it, the reefs to the south made me stay away from there!

Next time no problem and I had been there plenty of times, I will take a photo after lockdown.

 

My garmin doesn't show a navigable gap on the northern side/inside of that bombie at the entrance to Coralie.  Yet later versions do.

Last year right on dark I was going into Administration bay for the first time, had checked plotter for hard things poking up from bottom which showed nothing, at the last minute I turned on navionics on my phone, it takes a few seconds to fire up and bugger me days I was right beside this rock below.  It doesn't show on my garmin, I've looked and zoomed and looked, it's not there.  No idea if I was 1 inch away or 1 metre but doubt it was more.

adbay.png

  • Upvote 1
Link to post
Share on other sites
30 minutes ago, muzled said:

My garmin doesn't show a navigable gap on the northern side/inside of that bombie at the entrance to Coralie.  Yet later versions do.

Last year right on dark I was going into Administration bay for the first time, had checked plotter for hard things poking up from bottom which showed nothing, at the last minute I turned on navionics on my phone, it takes a few seconds to fire up and bugger me days I was right beside this rock below.  It doesn't show on my garmin, I've looked and zoomed and looked, it's not there.  No idea if I was 1 inch away or 1 metre but doubt it was more.

adbay.png

Its there on Navionics and Cmap. Update your charts.... Oh, and just in case you were not aware, Navionics is owned by Garmin

Link to post
Share on other sites

On accuracy, just to think about:

Do you know the accuracy of your:

- charts

- sensors / GPS

- Is your GPS antenna position accurate? Does it matter?

The portable systems I'm currently looking after charts are 0.5m position and 0.2m depth, sensors are 0.5m or better. 

I doubt there are many recreational systems that have combined accuracy that those portable systems have, mind you cost per system is around the 10k mark, cost of the high density electronic charts was rather expensive, updating costs every 12 to 18months a chunk more. 

Link to post
Share on other sites
2 hours ago, rigger said:

On accuracy, just to think about:

Do you know the accuracy of your:

- charts

- sensors / GPS

- Is your GPS antenna position accurate? Does it matter?

The portable systems I'm currently looking after charts are 0.5m position and 0.2m depth, sensors are 0.5m or better. 

I doubt there are many recreational systems that have combined accuracy that those portable systems have, mind you cost per system is around the 10k mark, cost of the high density electronic charts was rather expensive, updating costs every 12 to 18months a chunk more. 

Ok Rigger, yep, that is good. Most of the late model B&G units use a 10hz 34 channel GPS, giving accuracy of 5m or better. Mostly better, often within a meter,  but does depend where on earth you are, and the antenna must have a clear view...

Link to post
Share on other sites
20 hours ago, muzled said:

Last year right on dark I was going into Administration bay for the first time

That rock in Administration Bay is a newly discovered rock, found about 10 years ago by someone hitting it, and reported to all chart makers by my friend.

It probably still isn't shown on all charts.

 

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...