Why even bother with a plotter when you can get this!

[pnw2022]

Originally Posted by valhalla360

Assuming you have access to them, it's poor seamanship not to use all the available navigational information.

That was kinda my point about integrating satellite info into OpenCPN.
Use all the available data points, then use your best judgment.

I think the gentleman that posted about this, although the way he kinda described the original topic as using 'only this' has an entirely valid point.

Probably one of the key reasons that this has not done already is related to liability? There is a reason that after downloading our NOAA or other government supplied charts, we also have to go through a clickwrap step as well?

[valhalla360]

Originally Posted by El Pinguino

Bog standard Google Earth Pro . Can I get apple maps for Mac/oCPN or other systems?

Bog standard Google Earth Pro can directly use a GPS puck and create routes, tracks and waypoints.

[pnw2022]

Originally Posted by valhalla360

Crowd sourcing chart updates. It's nothing to track routes and tie depth info to those tracks. Once back at dock with wifi available, the system could upload the data to a central system for processing and updates.

It would take some protocols to ensure the data is good but suddenly, you would have charts that are constantly being updated with much better data.

Exactly. Some things like sand bars change rapidly, other things not so much.

[rslifkin]

I can't say I've ever used satellite images entirely instead of charts, but I do often use them (even in well charted areas) as a supplement. The combination of the 2 often gives a better sense of what I need to do to get into somewhere safely.

I can think of one harbor locally as an example. It's a fairly short channel coming in and it's well marked (and the marks are accurate). But it's also unforgiving. The channel isn't all that wide, has a 90* turn halfway through it and for the outer part of the channel, there's a submerged jetty on either side. The inner part has a visible jetty on one side and the other side is bordered by shoaling sand in one area, a jetty in another. So if you end up out of the channel, you're going to hit rock unless you have a very shallow draft. But even when the water is pretty clear and the light is good enough to see down 10+ feet, I've never been able to actually see those jetties if I'm in the middle of the channel.

For my example channel, the chart tells you some useful things. One of them being where the best water coming up to the outer channel marks is. Coming from the east, you can come in at pretty much any angle and be good. From the west, you really want to stay a 1/4 mile further out and then turn straight in, otherwise you get needlessly close to some shallow, rocky areas (but they don't look any more threatening on a satellite view or in person than the good areas to the east). The charts also tell you that there are 2 ranges to mark the channel in addition to the buoys. The satellite view gives confirmation of where the submerged piers are and also where the buoys are relative to them. And it gives a good lay of the land for what you should expect to see as you come into the harbor.

[s/v Jedi]

I think we have all seen that according to our charts we’re anchored or sailing over dry land. Charts are simply positioned in the wrong location because there was no accurate positioning when they were drawing them.

More and more are being corrected though. What we need is a sea version of OpenMaps for land. Completely open, a centralized system to upload, integrate and distribute, compatible with OpenCPN

[rslifkin]

Originally Posted by s/v Jedi

I think we have all seen that according to our charts we’re anchored or sailing over dry land. Charts are simply positioned in the wrong location because there was no accurate positioning when they were drawing them.

More and more are being corrected though. What we need is a sea version of OpenMaps for land. Completely open, a centralized system to upload, integrate and distribute, compatible with OpenCPN

That's the situation where radar overlay can be handy. See how the actual land lines up to the charted land and you'll get a sense of whether the chart in question has decent position accuracy or not.

[sv_pelagia]

It has already been stated (and lost) upthread, but worth repeating (I think):

Google Earth satellite images are usually (though not always) far inferior to ArcGIS ESRI and BING satellite images.

(A benefit of a program such as Sasplanet is that one can compare satellite images from numerous sources, as well as Navionics and CMAP, and select the best.)

[s/v Jedi]

Another good example of an excellent nautical chart and the same area in Apple Maps.

So when you look for the magenta line to follow then you want the chart. But it’s just a line drawn by someone. The photo shows the channel precisely and it’s easy enough to navigate it once you get used to navigating over satellite ohotos instead of following the magenta lines

[El Pinguino]

Originally Posted by pnw2022

Haha - yeah, and charts that haven't been updated since the Portuguese were doing their thing a few hundred years ago are always problematic as well . Crossing bars is a different thing, and even Apple Maps can't help there without historical data . Sometimes local knowledge still rules.

Whats your lat/lon, give me a fair chance to respond to your challenge!
- no I am not going re-read this entire thread to find that.

I take it you want to know where Caleta Notch is.
About 53*23'S, 72*48'W

The Portuguese? There is a reason so many of the place names in Patagonia are British and it doesn't involve the pork and beans.

[El Pinguino]

Originally Posted by s/v Jedi

Wait, I found what you mean. Very good example. I took the most precise image from your chart with the photo of the exact same area. You can see that the chart is wrong…. (It’s above the text Paso Largo in my screen dump)

I imagine that if I hadn't told you about that rock you would not have noticed it. However you would have been OK if you had stayed on the leads.

Meanwhile I accept that I am old and slow having only just discovered that apple maps have satellite images.

This idea may work well in clear tropical waters with the sun high in the sky.
High latitudes and high ground maybe not so much.

Also dependent on the state of the tide when the photo was taken.
Three examples - in front of a chum's house in Estero Puluqui.
In the Applemaps shot you can not only his two moorings but also the drying bank to the north.
Go to GE Pro and the latest photo is taken at high tide - no bank
2021 and the tide is out.

[wingssail]

Originally Posted by El Pinguino

I imagine that if I hadn't told you about that rock you would not have noticed it. However you would have been OK if you had stayed on the leads.

Meanwhile I accept that I am old and slow having only just discovered that apple maps have satellite images.

This idea may work well in clear tropical waters with the sun high in the sky.
High latitudes and high ground maybe not so much.

Also dependent on the state of the tide when the photo was taken.
Three examples - in front of a chum's house in Estero Puluqui.
In the Applemaps shot you can not only his two moorings but also the drying bank to the north.
Go to GE Pro and the latest photo is taken at high tide - no bank
2021 and the tide is out.

This is astonishing: If I took a google earth sample to navigate into this place I could get either photo 1, 2 or 3. Is it just a matter of luck which one is on my new MBtiles chart?

Honestly, that is playing russian roulette.

I can't believe that anyone would enter a harbor with at level of inaccuracy.

[arsenelupiga]

regarding sas planet. I practice now creating backups of whole sas planet . Meaning that i store pics of areas at point in time. So, instead of 6 sat photos of the area, i get 12 or more if needed. Helps when one reallly needs details, typically of anchorage and deciding where are those pesky underwater rocks. Some pics are at high tide, some when muddy water etc so one can calculate safer anchoring spot. Also I set it to not update pics, to keep these older pics.

[s/v Jedi]

That set of satellite pictures nicely show the roleof the tide in anchorages.

But come on people, do you really want to say that when using the high tide picture that doesn’t show the shallows at all, but navigating there at low tide, that you would drive your boat up the rocks? You would not look around you? You would not use your depth sounder?

I regularly sail into places that have no chart at all. You would call that going in blind? In the couple of occasions that I really can not tell where a passage is, I either skip it and anchor further out, or I launch the dinghy to find it when I’m sure it’s there.

I have gone through an uncharted passage that is 300 yards long and width varying between 50’ and 30’ with rock at each side, sticking up 12” above the water. I first did this a number of times with the dinghy, acting like if I’m aboard the big boat, until confident I can do it.

All the charts were drawn by people who navigated there without charts. If you can’t do it with satellite photos plus modern instruments then what can I say?

[s/v Jedi]

Here’s the chart and photo. It’s not the wider passage on the right, because it has a bar at the north entrance that we can’t pass during hight tide… it’s the smaller one on the left.

The chart is useless, it’s simply discovered but not charted. It’s the dinghy and handheld depth sounder that made this possible.

Now I have this satellite picture (I didn’t have it at the time) and it would have made it much easier, but I would still scout with the dinghy first.

[s/v Jedi]

And here is a little zoomed out screen from that area on the chart. At the time I had a Raytheon chartplotter with C-Map charts and they were the exact same as this. None of the markers was there in reality and all you see was at least a mile shifted in position… hooe that is corrected now. I used a radar overlay and manual calibration that allowed me to shift the chart so that it matched the radar echoes.

Now there’s houses on every little piece that is level enough… back then there were only a handful and the only local boat was the schoolboat picking up the kids and cayucas to go out fishing.