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

[wholybee]

Originally Posted by Mike OReilly

Using satellite images is a great tool, but there can be significant differences in resolution and general image quality from image to image on those made available through "free" services like Google. The image may, or may not, be showing the whole picture.

Nautical charts suffer from the same uncertainty, but at least they are intended to be used for marine navigation. Publicly available satellite images are not.

It's certainly a useful tool, and one that can be integrated with other navigation tools, but I don't see it as a primary source.

There are areas where official charts not only have uncertainty but are downright dangerous. You are better off skipping the chart and sending someone up to the spreaders as a lookout.

In those areas, the satellite maps are better as your primary. Also, when making MBtiles, you can compare images from several sources, and choose the one with the best detail and contrast. So, while it can be an issue, it's usually not.

[Jammer]

I like my chartplotter because it is visible in daylight, is waterproof, can be used in the rain, and displays radar data.


In practice I also use my phone with either satellite data or the Navionics crowdsourced depth contours, especially in tricky areas where the official charts are poor -- but I only use it as a supplemental source of information.


I would not want to rely on satellite data alone. It does not show clearance below bridges, the amount of water above reefs and wrecks, the presence of restricted areas, bottom composition, shipping lanes, the location of ranges, the color, sector, and flash rate of lights, etc.

[Mike OReilly]

Originally Posted by wholybee

There are areas where official charts not only have uncertainty but are downright dangerous. You are better off skipping the chart and sending someone up to the spreaders as a lookout.

In those areas, the satellite maps are better as your primary. Also, when making MBtiles, you can compare images from several sources, and choose the one with the best detail and contrast. So, while it can be an issue, it's usually not.

I disagree. In areas where charts are sketchy, it likely means it is a low-population, low commercial area. This is EXACTLY where satellite images will also be their most dubious. The point is, there is no reason to believe satellite images are any more accurate, or show the full picture. They may, but they may not -- just like charts. All you can really know is they aren't intended for marine navigation.

I do agree with the use of Mark I Eyeballs as the best answer. Up the spreaders, or maybe even a drone if you want to get fancy. That, at your depthsounder, and/or good old leadline, is the best choice in areas of poor charting/imaging.

[s/v Jedi]

Originally Posted by wholybee

Curious, what software did you use on the ipad for autopilot?

I still use it: iSailor, but ever since Transas sold it, it’s been downhill with it (the app is still good but pricing went crazy)

Autopilot control is an in-app purchase. It even works with an Apple Watch… can control the autopilot from your watch

[sv_pelagia]

Originally Posted by Mike OReilly

I disagree. In areas where charts are sketchy, it likely means it is a low-population, low commercial area. This is EXACTLY where satellite images will also be their most dubious

Mike, can you give more details on your comment? It doesn’t make sense to me.

I use satellite images in places with zero population/zero commercial activity -- west coast of Haida Gwaii, BC -- and the images are as clear as populated areas.

[paralog]

Originally Posted by s/v Jedi

So these chart plotters cost thousands!

The other day I got a smartphone and it turns out it has Google Maps which does navigation just fine! For free!

It's pointless asking this question on here as there are some who are still using the stars to navigate and will give you nothing but grief because you want to use the latest navigation systems on phones and Ipads.

Personally i don't mind chartplotters but they are still very expensive and really don't offer many advantages to ipads etc unless you have other systems integrated into them. Many chart plotter systems have lots of hidden stuff most of us will never use.

Oh and according to most of those posting on these forums -chart plotters never fail but tablets and computers always fail.

[SeanPatrick]

Originally Posted by paralog

It's pointless asking this question on here as there are some who are still using the stars to navigate and will give you nothing but grief because you want to use the latest navigation systems on phones and Ipads.

That's funny. My experience here has been the exact inverse.

[wholybee]

Originally Posted by Mike OReilly

I disagree. In areas where charts are sketchy, it likely means it is a low-population, low commercial area. This is EXACTLY where satellite images will also be their most dubious. The point is, there is no reason to believe satellite images are any more accurate, or show the full picture. They may, but they may not -- just like charts. All you can really know is they aren't intended for marine navigation.

I do agree with the use of Mark I Eyeballs as the best answer. Up the spreaders, or maybe even a drone if you want to get fancy. That, at your depthsounder, and/or good old leadline, is the best choice in areas of poor charting/imaging.

In Fiji, charts are dangerous, and Satellite images are dead on perfect. Much of the popular south pacific islands are that way. When I was in Fiji in 2018 and 2019, almost all cruisers used satellite imagery. I switched to satellites after the 3rd time I found an uncharted reef. I would now be comfortable navigating Fiji with satellite maps at night. It really is incredible how perfect they are.

[Mike OReilly]

Originally Posted by sv_pelagia

Mike, can you give more details on your comment? It doesn’t make sense to me.

I use satellite images in places with zero population/zero commercial activity -- west coast of Haida Gwaii, BC -- and the images are as clear as populated areas.

I'd guess that the west coast, especially Haida Gwaii, gets special coverage.

It's not hard to find what I'm talking about. Here is one good example which actually illustrates the issue. This is an area I know well: The Slate Islands of Lake Superior. Here is the screen capture of the Google satellite offering. You can plainly see the west portion is lower rez than the eastern side. Not sure why the difference, but if you didn't have it overlap like this, you might not even know.

The other issue for many Canadian waters is that 1/2 the images will be taken in the winter, with ice and snow cover. Again, not much use for navigation.

[Mike OReilly]

Originally Posted by wholybee

In Fiji, charts are dangerous, and Satellite images are dead on perfect. Much of the popular south pacific islands are that way. When I was in Fiji in 2018 and 2019, almost all cruisers used satellite imagery. I switched to satellites after the 3rd time I found an uncharted reef. I would now be comfortable navigating Fiji with satellite maps at night. It really is incredible how perfect they are.

And that's great to know . Clearly some areas are better served by charts and some by satellite imaging. I'm not saying never use the images, or charts. What I'm saying is, there's no universal truth here. And satellite imaging can be just as fraught and faulty as charts.

I tend to use both in my waters. Charts are general guides, at best, in some areas I travel. Satellite imaging helps, but it's mostly the lower rez versions that I showed in the previous post.

The other variable with satellite imagery is the variability of depth visibility. It will depend on the angle of the sun vs the satellite, and the turbidity of the water, amongst likely other factors.

Again, it's a useful tool, and in some areas it sounds like it's better than charts. But just like charts, I take them with a deep grain of sand.

[sv_pelagia]

Originally Posted by Mike OReilly

I'd guess that the west coast, especially Haida Gwaii, gets special coverage.

It's not hard to find what I'm talking about. Here is one good example which actually illustrates the issue. This is an area I know well: The Slate Islands of Lake Superior. Here is the screen capture of the Google satellite offering. You can plainly see the west portion is lower rez than the eastern side. Not sure why the difference, but if you didn't have it overlap like this, you might not even know.

The other issue for many Canadian waters is that 1/2 the images will be taken in the winter, with ice and snow cover. Again, not much use for navigation.

Nothing to do with Haida Gwaii.

Your problem is relying on Google Earth!

ArcGIS(ESRI) and BING typically provide much better images than GE.
SASPLANET gives all these to compare and use best.

Yes, sometimes in Winter, so even more important to compare different images and pick best.

Here is a quick view of Slate I from ArcGIS app on my Android, so not the best compared to SASPLANET.

[sv_pelagia]

for Mike re Slate Islands Provincial Park


Interesting and nice looking place (in the summer...).


I've looked at SAT images (Google the worst), CHS ENC chart, Navionics chart, AND CHS "NONN10" soundings (which provide greater soundings detail, and can be placed on a satellite chart using SAT2CHART).


See attached:

[valhalla360]

Originally Posted by GreenWave

When out of cell range will it still track properly without having downloaded the map area?

You want the map downloaded of course but then no problem tracking.

Of course, google maps wouldn't be my first choice when you can download free chartplotting apps.

That said, years ago, we had the chartplotter crab out and we did switch to google maps to get into port.

[valhalla360]

Originally Posted by Sailing August

Beware!
Google Maps and that little blue dot can be off as much as a 1/4 mile depending on your connection to the cellular network and refresh rate.
Very dangerous in shallow waters in and around reefs.
GPS driven chart plotters are accurate to +/- 3 feet. much safer

Only time I've been off by a significant amount is coming out of a subway station in an urban area surrounded by tall buildings. Then it often takes a few minutes before the location is accurate.

I think you may be thinking of 20-30yrs ago when many phones didn't include an actual GPS chip and some tried to triangulate based on cell towers.

[valhalla360]

Originally Posted by Locquatious

As someone once mentioned before, cell phones, iPads, and computers are as waterproof as tissue paper. If you are out in foul weather and reduced visibility, do you really want to be holding a cell phone in your hand to give you navigation assistance?

It's nice having a helm position protected from the weather. These issues are non-existent.

Or you can get a waterproof cover. They are available for most common phones.