Chart Overlay Google Earth Question

[David M]

Is there a way to show a vessels position including heading, COG and velocity vector, overlayed onto a Google Earth image? I would only have a cellular internet connection and at times no internet connection depending on the location. I am figuring I would need to download the images ahead of time.

Does Google Earth have pretty accurate WGS84 positions?

The reason I ask is sometimes I need to go into the small inlets into relatively shallow salt marshes and the NOAA charts are just not accurate enough or detailed enough for myself or the scientists.

If this can be done, how could I do this on a PC with Windows XP?

[Highlander40]

Photo nav is way cool for places that don't have charts.
The Chatham, South beach, Monomoy area south of Cape Cod MA is a great example.

Ive done it but using images on a Navionics chart chip and Maptech discs.
To be sure of the data I took waypoints with a handheld GPS in the dinghy then entered them into the Raymarine on the boat. A twist of the sat overlay knob and for the most part it was an exact fit.

Active Captain may be getting there too.

Google Earth takes a big pipe to load and the imagery isn't any more up to date than what you can get on a disc. Just get a USB GPS and your set to go. Have fun!

[Viking Sailor]

Dave,

Not an overlay -- but how about something like this?

Paul

[hellosailor]

David, I wouldn't count Google Earth as being more suitable than NOAA charts for navigating inlets. Google's imagery is not live, it is often 2-3 years old and marshes and inlets will have shifted in that time.

Can you do it? Sure, a simple matter of programming, if you find someone who can do a Google Earth "mash-up". Would it be worth doing? I really would advise against it. Better to look over the side and use a depth sounder or local knowledge.

[AnchorageGuy]

David, There is a product called EarthNC which can be used as a charting software with their GPS software.
www.earthnc.com

[David M]

Hello,
Thanks...I am not too concerned about scraping bottom at very slow speeds. I do it all the time in the shallows with this boat. The props are above the bottom of a full length keel.

Waterway,
Thanks for that link. That seems to be what I am looking for.

Paul,
Can OpenCpn put a boat icon over a Google Earth image?

[hummingway]

I'm writing an application at the moment that uses gps and google. You read the GPS location from the serial feed and send a request to Google for a map. I'm using the static maps api since it doesn't require a registration. You can request a marker at the gps location. There is a limit on how many requests you can make in a day.

When I download the map there is a centre point (i.e. the gps location) and a scale factor. I don't know if you could download a tile based on four corner points or not. If you could it would be just math to plot where the boat was on the downloaded map. The map can also be a sat image by the way.

I'll have a look at googles documentation and see what it says.

[Hud3]

Just be careful, David. I've been plotting my hiking expeditions on Google Earth, and here on Nevis GE is about 90' out of whack.

[Highlander40]

Don't let the "instant" feeling of Google Earth fool you.
A few of the photos are 2 or 3 years old. Most are 5 or 6 or more years old. The date of the photos are displayed in the lower left hand corner.
You can also use the historical view button to see how the shoreline has changed.

Existing software and Maptech chart / photo discs will do the trick. A USB- GPS device is around 100 bucks. Use any laptop.
Of course you have to pay for the discs.

Most software will also leave a trail for later use.

[hummingway]

In looking through the documentation they don't expose the lat/long overlay in any way for static maps. Google earth is a js api that exposes their plugin so is a very different beast. It maybe with a commercial license you get something different but it looks like they are oriented to websites - their licensing only refers to websites, internal or external. The url format is pretty simple for the static maps but as mentioned you never know when the photo was taken. Lat/long in the url needs to be in decimal format. GPS gives it in what looks like decimal format but isn't so there is a conversion that has to take place.

http://maps.google.com/maps/api/stat...e&sensor=false

[Bill Stockton]

Hi,

Does anyone know about Maptech's Navigation Photos (*.sph) file format? I want to convert my Google *.jpg to *.sph.

I can then overlay the photos on top of my existing charts using Nobletec, Coastal Explorer, Chart Navigator, ....

I can already convert them to BSB Charts (*.kap) but navigation photo overlay is much better way of displaying the information.

Thanks.

[Highlander40]

Bill,
What you are really saying is that you want to avoid paying maptech for the photos that can be gotten free from Google? Cause the photos all come from the same place.

[Viking Sailor]

Dave,

It has been awhile since I looked into running GE and OpenCPN together as shown. I do remember that GE either can display a GPS location directly or via add-on software. You will also need software that allows two programs to have access to the same GPS data so that GE and OpenCPN can be run in parallel. I hope to get back on this project this fall assuming that the retro-fit goes as planned.

Paul

[hummingway]

Originally Posted by Viking Sailor

Dave,

It has been awhile since I looked into running GE and OpenCPN together as shown. I do remember that GE either can display a GPS location directly or via add-on software. You will also need software that allows two programs to have access to the same GPS data so that GE and OpenCPN can be run in parallel. I hope to get back on this project this fall assuming that the retro-fit goes as planned.

Paul

Yes, you actually needs a driver that duplexes the serial stream. I would expect a performance hit from such a thing.

[Viking Sailor]

Originally Posted by hummingway

Yes, you actually needs a driver that duplexes the serial stream. I would expect a performance hit from such a thing.

Why would there be a performance hit? Both Windows and Linux are multi-tasking operating systems. That means the when the cpu isn't doing one thing it will do something else. And, as long as the cpu is not running at 100 percent utilization, there is time enough for all tasks to complete with time to spare.