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Old 30-03-2012, 22:18   #1
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Sharing kap Files made from GE into OpenCpn

Can anyone tell me if someone started a public library of chartlets made from Google Earth. These chartlets are fairly easy to make yourself but why not share our work ... so we don't have to all do the same work!

Last year in Majuro, we had some experts (I think about Leslie, Naomi & Heather) showing us how to make these chartlets. I suggested uploading them on OpenCPN website ... anyone has any ideas, propositions??

I can start making charlets about Micronesia ... and I will be ready to upload them somewhere And I hope that someone share his chartlets from SE Asia ...
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Old 31-03-2012, 07:01   #2
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Re: sharing kap files made from GE into OpenCpn

I have hundreds of hours invested in making the chartlets you are talking about.

1849 kap files of every open ocean island in the world excluding those lying close to major land masses. These also include close ups of passes and harbors. Some shallow banks that may be a hazard to navigation or provide interesting fishing are in there too. Tropical islands are better represented detail wise than the cold climate ones.

All are grouped by island and political boundaries. I took it a step further and have downloaded wiki pages, seadot pages, picasa pictures, google pictures, old charts and other interesting tidbits for every island and country.

There is also a GE poi (hollow diamond) for each island colored by political groupings and check in/out islands being a solid diamond. These are great when using CM93 because the islands disappear if you zoom out but the waypoints in the layers do not. My plan is to convert these to gpx and add the links, pictures and stuff to the poi's locally.

I might create a torrent if there is an interest. 5.4gigs!
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Old 31-03-2012, 07:46   #3
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Re: sharing kap files made from GE into OpenCpn

Hi Luc - We'd be willing to provide the web space for such a project. We're already trying to be a repository for folks to upload & download track files, so adding KAP files would be a natural. (BTW, we have no track files for Micronesia, or even Vanuatu, so would appreciate yours)

Surveyor, sounds like you're way ahead here. Any chance we could see a sample?
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Old 31-03-2012, 08:23   #4
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Re: sharing kap files made from GE into OpenCpn

Quote:
Originally Posted by Jon Hacking View Post
Surveyor, sounds like you're way ahead here. Any chance we could see a sample?
Penrhyn - Cook Islands


The Western pass at Penrhyn


The kaps are too big to attach here as docs. I saved a bmp of each kap as I created them and that is what is pictured above. I took great pains to make sure I was getting good detail and used the best historic images in GE. Most islands have a full overview and then a better resolution series either N and S,E and W or more plus the pass and harbor close ups. Harbors were generally all taken using the latest imagery.

There are many islands that do not appear in GE. I still grabbed a kap of the area, created a poi and downloaded pages, pics etc if this was the case. St Peter and Paul Rocks for instance.

I tried to attach a complete directory/file listing in cvs format but it is also too big to upload here.

Edit:
Areas that I have not done are all of the Caribbean, Philippines, Maylasia/Indonesia, the Andamans or any port on any continental mainland. These are just islands floating around out in the open ocean.
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Old 31-03-2012, 10:06   #5
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Re: sharing kap files made from GE into OpenCpn

Sweet! The reefs show up really well - a huge advantage, as the charts usually don't have bommies & such (or, if they do, they're not positioned correctly). I'll PM you my eddress.
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Old 31-03-2012, 10:57   #6
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Re: sharing kap files made from GE into OpenCpn

That is an awesome chart of Penrhyn! I wish I had had the technology when I was there. How close to the WGS84 datum are the GE-derived charts? I still wouldn't want to move around the lagoon without good light, but they are a huge improvement!
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Old 31-03-2012, 11:24   #7
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Re: sharing kap files made from GE into OpenCpn

We publish GE imagery on our Cruising Indonesia page (& several others, like Cruising Australia & Cruising Madagascar). They seem to be spot-on with our GPS (as seen by our tracks in those images). Even out of the way places in Indonesia seemed to be spot on. Not sure how they do it, but GE seems to be wonderfully accurate everywhere we've looked.
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Old 31-03-2012, 12:12   #8
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Re: sharing kap files made from GE into OpenCpn

Google buys those satellite views from ventures (such as DigitalGlobe DigitalGlobe Products in the case of Penrhyn) that, using sophisticated algorithms, compute the geolocalization of selected image pixels from data from the time, location, altitude, and 3-axis attitude of the satellite camera and a model of the earth geoid.
Other pixels are corrected from parallax effects. The precision is the same in any corner of the world and is independent of previous land surveys.
Professionnal land surveyors estimate the typical residual errors at around 10 meters, which is way too huge for them to use GE in their trade (but I suppose good enough for us) !

One can enhance the value of GE pics by adding a transparent layer of nautical data from charts. One can thus verify the geolocalization of the charts, and have the best of both worlds.
See the GE2KAP thread from Paul Phiggins in CF (Google Earth to BSB / KAP)

Pic1: NZ chart courtesy of GPS-Marco (on CF as well New Zealand Charts)
Pic 2: CMap 93
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Old 31-03-2012, 12:40   #9
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Re: sharing kap files made from GE into OpenCpn

They are really only good for getting an idea of what to expect in a very general way. I would never ever use only a GE derived kap of a pass/inlet for navigation through said inlet. I would however use it to help make decisions like which side to favor or when to bear off.

They are great for geeking out over looking at them when you are in route and without internet. Also for when you are there and trying to decide where to explore.
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Old 31-03-2012, 13:36   #10
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Re: sharing kap files made from GE into OpenCpn

Quote:
Originally Posted by Surveyor View Post
They are really only good for getting an idea of what to expect in a very general way. I would never ever use only a GE derived kap of a pass/inlet for navigation through said inlet. I would however use it to help make decisions like which side to favor or when to bear off.

They are great for geeking out over looking at them when you are in route and without internet. Also for when you are there and trying to decide where to explore.
I wouldn't go without GE views in some areas:
Look at these charts (date of survey !)

using GE I can test that Manihiki is pretty decent, but not perfect, whereas Uafato is worse...
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Old 31-03-2012, 14:39   #11
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Re: sharing kap files made from GE into OpenCpn

public repo would be a superb idea, ideally with user comments on veracity of data.. daydreaming here
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Old 31-03-2012, 14:42   #12
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Re: sharing kap files made from GE into OpenCpn

Quote:
Originally Posted by sailorF54 View Post
I wouldn't go without GE views in some areas:
Look at these charts (date of survey !)

using GE I can test that Manihiki is pretty decent, but not perfect, whereas Uafato is worse...
That is a very dangerous conclusion about Manihiki. If you drop a hook there itś anyones guess if you can get it back up again. You are also dangerously close to the reef, with out any margins. It's not my idea of a decent anchorage, and GE did not help at all in this case.
But ... GE found an interesting landing blasted through the reef at the NW point.

Thomas
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Old 31-03-2012, 15:26   #13
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Re: sharing kap files made from GE into OpenCpn

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Originally Posted by cagney View Post
That is a very dangerous conclusion about Manihiki. If you drop a hook there itś anyones guess if you can get it back up again. You are also dangerously close to the reef, with out any margins. It's not my idea of a decent anchorage, and GE did not help at all in this case.
But ... GE found an interesting landing blasted through the reef at the NW point.

Thomas
You're quite right... But I was only refering to geolocalization accuracy...
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Old 31-03-2012, 19:02   #14
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Re: sharing kap files made from GE into OpenCpn

That's great that you already have done so much work! Can we download some of your kap files? If yes, where should we go for them?
I think it is great that you organized the chartlets by regions, ... as most of us do not need the whole globe but only these places we are planning to explore in the near future

If we get a general depository, would you share what you have done so far?

Have a great WE

Luc

Quote:
Originally Posted by Surveyor View Post
I have hundreds of hours invested in making the chartlets you are talking about.

1849 kap files of every open ocean island in the world excluding those lying close to major land masses. These also include close ups of passes and harbors. Some shallow banks that may be a hazard to navigation or provide interesting fishing are in there too. Tropical islands are better represented detail wise than the cold climate ones.

All are grouped by island and political boundaries. I took it a step further and have downloaded wiki pages, seadot pages, picasa pictures, google pictures, old charts and other interesting tidbits for every island and country.

There is also a GE poi (hollow diamond) for each island colored by political groupings and check in/out islands being a solid diamond. These are great when using CM93 because the islands disappear if you zoom out but the waypoints in the layers do not. My plan is to convert these to gpx and add the links, pictures and stuff to the poi's locally.

I might create a torrent if there is an interest. 5.4gigs!
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Old 31-03-2012, 19:15   #15
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Re: sharing kap files made from GE into OpenCpn

Quote:
Originally Posted by Jon Hacking View Post
Hi Luc - We'd be willing to provide the web space for such a project. We're already trying to be a repository for folks to upload & download track files, so adding KAP files would be a natural. (BTW, we have no track files for Micronesia, or even Vanuatu, so would appreciate yours)

Surveyor, sounds like you're way ahead here. Any chance we could see a sample?
Hi Jon,

Good to hear from you! Ok, thanks for the offer of hosting the GE kap files. I think it would be a great idea to have 2 repositories so that way we have a back up. Anyone from OpenCpn out there??? OpenCpn seems a logical place to store these chartlets too ..
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