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Old 07-12-2017, 18:13   #1
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GSHHS High Resolution Source - ZyGrib?

Under zyGrib Telechargements - Download page
zyGrib: grib file, weather data visualization

There are GSHHS High Res downdownloads. Cartes du monde GSHHS
"résolution (≈25 km, ≈5 km et ≈1 km). Vous pouvez ajouter des cartes plus détaillées (≈200 m et ≈100 m). Attention à la taille du fichier si vous avez une connexion lente. "

Does anyone know if these will work with OpenCPN, if they are more current and updated, and if they are higher resolution?

Should we reference these high res GSHHS in the Opencpn Documentation?

Incidently zyGrib has a Mac version (and Ubuntu) and with a zyGrib forum login name and pass, zyGrib is a reasonable way for Mac users to obtain grib files if they are having trouble configuring Grib-Pi it use email.
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Old 07-12-2017, 21:44   #2
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Re: GSHHS High Resolution Source - ZyGrib?

They work with OpenCPN and are from 2008.
At least for Europe they seem to be recent ones.

However found the gshhs files downloaded as part of qtVlm even more accurate.
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Old 08-12-2017, 14:35   #3
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Re: GSHHS High Resolution Source - ZyGrib?

Shouldn't we be updating the GSHHS files to be more current?

They are now GSHHG - GSHHG - A Global Self-consistent, Hierarchical, High-resolution Geography Database

NOAA -https://www.ngdc.noaa.gov/mgg/shorelines/gshhs.html
As of version 2.2.2, GSHHG is released under the GNU Lesser General Public license.

Hawaii - GSHHG - A Global Self-consistent, Hierarchical, High-resolution Geography Database
Version 2.3.7 Released June 15, 2017
GSHHG is developed and maintained by
Paul Wessel, SOEST, University of Hawai'i, Honolulu, HI.

Perhaps these are different format? Yes.
I believe they can be converted to GSHHS with
The native binary shoreline data can also be converted into a GRASS GIS database with v.in.gshhs, a GRASS add-on by Markus Metz.

There is an even higher res version:
A related product is a global netCDF grid with distances to the nearest GSHHG shoreline in km (with negative distances in the oceans). This is a 1x1 arc minute grid based on GSHHS version 2.3.4 and can be obtained here: dist_to_GSHHG_v2.3.4_1m.nc [Note: it is 454 Mb].

I wonder if these will work with OpenCPN. Perhaps someone will try? It looks like it was just a name change because lakes and rivers are included, but I don't know if our version is using shapefiles or not.
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Old 10-12-2017, 13:17   #4
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Re: GSHHS High Resolution Source - ZyGrib?

Hello RGleason,

It seems to me that Zygrib's more detailed coastline files are the same as the more detailed coastline files we already use in OpenCPN.
Am i wrong ?

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Old 10-12-2017, 19:34   #5
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Re: GSHHS High Resolution Source - ZyGrib?

Quote:
Originally Posted by Gilletarom View Post
Hello RGleason,

It seems to me that Zygrib's more detailed coastline files are the same as the more detailed coastline files we already use in OpenCPN.
Am i wrong ?

Gilletarom
Hi, I don't know that. What makes you think so?
The newer files from the source I listed below (not zygrib) are bigger, and the highest res is something like 435mb!

Have you tried downloading a medium resolutiong "GSHHG" (not GSHHS) and running it in OpenCPN? - I would be interested.
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Old 10-12-2017, 20:40   #6
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Re: GSHHS High Resolution Source - ZyGrib?

Isn't that sweet. Pavel Thank you.

https://github.com/nohal/clip_gshhs
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Old 11-12-2017, 05:22   #7
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Re: GSHHS High Resolution Source - ZyGrib?

Quote:
Originally Posted by rgleason View Post
....
Hawaii - GSHHG - A Global Self-consistent, Hierarchical, High-resolution Geography Database
Version 2.3.7 Released June 15, 2017
GSHHG is developed and maintained by
Paul Wessel, SOEST, University of Hawai'i, Honolulu, HI.
...
I see this link. But, NetCDF format or Shape file format ...

How acn we use these data with OCPN ?
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Old 11-12-2017, 05:32   #8
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Re: GSHHS High Resolution Source - ZyGrib?

Perhaps Pavel is converting the better data. See his github link.
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Old 12-12-2017, 09:39   #9
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Re: GSHHS High Resolution Source - ZyGrib?

The GSHHG data do have a resolution of about 90m.

Some additional information about GSHHG and other (free & distributable) alternatives:
Quote:
GSHHG/NOAA. A world shore line repository gained from satellite data with an estimated resolution of 90m. There is no clear statement about an equivalent scale but comparisons with standard chart material show a best scale: 1:800.000 (others, more optimistically, say 1:250.000). In any case it is not sufficient to georeference or cross check other chart material for navigation. The project is stable, only minor updates are added in longer periods. Access is open and free according to the open data policy of the USA. As of version 2.2.2, GSHHG is released under the GNU Lesser General Public license.

SRTM/SWDB. The SRTM Water Body Data (SWDB format) files are a by-product of the data editing performed by the National Geospatial-Intelligence Agency (NGA) to produce the finished SRTM Digital Terrain Elevation as a product from the Space Shuttle missions. The shorelines resulting from the one arc second (approx. 30-meter) resolution – are already improved in comparison with the GSHHG data.
In most cases, two orthorectified image mosaics (one for ascending passes and one for descending passes) at a one arc second resolution were available for identifying water bodies and delineating shorelines in each 1°x1° cell. These were used as the primary source for water body editing. The guiding principle for this editing was that water must be depicted as it was in February 2000 at the time of the shuttle flight. The SWDB data are used in research projects, but no application for a (sailing) end-user is known to us. In the documentation of the project the minimum size of an object to be included into the data set is defined.
It is an important improvement over the GSHHG data, download is free as well. No update is planned as far we are informed.

OSM (OpenStreetMap, OpenSeaMap.) OpenSeaMap is a sister project to OpenStreetMap and uses the same shoreline information. As a community project, reliability and precision are varying and cannot be assured. A big (manual) effort has been done to digitalize and georeference existing photographic material to create shore lines. Errors detected by users are fed back into the map database to improve the datasets on a daily basis. It is not possible to trace the quality of resolution, scale or georeferencing. Some automatic checks are being run however.
License: Open Database License
Coastlines ready for download - in WGS84 or Mercator projection - and as well complementing information about the coastline project can be found here:
Coastline datasets | Data | OpenStreetMapData
In Europe quite a number of official bodies are using the OSM coastline for publications.
In any case some effort to bring these datasets into a format ready for OpenCPN would be required.
The SRTM is a water body model delivered in 1°x1° (water)cells: it has to be inverted and the resulting lines have to be stitched together to get a land mass.

Shoreline detection for routing in the absence of vector charts can be improved quite a lot with those alternatives for background maps.

Hubert
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Old 12-12-2017, 10:12   #10
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Re: GSHHS High Resolution Source - ZyGrib?

Thank you Hubert, for the informative shoreline study.

Did you see what did-g was doing here?
Feature Requests

It could possibly create a better map for weather_rouuting too, by leaving a margin of safety, which is always wise. If I understand it correctly he is using CM93 to create the offset outline.

I wonder if it could be applied to any shape or format.

Question: Are these old CM93 more or less accurate than the new GSHHG insofar as the shoreline definition? - ( My guess is probably not.)

Could Did-g's program provide an offset for the newer GSHHG converted to > GSHHS? or even SRTM converted?

I think Pavel had started a conversion here, 3 days ago.
https://github.com/nohal/clip_gshhs
Update to generate data from GSHHG 3.4.7 for use in OpenCPN
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Old 28-12-2017, 04:40   #11
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Re: GSHHS High Resolution Source - ZyGrib?

Pavel has given us all a nice xmas present with his Gshhg Pull Request which uses a github repository for the background charts, updates the background charts and integrates them into the chartdownloader. How sweet is that?
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Old 28-12-2017, 13:29   #12
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Re: GSHHS High Resolution Source - ZyGrib?

Quote:
Originally Posted by rgleason View Post
Pavel has given us all a nice xmas present with his Gshhg Pull Request which uses a github repository for the background charts, updates the background charts and integrates them into the chartdownloader. How sweet is that?
It rocks, man !

Three cheers for Pavel
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Old 28-12-2017, 20:08   #13
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Re: GSHHS High Resolution Source - ZyGrib?

Pavel, Dave merged your PR. I've git fetched upstream and compiled.
Then used Chartdownloader to get the GSHHG catalog and downloaded the files.
I created an empty folder and a GSHHG Chart Folder and inserted the gshhg path into the Gshhg Folder.

I checked the opencpn.ini file, searching for GSHHG and correcting some paths to go to the now path. Then I removed the gshhs folder in ProgamFile (x86) and restarted Opencpn.

I still don't see the background files in the display.
What am I doing wrong?
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Old 28-12-2017, 23:10   #14
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Re: GSHHS High Resolution Source - ZyGrib?

Rick,

decompress the files.....

Hubert
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Old 29-12-2017, 04:11   #15
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Re: GSHHS High Resolution Source - ZyGrib?

Maybe still some work to do. The downloader should unzip the files automatically.
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