Help / FAQ

[lynnrival]

Is there a work around for version 4 not loading charts with a blank geodetic datum? Unfortunately this seems to rule out about 50% of the official Brazilian charts, which is ironic as their free availability features prominently in the User Manual. I have just reentered Brazilian waters and was surprised to find many charts not loaded (last year using version 3.2 they were all loaded OK).

[nohal]

For now fixing the charts.

[lynnrival]

Fixing the charts - the only way I could think of is to separate out the header and image from the KAP files, write 'GD=unknown' in each header and form new kap files. I know this can be done using imgkap but it is a long and tedious process for so many charts. Is this what you mean?

The Brazil Hydrographic office obviously don't see these charts as broken; many of them were updated and issued last month!

[nohal]

Open the file in any decent text editor, replace "GD=" with "GD=UNKNOWN", run bsbfix on it. Takes about 15 seconds per chart.
Or wait for the OpenCPN 4 maintenance release and use 3.2.2 for now.
The Brazilian charts are unfortunately quite a mess, updated or not.
Sorry for the inconvenience, where were you during the beta test?

[lynnrival]

Originally Posted by nohal

Open the file in any decent text editor, replace "GD=" with "GD=UNKNOWN", run bsbfix on it. Takes about 15 seconds per chart.
Or wait for the OpenCPN 4 maintenance release and use 3.2.2 for now.
The Brazilian charts are unfortunately quite a mess, updated or not.
Sorry for the inconvenience, where were you during the beta test?

Thanks - that will be a bit quicker. I wouldn't have noticed during the beta test because I haven't been in Brazil for 18 months.

[cagney]

Originally Posted by lynnrival

Thanks - that will be a bit quicker. I wouldn't have noticed during the beta test because I haven't been in Brazil for 18 months.

Please report back on the accuracy of the charts.
Setting GD=UNKNOWN will treat the chart as if it's WGS84.
Many Brazilian chart are GD=COA (or GD=COABR).
There may be a couple of hundred meters difference between the two.
The Brazilian cartographers knows the geodetic datum. To bad they don't bother to tell us for each and every chart.

Thomas

[lynnrival]

Originally Posted by cagney

Please report back on the accuracy of the charts.
Setting GD=UNKNOWN will treat the chart as if it's WGS84.
Many Brazilian chart are GD=COA (or GD=COABR).
There may be a couple of hundred meters difference between the two.
The Brazilian cartographers knows the geodetic datum. To bad they don't bother to tell us for each and every chart.

Thomas

We sailed the coast from Salvador south and on to Uruguay in 2013, using the Brazilian charts. Didn't find any (for our purposes) serious errors, ie more than say 50m.

it is a shame they omit the datum. but at least they realise it is good to allow free use of us the charts - we come from the UK where the Admiralty jealously guards such information, even the tidal data!

[seandepagnier]

maybe you can fix them all with something like:
$ for i in `ls`; do sed -i 0,/GD=/{s/GD=/GD=UNKNOWN/} $i; done

[lynnrival]

Originally Posted by boat_alexandra

maybe you can fix them all with something like:
$ for i in `ls`; do sed -i 0,/GD=/{s/GD=/GD=UNKNOWN/} $i; done

Maybe a good solution, but I don't use Linux much so I don't know if you would still need to run bsbfix afterwards. I have changed the 79 relevant charts using the method suggested by Nohal.

Have also tried to pin down the actual datum. All the KAP files have a KNP section, including the offending GD=, (so that OpenCPN won't load them), but they also have a KNQ section, including (mostly) GD=COA, which is the datum used in the past in much of Brasil. COA is offset from WGS84 by about 200m in both northings and eastings. Having amended the KAPS by putting GD=UNKNOWN my charts are now treated as WGS84. I have made a couple of checks in locations where the position can be accurately determined and find the charts treated this way are within 10m of WGS84. My guess is that the Brazilian Navy have 'converted' the charts to WGS84 during the georeferencing.

[seandepagnier]

you could use cygwin if you have windows and need bash. stuck bsbfix in the for loop?

Or just recompile opencpn from git. I can't imagine doing the same action twice in a row let alone 79 times.

[.Paul.]

Most of the BSB/KAP charts from Brazil with missing geographic datum (GD=) names have the datum shifts needed for WGS84 positioning. These datum shifts are in the "DTM/..." line in the header of the KAP file. The chart image still shows "Datum Horizontal: Corrego Alegre - MG" in the title block, and the latitude and longitudes at two corners also refer to the COA datum.

Paul

[P_Dub]

Anybody has charts of the Demarara River, Guyana?
Thanks in advance.

[mike388]

Hi
Not sure if I am doing this in the right place.
I am using CPN in Asia as a backup to navonics on iPad .
Where I find it is useful for open water, around Singapore there a lot of inacuraces on the charts maybe there are updated charts ? But I am not sure where to find them.
Mike

[bcn]

Mike,

in Help - "?" Button there is a list of chart sources.

For Singapore there should exist up-to-date official ENCs.

These charts are distributed/licensed in the encrypted S-63 format.

To use them you will need the S-63 plug-in.
More info in Help and at o-charts.org as the gateway of OCPN for the S-63 stuff.
A chart catalogue you will find at Chartworld.com

Hubert

[catakate]

Hi,
I tried the search but found nothing so here goes

After downloading all the plugins available on the download page and copied them into the appropriate folder, I found that not all of them are listed in the Plugins tab of the Options window.

Double checked, looked into the log file and found an error related to the weatherfax plugin, to be researched at a later date.

Found nothing relevant in the config file.

Only 7 plugins are visible out of the whole bunch. Anyone experienced this behavior?

Thanks!