Where are Offsets Stored ?

[yachtvalhalla]

I've been making a lot of offsets for cells that are not properly registered in cm93. These offsets must be stored somewhere??? Where??
Terry

[nohal]

Terry...
In your config folder, there's a subdir cm93, containing files <name_based_on_cm93_path_>_coverset_sig.[A-G]
The offsets are saved there.

Pavel

[yachtvalhalla]

Originally Posted by nohal

Terry...
In your config folder, there's a subdir cm93, containing files <name_based_on_cm93_path_>_coverset_sig.[A-G]
The offsets are saved there.

Pavel

Thanks Pavel!

I have successfully copied this subdir 'cm93' to another machine to obviate the lengthy task of entering the offsets again.

Anyone wanting my collection of offsets for the Philippines and Micronesia let me know.

Terry

[PjotrC]

Originally Posted by yachtvalhalla

Anyone wanting my collection of offsets for the Philippines and Micronesia let me know.

I'm interested. How can I get these, please?

Piotr

[yachtvalhalla]

Originally Posted by PjotrC

I'm interested. How can I get these, please?

Piotr

Click on this link. Download should contain an Excel description of each offset and the 'cm93' folder for the config folder as per Pavel's previous.

I've created these using GE images for reference, thanks to GE2KAP. No guarantees and I'm open to corrections if anyone finds some.

Terry

[yachtvalhalla]

My 'tutorial' on doing this is at How to create offsets of cm93 charts

Hope it helps

Terry

[Talbot]

Originally Posted by yachtvalhalla

My 'tutorial' on doing this is at How to create offsets of cm93 charts

Hope it helps Terry

I think I understand what you are doing, but it appears to depend on Google earth being more accurate than CM93. Have you established that these ofsets are correct by actual observation?

Which version of CM93 do they relate to?

[yachtvalhalla]

Originally Posted by Talbot

I think I understand what you are doing, but it appears to depend on Google earth being more accurate than CM93. Have you established that these ofsets are correct by actual observation?

Which version of CM93 do they relate to?

Talbot

GE Accuracy: In most cases yes. I have a high level of confidence in the GE positions but, as I say on my site:
"The fine print: My disclaimer ... these offsets have not been verified in all cases so you use them at your own risk."

cm93 Versions: I had that same question in my mind so used the offsets on three versions of cm93 (2009, Jan 2011 and Aug 2011). They all appear to work fine.

Terry

[PjotrC]

Originally Posted by yachtvalhalla

I've created these using GE images for reference, thanks to GE2KAP. No guarantees and I'm open to corrections if anyone finds some.

Thank you for posting these files, especially the spreadsheet.

I find the interactive process and opaque file manipulation somewhat error-prone. It would be useful to have an offset configuration tool that can produce and read back a text list of cells (maybe: positions/scales?) with offsets. It would be safer and also an immense help when comparing and merging offset data from multiple sources. Also, perhaps the description language might be rephrased towards the traditional way, more familiar to mariners (instead of "Y Offset" and "positive towards North" maybe "actual latitude is ... to North of charted position") ?

I think it would be good to flag user offsets applied on the chart in a readily visible way, so that thay are easier to spot than by going to Offsets Dialog. This would be important if offset files are to be given to someone else, who may not even be familiar with this Dialog... Otherwise one might misinterpret some Notes that are part of Chart Cells themselves, e.g. for Gaferut Island (happens not to be true in this case...)

Feature Class: CTNARE

Position: 009 13.8224 N   145 22.4532 E

Attributes
   INFORM          (Rep to lie 2 5 miles west 
                   Source date: 1971)

As I am in regular contact with a friend crossing the Micronesia right now, here are some on-the-spot reports, compared to respective Google Earth coordinates. Only large scale charts considered:

Pohnpei Kolonia - 6° 58′ N 158° 12′ E - on position - (GE: on position)
Ulul Island in the Namonuito Atoll - 8° 56' N 150° 4' E - lies 1.5 nm to W (275°) from CM charted position - (GE: lies 1.5 nm to E (100°) from CM charted position)
Gaferut Island - 9° 14′ N 145° 23′ E - on position - ( GE: lies 0.3 nm to SSE (160°) from CM charted position )

Near Gaferut anchoring proved impossible due to currents and surf conditions, so estimate only...
For Ulul I requested double confirmation and got it ...

Another source, a blog from s/v "Quest" ( Kosrae, FSM ) reports:

Kosrae Lelu entrance - lies about 0.5 nm to S from charted position - (GE: lies 50 mtr to SbW (200°) from CM charted position)

The s/v "Quest" report seemingly refers to a Navionics chart, but I think the result would be similar with CM.

One can also find interesting data in the blog from catamaran "Two Oceans" ( On in Micronesia « Catamaran “Two Oceans” Weblog ), e.g. for the Pioneer Pass in the Oroluk Atoll.

[SoggyPaws]

I too am looking for a good/easy way to backup and share the offsets I have poked into OpenCPN. I would think a new feature to dump the offsets as a text file (as a minimum) would be very useful. Doing it as a GPX that you could import would be better.

Though I haven't tried importing Valhalla's offsets (I have downloaded them), it looks like the current mechanism encodes the pathname of the CM93 charts as part of the information. (because we all seem to have several sets of charts), so you probably need to have your CM93 charts stored in the same place, and with the folder named the same, as the guy you're sharing with. Not impossible, but clumsy.

Has anyone done anything more with this? In the Marshall Islands, it is incredibly useful, because in some places, there are fairly detailed charts, but they are off. Google Earth (thanks to GE2KAP) is very useful, but doesn't always reveal everything. So being able to re-reference the CMap chart is very useful.

Sherry
s/v Soggy Paws
in the Marshall Islands