Projection Errors

[kjames]

Originally Posted by barnakiel

Yep. Run a quick test with the most archaic to the most recent on this machine: netbook/puck/raster/vector/google for our current location. Below you have the results.

1 cable off is not acceptable in the area you are.

Cheers,
b.

B, that's the stuff - what I'm after! That would be better than 10' wouldn't it?

PS, I just found what unit of measure a cable is - yeah, what I've got at the minute.

Cheers

[r.fairman]

Post your track as a gpx here and I can check against vectors and rasters

Regards Richard

[r.fairman]

Thanks for the gpx file
Here are the results
Track plots mid channel ok in GE
Track plots mid channel ok in Bing
Track plots offset in OpenCPN with Cmap 93 as below



I do not have any raster charts of the area to test

I think the problem is a chart data problem for your area. Can you get the gps position of a known landmark in your area Better if you can do this yourself Then plot the position as a waypoint in your chart. If the waypoint does not allign the landmark problem is likely to be chart data problem Your chart may have been derived from the cmap 93 data so any errors just carry over. I have used Navionics charts for my area and exactly the same spelling mistakes on the cmap 93 charts appear on the navioncs charts With a good sat fix you can expect accuracy of 10 m and certainly not worse than 50 m If you get an error ask why a known good gps position is offset on your chart. We all would be interested in their response. Glad to see you did not run into the overhead cables clearly shown on GE and Bing but not on the cmap 93 plot. With opencpn you can offset a local chart to compensate for any offset in the chart data

regards

Richard Fairman Author SeaClear Unleashed

[kjames]

Many thanks Richard. I believe all charts from around here are derived from Australian Hydrographic Dept data / surveys, so not surprising that cmap also showing a problem. I have operated oziexplorer for years and have raster maps (not marine charts) from around here so I will get that to you for a look - might be of some interest. Cheers

[barnakiel]

Or else the rived bed changed. But could it change this much?

b.

[r.fairman]

Here is source of Australian BSB kap chart I dont know how you woud get them into inavx Is there a way?

Chart Download

regards

Richard

[kjames]

Hi all

There was a bit of interest in this issue so just wanted to let people know that Navionics emailed yesterday to let me know the issue has now been fixed.

They advised me to "update chart list" in InavX. That was easy to do. All Oz maps downloaded / updated, so it would probably be a good idea for anyone in Oz using InavX to do this.

Cheers