Expedition Navigation Software / Filter GPS outliers?

**Posted by Nick** 9/04/2018 11:50 am

Mail me a sample of the data from the raw data window and a screen shot of the instrument connection page in Exp.

It is still probably a problem with your GPS.

**Posted by DuncanR** 9/04/2018 12:39 pm

Fredrik, again, this is not an Expedition problem it is certainly a GPS problem. Try a different GPS, preferably hooked up a different way, and see what happens.
From your tracks above you can do that at a mooring, you will know soon enough if it has worked!

**Posted by David** 9/04/2018 3:41 pm

DuncanR wrote:
Fredrik, again, this is not an Expedition problem it is certainly a GPS problem. Try a different GPS, preferably hooked up a different way, and see what happens.
From your tracks above you can do that at a mooring, you will know soon enough if it has worked!

There's no doubt it's a GPS Problem, I've seen it too on old plotters.
I've cleaned the resulting corrupted log files using smart sorting and filtering techniques then MS Excel commands to fix the GPS outliers (where there's a big jump in Lat or Lon, ignore the error value and replace it with the average of the two either side - works pretty well)
The KND log File Cleaner may also sort out the error data post fact - haven't tried as I don't currently have the problem. I believe it's freely available.
For a quick fix for use on-water, buy a simple $30 USB puck GPS, stick it on the nav desk with blu tack and use it as an alternative GPS source in the interim while you work out the GPS issue. Easy to set up in Expedition. I ran a race boat for about 5 years with this setup until we eventually ditched the old plotter.

Last edited by David (9/04/2018 3:48 pm)

**Posted by DuncanR** 9/04/2018 10:06 pm

Dave, you have more persistence than me in the face of variations of the scale of Fredrik's from the ;ictures above. In my experience the outliers haven't been sufficient to bend the results, but this set could be in that category.
Note I use KND Log Cleaner every race, it would remove the outliers, but I have never been able to reload a KND-cleaned file back into Expedition, so I maintain the unclean and cleaned in parallel and work on both in analysis.

**Posted by Steve** 6/18/2024 5:56 am

Nick,
I just installed a new chart plotter (B&G) and I am seeing a problem with the different GPS data coming thru the feed. It turns out I have 3 different GPS, one on the chart plotter, one on the AIS unit and one on my older Raymarine network. In the chart plotter I can choose which one I use, but I don't see a way to filter out the different ones on expedition. the other issue i see is that the positions of the different GPS also causes the location to jump back and forth. One GPS is located on the transom and the others midship, about 20 feet away.
Any suggestion on how to filter the different GPS?
Thanks

**Posted by Campbell_Field** 6/18/2024 7:44 am

Select what port to use for GPS in the instrument dialogue (above com1 etc)

If NMEA2000 is your pos source, then in the NMEA2000 settings (Actisense etc) select which source on the N2k bus to use.

**Posted by Steve** 6/24/2024 1:47 pm

Thanks for the ideas, the problem is that everything is on the 2000 bus. I will need to filter out the yacht device gateway. the next challenge is figuring out how to identify the one I want to use.