Track Splitter

 UPDATE: Many thanks to Joe Cain for bringing the original Track Splitter back from the dead (he cloned the old Track Splitter which had been retired). It seems to work just like the old Track Splitter. Give it a try and let me know if you have any problems. 

Garmin chartplotters typically have a maximum trackpoint count of 5000. Garmin advertises up to a 50,000 trackpoint storage but that applies only to the active track, not imported tracks that have the 5000 point limit. Here's a program for use to easily split tracks that seem to work well with B423 Long Tracks in getting under the 5000 trackpoint limit. You do not need to use this program for loading Long Tracks into Aqua Map or Navionics apps, only for loading into Garmin chartplotters. Once the split tracks are un-zipped, they can be loaded to the Garmin Active Captin app too, and transferred to a chartplotter via the WiFi interface on chartplotters with that feature. 
I spent the morning looking at ways to split long tracks into smaller segments that will load into Garmin Chartplotters. I've settled on the one at this site.
Track Splitter

I've tested the following settings that seem to work well using a PC:
1 - Select 1 meter accuracy (for smoothing to reduce trackpoint counts)
2 - Retain Timestamps = No
3 - Retain Elevation = No (this program is also used for hiking)
4 - Do not adjust time stamps
5 - Spilt Track = Yes
6 - Track Prefix = (not needed, each split track with have a suffix 01, 02, 03, etc.)
7 - Use 300 km for the maximum length of each split track, it seems to work with the B423 tracks and keeps the trackpoint count well under 5000. 
8 - Waypoint Proximity Alarms = None 

Then chose a GPX file that you have already downloaded to your PC. If you didn't specify a saved location, it will be in the default location "Downloads" on your PC. After selecting the file, the program will upload and split it as per your settings and send it back to you for saving in "Downloads" as a zipped file.

Unzip the file and you have two options:
1 - Load to Homeport (there will be no errors) and then to an SD card for transferring to your chartplotter. Some Garmin chartplotter users have reported skipping the step of loading to Homeport and just export the zipped file directly to an SD card which is then read by the chartplotter (without the need for the Homeport step).
2 - Download to your Garmin Active Captain app and use its WiFi transfer capability to load to your chartplotter.

They are all well under the 5000 trackpoint limit so should load okay. I've successfully loaded a split track to Garmin Active Captain app. The Norfolk to Southport 111320 Long Track splits into two pieces and each piece loads successfully. 

This technique is as easy as I could find, no cutting of tracks, just running the program and unpacking a zip file. You will also get a small text file with each splitting giving the trackpoint counts of each split track. 

Let me know if you have any problems with this procedure.

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