Export all your tracks from the Navionics app and you get one file called
Shared with the Navionics app, with no .gpx on the end and no
.zip either. It can be hundreds of megabytes. Most tools will not open it, and several
will not even offer it in the file picker.
It is a perfectly ordinary GPX document containing every track you own. Log reads it.
In the Navionics app, go to your saved tracks and select all of them.
Export or share the selection. The app writes one document for the whole set.
It lands in your Downloads or your share sheet as Shared with the Navionics app.
Do not rename it and do not try to "fix" the extension — you do not need to, and
renaming is how people accidentally convince a tool it is a ZIP.
Keep the original. Everything below is derived from it, and any later improvement to the
analysis can only reach your old recordings by reading it again.
Why it defeats most importers
It has no extension. Anything that decides a file's type from its name rejects
it before reading a byte, and an accept=".gpx" file picker will not even list it.
It is one document, not one per outing. A hundred separate days arrive as a
single track list that has to be split back apart on time and distance.
It is enormous. Navionics records at roughly one fix a second and has no
recording-frequency setting, so a few seasons is a file that an importer reading the whole XML into
memory simply dies on.
What Log does with it
Identifies the file by its first few kilobytes, never its name — a ZIP
signature, a <gpx> root, or nothing recognisable. The picker filters nothing and
you can drop the file straight onto the page.
Streams it. Points are staged on your device and read in timestamp order, so a
single GPX can hold years of unsorted tracks without the whole thing going into memory. The work
happens in your browser; nothing is uploaded until you say so.
Splits it back into outings on gaps and time at rest, and merges two devices
that recorded the same day into one.
Keeps the names you typed. "Milford to New Haven move Vayu (Jacob, Michael,
Seth)" becomes the trip title — often the only surviving record of who was aboard and why.
Names the app generated for you — "Track 057", a bare date — are discarded, so a hundred-track
import does not arrive as a hundred identical rows.
Trims the drive. The ends of each recording are judged against the coastline,
so the trip to the ramp comes off, and a recording that never touched water is unticked with the
reason shown.
Thins rather than refuses. An outing too dense to store is thinned in
time, keeping both ends. Every fix kept is a fix that was really recorded — nothing is
invented, averaged or truncated — and you are told the interval it actually achieved.
Cannot duplicate. A day already in your log is recognised and skipped, so
re-importing the same export costs you time and nothing else.
Shows you what it found before anything uploads, page by page, with the
reason beside every row it passed over.
Then what
Once they are in: replay any outing on the chart, group passages into journeys with a story and
an album, see your seasons and boats in an overview, count the days toward
a captain's licence, and share a single outing at a precision you
choose. Everything is private to your account until you decide otherwise, and it all downloads
back out as GPX.
Coming from a different app? OpenCPN, Garmin and anything else that writes GPX or a ZIP of GPX
files works the same way — and so do the days with no track at all, from photos, a spreadsheet or
a written account. Bring in your history.