(Known Issue) GPS accuracy on Jan 01 2021?

Ok, someone asked privately more explanation/file.. Well let's do it like this:

Take this, and then search&replace ":4spaces:" with "    " and it should be properly indented.

import re

latOffset = 0.00011022202
lonOffset = 0.00432430766

with open('output.gpx', 'w') as writer:

:4spaces:# change the filename below to match your garmin gpx filename
:4spaces:with open('activity_XXXXXXXXX.gpx', 'r') as reader:
:4spaces::4spaces:try:
:4spaces::4spaces::4spaces:line = reader.readline()
:4spaces::4spaces::4spaces:while line != '':
:4spaces::4spaces::4spaces::4spaces:latlon = re.search("(.*lat=\")([0-9|-]+\.[0-9]+)(.*lon=\")([0-9|-]+\.[0-9]+)(.*)", line)

:4spaces::4spaces::4spaces::4spaces:if latlon:
:4spaces::4spaces::4spaces::4spaces::4spaces:lat = float(latlon.group(2)) + latOffset
:4spaces::4spaces::4spaces::4spaces::4spaces:lon = float(latlon.group(4)) + lonOffset
:4spaces::4spaces::4spaces::4spaces::4spaces:writer.write(latlon.group(1)+str(lat)+latlon.group(3)+str(lon)+latlon.group(5))
:4spaces::4spaces::4spaces::4spaces:else:
:4spaces::4spaces::4spaces::4spaces::4spaces:writer.write(line)

:4spaces::4spaces::4spaces::4spaces:line = reader.readline()
:4spaces::4spaces:finally:
:4spaces::4spaces::4spaces:reader.close()
:4spaces::4spaces::4spaces:writer.close()

Yesterday completely off. Today 30 min walk - GPS+ Galileo exactly on track. Alsace/France

Looks like the issue was sorted for new runs. I am off today but my 945 is showing CPE as Current (yesterday was expired).

On the 1st my run was fine, yesterday, 2nd, it started fine but on my way back (same route just eventually the opposite side of the road) it was way off. I am taking the day off but may go for a walk later just to confirm.

The path on my walk yesterday (in Chicago) was way off, just like my walk on New Year's day.

However, the distance/mileage seems to be accurate, but it's hard to know.

Is this a Sony chip issue (as it seems that only newer Garmins and some other non-Garmin devices are affected), or software?

This is fantastic jmto. I actually got it to work this morning. I was still getting some type of error but it did spit out an output file and the offset worked perfectly! Thank you so much!

Well, thank DavidJJones for making it.

My opinion is that is pointless and it will not fix the tracks properly as my errors doesn't seem to constantly enough broken as the start and end points differ and they should be the same, but of course YMMV.

“Pointless” is a bit harsh...it fixed three people’s runs in a few minutes, but I accept it’s not a cure all.

Incidentally, my CPE on a forerunner 945 is now “Current”, so we can all return to as we were.

I wouldn't recommend updating until Garmin fixes the issue. I just updated on Jan 1st and Ive had GPS accuracy problems too. 

Long runs are still affected. My friend's GPS track. At the beginning everything was OK, at the end it shifted him 4 km North. Also elevation is 1500 metres, it should be 50 meters.