https://www8.garmin.com/support/download_details.jsp?id=563
Garmin: GPSMAP 172C Updates & Downloads
garmin gpsmapupdatesdownloads
https://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?type=REFERENCE&bibcode=2018RNAAS...2..172C
2018RNAAS...2..172C