GPSlogger Kalman 4+

Record GPX tracks using Apple Watch with GPS, iPhone or iPad with GPS. The app uses Kalman filtering on the GPS and Altimeter data to improve accuracy.

Features direct 1-click export to Strava when the Strava app is installed on the iPhone, otherwise the Strava authentication form needs to be filled out for export.
Can import multiple tracks with different sampling rates.

MapKit is used to acquire GPS / GNSS location data.
On Apple Watch, HealthKit is used to acquire heart rate data and to export it into the Health app together with the workout activity.

RECORDING FEATURES
-Creates one GPX track with Kalman filtering and another one without. Kalman filtering for altitude can be disabled separately in case pressure sensor data is not reliable, e.g. wind pressure or water impact pressure.
-Works on iOS, iPadOS and watchOS. On watchOS, works either with GPS paired to iPhone or standalone.
-GPX tracks can be imported / exported with the Apple Files app, exported by email or directly via Strava. It also supports direct imports by opening any file with .gpx extension that is available locally on the device.
-Speed unit can be switched between km/h and knots.


ANALYSIS FEATURES
-Calculates polar plot and estimates wind direction based on symmetry.
-Calculates VMG (Velocity Made Good) on iOS and iPadOS
-Calculates / finds maximum speeds segments over 10m, 100m, 1000m and 1852m. As an option, finds segments with highest VMGs. Click on segment to show on map (iOS and iPadOS only).
-Calculates climb / decent.
-Calculates moving time
-Calculates average speed of whole session
-Calculates course
-Toggle data graph between speed, altitude, course, heart rate (if available) and horizontal accuracy
-Allows to select a segment with marker to calculate distance, time and average speed
-Shows x-axis as time elapsed from recording start or time of the day
-Allows to zoom out / in
-Allows to crop samples before and after to reduce the track log and save it
-Supports importing multiple tracks (iOS and iPadOS only) with overlay in the chart metric
-Supports import of GPX tracks with sub-second accuracy for the track points.
-Local GPX files (recorded or imported) can be renamed, deleted in the app and pinned for quicker access. Can also be filtered by file name.

WATCHOS EXTRA FEATURES
-The heart rate on watchOS uses linear interpolation between heart rate updates so that each GPS sample point will have a valid value in the GPX log. The frequency of the heart rate updates depends on workout intensity which is determined by watchOS.
-The workout will also appear in the iOS Fitness app together with the track log (HealthKit).
-The total distance is shown as a complication which updates every 60 seconds.
-Uses always-on display to display data. Data shown can be cycled by screen taps through different screens to trade amount of information against font size.
-Run-time (battery) is several hours with always-on display enabled. Can run even longer when the app is minimized.