1 files changed, 51 insertions, 0 deletions
diff --git a/fietsboek/convert.py b/fietsboek/convert.py
new file mode 100644
index 0000000..bf0664a
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+++ b/fietsboek/convert.py
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+"""Conversion functions to convert between various recording formats."""
+import fitparse
+from gpxpy.gpx import GPX, GPXTrack, GPXTrackPoint, GPXTrackSegment
+
+FIT_RECORD_FIELDS = ["position_lat", "position_long", "altitude", "timestamp"]
+
+
+def semicircles_to_deg(circles: int) -> float:
+    """Convert semicircles coordinate to degree coordinate.
+
+    :param circles: The coordinate value in semicircles.
+    :return: The coordinate in degrees.
+    """
+    return circles * (180 / 2**31)
+
+
+def from_fit(data: bytes) -> GPX:
+    """Reads a .fit as GPX data.
+
+    This uses the fitparse_ library under the hood.
+
+    .. _fitparse: https://pypi.org/project/fitparse/
+
+    :param data: The input bytes.
+    :return: The converted structure.
+    """
+    fitfile = fitparse.FitFile(data)
+    points = []
+    for record in fitfile.get_messages("record"):
+        values = record.get_values()
+        try:
+            if any(values[field] is None for field in FIT_RECORD_FIELDS):
+                continue
+            point = GPXTrackPoint(
+                latitude=semicircles_to_deg(values["position_lat"]),
+                longitude=semicircles_to_deg(values["position_long"]),
+                elevation=values["altitude"],
+                time=values["timestamp"],
+            )
+        except KeyError:
+            pass
+        else:
+            points.append(point)
+    track = GPXTrack()
+    track.segments = [GPXTrackSegment(points)]
+    gpx = GPX()
+    gpx.tracks = [track]
+    return gpx
+
+
+__all__ = ["from_fit"]