Assume I have recorded the following values during a bike trip. One such dataset has been recorded every 5 seconds:

timestamp, longitute, latitude, pulse rate, pedal frequency

What is the best way to store them in a GeoDjango application? I thought about using a model similar to the following.

class Measurement(models.Model):
    comment = models.CharField()

class MeasurementPoint(models.Model):
    measurement = models.ForeignKey(Measurement)
    timestamp = models.DateTimeField()
    point = models.PointField(srid=4326)
    pulse = models.IntegerField()
    pedal = models.IntegerField()

This works and I can query the measurement points. But now I want to display the bike trip on a map, so I have to convert the individual points to a LineString. How is this done? And how would it bit possible to use different colors to highlight for example the pulse rate with different colors?


Finally I came to the following solution using the geojson python package. Surely not the best way, but working...

The example below shows a view to get the measurement of the pulse as an array of LineStrings. Regions where the pulse is at the same level are aggregated to LineStrings.

def getPulseLineString(request):
    request_data = request.query_params
    measurementID = request_data['measurementID']
    points = MeasurementPoint.objects.filter(measurement=measurementID).
    features = []
    pulse = -1
    segments = []
    for p in points:
        if pulse == -1:
            pulse = p.pulse
            segments.append((p.geom.x, p.geom.y))
        elif p.pulse == pulse:
            segments.append((p.geom.x, p.geom.y))
            features.append(geojson.Feature(geometry=geojson.LineString(segments), properties={'pulse': pulse}))
        segments= []
        pulse = -1
    return Response(features, status=status.HTTP_200_OK, content_type='application/json')

Maybe it would be better to use the MakeLine functionality, but as I want to use a SQLite database this is not supported at the moment.

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