[GIS] How to set time field when generating a GPX track with Python OGR

gpxogrpythontime

I want to generate a GPX file with Python OGR. In particular I want to generate a tracks (layer of features of OGR type wkbMultiLineString)

My script is below. I get the error ERROR 1: No such field: 'time'
Also it won't let me create a field time because it is a default field in GPX.

Any ideas how to solve that?

import ogr, osr

in_data_source = ogr.Open('test.geojson')
in_layer = in_data_source.GetLayer()
feature_count = in_layer.GetFeatureCount()

driver = ogr.GetDriverByName("GPX")
out_data_source = driver.CreateDataSource("t1.gpx")
srs = osr.SpatialReference()
srs.ImportFromEPSG(4326)
out_layer = out_data_source.CreateLayer("t1", srs, ogr.wkbMultiLineString)

line = ogr.Geometry(ogr.wkbLineString)

c = 0
while c in range(feature_count-1):
    print c
    f1 = in_layer.GetFeature(c)
    f2 = in_layer.GetFeature(c+1)
    g1 = f1.GetGeometryRef()
    g2 = f2.GetGeometryRef()

    line.AddPoint(g1.GetX(), g1.GetY())
    line.AddPoint(g2.GetX(), g2.GetY())
    time = f1.GetField("datetime")

    feature = ogr.Feature(out_layer.GetLayerDefn())
    # feature.SetField("time", time)
    feature.SetGeometry(line)
    out_layer.CreateFeature(feature)

    c += 1

This problem can also be solved by using the gpxpy library, though I am interested in solving it with OGR.

Best Answer

I'm not an expert regarding python + GDAL/OGR, but looking into something similar I found a possible answer to your question.

import ogr, osr
import fileinput
from datetime import datetime

srs = osr.SpatialReference()
srs.ImportFromEPSG(4326)

driver = ogr.GetDriverByName("GPX")

out = driver.CreateDataSource('/tmp/test.gpx')

# layer creation: if you use 'track_points', points are accepted
oL = out.CreateLayer("track_points", srs, ogr.wkbPoint)

# loop over tab-separated input stream with timestamps + lon + lat
for l in fileinput.input():
    (timest, lon, lat) = l.split('\t')

    # create point
    p = ogr.Geometry(ogr.wkbPoint)
    # initialise point with coordinates
    p.AddPoint(float(lon), float(lat))

    # prepare new "feature" using the layer's "feature definition", 
    # initialize it by setting geometry and necessary field values
    featureDefn = oL.GetLayerDefn()
    oF = ogr.Feature(featureDefn)
    oF.SetGeometry(p)
    oF.SetField("track_fid", "1")
    oF.SetField("track_seg_id", "1")    

    # adapt this according to the timestamp format of your data source
    timest = datetime.strptime(timest, '%m/%d/%Y %H:%M:%S').isoformat()
    oF.SetField("time", timest)
    oL.CreateFeature(oF)    

del(out)

The script reads tab-separated timestamps + longitude + latitude from the commandline or a file and writes to /tmp/test.gpx.

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