Summarize GPS information in a regular grid#

This functionality of tracklib reduce the full dataset of GPS traces into a regular grid of summarized features. In each cell, n aggregated features (such as mean and standard deviation of speeds, number of traces, most frequent bearing …) are computed to produce a set of raster maps, which may be seen as a single image with n channels.

These process has been used in works presented in (1).

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Figure 1 : Workflow presented in (1) to produce raster images (5 meter-resolution grid)

Reference:(1) - Y. Méneroux and al. Convolutional Neural Network for Traffic Signal Inference based on GPS Traces. Proceedings of Spatial big data and machine learning in GIScience Workshop’18, August 28-31, 2018, Melbourne, Australia. GIScience.

Import de la librairie tracklib#

Il faut importer tracklib si la librairie n’est pas dans le python path

[1]:
# -*- coding: utf-8 -*-
import matplotlib.pyplot as plt
import os.path
import sys

#-------------------------------------------------------
# Import de tracklib
module_path = os.path.abspath(os.path.join('../../..'))
if module_path not in sys.path:
    sys.path.append(module_path)

import tracklib as trk

Chargement du jeu de traces#

The dataset comprises a set of 11862 GPS traces, located in Mitaka city (16 km2), suburbs of Tokyo (Japan).

[2]:
PATH = '../../../../../PROJET/FINI/MITAKA/DATA/mitaka/complet'
trk.ObsTime.setReadFormat("4Y-2M-2D 2h:2m:2s")
param = trk.TrackFormat({
    'ext': 'CSV',
    'id_E':2,
    'id_N':3,
    'id_T':1
})
collection = trk.TrackReader.readFromFile(PATH, param)
print ('Number of tracks: ' + str(collection.size()))
Number of tracks: 11872

Sélection des traces sur une zone restreinte de type Rectangle#

[3]:
import matplotlib.pyplot as plt

Xmin = 370250
Xmax = 371250
Ymin = 3949050
Ymax = 3950050

ll = trk.ENUCoords(Xmin, Ymin)
ur = trk.ENUCoords(Xmax, Ymax)
bbox = trk.Rectangle(ll, ur)

constraintBBox = trk.Constraint(shape = bbox, mode = trk.MODE_INSIDE, type=trk.TYPE_CUT_AND_SELECT)
selections = constraintBBox.select(collection)
print ('Number of tracks: ' + str(selections.size()))

for track in selections:
    if track.size() < 10:
        selections.removeTrack(track)
selections.plot('k')

plt.xlim((Xmin, Xmax))
plt.ylim((Ymin, Ymax))
plt.show()

print ('Number of tracks: ' + str(selections.size()))
collection = selections
Number of tracks: 3850
../_images/usecase_Summarize_6_1.png
Number of tracks: 3802

Raster de la moyenne des vitesses et de l’orientation de la plus fréquente par cellule#

Les AF seront calculées si elles n’ont pas encore été créées

Les scripts des deux AF qu’on prend existent déjà dans la librairie, sinon il aurait fallu les écrire

[4]:
# On crée l'AF speed
collection.addAnalyticalFeature(trk.speed)
collection.addAnalyticalFeature(trk.orientation)

af_algos = [trk.speed, trk.orientation]
cell_operators = [trk.co_avg, trk.co_dominant]

marge = 0
resolution = (5, 5)
raster = trk.summarize(collection, af_algos, cell_operators, resolution, marge)

Conversion des indicateurs en 8-bit grayscale#

Feature values are converted on a 8-bit grayscale.

[5]:
# the mean of speeds is distributed between 16 and 255
mapAvgSpeed = raster.getAFMap('speed#co_avg')
for i in range(raster.nrow):
    for j in range(raster.ncol):
        val = mapAvgSpeed.grid[i][j]
        if val != raster.getNoDataValue():
            if val > 25:
                mapAvgSpeed.grid[i][j] = 10
            else:
                mapAvgSpeed.grid[i][j] = 100 - val/25*90

# The dominance of orientations is discretized in 8 eight values
mapDominantOrientation = raster.getAFMap('orientation#co_dominant')
for i in range(raster.nrow):
    for j in range(raster.ncol):
        val = mapDominantOrientation.grid[i][j]
        if val != raster.getNoDataValue():
            if val == 1:
                mapDominantOrientation.grid[i][j] = 156
            elif val == 2:
                mapDominantOrientation.grid[i][j] = 218
            elif val == 3:
                mapDominantOrientation.grid[i][j] = 249
            elif val == 4:
                mapDominantOrientation.grid[i][j] = 187
            elif val == 5:
                mapDominantOrientation.grid[i][j] = 125
            elif val == 6:
                mapDominantOrientation.grid[i][j] = 63
            elif val == 7:
                mapDominantOrientation.grid[i][j] = 32
            elif val == 8:
                mapDominantOrientation.grid[i][j] = 94
            else:
                mapDominantOrientation.grid[i][j] = 0

Affichage#

[6]:
import matplotlib.pyplot as plt

# make an image, just to create the icon for the use case gallery
mapAvgSpeed.plotAsImage(novaluecolor='teal')
plt.show()
../_images/usecase_Summarize_12_0.png
[7]:
fig = plt.figure(figsize=(16, 8))

ax1 = fig.add_subplot(121)
mapAvgSpeed.plotAsImage(ax1, novaluecolor='teal')

ax2 = fig.add_subplot(122)
mapDominantOrientation.plotAsImage(ax2, novaluecolor='teal')
print ('')

../_images/usecase_Summarize_13_1.png