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Mapping GPX tracks from AAT for Android, in R

DATE: 2018-04-28

AUTHOR: John L. Godlee

I stopped using Strava to track my cycle rides, because I didn't feel comfortable giving away all that GPS data to a third party. I know lots of other things I do give away my location, but this is a small step in the right direction. It also prompted me to play with new GPS tracking apps.

The one I have settled on is called AAT[1], which is a lovely brutalist piece of open source software that is designed around tracking cycling.

1: https://f-droid.org/en/packages/ch.bailu.aat/

It stores tracks as GPX files, which can then be manipulated and plotted in other softwares. In this case, I wanted to use R. The script is below and here[2] and an example GPX file from AAT can be found here[3].

2: /files/gpx/import_gpx_tracks.R

3: /files/gpx/2018_04_19_0.gpx

Note that you may have to install ggmap from the github repository like this: devtools::install_github("dkahle/ggmap"), as the CRAN mirror is often way behind.

# Packages ----
library(rgdal)  # readOGR(), ogrListLayers()
library(ggplot2)  # ggplot()
library(ggmap)  # get_map(), ggmap()

# setwd ----
setwd("~/tracks")

# Import file ----
# Find out what layers are in the file
(layers <- ogrListLayers("2018_04_19_0.gpx"))

# Import the points layer, which contains elevation data
track_points <- readOGR("2018_04_19_0.gpx", layer = layers[5])
# Import the tracks layer as a spatiallinesdataframe

# Test plot
plot(track_points)

# Transform data to data frame for plotting ----
# Create data frame from spatial object
track_df <- data.frame(track_points@coords, 
    track_points$ele, 
    track_points$time,
    track_points$track_seg_point_id)

# Rename columns
names(track_df) <- c("lon", "lat", "elev", "time", "seg_id")

# Convert time to posixCT
track_df$time_posix <- track_df$time %>%
    as.POSIXct(., format = "%Y/%m/%d %H:%M:%S ")

# Create plots ----
# Create elevation plot
(elev_plot <- ggplot(track_df, aes(x = time_posix, y = elev)) + 
    geom_point() + 
    geom_smooth(method = "loess", span = 0.1) + 
    scale_x_datetime() + 
    theme_classic() + 
    xlab("Elevation (m)") + 
    ylab("Time"))

# Plot map using ggmap
goog_map <- get_map(location = track_points@bbox, 
    zoom = 15, 
    maptype = "roadmap", color = "bw")

(route_map <- ggmap(goog_map) + 
    geom_path(data = track_df,
    aes(colour = elev), size = 1.5) + 
    scale_color_gradientn(colours = rainbow(4)) +
    guides(colour = guide_colourbar(title="Elevation (m)")) + 
    xlab("Longitude") + 
    ylab("Latitude"))

The script outputs an elevation plot and a map which shows the track, coloured by elevation.

Elevation profile

Route map