snapPointsToLines_enviroCar.Rmd

Map-Matching enviroCar trajectories to OSM roads
========================================================


```{r}
importEnviroCar = function(file) {
  require(rjson)  # fromJSON
  require(maptools)  # spCbind
  # read data as spatial object:
  features = readOGR(file, layer = "OGRGeoJSON")
  # convert time from text to POSIXct:
  features$time = as.POSIXct(features$time, format = "%Y-%m-%dT%H:%M:%SZ")
  # the third column is JSON, we want it in a table (data.frame) form: 1. form
  # a list of lists
  l1 = lapply(as.character(features$phenomenons), fromJSON)
  # 2. parse the $value elements in the sublist:
  l2 = lapply(l1, function(x) as.data.frame(lapply(x, function(X) X$value)))
  # bind these value elements, row by row, together
  ret = do.call(rbind, l2)
  # read the units:
  units = lapply(l1[1], function(x) as.data.frame(lapply(x, function(X) X$unit)))
  # add a units attribute to layer
  features$phenomenons = NULL
  # add the table as attributes to the spatial object
  if (length(features) == nrow(ret)) {
    features = spCbind(features, ret)
    attr(features, "units") = units[[1]]
    features
  } else NULL
}

require(RCurl)
require(rgdal)
require(maptools) #snapPointsToLines function
url <- "https://giv-car.uni-muenster.de/stable/rest/tracks/5207d871e4b058cd3d669afe"
layer = readOGR(getURL(url, ssl.verifypeer = FALSE), layer = "OGRGeoJSON")
# feature extracted OSM shape file containing subset of roads in Muenster
shape <- readOGR(dsn=".", layer="road_selection")
# points 
points <- importEnviroCar(url)
res <- snapPointsToLines(points, shape)
# plotting raw points 
plot(points, col="deepskyblue")
# adding OSM roads
plot(shape, add=TRUE)
# adding map matched points
plot(res, add=TRUE, col="red")

# sample code for using OSM and R (OSMAR) package
#library("osmar")
#src <- osmsource_api()
# center of Muenster with a 2km * 2km bounding box
#bb <- center_bbox(7.667724, 51.928308, 1500, 1500)
#bb <- corner_bbox(7.650558,51.927938,7.690977,51.935649)
# 7.557603,52.004258,7.689218,51.923227
# bbb <- corner_bbox(7.473833,52.06002,7.774362,51.840151)
# bbbb <- corner_bbox(7.557603,52.004258,7.689218,51.923227)
# creating osmar object from bounding box
#ms <- get_osm(bb, source = src)
# subset data: choose only 
# ms_hw_ids <- find(ms, way(tags(k == "highway")))
# transform from osmar object to sp object 
# ms_as_sp <- as_sp(ms, what = c("points", "lines", "polygons"), crs = osm_crs(), simplify = TRUE)
# plot(ms_as_sp)
# create spatial lines data frame from ms_as_sp
# Sldf <- ms_as_sp$lines
# url to track in geosjon format

```