How to create spatial line dataframe from encoded polylines?

Question

I'm working with transportation network dataset and I want to import traffic speed data provided as JSON format.

I could read the data in R using read.scorata(). However, I couldn't covert it to a spatial dataframe to be used for further analysis. There is one field in the current dataframe which is encoded polyline. How can I convert using this field?

library(RSocrata)

#Loading only two rows for easy reproduction
Test_TSD <- read.socrata("https://data.cityofnewyork.us/resource/i4gi-tjb9.json?borough=Manhattan&id=225")

This package may help: https://cran.r-project.org/web/packages/googlePolylines/vignettes/sfencode.html — Brian, Aug 20 '19 at 18:48

score 3 · Accepted Answer · answered Sep 03 '19 at 00:27

library(googlePolylines) can decode those polylines into coordinates.

To convert to an sf object currently requires a couple of steps. (There are plans to make this part of the googlePolylines library)

coords <- googlePolylines::decode( Test_TSD$encoded_poly_line )

sfg <- lapply( coords, function(x) sf::st_linestring( x = as.matrix(x) ) )

sfc <- sf::st_sfc( sfg )

sf <- sf::st_as_sf( cbind( Test_TSD, sfc ) )

You now have a simple feature (sf) object. Given sf is the successor to sp you can stop here. But, if you still need the SpatialDataFrame you can do

sp <- as( sf, "Spatial" )

How to create spatial line dataframe from encoded polylines?

1 Answers1