mthh / gepaf

Encode and decode the Google Encoded Polyline Algorithm Format

gepaf: Google Encoded Polyline Algorithm Format

Encode and decode the Google Encoded Polyline Algorithm Format

Usage

Encoding

> coords <- data.frame(lat = c(38.5, 40.7, 43.252),
+                      lon = c(-120.2, -120.95, -126.453))
> encpoly <- encodePolyline(coords)
> encpoly
[1] "_p~iF~ps|U_ulLnnqC_mqNvxq`@"

Decoding

> coords <- decodePolyline(enc_polyline = "_p~iF~ps|U_ulLnnqC_mqNvxq`@")
> coords
     lat      lon
1 38.500 -120.200
2 40.700 -120.950
3 43.252 -126.453

Notes :

• Performances can probably be tuned up
• Just a single file from which copy/paste the code

References :

Mostly a translation of http://github.com/mthh/polyline_ggl/ (itself a modest translation (i.g no GeoJSON wrapper, etc.) of other well known available implementations such as Node.js Mapbox one)

gepaf's Issues

Dataframe

Hi,

How can I use decodepolyline on a datraframe of encoded polylines ?
I would like to create a new column in the same dataframe.

Thks!

Precision problem?

seems to work with factor=6.

library(gepaf)
input <- structure(list(lat = c(52.5268482, 52.5151744, 52.5280282, 52.528001, 
                                52.5278625, 52.5278929, 52.5279303, 52.5280371,
                                52.5280326), 
                        lon = c(13.4106511, 13.3976472, 13.4267825, 13.426547, 
                                13.4267372, 13.4265403, 13.4265266, 13.4265794, 
                                13.4266821)), 
                   .Names = c("lat", "lon"), row.names = 90:98, 
                   class = "data.frame")
temp <- encodePolyline(df_coords = input, factor = 5)
output <- decodePolyline(enc_polyline = temp, factor = 5)
input
output

=> problem with the last row

temp2 <- encodePolyline(df_coords = input, factor = 6)
output2 <- decodePolyline(enc_polyline = temp2, factor = 6)
input
output2

seems to work as expected