Efficiently break-up network

[Robinlovelace]

We already have code to break up bits on the OSM network but this fails for the rnet use case:

# Aim: test breaking-up long linestrings

rnet = pct::get_pct_rnet("hereford-and-worcester")
rnet$length = as.numeric(sf::st_length(rnet))
#> Linking to GEOS 3.8.0, GDAL 3.0.4, PROJ 7.0.0
summary(rnet$length)
#>      Min.   1st Qu.    Median      Mean   3rd Qu.      Max. 
#>     0.133    54.516   190.069   552.491   514.810 15207.218

rnet = sf::st_transform(rnet, 27700)
rnet_updated = trafficalmr::osm_consolidate(rnet, segment = 500)
#> Error in trafficalmr::osm_consolidate(rnet, segment = 500): all(c("name", "ref", "highway") %in% n) is not TRUE

^{Created on 2020-10-27 by the reprex package (v0.3.0)}

Challenge: starting with the rnet object above, efficiently break up any lines over 500m.
Implementation based on new stplanr code is quite slow.

[Robinlovelace]

He's a reproducible example showing it working with the new stplanr function - a bit slow:

# Aim: test breaking-up long linestrings

library(sf)
library(stars)
library(dplyr)

rnet = pct::get_pct_rnet("hereford-and-worcester")
rnet$length = as.numeric(sf::st_length(rnet))
summary(rnet$length)

rnet = sf::st_transform(rnet, 27700)
r = raster::raster(rnet, resolution = 500)
raster::values(r) = 1
rast_template_polys = r %>% stars::st_as_stars() %>% sf::st_as_sf(as_points = FALSE)
rast_template_polys

system.time({
rnet_updated = trafficalmr::osm_consolidate(rnet, segment = 500)
})

rnet_long = rnet %>% filter(length > 1000)
summary(rnet_long$length)
system.time({
rnet_updated = stplanr::line_breakup(l = rnet_long, z = rast_template_polys)
})
summary(st_length(rnet_updated))

[Robinlovelace]

Update: using multithreaded code documented here r-spatial/qgisprocess#26

[Robinlovelace]

Multithreaded implementation in GRASS via the qgisprocess package did it in 5 minutes for the national route network.

Details: https://github.com/saferactive/saferactive/blob/master/code/tests/line_breakup_qgis.R#L92