[GIS] Converting polylines to raster, assigning value of total length of lines within cell

arcgis-10.2arcgis-desktoplinerasterization

I have a polyline shapefile representing a road network. I want to rasterise this data, with the resulting values in the raster showing the total length of lines that fall within the raster cell, similar to this question: Convert line shapefile to raster, value=total length of lines within cell – however I wish to use ArcGIS 10.2. The data is projected so the units will be metres.

I have attempted to do this via the polyline to raster tool (however the value assigned is the length of the whole segment) and also some spatial analyst tools such as line density (which requires a radius). I'm sure I am missing an easy way to do it but I can't seem to find it.

Best Answer

A way of doing this is this:

Create a vector grid using the fishnet tool to the required cell resolution.
Run the intersect tool, this will cut up your road network and attach the polygon ID to the cut road segments.
Run the summary statistics tool on your intersected data grouping by polygon ID and summing polyline length.
Join the summary table back to the vector grid by the ID. This attaches the summed polyline lengths to the grid. Where there are no polylines you'll have null entries.
Run the polygon to raster tool using the summed length field.

Related Solutions

R – Convert Line Shapefile to Raster with Total Length of Lines Within Cell

You can now do this with terra::rasterizeGeom

Example data:

library(terra)
v <- vect(system.file("ex/lux.shp", package="terra"))
r <- rast(v)

Solution:

x <- rasterizeGeom(v, r, "length")    
plot(x); lines(v)

The below is a solution with the older spatial packages. It is based on Jeffrey Evans' answer, but this one is much faster as it does not use rasterize

library(raster)
library(rgdal)
library(rgeos)

roads <- shapefile("TZA_roads.shp")
roads <- spTransform(roads, CRS("+proj=utm +zone=37 +south +datum=WGS84"))
rs <- raster(extent(roads), crs=projection(roads))
rs[] <- 1:ncell(rs)

# Intersect lines with raster "polygons" and add length to new lines segments
rsp <- rasterToPolygons(rs)
rp <- intersect(roads, rsp)
rp$length <- gLength(rp, byid=TRUE) / 1000
x <- tapply(rp$length, rp$layer, sum)
r <- raster(rs)
r[as.integer(names(x))] <- x

[GIS] Appending interpolated or nearest raster cell value to vector point on a cell with no data

I came up with another solution that works for me. I really didn't like the idea of converting a raster to a vector point layer.

I ended up using a conditional statement in the Raster Calculator to replace all NoData cells with a mean of nearby cells within a rectangle of a specified size. I found this solution on the ESRI Support page, HowTo: Remove and replace no data values within a raster using statistical information from the surrounding data values.

This allows me to use a value based on nearby cells up to a specified distance that I feel will still be reasonable, and then I will extract values to points from the new raster (I just need to put it all into Model Builder to iterate through a lot of them now). As you can see below, the bluish cells are the recalculated cells that now have a value associated with them (the original raster is displayed in gray-scale over the new raster here):

enter image description here

Best Answer

Related Solutions

R – Convert Line Shapefile to Raster with Total Length of Lines Within Cell

[GIS] Appending interpolated or nearest raster cell value to vector point on a cell with no data

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