Awesome
<!-- README.md is generated from README.Rmd. Please edit that file -->prepr <img src="man/figures/hex-prepr.png" align="right" height="139" />
<!-- badges: start --> <!-- badges: end -->An R package to repair broken GIS polygons using the
prepair
C++ library.
Installation
The prepair
C++ library need these two libraries to compile:
The R package prepr
solves the CGAL dependencies by shipping with a
subset of the CGAL header. We also use
rwinlib
to provide GDAL
on Windows in
order to build this package from source. You will need the latest
version of rtools
in
order to build the source code on Windows.
prepair
can also use these optional libraries:
They are disabled by default on Windows but required if you want to
build the package in a Linux/OS X environment. After installing all
these libraries, you can now install the development version of the
prepr
R package from Gitlab using
the remotes
R package with:
# install.packages("remotes")
remotes::install_gitlab("dickoa/prepr")
remotes::install_github("dickoa/prepr") ## mirror
A quick tutorial
This is a simple tutorial which shows you how to solve common problems we can find with polygons:
A ‘bowtie’ polygon:
library(prepr)
library(sf)
p1 <- st_as_sfc("POLYGON((0 0, 0 10, 10 0, 10 10, 0 0))")
st_is_valid(p1, reason = TRUE)
#> [1] "Self-intersection[5 5]"
p11 <- st_prepair(p1)
st_is_valid(p11)
#> [1] TRUE
st_as_text(p11)
#> [1] "MULTIPOLYGON (((0 0, 5 5, 0 10, 0 0)), ((5 5, 10 0, 10 10, 5 5)))"
par(mfrow = c(1, 2))
plot(p1, main = "RAW", col = "#D7722C")
plot(p11, main = "Repaired", col = "#D7722C")
<img src="man/figures/README-p1-1.svg" width="100%" />
Square with wrong orientation:
p2 <- st_as_sfc("POLYGON((0 0, 0 10, 10 10, 10 0, 0 0))")
st_is_valid(p2, reason = TRUE)
#> [1] "Valid Geometry"
plot(p2, main = "RAW", col = "#D7722C")
<img src="man/figures/README-p2-1.svg" width="100%" />
Inner ring with one edge sharing part of an edge of the outer ring:
p3 <- st_as_sfc("POLYGON((0 0, 10 0, 10 10, 0 10, 0 0),(5 2, 5 7, 10 7, 10 2, 5 2))")
st_is_valid(p3, reason = TRUE)
#> [1] "Self-intersection[10 2]"
p33 <- st_prepair(p3)
st_is_valid(p33)
#> [1] TRUE
st_as_text(p33)
#> [1] "POLYGON ((0 0, 10 0, 10 2, 5 2, 5 7, 10 7, 10 10, 0 10, 0 0))"
par(mfrow = c(1, 2))
plot(p3, main = "RAW", col = "#D7722C")
plot(p33, main = "Repaired", col = "#D7722C")
<img src="man/figures/README-p3-1.svg" width="100%" />
Dangling edge:
p4 <- st_as_sfc("POLYGON((0 0, 10 0, 15 5, 10 0, 10 10, 0 10, 0 0))")
st_is_valid(p4, reason = TRUE)
#> [1] "Self-intersection[15 5]"
p44 <- st_prepair(p4)
st_is_valid(p44)
#> [1] TRUE
st_as_text(p44)
#> [1] "POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))"
par(mfrow = c(1, 2))
plot(p4, main = "RAW", col = "#D7722C")
plot(p44, main = "Repaired", col = "#D7722C")
<img src="man/figures/README-p4-1.svg" width="100%" />
Two adjacent inner rings:
p6 <- st_as_sfc("POLYGON((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 1 8, 3 8, 3 1, 1 1), (3 1, 3 8, 5 8, 5 1, 3 1))")
st_is_valid(p6, reason = TRUE)
#> [1] "Self-intersection[3 8]"
p66 <- st_prepair(p6)
st_is_valid(p66)
#> [1] TRUE
st_as_text(p66)
#> [1] "POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 1 8, 3 8, 5 8, 5 1, 3 1, 1 1))"
par(mfrow = c(1, 2))
plot(p6, main = "RAW", col = "#D7722C")
plot(p66, main = "Repaired", col = "#D7722C")
<img src="man/figures/README-p6-1.svg" width="100%" />
Polygon with an inner ring inside another inner ring:
p7 <- st_as_sfc("POLYGON((0 0, 10 0, 10 10, 0 10, 0 0), (2 8, 5 8, 5 2, 2 2, 2 8), (3 3, 4 3, 3 4, 3 3))")
st_is_valid(p7, reason = TRUE)
#> [1] "Holes are nested[3 3]"
p77 <- st_prepair(p7)
st_is_valid(p77)
#> [1] TRUE
st_as_text(p77)
#> [1] "MULTIPOLYGON (((0 0, 10 0, 10 10, 0 10, 0 0), (2 2, 2 8, 5 8, 5 2, 2 2)), ((3 3, 4 3, 3 4, 3 3)))"
par(mfrow = c(1, 2))
plot(p7, main = "RAW", col = "#D7722C")
plot(p77, main = "Repaired", col = "#D7722C")
<img src="man/figures/README-p7-1.svg" width="100%" />
<!-- ## A exemple with a real dataset -->
<!-- ### Reading the data -->
<!-- ```{r read_data, cache = TRUE} -->
<!-- (clc1 <- read_sf("https://github.com/tudelft3d/prepair/raw/master/data/CLC2006_180927.geojson")) -->
<!-- (clc2 <- read_sf("https://github.com/tudelft3d/prepair/raw/master/data/CLC2006_2018418.geojson")) -->
<!-- par(mfrow = c(1, 2)) -->
<!-- plot(st_geometry(clc1), main = "CLC2006_180927", col = 'lightblue', axes = TRUE, graticule = TRUE, lwd = 0.2, cex.axis = 0.5) -->
<!-- plot(st_geometry(clc2), main = "CLC2006_2018418", col = "lightblue", axes = TRUE, graticule = TRUE, lwd = 0.2, cex.axis = 0.5) -->
<!-- ``` -->
<!-- ### Check if it's valid and repair it -->
<!-- ```{r clean_it, cache = TRUE} -->
<!-- st_is_valid(clc1, reason = TRUE) -->
<!-- (clc1_rpr <- st_prepair(clc1)) -->
<!-- st_is_valid(clc1_rpr) -->
<!-- st_is_valid(clc2, reason = TRUE) -->
<!-- (clc2_rpr <- st_prepair(clc2)) -->
<!-- st_is_valid(clc2_rpr) -->
<!-- ``` -->
<!-- ### How fast is `st_prepair` ? -->
<!-- `prepr::st_prepair` is fast and can be in some cases faster than `sf::st_make_valid` -->
<!-- ```{r bench, cache = TRUE} -->
<!-- (bnch1 <- bench::mark(st_make_valid(clc1), st_prepair(clc1), check = FALSE)) -->
<!-- summary(bnch1, relative = TRUE) -->
<!-- (bnch2 <- bench::mark(st_make_valid(clc2), st_prepair(clc2), check = FALSE)) -->
<!-- summary(bnch2, relative = TRUE) -->
<!-- ``` -->
<!-- You also have cases where it's slower to `sf::st_make_valid`, let's use this data from a [closed issue](https://github.com/r-spatial/sf/issues/1280) in the `sf` R package. -->
<!-- ```{r new_data, cache = TRUE} -->
<!-- ## need vsicurl -->
<!-- (agb <- read_sf("/vsicurl/http://files.hawaii.gov/dbedt/op/gis/data/2015AgBaseline.shp.zip")) -->
<!-- all(st_is_valid(agb)) -->
<!-- all(st_is_valid(st_make_valid(agb))) -->
<!-- all(st_is_valid(st_prepair(agb))) -->
<!-- plot(st_geometry(agb), main = "2015 Agriculture baseline", col = 'lightblue', axes = TRUE, graticule = TRUE, lwd = 0.2, cex.axis = 0.5) -->
<!-- ``` -->
<!-- `sf::st_make_valid` is faster with this data. -->
<!-- ```{r bench2, cache = TRUE} -->
<!-- (bnch3 <- bench::mark(st_make_valid(agb), st_prepair(agb), check = FALSE)) -->
<!-- summary(bnch3, relative = TRUE) -->
<!-- ``` -->
Details and how to cite
Details of how we automatically repair broken polygons, and what results
you can expect, are available in this scientific article by the original
authors of prepair
:
Ledoux, H., Arroyo Ohori, K., and Meijers, M. (2014). A triangulation-based approach to automatically repair GIS polygons. Computers & Geosciences 66:121–131. [DOI] [PDF]
If you use the R package prepr
for a scientific project, please cite
their original work.
License
This package is released under the GPL-3 license.