Distance-weighted landscape composition in buffers around point locations, computed directly from vector polygons.
Given point locations and land-cover polygons,
bufferscape returns for every point and every class the
exact area inside a buffer and a distance-decay weighted
effective area. Polygons may overlap. Point features are
counted separately, and distances to off-buffer reference features are
measured.
It is built for fine-scale work, where the relevant neighbourhood is tens to hundreds of metres and rasterising would destroy the features that matter – a 3 m alley, a 2 m water tank, the edge between a roof and a canopy. Typical designs:
| field | points | classes that matter |
|---|---|---|
| air-quality exposure, land-use regression | monitors, home addresses | road surface, industry, tree cover |
| environmental epidemiology | addresses in a cohort | greenspace, water, built surface |
| food environment | schools, homes | outlet types within walking distance |
| vector surveillance | ovitraps, light traps, tick drags | roofing, vegetation, standing water |
| WASH | water points, households | sanitation infrastructure, drainage |
| landscape ecology | camera traps, nest sites, quadrats | habitat classes, edge, canopy |
# install.packages("remotes")
remotes::install_github("mplanta-lab/bufferscape")library(bufferscape)
kml <- system.file("extdata", "example_site.kml", package = "bufferscape")
res <- buffer_composition(kml, radii = 50)
head(res$long[res$long$area_m2 > 0, c("label_en", "area_m2", "area_w")])Any radius works; scale bars on the figures adapt.
res <- buffer_composition(kml, radii = c(100, 250, 500), lambda = 300)A whole folder at once, writing a workbook, maps and charts:
out <- batch_composition("path/to/kml", radii = c(20, 30, 40, 50))Weighting a polygon by the distance to its centroid is cheap and, for compact features, harmless. For an elongated feature passing close to the point it is not: the centroid can sit almost on the point while most of the polygon lies far away, so the entire area is weighted as if adjacent.
Measured on real data, the centroid approximation overstates the
weighted area of a road passing beside the sampling point by up to
45%, while compact roofs stay under 1%. Roads, drainage
channels, alleys, rivers and field margins are exactly the geometry that
breaks it, and usually the features of interest.
bufferscape integrates the kernel over each polygon and
reports the centroid version alongside, so the bias can be quantified
rather than assumed away.
Four schemes, or your own colours:
map_composition(res, "SITE_1", palette = "aerial") # appearance-matched
map_composition(res, "SITE_1", palette = "colorblind") # colour-vision-safe
map_composition(res, "SITE_1", palette = "greyscale") # print
map_composition(res, "SITE_1", palette = c("7" = "#FF00FF"))A palette of 29 nominal colours cannot be made safe for colour-vision
deficiency; the space is not large enough. The "colorblind"
scheme therefore uses colour for the coarse group only
and separates members within a group by lightness and texture, so no
class depends on hue alone. Counting texture as a cue, it leaves
0 of 406 class pairs ambiguous under simulated
deuteranopia, against 3 for the appearance-matched palette and 11 for
viridis.
Maps and charts take the same palette argument, so a
figure pair can be made to match.
write_composition_report(res, "out.xlsx",
radii = c(30, 50),
metrics = c("exact", "weighted"),
digits = 2)metrics matters: carrying all four metrics for 29
classes is 126 columns. Dropping the centroid comparison when you are
not doing the methods analysis roughly halves that.
bias <- centroid_bias(kml, radii = 50)
summarise_centroid_bias(bias) # by polygon geometryown <- data.frame(
id = 1:3,
category = c("water", "built", "vegetation"),
description = c("pond", "roof", "canopy"),
fill = c("#2C7FB8", "#BDBDBD", "#31A354")
)
res <- buffer_composition(kml, categories = own)Only id, category and
description are required.
validate_dictionary() checks a dictionary before a long
run. The 29-class schema used in the worked example ships as
mare_categories.
citation("bufferscape")Archived on Zenodo: https://doi.org/10.5281/zenodo.21577714
That is the concept DOI and always resolves to the most recent version. Cite it unless you need to point at one specific release, in which case use the version DOI shown on that release’s Zenodo record.
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