intersect_points: Intersect environmental or contextual layers at a given a set of points (coordinates)

Description

This function allows the user to sample environmental/contextual layers at arbitrary locations. It complements the occurrences function, which allows values of the same set of layers to be downloaded at species occurrence locations. NOTE: Requests are currently processed in a *single queue* on the ALA servers. Processing times may be slow if there are many requests in the queue. Note also that the actual processing of batch requests is inherently slow: a large number of points may take quite some time. Be warned.

Usage

intersect_points(
  pnts,
  layers,
  SPdata.frame = FALSE,
  use_layer_names = TRUE,
  verbose = ala_config()$verbose
)

Arguments

pnts

numeric: vector of latitude/longitude pairs, or a 2 column data.frame or matrix of lat, lons. NOTE: the number of locations must be less than 100000

layers

string vector: ids of layers to be intersected. The list of possible layers is available from ala_fields("layers"). Names can be passed as full layer names (e.g. "Radiation - lowest period (Bio22)") rather than id ("el871"). Note: if more than one location has been provided in pnts, the number of layers must be less than 700

SPdata.frame

logical: should the output should be returned as a SpatialPointsDataFrame of the sp package or simply as a data.frame?

use_layer_names

logical: if TRUE, layer names will be used as column names in the returned data frame (e.g. "radiationLowestPeriodBio22"). Otherwise, layer id value will be used for column names (e.g. "el871")

verbose

logical: show additional progress information? [default is set by ala_config]

Value

A SpatialPointsDataFrame containing the intersecting data information. Missing data or incorrectly identified layer id values will result in NA data

References

The associated ALA web service: https://api.ala.org.au/#ws84

Descriptions of the spatial layers: https://spatial.ala.org.au/ws/layers/index/

Examples

Run this code

# NOT RUN {
 ## single point with multiple layers
 layers <- c("cl22", "cl23", "el773")
 pnts <- c(-23.1, 149.1)
 intersect_points(pnts, layers)

 ## equivalent direct web service call:
 ## https://spatial.ala.org.au/ws/intersect/cl22,cl23,el773/-23.1/149.1

 ## multiple points as a grid sampling multiple layers
 layers <- c("cl22", "cl23", "el773")
 pnts <- data.frame(expand.grid(lat=seq(-29, -19, by=2),
 lon=seq(130, 140, by=2)))
 intersect_points(pnts, layers)
# }