Narrow a query to within a specified area

Restrict results to those from a specified area using galah_geolocate(). Areas can be specified as either polygons or bounding boxes, depending on type. Alternatively, users can call the underlying functions directly via galah_polygon(), galah_bbox() or galah_radius(). It is possible to use sf syntax by calling st_crop(), which is synonymous with galah_polygon().

Use a polygon If calling galah_geolocate(), the default type is "polygon", which narrows queries to within an area supplied as a POLYGON or MULTIPOLYGON. Polygons must be specified as either an sf object, a 'well-known text' (WKT) string, or a shapefile. Shapefiles must be simple to be accepted by the ALA.

Usage

galah_geolocate(..., type = c("polygon", "bbox", "radius"))

galah_bbox(...)

galah_polygon(...)

galah_radius(...)

# S3 method for data_request
st_crop(x, y, ...)

Arguments

...

a single sf object, WKT string or shapefile. Bounding boxes can be supplied as a tibble/data.frame or a bbox

type

string: one of c("polygon", "bbox"). Defaults to "polygon". If type = "polygon", a multipolygon will be built via galah_polygon(). If type = "bbox", a multipolygon will be built via galah_bbox(). The multipolygon is used to narrow a query to the ALA.

x

An object of class data_request, created using galah_call()

y

A valid Well-Known Text string (wkt), a POLYGON or a MULTIPOLYGON

Value

If type = "polygon" or type = "bbox", length-1 string (class character) containing a multipolygon WKT string representing the area provided. If type = "radius", list of lat, long and radius values.

Details

Use a bounding box Alternatively, set type = "bbox" to narrow queries to within a bounding box. Bounding boxes can be extracted from a supplied sf object or a shapefile. A bounding box can also be supplied as a bbox object (via sf::st_bbox()) or a tibble/data.frame.

Use a point radius Alternatively, set type = "radius" to narrow queries to within a circular area around a specific point location. Point coordinates can be supplied as latitude/longitude coordinate numbers or as an sf object (sfc_POINT). Area is supplied as a radius in kilometres. Default radius is 10 km.

If type = "polygon", WKT strings longer than 10000 characters and sf objects with more than 500 vertices will not be accepted by the ALA. Some polygons may need to be simplified. If type = "bbox", sf objects and shapefiles will be converted to a bounding box to query the ALA. If type = "radius, sfc_POINT objects will be converted to lon/lat coordinate numbers to query the ALA. Default radius is 10 km.

Examples

if (FALSE) {
# Search for records within a polygon using a shapefile
location <- sf::st_read("path/to/shapefile.shp")
galah_call() |>
  galah_identify("vulpes") |>
  galah_geolocate(location) |>
  atlas_counts()
  
# Search for records within the bounding box of a shapefile
location <- sf::st_read("path/to/shapefile.shp")
galah_call() |>
  galah_identify("vulpes") |>
  galah_geolocate(location, type = "bbox") |>
  atlas_counts()

# Search for records within a polygon using an `sf` object
location <- "POLYGON((142.3 -29.0,142.7 -29.1,142.7 -29.4,142.3 -29.0))" |>
 sf::st_as_sfc()
galah_call() |>
  galah_identify("reptilia") |>
  galah_polygon(location) |>
  atlas_counts()
  
# Alternatively, we can use `st_crop()` as a synonym for `galah_polygon()`. 
# Hence the above example can be rewritten as:
request_data() |>
  identify("reptilia") |>
  st_crop(location) |>
  count() |>
  collect()
   
# Search for records using a Well-known Text string (WKT)
wkt <- "POLYGON((142.3 -29.0,142.7 -29.1,142.7 -29.4,142.3 -29.0))"
galah_call() |>
  galah_identify("vulpes") |>
  galah_geolocate(wkt) |>
  atlas_counts()

# Search for records within the bounding box extracted from an `sf` object
location <- "POLYGON((142.3 -29.0,142.7 -29.1,142.7 -29.4,142.3 -29.0))" |>
  sf::st_as_sfc()
galah_call() |>
  galah_identify("vulpes") |>
  galah_geolocate(location, type = "bbox") |>
  atlas_counts()

# Search for records using a bounding box of coordinates
b_box <- sf::st_bbox(c(xmin = 143, xmax = 148, ymin = -29, ymax = -28), 
                     crs = sf::st_crs("WGS84"))
galah_call() |>
  galah_identify("reptilia") |>
  galah_geolocate(b_box, type = "bbox") |>
  atlas_counts()

# Search for records using a bounding box in a `tibble` or `data.frame`
b_box <- tibble::tibble(xmin = 148, ymin = -29, xmax = 143, ymax = -21)
galah_call() |>
  galah_identify("vulpes") |>
  galah_geolocate(b_box, type = "bbox") |>
  atlas_counts()

# Search for records within a radius around a point's coordinates
galah_call() |>
  galah_identify("manorina melanocephala") |>
  galah_geolocate(lat = -33.7,
                  lon = 151.3,
                  radius = 5,
                  type = "radius") |>
  atlas_counts()

# Search for records with a radius around an `sf_POINT` object
point <- sf::st_sfc(sf::st_point(c(-33.66741, 151.3174)), crs = 4326)
galah_call() |>
  galah_identify("manorina melanocephala") |>
  galah_geolocate(point,
                  radius = 5,
                  type = "radius") |>
  atlas_counts()
}