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Download airphoto files from BC Data Catalogue URLs

Source: R/fly_fetch.R
fly_fetch.Rd

Downloads thumbnail images, flight logs, camera calibration reports, or geo-referencing files for selected airphotos. The URL columns must be present in the input data (available from the full BC Data Catalogue centroid layer).

Usage

fly_fetch(
  photos_sf,
  type = "thumbnail",
  dest_dir = "photos",
  overwrite = FALSE,
  workers = 1
)

Arguments

photos_sf

An sf object with airphoto metadata, typically output from fly_select() or fly_filter(). Must contain the relevant URL column for the requested type.

type

File type to download. One of "thumbnail", "flight_log", "calibration", or "georef".

dest_dir

Directory to save downloaded files. Created if it does not exist.

overwrite

If FALSE (default), skip files that already exist in dest_dir.

workers

Number of parallel download workers. 1 (default) runs sequentially. Values greater than 1 use furrr::future_map_dfr() with future::multisession — requires furrr and future packages.

Value

A tibble with columns airp_id, url, dest, and success.

Details

URL column mapping:

  • "thumbnail" → thumbnail_image_url

  • "flight_log" → flight_log_url

  • "calibration" → camera_calibration_url

  • "georef" → patb_georef_url

Photos with missing (NA or empty) URLs are skipped and reported as success = FALSE in the output.

When workers > 1, a future::multisession plan is set for the duration of the call and restored on exit. Each download is independent so parallelism is safe.

Examples

centroids <- sf::st_read(system.file("testdata/photo_centroids.gpkg", package = "fly"))
#> Reading layer `photo_centroids' from data source 
#>   `/home/runner/work/_temp/Library/fly/testdata/photo_centroids.gpkg' 
#>   using driver `GPKG'
#> Simple feature collection with 20 features and 16 fields
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: -126.7631 ymin: 54.34512 xmax: -126.449 ymax: 54.47635
#> Geodetic CRS:  WGS 84

# Download thumbnails for first 2 photos
result <- fly_fetch(centroids[1:2, ], type = "thumbnail",
                    dest_dir = tempdir())
#> Downloaded 2 of 2 files
result
#> # A tibble: 2 × 4
#>   airp_id url                                                      dest  success
#>     <int> <chr>                                                    <chr> <lgl>  
#> 1  699370 https://openmaps.gov.bc.ca/thumbs/1968/bc5282/bc5282_17… /tmp… TRUE   
#> 2  699415 https://openmaps.gov.bc.ca/thumbs/1968/bc5282/bc5282_22… /tmp… TRUE