ee_imagecollection_to_local: Save an EE ImageCollection to the local system.

Description

Save an EE ImageCollection to the local system.

Usage

ee_imagecollection_to_local(
  ic,
  region,
  dsn = NULL,
  via = "drive",
  container = "rgee_backup",
  scale = NULL,
  maxPixels = 1e+09,
  lazy = FALSE,
  public = TRUE,
  add_metadata = TRUE,
  timePrefix = TRUE,
  quiet = FALSE,
  ...
)

Value

If add_metadata is FALSE, ee_imagecollection_to_local will return a character vector containing the filename of the images downloaded. Otherwise, if add_metadata is TRUE, will return a list with extra information related to the exportation (see details).

Arguments

ic: ee$ImageCollection to be saved to the system.
region: EE Geometry (ee$Geometry$Polygon). The CRS needs to be the same that the ic argument. Otherwise, it will be forced.
dsn: Character. Output filename. If missing, a temporary file will be created for each image.
via: Character. Method to export the image. Two methods are available: "drive", "gcs". See details.
container: Character. Name of the folder ('drive') or bucket ('gcs') to be exported into (ignored if via is not defined as "drive" or "gcs").
scale: Numeric. The resolution in meters per pixel. Defaults to the native resolution of the image.
maxPixels: Numeric. The maximum allowable number of pixels in the exported image. If the exported region covers more pixels than the specified limit in the given projection, the task will fail. Defaults to 100,000,000.
lazy: Logical. If TRUE, a future::sequential object is created to evaluate the task in the future. See details.
public: Logical. If TRUE, a public link to the image is created.
add_metadata: Add metadata to the stars_proxy object. See details.
timePrefix: Logical. Add current date and time (Sys.time()) as a prefix to export files. This parameter helps to avoid exporting files with the same name. By default TRUE.
quiet: Logical. Suppress info message
...: Extra exporting argument. See ee_image_to_drive and

Details

ee_imagecollection_to_local supports the download of ee$Images using two different options: "drive" (Google Drive) and "gcs" ( Google Cloud Storage). In both cases, ee_imagecollection_to_local works as follow:

1. A task is initiate (i.e., ee$batch$Task$start()) to transfer the ee$Image from Earth Engine to the intermediate container specified in the argument via.
2. If the argument lazy is TRUE, the task will not be monitored. This is useful to lunch several tasks simultaneously and calls them later using ee_utils_future_value or future::value. At the end of this step, the ee$Images are stored on the path specified in the argument dsn.
3. Finally, if the add_metadata argument is set to TRUE, a list containing the following elements will be appended to the dsn argument.
- if via is "drive":
  - ee_id: Name of the Earth Engine task.
  - drive_name: Name of the Image in Google Drive.
  - drive_id: Id of the Image in Google Drive.
  - drive_download_link: Download link to the image.
- if via is "gcs":
  - ee_id: Name of the Earth Engine task.
  - gcs_name: Name of the Image in Google Cloud Storage.
  - gcs_bucket: Name of the bucket.
  - gcs_fileFormat: Format of the image.
  - gcs_public_link: Download link to the image.
  - gcs_URI: gs:// link to the image.

For getting more information about exporting data from Earth Engine, take a look at the Google Earth Engine Guide - Export data.

Examples

Run this code

if (FALSE) {
library(rgee)
library(raster)
ee_Initialize(drive = TRUE, gcs = TRUE)

# USDA example
loc <- ee$Geometry$Point(-99.2222, 46.7816)
collection <- ee$ImageCollection('USDA/NAIP/DOQQ')$
  filterBounds(loc)$
  filterDate('2008-01-01', '2020-01-01')$
  filter(ee$Filter$listContains("system:band_names", "N"))

# From ImageCollection to local directory
ee_crs <- collection$first()$projection()$getInfo()$crs
geometry <- collection$first()$geometry(proj = ee_crs)$bounds()
tmp <- tempdir()

## Using drive
# one by once
ic_drive_files_1 <- ee_imagecollection_to_local(
  ic = collection,
  region = geometry,
  scale = 250,
  dsn = file.path(tmp, "drive_")
)

# all at once
ic_drive_files_2 <- ee_imagecollection_to_local(
  ic = collection,
  region = geometry,
  scale = 250,
  lazy = TRUE,
  dsn = file.path(tmp, "drive_")
)

# From Google Drive to client-side
doqq_dsn <- ic_drive_files_2 %>% ee_utils_future_value()
sapply(doqq_dsn, '[[', 1)
}