mf_download_data: Download several datasets given their URLs and destination...

In modisfast: Fast and Efficient Access to MODIS Earth Observation Data

Download several datasets given their URLs and destination path

Description

This function enables to download datasets. In a data import workflow, this function is typically used after a call to the mf_get_url function. The output value of mf_get_url can be used as input of parameter df_to_dl of mf_download_data.

The download can the parallelized.

Usage

mf_download_data(
  df_to_dl,
  path = tempfile("modisfast_"),
  parallel = FALSE,
  num_workers = parallel::detectCores() - 1,
  credentials = NULL,
  verbose = TRUE,
  min_filesize = 5000
)

Arguments

df_to_dl	data.frame. Urls and destination files of dataset to download. Typically output of mf_get_url. See Details for the structure
path	string. Target folder for the data to download. Default : temporary folder.
parallel	boolean. Parallelize the download ? Default to FALSE
num_workers	integer. Number of workers in case of parallel download. Default to number of workers available in the machine minus one.
credentials	vector string of length 2 with username and password. optional if the function mf_login was previously executed.
verbose	boolean. optional. Verbose (default TRUE)
min_filesize	integer. Minimum file size expected (in bites) for one file downloaded. If files downloaded are less that this value, the files will be downloaded again. Default 5000.

Details

Parameter df_to_dl must be a data.frame with the following minimal structure :

id_roi

An id for the ROI (character string)

collection

Collection (character string)

name

url

URL of the file to download (character string)

Value

a data.frame with the same structure of the input data.frame df_to_dl + columns providing details of the data downloaded. The additional columns are :

fileDl

Booloean (dataset downloaded or failure)

dlStatus

Download status : 1 = download ok ; 2 = download error ; 3 = dataset was already existing in destination file

fileSize

File size on disk

Examples

## Not run: 

### Login to EOSDIS Earthdata with your username and password
log <- mf_login(credentials = c("earthdata_un","earthdata_pw"))

### Set-up parameters of interest
coll <- "MOD11A1.061"

bands <- c("LST_Day_1km","LST_Night_1km")

time_range <- as.Date(c("2017-01-01","2017-01-30"))

roi <- sf::st_as_sf(data.frame(
id = "roi_test",
geom="POLYGON ((-5.82 9.54, -5.42 9.55, -5.41 8.84, -5.81 8.84, -5.82 9.54))"),
wkt="geom",crs = 4326)

### Get the URLs of the data
(urls_mod11a1 <- mf_get_url(
collection = coll,
variables = bands,
roi = roi,
time_range = time_range
))

### Download the data
res_dl <- mf_download_data(urls_mod11a1)

### Import the data as terra::SpatRast
modis_ts <- mf_import_data(dirname(res_dl$destfile[1]), collection = coll)

### Plot the data
terra::plot(modis_ts)


## End(Not run)

modisfast documentation built on Sept. 11, 2024, 8:15 p.m.