IceSat2R (version 1.0.7)

getTracks: Get the ICESAT-2 Tracks

Description

Get a list of ICESat-2 tracks using a bounding box as input

Usage

getTracks(
  minx,
  miny,
  maxx,
  maxy,
  date,
  outputFormat = "csv",
  download_method = "curl",
  verbose = FALSE
)

Value

either a data.table (if outputFormat is 'csv') or a nested list (if outputFormat is 'json')

Arguments

minx

the 'minx' parameter of the bounding box

miny

the 'miny' parameter of the bounding box

maxx

the 'maxx' parameter of the bounding box

maxy

the 'maxy' parameter of the bounding box

date

a character string specifying the Data collection date in the format 'yyyy-MM-dd' (such as '2020-01-01')

outputFormat

a character string specifying the output format of the downloaded data. One of 'csv' or 'json'

download_method

a character string specifying the download method to use. Can be one of 'internal', 'wininet' (Windows only), 'libcurl', 'wget', 'curl' or 'auto'. For more information see the documentation of the 'utils::download.file()' function

verbose

a boolean. If TRUE then information will be printed out in the console

References

https://openaltimetry.earthdatacloud.nasa.gov

https://nsidc.org/data/icesat-2

Examples

if (FALSE) {

require(IceSat2R)
require(magrittr)
require(sf)

sf::sf_use_s2(use_s2 = FALSE)

#..........................................................
# In case we are interested to find the ICESat-2 tracks for
#     - a specific area (or bounding box)
#     - a specific time interval (close to September 2021)
#..........................................................

#...............
# Ice sheet area
#...............

data(ne_10m_glaciated_areas)

ice_sheet = 'Kluane Ice Cap'

ice_sheet_geom = ne_10m_glaciated_areas %>%
  subset(!is.na(name)) %>%
  subset(name == ice_sheet)

ice_sheet_geom

#..............
# time interval
#..............

approx_date_start = "2021-09-05"
approx_date_end = "2021-09-20"

res_rgt_many = time_specific_orbits(date_from = approx_date_start,
                                    date_to = approx_date_end,
                                    RGT_cycle = NULL,
                                    download_method = 'curl',
                                    threads = parallel::detectCores(),
                                    verbose = TRUE)

res_rgt_many

# table(as.Date(res_rgt_many$Date_time))

#..............................................
# create the bounding box of the ice
# sheet so that I use the same area in the
# 'st_intersects()' and 'getTracks()' functions
# ('getTracks()' takes a bounding box as input)
#..............................................

bbx_ice_sheet = sf::st_bbox(obj = ice_sheet_geom)
sf_obj_ice_sheet = sf::st_as_sfc(bbx_ice_sheet)

#.........................................
# intersection of the Ice Sheet with
# the tracks for the specified time period
#.........................................

res_inters = sf::st_intersects(x = sf::st_geometry(sf_obj_ice_sheet),
                               y = sf::st_geometry(res_rgt_many),
                               sparse = TRUE)

#...........................................
# one or more intersected RGT's for the area
#...........................................

df_inters = data.frame(res_inters)
rgt_subs = res_rgt_many[df_inters$col.id, , drop = FALSE]


#.......................................................
# Keep the Date and the bounding box to
# verify with the 'getTracks()' function
# an alternative is to use the "verify_RGTs()" function
#.......................................................

for (item in 1:nrow(rgt_subs)) {

  dat_item = rgt_subs[item, , drop = F]
  Date = as.Date(dat_item$Date_time)

  op_tra = getTracks(minx = as.numeric(bbx_ice_sheet['xmin']),
                               miny = as.numeric(bbx_ice_sheet['ymin']),
                               maxx = as.numeric(bbx_ice_sheet['xmax']),
                               maxy = as.numeric(bbx_ice_sheet['ymax']),
                               date = as.character(Date),
                               outputFormat = 'csv',
                               download_method = 'curl',
                               verbose = FALSE)

  date_obj = dat_item$Date_time
  tim_rgt = glue::glue("Date: {date_obj} Time specific RGT: '{dat_item$RGT}'")

  if (nrow(op_tra) > 0) {
    iter_op_trac = paste(op_tra$track, collapse = ', ')
    cat(glue::glue("{tim_rgt}  OpenAltimetry: '{iter_op_trac}'"), '\n')
  }
  else {
    cat(glue::glue("{tim_rgt} without an OpenAltimetry match!"), '\n')
  }
}

}