Utilizing Virtual File Systems (vsi) and Well Known Text (WKT) to access the 'nominal orbits'

vsi_nominal_orbits_wkt(
  orbit_area,
  track = "GT7",
  rgt_repeat = 1,
  wkt_filter = NULL,
  download_method = "curl",
  download_zip = FALSE,
  verbose = FALSE
)

Arguments

orbit_area: a character string specifying the earth partition to use, it can be one of 'antarctic', 'arctic', 'western_hemisphere' and 'eastern_hemisphere'
track: a character string specifying the orbit track. Can be one of 'GT1L','GT1R','GT2L','GT2R','GT3L','GT3R' or 'GT7'
rgt_repeat: an integer specifying the orbit repeat. This parameter defaults to 1 and it is relevant if a user chooses one of the 'western_hemisphere' or 'eastern_hemisphere' where there are 8 orbit repeats, whereas for the 'antarctic' and 'arctic' there is only 1 repeat
wkt_filter: either NULL, or a Well Known Text (WKT) character string to allow a user to restrict to an area of interest rather than processing all data (this parameter will be used as input to the 'sf::st_read()' function)
download_method: a character string specifying the download method. Corresponds to the 'method' parameter of the 'utils::download.file()' function. Can be one of 'internal', 'wininet' (Windows only), 'libcurl', 'wget', 'curl' or 'auto'
download_zip: a boolean. If TRUE the .zip file will be first downloaded and then the .kml files will be returned, otherwise the 'gdalinfo' function will be used as input to the R 'system2()' function to read the .kml files without downloading the .zip file. The 'gdalinfo' command requires that the user has configured GDAL properly. Set the parameter 'download_zip' to TRUE if GDAL is not (properly) installed.
verbose: a boolean. If TRUE then information will be printed out in the console

Value

an 'sf' object

References

https://icesat-2.gsfc.nasa.gov/science/specs

https://gdal.org/user/virtual_file_systems.html

Examples


if (FALSE) {

require(IceSat2R)
require(magrittr)

#......................................
# processing all data of the orbit area
#......................................

dat_rgt = vsi_nominal_orbits_wkt(orbit_area = 'eastern_hemisphere',
                                 track = 'GT7',
                                 rgt_repeat = 1,
                                 wkt_filter = NULL,
                                 download_method = 'curl',
                                 download_zip = FALSE,
                                 verbose = TRUE)
str(dat_rgt)


#...........................................
# extracting nominal orbits only for the WKT
#...........................................

WKT = 'POLYGON ((-14.765 18.979, -11.25 18.979, -11.25 21.943, -14.765 21.943, -14.765 18.979))'

dat_rgt = vsi_nominal_orbits_wkt(orbit_area = 'western_hemisphere',
                                 track = 'GT3R',
                                 rgt_repeat = 8,
                                 wkt_filter = WKT,
                                 download_method = 'curl',
                                 download_zip = FALSE,
                                 verbose = TRUE)
str(dat_rgt)
dat_rgt[[1]]$RGT                 # Reference Ground Tracks of input WKT

#.............................
# Visualize the results
# (first compute the centroid)
#.............................

wkt_sf = sf::st_as_sfc(WKT, crs = 4326)
centr_wkt = sf::st_coordinates(sf::st_centroid(wkt_sf))

RGTs = mapview::mapview(dat_rgt, legend = F)
AOI_wkt = mapview::mapview(wkt_sf, legend = F)

lft = RGTs + AOI_wkt
lft@map %>% leaflet::setView(lng = centr_wkt[, 'X'],
                             lat = centr_wkt[, 'Y'],
                             zoom = 7)
}