IceSat2R (version 1.0.7)

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

Description

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

Usage

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

Value

an 'sf' object

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

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 = as.numeric(centr_wkt[, 'X']),
                             lat = as.numeric(centr_wkt[, 'Y']),
                             zoom = 7)
}