mf_get_opt_param: Precompute the parameter 'opt_param' of the function...

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

Precompute the parameter opt_param of the function mf_get_url

Description

Precompute the parameter opt_param to further provide as input of the mf_get_url function. Useful to speed-up the overall processing time.

Usage

mf_get_opt_param(collection, roi, credentials = NULL, verbose = TRUE)

Arguments

collection	string. mandatory. Collection of interest (see details of mf_get_url).
roi	object of class sf. mandatory. Area of region of interest. Must be a Simple feature collection with geometry type POLYGON, composed of one or several rows (i.e. one or several ROIs), and with at least two columns: 'id' (an identifier for the roi) and 'geom' (the geometry).
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)

Details

When it is needed to loop the function mf_get_url over several time frames, it is advised to previously run the function mf_get_opt_param and provide the output as input opt_param parameter of the mf_get_url function. This will save much time, as internal parameters will be calculated only once.

Value

a list with the following named objects :

roiSpatialIndexBound

OPeNDAP indices for the spatial coordinates of the bounding box of the ROI (minLat, maxLat, minLon, maxLon)

availableVariables

Variables available for the collection of interest

roiSpatialBound

The spatial coordinates of the bounding box of the ROI expressed in the CRS of the collection

OpenDAPXVector

The X (longitude) vector

OpenDAPYVector

The Y (longitude) vector

OpenDAPtimeVector

The time vector, or NULL if the collection does not have a time vector

modis_tile

The MODIS tile(s) number(s) for the ROI or NULL if the collection is not MODIS

Examples

## Not run: 

# Login to Earthdata

log <- mf_login(credentials = c("earthdata_un","earthdata_pw"))

# Get the optional parameters for the collection MOD11A1.061 and the following roi :
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)

opt_param_mod11a1 <- mf_get_opt_param("MOD11A1.061",roi)
str(opt_param_mod11a1)

# Now we can provide opt_param_mod11a1 as input parameter of the function mf_get_url().

time_ranges <- list(as.Date(c("2016-01-01","2016-01-31")),
                   as.Date(c("2017-01-01","2017-01-31")),
                   as.Date(c("2018-01-01","2018-01-31")),
                   as.Date(c("2019-01-01","2019-01-31")))

(urls_mod11a1 <- map(.x = time_ranges, ~mf_get_url(
 collection = "MOD11A1.061",
 variables = c("LST_Day_1km","LST_Night_1km","QC_Day","QC_Night"),
 roi = roi,
 time_range = .x,
 opt_param = opt_param_mod11a1)
))


## End(Not run)

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