rts (version 1.0-49)

VHPdownload: Download AVHRR-based Vegetation and Drought satellite image products

Description

'VHPdownload' downloads a series of AVHRR and VIIRS images in a specific date or a period of dates. The format of the files are downloaded as GeoTiff, and they can be optionally returned as a Raster Time Series Object.

Usage

VHPdownload(x,dates,rts,ncore,...)

Arguments

x

product name; it can be either of c('VHI','VCI','SMN','SMT','TCI')

dates

a vector, character or Date, with one or two items, specifiying an individual date or a range of dates as the form of c(from, to)

rts

logical; specifies whether the downloaded files should be returned as a Raster Time Series object

ncore

numeric; specifies the number of cores to use for parallel downloading of the files

...

additional arguments (Not implemented yet.)

Details

This function assists to download Blended Vegetation Health Indices Product (blended VIIRS (2013-present) and AVHRR (1981-2012), below, referred as Blended-VHP or VHP). These images for are available with a weekly temporal resolution and a spatial resolution of 4 KM. Five products are available that are specified with the following abbreviations:

- 'SMT': Smoothed Brightness Temperature - 'SMN': Smoothed NDVI - 'TCI': Temperature Condition Index - 'VHI': Vegetation Health Index - 'VCI': Vegetation Condition Index

Data arrays are in geographic projection (grid with equal latitude and longitude interval).

Examples

# NOT RUN {
library(raster)

library(RCurl)


# download Vegetation Health Index for two months
vhi <- VHPdownload(x='VHI',dates=c('2015.01.01','2015.02.28'),rts=TRUE) # output is as rts object

vhi

plot(vhi[[1]])

plot(vhi[2120000]) # plot time series at the specified cell number


# to make sure the dates are appropriately specified, use a Date object:

dates <- as.Date(c('2015.01.01','2016.12.31'),format="<!-- %Y.%m.%d") -->

dates

class(dates)

dates <- as.Date(c('2012-01-01','2012-12-31'),format="<!-- %Y-%m-%d") -->

dates
 
# If your machine has multiple cores, you can use parallel downloading to speed up the downloads
# Vegetation Condition Index for two years
vci <- VHPdownload(x='VCI',dates=dates,rts=TRUE,ncore=4)

vci

plot(vci[[1:2]])



# }
# NOT RUN {
# }