In this post, we are introducing MODIStsp a new “R” package allowing to automatize the creation of time series of rasters derived from Land Products data derived from MODIS satellite data (; www.sciencedirect.com/science/article/pii/S0098300416303107).
MODIStsp started from modifications of the ModisDownload “R”
script by Thomas Hengl (spatial-analyst.net/wiki/index.php?title=Download_and_resampling_of_MODIS_images), and successive
adaptations by Babak Naimi (r-gis.net/?q=ModisDownload).
Their functionalities were gradually incremented with the aim of:
- Developing a standalone application allowing to perform several preprocessing steps (e.g., download, mosaicking, reprojection and resize) on all available MODIS land products by exploiting a powerful and user-friendly GUI front-end;
- Allowing the creation of time series of both MODIS original layers and additional Quality Indicators (e.g., data acquisition quality, cloud/snow presence, algorithm used for data production, etc. ) extracted from the aggregated bit-field QA layers
- Allowing the automatic calculation and creation of time series of several additional Spectral Indexes starting form MODIS surface reflectance products
Installation and usage
Basic interactive usage
After installing and loading the package, launching the
MODIStsp function without
additional parameters opens a user-friendly GUI for the selection of processing
options required for the creation of the desired MODIS time series (e.g., start
and end dates, geographic extent, type of product and parameters of interest, etc.).
The main GUI of MODIStsp
After selecting the product, the user can select the MODIS original, QI and SI layers to be processed by pressing the Select Layers button, which opens a separate layers’ selection panel. Although some of the most common SIs available for computation by default users can add custom ones without modifying MODIStsp source code by clicking on the Add Custom Index button, which allows specifying the formula of the additional desired SI using a simple GUI interface.
Upon clicking the “Start” button in the main GUI, required MODIS HDF files are automatically downloaded from NASA servers and resized, reprojected, resampled and processed according to user’s choices.
Non-interactive execution and scheduled processing
Non-interactive execution exploiting a previously created Options File is also possible, as well as stand-alone execution outside an “R” environment. This allows to use scheduled execution of MODIStsp to automatically update time series related to a MODIS product and extent whenever a new image is available. For additional details see the main github page !
For each desired output layer, outputs are saved as single-band rasters corresponding to each acquisition date available for the selected MODIS product within the specified time period.
R RasterStack objects with temporal information as well as Virtual raster
files (GDAL vrt and/or ENVI META files) facilitating access to the entire time
series can be also created.
Accessing and analyzing the processed time series from R
Preprocessed MODIS data can be retrieved within R scripts either by accessing the
single-date raster files, or by loading the saved RasterStack objects. This second
option allows accessing the complete data stack and analyzing it using the
functionalities for raster/raster time series analysis, extraction and plotting
provided for example by the
MODIStsp provides however also an efficient function (
for extracting time series data at specific locations. The function takes as input
rasterStack object with temporal information created by MODIStsp, the
starting and ending dates for the extraction and a standard R
Sp* object (or an
ESRI shapefile name) specifying the locations (points, lines or polygons) of interest,
and provides as output a R xts object or data.frame containing time series for
those locations. As an example the following code:
#Set the input paths to raster and shape file infile <- 'in_path/MOD13Q1_MYD13Q1_NDVI_49_2000_353_2015_RData.RData' shp_name <- 'path_to_file/rois.shp' #Set the start/end dates for extraction start_date <- as.Date("2010-01-01") end_date <- as.Date("2014-12-31") #Load the RasterStack inrts <- get(load(infile)) # Compute average and St.dev dataavg <- MODIStsp_extract(inrts, shp_name, start_date, end_date, FUN = 'mean', na.rm = T) datasd <- MODIStsp_extract(inrts, shp_name, start_date, end_date, FUN = 'sd', na.rm = T) # Plot average time series for the polygons plot.xts(dataavg)
, loads a
RasterStack object containing 8-days 250 m resolution time series for
the 2000-2015 period and extracts time series of average and standard deviation
values over the different polygons of a user’s selected shapefile on the 2010-2014
period. The function exploits rasterization of the input
Sp* object and fast
summarization based on the use of _data.table _objects to greatly increase the
speed of data extraction with respect to standard R functions.
The package is developed and maintained by Lorenzo Busetto and Luigi Ranghetti (Institute for Remote Sensing of Environment - National Research Council of Italy).
Problems and issues
Any problems/issues can be reported at: github.com/ropensci/MODIStsp/issues
Publication and citation
A paper on MODIStsp was recently published in the “Computers & Geosciences” journal www.sciencedirect.com/science/article/pii/S0098300416303107.To cite MODIStsp please use:
L. Busetto, L. Ranghetti (2016) MODIStsp: An R package for automatic preprocessing of MODIS Land Products time series, Computers & Geosciences, Volume 97, Pages 40-48, ISSN 0098-3004, http://dx.doi.org/10.1016/j.cageo.2016.08.020.