DESCRIPTION

i.modis.download downloads selected MODIS products (Moderate Resolution Imaging Spectroradiometer, flown on the two NASA spacecrafts Terra and Aqua). The module can download several tiles at once and also multiple observation dates for each MODIS product.

NOTES

The i.modis modules need the pyModis library. Please install it beforehand.

To be able to download data the user needs to obtain user and password for the NASA Earthdata Login:

First time user: The user has to register at https://urs.earthdata.nasa.gov/users/new; then login and change to his/her profile page. Once there, under the "My applications" tab, the user needs to approve the following applications: "LP DAAC Data Pool" and "Earthdata Search".
If the user is already registered, he/she just needs to login and enable the aforementioned applications at https://urs.earthdata.nasa.gov/home if not already done.

In order to download the desired MODIS product(s), the username and password must be provided through the settings option. There are three ways:

using the .netrc file as showed below:

machine e4ftl01.cr.usgs.gov
login your_NASA_username
password your_NASA_password

pass a file in which the first row is the username, and the second row is the password, as showed below:
```
your_NASA_username
your_NASA_password
```
the user can pass the values from the standard input when prompted.

Warning: As per NASA policy no more than ten simultaneous connections are permitted in parallel with their server. Hence, no more than ten processes of i.modis.download should run at the same time to avoid that user's actual IP address gets blacklisted.

By default, the downloaded files are stored in the path in which the settings file was saved. The user can change this directory with the folder option. The folder option is required when user and password are passed through the standard input.

The needed time for the download depends on the number of requested tiles, days and the type of MODIS product. For example, the NDVI product ranges from 5 MB to 270 MB and the LST product ranges from 2 MB to 21 MB.

EXAMPLES

MODIS Land Surface Temperature

Download of the daily MODIS LST product "lst_terra_daily_1000" from the Terra satellite using the default options (all available tiles from newest available date) and passing the user and password through standard input. Note that when settings is read from standard input, the option folder must be specified:

i.modis.download settings=- folder=/tmp

Reading the user and password options from a file (this will download by default the "lst_terra_daily_1000" product). MODIS data will be downloaded to the folder where the SETTING file is:

i.modis.download settings=$HOME/.grass7/i.modis/SETTING

Download of the LST Terra product using the default options and change of the starting and ending dates to custom values:

i.modis.download settings=$HOME/.grass7/i.modis/SETTING startday=2011-05-01 endday=2011-05-31

MODIS Snow

Download of a different product (here: Snow eight days 500 m), default options (for settings, see example above):

i.modis.download settings=$HOME/.grass7/i.modis/SETTING product=snow_terra_eight_500

MODIS NDVI Global

Download of a global MODIS product (here: MOD13C1 - MODIS/Terra Vegetation Indices 16-Day L3 Global 0.05Deg CMG V006), of a specific month (for settings, see example above):

# note: provided in Geographic Lat/Long Grid
i.modis.download settings=$HOME/.grass7/i.modis/SETTING product=ndvi_terra_sixteen_5600 startday=2011-05-01 endday=2011-05-31

Download of MODIS data in scripts

To use i.modis.download in a script and to concatenate it with another module, the user needs to set the -g flag to return the name of the file that contains the list of downloaded HDF files:

i.modis.download -g settings=$HOME/.grass7/i.modis/SETTING startday=2011-05-01 endday=2011-05-31

AUTHOR

Luca Delucchi, Google Summer of Code 2011; subsequently updated.

Last changed: $Date$