How to Use LAADS DAAC Post-Processing Tools
The LAADS DAAC provides tools for researchers to download data with post processing transformations. This allows researchers to download data in several formats.
Before we begin:
- Make sure you have an Earthdata login before you start using the LAADS search and order interface.
- Log in to LAADS Web by selecting “Earthdata Login” under “Profile” in the top-right and provide your login credentials.
Now that you are logged in, open the LAADS Search and Order interface:
Follow the instructions on How to Search and Order Data with the LAADS “Find Data” Interface until you reach step 5, “Review and order the selected data products, applying post processing transformations.”
Apply post-processing: Post-processing may include many data transformation options
such as parameter subsetting to deliver only those Science Data Set (SDS) variables that you require,
spatial subsetting to reduce the geographic footprint, format conversion, resampling, etc. Offered
post-processing options vary with each product type.
Types of post-processing:
- All combined files will be from the same date (for lists of files from multiple dates, there will be a result file for each separate date).
- Data sets remain separate – our tool does not combine data from different data sets together.
- Where files overlap geographically, we will favor pixels based on whether the pixel contains a measurement value or not, and then favor the pixel nearest to the satellite's nadir position.
- HDF Files HDF files are open-source file formats that support large, complex, heterogeneous data, using a “file directory” like structure. HDF formats also allow for embedding of metadata, making them self-describing.
- HDF 4 - Hierarchical Data Format Four (HDF4), an older hierarchical data format, is the primary data format adapted for MODIS data products distributed and archived at LAADS DAAC.
- HDF 5 - Hierarchical Data Format Five (HDF5) is the preferred data structure to use on newer data products.
Subsetting data sets allows data users to select only the desired data sets from a file. Most LAADS products contain many data sets (some contain thousands of data sets). If you will not need most of them, choose only the ones you will use. This can reduce the size and number of files you will need to download.
Select only the data from the geographic region you specify. Even if you searched for data from only a specific region, the files can contain more data, with only some of it actually intersecting the region you specified. By selecting this option, we will slice out all data that are not in your specified region. This can further reduce the size of files you will need to download and will also reduce the amount of data you need to process.
This option can combine the data from multiple files into one file, with all the data correctly geolocated. Some caveats:
Change the format of the file to one of the following options:
Network Common Data Form (NetCDF) is a set of software libraries and self-describing, machine-independent data formats that support the creation, access, and sharing of array-oriented scientific data.
GeoTIFFs are commonly used in Geographic Information System (GIS) tools, where geographically referenced data is embedded in the TIFF file.
Change the Map Projection or Sample Size. Many maps and data sets from other instruments do not use the Geographic, or Cartesian, coordinate system. When overlaying data sets, they will line up better if they use the same coordinate system. The Reproject option allows one to specify parameters that govern the reproject operation. Refer to the U.S. Geological Survey Professional Paper 1395, "Map Projections – A Working Manual", U.S. Government Printing Office, Washington: (C)1987, for detailed information on map projections.
Include process log files with the output. Most users will not find this option particularly useful.
- Select delivery method: You can select a delivery method, the default being “Pull” and hit the “Submit Order” button. Once your order is processed and ready, you are notified by e-mail with details on how to download your ordered data products.
- Manage your orders: You can access your User Profile (the last link called “Past Orders” on the left-side in the search and order interface) to check the status of your order, resubmit a previously submitted order, cancel an order, etc
Last updated: November 21, 2022