MODIS Preparation module

Description

Download and prepare, or simulate MODIS MCD43A2 and MCD43A4 products so that they can be used as the reference for spectrally normalizing the input orthorectified images.

Parameters

Name	Caption
Input Orthos	The set of orthorectified imagery to process
Output Folder	Output folder
MODIS Data Folder	Path of folder to downloaded MODIS data
MODIS Time Series Models	MODIS Time Series Models
Overwrite Results	Overwrite existing results
Days Before	Download all MODIS data for this number of days before the date of the ortho image
Days After	Download all MODIS data for this number of days after the date of the ortho image

Parameter descriptions

Input Orthos

The name of the folder that contains valid, GDB-supported orthorectified images.

This parameter can be specified by using any of the following:

Path and name of a folder of input orthorectified images; for example, C:\data
Path and name of a folder with a wildcard to filter the imagery by file name or type; for example, C:\data\*ORTHO_MS.pix
You can also specify an MFILE as input. An MFILE is a text file with an .mfile file name extension. For more information on this type of file, see About the MFILE format.

Output Folder

The path and name of the folder to which to write the output files.

MODIS Data Folder

MODIS data downloaded by this job is placed in this folder. Regardless of whether Overwrite Results is set, data is never downloaded if it already exists in this folder.

Downloading MODIS can be slow and consume a lot of bandwidth. It is recommended to use the same MODIS folder every time you run this job to prevent downloading data that has already been downloaded.

MODIS Time Series Models

The name of geo-package file contains time series models used to simulate MODIS.

Overwrite Results

Select this check box to overwrite the existing output files, if any exist. If this check box is left clear, and an output file exists in the relevant folder, the status of the job displays a message informing you of the existence and name of the output file. The message is also written to the event log of the job.

Days Before

MODIS products usually need to be composited in time to obtain sufficient number of pixels with valid MODIS data. Therefore, processing of multiple MODIS scenes for a single image is supported. Using "Days Before" and "Days After" you can select the date range of MODIS products to download for an image.

Days After

See "Days Before" for more details.

Details

General job details

Preprocessing requirements

Before running this module, the following requirements must be met to ensure the job processes successfully and produces accurate results:

The input orthorectified images must have a valid acquisition dates in the metadata

Module details

The MODIS Preparation module performs the following processing steps:

The module determines all MODIS scenes that need to be downloaded based on the overlapping tiles and acquisition dates of the orthorectified images, the selected "Days Before" and "Days After", and the files that already exist in the "MODIS folder". Each of these MODIS scenes is then downloaded.
If no MODIS scene is available for the ortho image, (i.e., the image was acquired before MODIS was available), user can specify a time series model file, which will be used to simulate a MODIS image based on the acquisition date and spatial extent of the ortho image. The time series model can be acquired by running MODIS Time-Series Model Generation module
Each MODIS scene consists of a pair of files, MCD43A2 (data sources, processing info and general quality indicators) and MCD43A4 (the actual spectral data and their per-band quality). The two files of each pair are processed jointly by this job, and during the spectral normalization process.
The module determines all overlapping date/tile MODIS pairs and temporally composites the MODIS data, if necessary.
The module determines which, if any, scenes overlap more than one MODIS tiles. For all sets of combinations of date/tiles a mosaic is generated.

Job results

On successful completion, the MODIS Preparation module creates one or more pairs of MCD43A2/MCD43A4 files to be used for spectral normalization. These MODIS pairs will be temporally composited and spatially mosaicked, if necessary, to cover more than one date or more than one tile respectively. One pair will be created for every required date/tiles. If two orthorectified images require the same MODIS data, then only one MODIS pair will be created to prevent duplicating work. Additionally an index.pix file will be created with the footprints of each orthorectified image indicating which MODIS pair should be used for spectral normalization.