The MODIS Conversion Toolkit User’s Guide
Apart from small spatial differences that stem from how each application implements specific
interpolation algorithms, the output is consistent with (and in some ways superior to) MRT and
MRTSwath. In addition to output being in scientifically meaningful units and collected into as
few files as possible, bilinear and cubic interpolated results are sharper, there are no artifacts
along the edges of NoData regions and along the outside edges of swaths and grid tiles, and
there are no gaps present after virtual or physical mosaicking for both swath and grid products.
The only way to avoid gaps during mosaicking for grid products processed using MRT is to
create a physical mosaic from the very beginning, which is not necessarily feasible for extremely
large areas (e.g., continental or global coverage).
IV. Converting MODIS data interactively in ENVI using MCTK
To bring a MODIS file into MCTK, launch the tool from the Open External File menu and in the
resulting window, click on Input HDF, and select the file you wish to input. By design, a file filter
is preset so that only files that begin with “M” and have an “.hdf” suffix will be displayed in the
file selection dialog. Only one file can be selected at a time for conversion. It is crucial that the
name of your input file follows standard MODIS naming convention. The tool uses the first part
of the file name (e.g., MOD02HKM) to determine the product type and appropriate processing
options. The best way to ensure compliance with the naming convention is to retain the
filenames assigned by your data provider. When a valid MODIS product is supplied to the tool,
the various fields in the window will update (Figure 2). Directly below the Input HDF button is a
field that will display metadata related to the inputted file. Georeferencing options for converted
data will appear directly below the metadata viewer, when appropriate. The Processing Options
area on the right side will provide you with an interactive list of what can be done with the
inputted data. This list is different for every product. If georeferencing options are available for
the inputted product, and one of them is chosen, the window will expand to include a section
that gives you control over several parameters including projection type, resampling method,
density, and pixel size (when appropriate).
