The MODIS Conversion Toolkit User’s Guide
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files can be generated by a single conversion process, it is useful to choose an intuitive and
descriptive rootname so data from the same input file can be easily grouped afterwards.
A. Level 1A Uncalibrated Radiance
When a Level 1A Uncalibrated Radiance file is provided as input, you will be presented with
several processing options. On the right side, you will see the four datasets stored inside of the
HDF that contain image data at three spatial resolutions (250m, 500m, and 1000m). MCTK
recognizes the fact that there are multiple resolutions within the file and displays them in the
metadata window under Pixel Size. You can choose to output any combination of the available
datasets, but each will be placed in a separate file due to how they are processed by the tool.
Each output file will contain appropriate band number designations and wavelength values.
After clicking on Process, you will see two ENVI progress bars: one related to the conversion of
the current dataset and one related to the overall conversion process.
The tool also recognizes that Level 1A data does not contain georeferencing information
(indicated by the Native Projection being set to None in the metadata viewer). However, if you
have access to the related Geolocation product (MOD03/MYD03), you can use it to project the
Level 1A data. To do so, select Projected or Standard and Projected under Output Type and
then click on Input Geolocation File. You will be prompted to supply an appropriate file. A filter
is provided to aid you in finding the correct product and the current Level 1A filename will show
up in the title bar of the file selection dialog. In order to proceed, the second, third and fourth
sections of the Level 1A filename and geolocation filename have to match. For example, a
Level 1A file with the name “MYD01.A2006007.0300.005.2007078081622.hdf” requires a
geolocation file with the name “MYD03.A2006007.0300.005.2006125230829.hdf.” If the
supplied filenames do not match, the projection options section will be greyed out and you will
not be allowed to proceed with the conversion. If the filenames do match, the most appropriate
UTM zone for the supplied data is automatically calculated and made available (Figure 3).
Standard resampling methods (Nearest Neighbor, Bilinear, and Cubic Convolution) are
available, as is Bow Tie Correction. If the latter is chosen, the former set of methods become
inaccessible since only one can be used during projection. The number of warp points to use is
set to 50 x 50 by default, which results in 2500 GCPs distributed evenly across the entire scene.
While this should be more than enough to carry out an accurate triangulation warp, you can
choose to use more or less points. This option is also not available when Bow Tie Correction is
chosen due to differences in how this method uses the supplied geolocation file. Output pixel
size is automatically determined based on product type and dataset. For projections that do not
use meters, the meter-based pixel size is automatically converted to one that is appropriate.
You also have the option of providing your own fill value to use during the conversion process
and your own background value to use during the projection process. The default value for both
is 0. If a value less than zero is provided, zero is used instead.
Filenames for converted data
For Level 1A files, two types of filenames are possible. They are constructed as follows:
• Rootname + Dataset Name + Raw_DN.img (unprojected data)
• Rootname + Dataset Name + Raw_DN_georef.img (projected data)
