Q:  What type of data does HEG work with?
A: HEG only works with HDF-EOS formatted data.

Q:  What is HDF-EOS data?
A: HDF-EOS is an extension of HDF data created to work for the EOS satellites. It is made up of Objects which are of either SWATH or GRID type.

Q:  What are SWATH and GRID HDF-EOS Objects?
A: GRID Objects contain data that is in a GRID format which models a Map Projection. All Map Projections are in grids. If one knows that data is in a Map Grid, then just about all that is needed to describe the grid is the Upper Left and Lower Right Corner points and the pixel resolution. The geographic location of each data point (which corresponds to a node on the grid) can be easily converted to a geolocation point using Map Projection algorithms. (In HEG, this is done with the GCTP library). Examples of GRID HDF-EOS data sets are the MOD09GHK.

SWATH Objects contain ungridded data. For each data point, there is an associated Latitude and Longitude point. Sometimes, in order to conserve space, there are a smaller number of geolocation data points than data points. In this case, interpolations of missing geolocation data points are expected to be made, which HEG will take into account. In this case, the SWATH Object will have offset and increment information describing how the geolocation data is distributed among the actual data points themselves.

More details about HDF-EOS formats can be obtained in the following documentation:

HDF-EOS Library User's Guide Volume 1: Overview and Examples
HDF-EOS Library User's Guide Volume 2: Function Reference Guide.

Q:  What types of data products are in HDF-EOS that work with HEG?
A: HEG works with the following instruments: MODIS, ASTER, MISR, AMSR-E, and AIRS. These instruments are on the TERRA and AQUA Satellites. HEG will hopefully continue to support future satellite data packed in the HDF-EOS format. User interest will drive the direction of work in HEG, so if you are interested a certain data set working with HEG, please make your voice heard.

Q:  Is there a list that specifies the data sets that work with HEG?
A: There is a Product List in the back of the HEG User's Guide. Also, the HEG Home Page (Product List Section) has this list.

Q:  Which platforms does HEG support?
A: HEG currently runs on LINUX, WINDOWS 32 & 64, SUN, and MAC Itel.

Q:  What programming language was used to create HEG?
A: HEG is written in C and JAVA. JAVA is used for the GUI and C is used for everything else.

Q:  How can I view the GeoTIFF output from HEG?
A: GeoTIFFs are generally viewed with GIS software such as ENVI, ArcInfo, and ERDAS. Any software that can view a TIFF or JPG can view the GeoTIFF, but you won't be able to use the geolocation information inside.

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