IMERG GIS / GeoTIFF Documentation

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NASA produces a GIS translation of IMERG for various accumulation periods. The GIS translation maintains the 0.1-degree spatial resolution of the original HDF5 data product. In July 2023, Version 7 IMERG was released in both HDF5 and GIS formats. In April 2019, Version 6 of IMERG had been released, covering June 2000 to 2019. The long- duration archive for all versions starting with Version 6 is a boon to scientific research and provides a training set for near real-time applications such as disaster monitoring. Prior to Version 6, the IMERG dataset covered only the GPM era (i.e., starting with June 2014). With few exceptions, everyone should use the latest version of IMERG because it is likely to provide the most accurate precipitation estimates. All research using IMERG should state the version used.

The purpose of the present document is to describe the GIS translation of IMERG, a data product commonly called "IMERG GIS." IMERG GIS is a Tagged Image File Format (TIFF) image file that contains a two-dimensional array of two-byte integers and geographic metadata. Because of the metadata in the TIFF file, an IMERG GIS file is also a Georeferenced Tagged Image File Format (GeoTIFF) file. Because some software has difficulty interpreting the geographic metadata stored in a GeoTIFF file, PPS also stores the geographic metadata in a separate file written in the Environmental Systems Research Institute (ESRI) WorldFile format.

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