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This document describes the LAADS MOD data files. This document is sub-divided into three sections: Terra MODIS Level 1, Terra MODIS Level 2, and Terra MODIS Level 3.
Please pay attention on the special usage of scale and offset attributes for some files.
For the swath files using the dimension map, users need to either find the corresponding geolocation HDF-EOS2 files or calculate the latitude/longitude based on dimension map parameters.
The size of dimension varies in geolocation fields and data fields. For example, in file MOD02HKM.A2000055.0005.005.2010029230803.hdf, the dimension size of geolocation is 406 (2*nscans) x 271 (1KM_geo_dim), while the dimension size of data fields is 2030 (10*nscans) x 1354 (Max_EV_frames)
The following table summarizes the information collected for the files:
| File type | File size(avg.) | Geolocation Field | Datafield Dim. Range | CF-compliant information | Other special issues |
|---|---|---|---|---|---|
| HDF-EOS2 (Swath) | 7MB - 42MB | Lat/Lon = 2D | 2D, 3D | 1. Geolocation fields have ‘units’ attribute, and Datafields have both ‘units’and 'long_name' attributes; 2.'units' attribute for latitude and longitude is 'degree'. | Some files contain following issues: 1. There are several pairs of 'scales' and 'offsets' attributes for some variables; 2. Use dimension map |
The following table summarizes the information collected for the files:
| File type | File size(avg.) | Number of grid | Has lat/lon | Projection | Datafield Dim. Range | CF-compliant information |
|---|---|---|---|---|---|---|
| HDF-EOS2
(Grid) |
553KB | 1 | No | SNSOID* | 2D, 3D | 1. Data fields do not have either 'units' or 'long_name' attributes';2. There are fill values inside the data but there is neither a 'Fill_Value' attribute nor a 'missing value' attribute; |
The pseudo eos_2 files contain between 120-138 datasets. They have no geolocation fields and their data fields are mostly 3-Dimension fields.
The MODCSR_G files do not have geolocation fields but the other HDF-EOS2 swath files do.
The following table summarizes the information collected for the files:
| File type | File size(avg.) | Geolocation Field | Datafield Dim. Range | CF-compliant information | Other special issues |
|---|---|---|---|---|---|
| HDF-EOS2 (Swath) | 50KM -1.2MB | Lat/Lon = 2D( MODCSR_G files do not have ) | 2D, 3D | Both geolocation fields and data fields have ‘units’ attribute and 'long_name' attributes. | Some files contain following issues: 1. Use dimension map; 2. Special usage of scale and offset attributes; |
The pseudo eos_2 file contain 37 datasets. It has 2 dimension latitude and longitude fields and its data fields are 2-Dimension or 3-Dimension fields.
The following table summarizes the information collected for the files:
| File type | File size(avg.) | Geolocation Field | Datafield Dim. Range | CF-compliant information |
|---|---|---|---|---|
| HDF-EOS2 (Swath) | 836MB | No | 2D | Datafields have both ‘units’and 'long_name' attributes. |
The following table summarizes the information collected for the files:
| File type | File size(avg.) | Number of grid | Has lat/lon | Projection | Datafield Dim. Range | CF-compliant information | Other special issues |
|---|---|---|---|---|---|---|---|
| HDF-EOS2
(Grid) |
49MB | 1 | No | GEO | 2D-4D | Data fields do not have either 'units' or 'long_name' attributes' | Special usage of scale and offset attributes; |
To retrieve sample MOD files and read the detailed description of these files, please click here.