MODIS Nomenclature
Last Update: August 3, 2006
Processing Levels
Once on the ground, data are processed to varying stages. Users should choose the data that meets their needs.
| Level 0 | Raw instrument data at original resolution, time ordered, with duplicate packets removed. |
| Level 1A | Reconstructed instrument radiance data (in sensor counts) at original resolution with calibration data appended. Geolocation data are stored in a separate file. |
| Level 1B | Level 1A data converted into calibrated radiances. |
| Level 2 | Derived geophysical parameters at the same resolution and location as the Level 1 data. In other words, data are in the instrument's swath geometry. For MODIS, each scene consists of 5 minutes of viewing by the instrument (approximately 203 scans). |
| Level 2G | MODIS Land products are processed into an intermediary step for storing information concerning Level 2 observations that fall within each Level 3 grid cell (includes the geophysical parameter and the sensing geometry for each Level 2 observation). The observations stored in the Level 2G products are examined by the Level 3 processes to extract the most relevant observations for each grid cell. |
| Level 3 | Geophyscial parameters that have been spatially or temporally resampled into an Earth-located grid using a common projection. |
| Level 4 | Model output and/or results of lower level data that are not directly derived by the instrument. |
Data Collections
Collections, or versions, indicate reprocessings of the data. The higher the collection number, the better the quality of the data. Each MODIS product and algorithm underwent improvements before each reprocessing. The following is a brief synopsis of the MODIS collections.
| Terra Collection 1 | Original, at-launch version. Most products released at beta quality. |
| Terra Collection 2 | Never produced. |
| Terra Collection 3 | Partial mission reprocessing to incorporate calibration and algorithm improvements. Most products released at provisional quality. Some products validated. |
| Terra Collection 4 | Entire mission reprocessing with calibration stabilization and refinements to the geophysical algorithms. Most products validated. |
| Terra Collection 5 | Entire mission reprocessing with latest calibration improvements and algorithm refinements. Products validated. |
| Aqua Collection 3 | Original, at-launch version, using MODIS algorithms at the maturity of Terra Collection 3. Thus, most Aqua products were released at provisional quality. |
| Aqua Collection 4 | Entire mission reprocessing with calibration stabilization and refinements to the geophysical algorithms. Most products validated. |
| Aqua Collection 5 | Entire mission reprocessing with latest calibration improvements and algorithm refinements. Products validated. |
Data Maturity
| Beta | Early release product with known problems and frequent algorithm updates. Scientific use of the product is not recommended. |
| Provisional | Some incremental improvements are still occurring, although QA tests show stability in the product. Scientific use should only be done with caution and careful reference to QA statements provided with the product. |
| Validated | Estimates of product accuracy and uncertainty have been obtained through comparisons with independent data. The results of validation are published in the peer-reviewed literature. The validation data are available. Scientific use is recommended and encouraged commensurate with the stage of validation achieved. |
| Stage 1 Validation | Product accuracy has been estimated using a small number of independent measurements obtained from selected locations and time periods and ground-truth/field program efforts. |
| Stage 2 Validation | Product accuracy has been assessed over a widely distributed set of locations and time periods via several ground-truth and validation efforts. |
| Stage 3 Validation | Product accuracy has been assessed, and the uncertainties in the product well-established, via independent measurements made in a systematic and statistically robust way that represents global conditions. |
Generalized Filenaming Convention
MOD01.A2002032.1015.003.2002034184356.hdf aaaaa bbbbccc dddd eee fffffffffffff ggg
a) MODIS product short name, e.g. "MOD01" refers to the MODIS Level 1A Radiance product. "MOD" signifies Terra/MODIS, whereas "MYD" signifies Aqua/MODIS.
b) Year in which data was collected by the instrument, e.g. 2002.
c) Day on which data was collected by the instrument, given in Day of Year. For example, "032" is February 1st, i.e. the 32nd day of the year.
d) Time at which data was collected, given in Universal Time Coordinate (UTC) or Greenwich Mean Time (GMT).
e) Collection (version) number.
f) Production date and time, given in year, day-of-year, hours, minutes, and seconds, in the form yyyydddhhmmss.
g) File type extension, e.g. "hdf" is Hierarchical Data Format. All MODIS data are available in HDF format.
