Aqua MODIS surface reflectance band 1-4-3 data from the MYD09GA product over the western United States, December 4, 2020.
View full-size imageThe MYD09GA Version 6.1 product provides an estimate of the surface spectral reflectance of Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) Bands 1 through 7, corrected for atmospheric conditions such as gasses, aerosols, and Rayleigh scattering. Provided along with the 500 meter (m) surface reflectance, observation, and quality bands are a set of ten 1 kilometer observation bands and geolocation flags. The reflectance layers from the MYD09GA are used as the source data for many of the MODIS land products.
Validation at stage 3 has been achieved for the MODIS Surface Reflectance products. Further details regarding MODIS land product validation for the MYD09 data product is available from the MODIS Land Team Validation site.
| Characteristic | Description |
|---|---|
| Collection | Aqua MODIS |
| DOI | 10.5067/MODIS/MYD09GA.061 |
| File Size | 84 MB |
| Temporal Resolution | Daily |
| Temporal Extent | 2002-07-04 to Present |
| Spatial Extent | Global |
| Coordinate System | Sinusoidal |
| Datum | N/A |
| File Format | HDF |
| Geographic Dimensions | 1200 km x 1200 km |
| Characteristic | Description |
|---|---|
| Number of Science Dataset (SDS) Layers | 22 |
| Columns/Rows | 2400 (500 m) and 1200 (1000 m) x 2400 (500 m) and 1200 (1000 m) |
| Pixel Size | 500 m and 1000 m |
| SDS Name | Description | Units | Data Type | Fill Value | No Data Value | Valid Range | Scale Factor |
|---|---|---|---|---|---|---|---|
| num_observations_1km | Number of observations within a pixel | N/A | 8-bit signed integer | -1 | N/A | 0 to 127 | N/A |
| state_1km_1 | 1km Reflectance Data State QA | Bit Field | 16-bit unsigned integer | 65535 | N/A | 0 to 57335 | N/A |
| SensorZenith_1 | Zenith angle to sensor | Degree | 16-bit signed integer | -32767 | N/A | 0 to 18000 | 0.01 |
| SensorAzimuth_1 | Azimuth angle to sensor | Degree | 16-bit signed integer | -32767 | N/A | -18000 to 18000 | 0.01 |
| Range_1¹ | Distance to sensor | Meters | 16-bit unsigned integer | 0 | N/A | 27000 to 65535 | 25.0 |
| SolarZenith_1 | Zenith angle to sun | Degree | 16-bit signed integer | -32767 | N/A | 0 to 18000 | 0.01 |
| SolarAzimuth_1 | Azimuth angle to sun | Degree | 16-bit signed integer | -32767 | N/A | -18000 to 18000 | 0.01 |
| gflags_1 | Geolocation flags | Bit Field | 8-bit unsigned integer | 255 | N/A | 0 to 248 | N/A |
| orbit_pnt_1 | Orbit pointer | N/A | 8-bit signed integer | -1 | N/A | 0 to 15 | N/A |
| granule_pnt _1 | Granule pointer | N/A | 8-bit unsigned integer | 255 | N/A | 0 to 254 | N/A |
| num_observations_500m | Number of observations per 500m pixel | N/A | 8-bit signed integer | -1 | N/A | 0 to 127 | N/A |
| sur_refl_b01_1² | Surface Reflectance Band 1 | N/A | 16-bit signed integer | -28672 | N/A | -100 to 16000 | 0.0001 |
| sur_refl_b02_1² | Surface Reflectance Band 2 | N/A | 16-bit signed integer | -28672 | N/A | -100 to 16000 | 0.0001 |
| sur_refl_b03_1 | Surface Reflectance Band 3 | N/A | 16-bit signed integer | -28672 | N/A | -100 to 16000 | 0.0001 |
| sur_refl_b04_1 | Surface Reflectance Band 4 | N/A | 16-bit signed integer | -28672 | N/A | -100 to 16000 | 0.0001 |
| sur_refl_b05_1 | Surface Reflectance Band 5 | N/A | 16-bit signed integer | -28672 | N/A | -100 to 16000 | 0.0001 |
| sur_refl_b06_1 | Surface Reflectance Band 6 | N/A | 16-bit signed integer | -28672 | N/A | -100 to 16000 | 0.0001 |
| sur_refl_b07_1 | Surface Reflectance Band 7 | N/A | 16-bit signed integer | -28672 | N/A | -100 to 16000 | 0.0001 |
| QC_500m_1 | Surface Reflectance 500m Quality Assurance | Bit Field | 32-bit unsigned integer | 787410671 | N/A | 0 to 4294966019 | N/A |
| obscov_500m_1 | Observation coverage | Percent | 8-bit signed integer | -1 | N/A | 0 to 100 | 0.01 |
| iobs_res_1 | Observation number | N/A | 8-bit unsigned integer | 255 | N/A | 0 to 254 | N/A |
| q_scan_1³ | 250m scan value information | N/A | 8-bit unsigned integer | 255 | N/A | 0 to 254 | N/A |
¹The scale factor for Range_1 is listed as 25.0 in the Variables table and 0.04 in the User’s Guide. The scale factors in this table are applied through multiplication.
²Data layers sur_refl_b01_1 and sur_refl_b02_1 may not always be present.
³Description information for the q_scan_1 layer is provided in Table 17 of the User Guide. Please note this layer may not be present in all products.
The state_1km_1 and QC_500m_1 layers are stored in an efficient bit-encoded manner. The unpack_sds_bits executable from the LDOPE tools is available to the user community to help parse and interpret these layers.
The QA bit flags for the state_1km_1 and the QC_500m_1 layers are given in the User Guide in table 13 and 10 respectively.
Quality assurance information should be considered when determining the usability of data for a particular science application. The ArcGIS MODIS-VIIRS Python Toolbox contains tools capable of decoding quality data layers while producing thematic quality raster files for each quality attribute.
In addition to data access and transformation processes, AppEEARS also has the capability to unpack and interpret the quality layers.
Prior to the Aqua MODIS launch, Band 6 exhibited several anomalous detectors. Band 6 performance degraded seriously after launch and presently a majority of the Band 6 detectors are non-functional. Science users should read and use the non-functional detector flags and decide for themselves the optimum manner to handle non-functional detector "gaps" for their products. For complete information please refer to the MODIS Characterization Support Team (MCST) website.
For complete information about known issues please refer to the MODIS/VIIRS Land Quality Assessment website.