i.modis.qc - GRASS GIS manual
Author: GRASS Development Team
Description: i.modis.qc: Extracts quality control parameters from MODIS QC layers.
Keywords: imagery, imagery quality assessment, reflectance, land surface temperature, vegetation, satellite, MODIS

## NAME

i.modis.qc - Extracts quality control parameters from MODIS QC layers.

## KEYWORDS

imagery, imagery quality assessment, reflectance, land surface temperature, vegetation, satellite, MODIS

## SYNOPSIS

i.modis.qc
i.modis.qc --help
i.modis.qc input=name output=name productname=string qcname=string [band=string] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

### Flags:

--overwrite
  Allow output files to overwrite existing files
--help
  Print usage summary
--verbose
  Verbose module output
--quiet
  Quiet module output
--ui
  Force launching GUI dialog

### Parameters:

input=name [required]
  Name of input surface reflectance QC layer [bit array]
output=name [required]
  Name for output QC type classification layer
productname=string [required]
  Name of MODIS product type
  Options: mod09Q1, mod09A1, mod09A1s, mod09GA, mod09GAs, mod09CMG, mod09CMGs, mod09CMGi, mod11A1, mod11A2, mod13A2, mcd43B2, mcd43B2q, mod13Q1
  mod09Q1: surf. refl. 250m 8-days
  mod09A1: surf. refl. 500m 8-days
  mod09A1s: surf. refl. 500m 8-days, State QA
  mod09GA: surf. refl. 500m daily
  mod09GAs: surf. refl. 500m daily, State QA
  mod09CMG: surf. refl. 5000m daily
  mod09CMGs: surf. refl. 5000m daily, State QA
  mod09CMGi: surf. refl. 5000m daily, Internal Climatology
  mod11A1: LST 1km daily (Day/Night)
  mod11A2: LST 1km 8-days (Day/Night)
  mod13A2: VI 1km 16-days
  mcd43B2: Brdf-Albedo Quality (Ancillary SDS) 1km 8-days
  mcd43B2q: Brdf-Albedo Quality (BRDF SDS) 1km 8-days
  mod13Q1: VI 250m 16-days
qcname=string [required]
  Name of QC type to extract
  Options: adjcorr, atcorr, cloud, data_quality, diff_orbit_from_500m, modland_qa, mandatory_qa_11A1, data_quality_flag_11A1, emis_error_11A1, lst_error_11A1, data_quality_flag_11A2, emis_error_11A2, mandatory_qa_11A2, lst_error_11A2, aerosol_quantity, brdf_correction_performed, cirrus_detected, cloud_shadow, cloud_state, internal_cloud_algorithm, internal_fire_algorithm, internal_snow_mask, land_water, mod35_snow_ice, pixel_adjacent_to_cloud, salt_pan, icm_cloudy, icm_clear, icm_high_clouds, icm_low_clouds, icm_snow, icm_fire, icm_sun_glint, icm_dust, icm_cloud_shadow, icm_pixel_is_adjacent_to_cloud, icm_cirrus, icm_pan_flag, icm_criteria_for_aerosol_retrieval, icm_aot_has_clim_val, modland_qa, vi_usefulness, aerosol_quantity, pixel_adjacent_to_cloud, brdf_correction_performed, mixed_clouds, land_water, possible_snow_ice, possible_shadow, platform, land_water, sun_z_angle_at_local_noon, brdf_correction_performed, modland_qa, vi_usefulness, aerosol_quantity, pixel_adjacent_to_cloud, brdf_correction_performed, mixed_clouds, land_water, possible_snow_ice, possible_shadow
  adjcorr: mod09: Adjacency Correction
  atcorr: mod09: Atmospheric Correction
  cloud: mod09: Cloud State
  data_quality: mod09: Band-Wise Data Quality Flag
  diff_orbit_from_500m: mod09: 250m Band is at Different Orbit than 500m
  modland_qa: mod13Q1: MODIS Land General Quality Assessment
  mandatory_qa_11A1: mod11A1: MODIS Land General Quality Assessment
  data_quality_flag_11A1: mod11A1: Detailed Quality Indications
  emis_error_11A1: mod11A1: Average Emissivity Error Classes
  lst_error_11A1: mod11A1: Average LST Error Classes
  data_quality_flag_11A2: mod11A2: Detailed Quality Indications
  emis_error_11A2: mod11A2: Average Emissivity Error Classes
  mandatory_qa_11A2: mod11A2: MODIS Land General Quality Assessment
  lst_error_11A2: mod11A2: Average LST Error Classes
  aerosol_quantity: mod13Q1: Quantity range of Aerosol
  brdf_correction_performed: mod13Q1: if BRDF correction performed
  cirrus_detected: mod09*s: StateQA Cirrus Detected
  cloud_shadow: mod09*s: StateQA Cloud Shadow
  cloud_state: mod09*s: StateQA Cloud State
  internal_cloud_algorithm: mod09*s: StateQA Internal Cloud Algorithm
  internal_fire_algorithm: mod09*s: StateQA Internal Fire Algorithm
  internal_snow_mask: mod09*s: StateQA Internal Snow Mask
  land_water: mod13Q1: separate land from various water objects
  mod35_snow_ice: mod09*s: StateQA mod35 Snow Ice
  pixel_adjacent_to_cloud: mod13Q1: if pixel is a cloud neighbour
  salt_pan: mod09*s: StateQA Salt Pan (mod09GAs)
  icm_cloudy: mod09*i: Internal CM: Cloudy
  icm_clear: mod09*i: Internal CM: Clear
  icm_high_clouds: mod09*i: Internal CM: High Clouds
  icm_low_clouds: mod09*i: Internal CM: Low Clouds
  icm_snow: mod09*i: Internal CM: Snow
  icm_fire: mod09*i: Internal CM: Fire
  icm_sun_glint: mod09*i: Internal CM: Sun Glint
  icm_dust: mod09*i: Internal CM: Dust
  icm_cloud_shadow: mod09*i: Internal CM: Cloud Shadow
  icm_pixel_is_adjacent_to_cloud: mod09*i: Internal CM: Pixel is Adjacent to Cloud
  icm_cirrus: mod09*i: Internal CM: Cirrus
  icm_pan_flag: mod09*i: Internal CM: Pan Flag
  icm_criteria_for_aerosol_retrieval: mod09*i: Internal CM: Criteria for Aerosol Retrieval
  icm_aot_has_clim_val: mod09*i: Internal CM: AOT (aerosol optical depth) has clim. val.
  vi_usefulness: mod13Q1: Quality estimation of the pixel
  mixed_clouds: mod13Q1: if pixel mixed with clouds
  possible_snow_ice: mod13Q1: if snow/ice present in pixel
  possible_shadow: mod13Q1: if shadow is present in pixel
  platform: mcd43B2: Quality of BRDF correction performed
  sun_z_angle_at_local_noon: mcd43B2: Quality of BRDF correction performed
band=string
  Band number of MODIS product (mod09Q1=[1,2],mod09A1=[1-7],m[o/y]d09GA=[1-7],m[o/y]d09CMG=[1-7], mcd43B2q=[1-7])
  Options: 1, 2, 3, 4, 5, 6, 7
  1: Band 1: Red
  2: Band 2: NIR
  3: Band 3: Blue
  4: Band 4: Green
  5: Band 5: SWIR 1
  6: Band 6: SWIR 2
  7: Band 7: SWIR 3

## DESCRIPTION

i.modis.qc extracts Requested Quality Assessment flags from the following MODIS products: MOD09A1, MOD09Q1, MOD11A1, MOD11A2, MOD13A2, MOD13Q1, MCD43B2. This does include MOD09A1 QA_state_500m layer (see Notes).
Added MOD09GA support in 2016, it follows MOD09A1 and its StateQA, but does not have BRDF State QA, instead has Salt Pan State QA.

### MOD09A1 and MOD09Q1

    MOD09A1/Q1: MODLAND QA Bits. bits=[0-1]

- [00]= class 0: Corrected product produced at ideal quality -- all bands
- [01]= class 1: Corrected product produced at less than ideal quality -- some or all bands
- [10]= class 2: Corrected product NOT produced due to cloud effect -- all bands
- [11]= class 3: Corrected product NOT produced due to other reasons -- some or all bands maybe be fill value (Note that a value of [11] overrides a value of [01])

    MOD09Q1: Cloud State. bits=[2-3]

- [00]= class 0: Clear -- No clouds
- [01]= class 1: Cloudy
- [10]= class 2: Mixed
- [11]= class 3: Not Set ; Assumed Clear

    MOD09Q1: Band-wise Data Quality 250m bits=[4-7][8-11]
    MOD09A1: Band-wise Data Quality 500m bits=[2-5][6-9][10-13][14-17][18-21][22-25][26-29]

- [0000]= class 0: highest quality
- [0111]= class 1: noisy detector
- [1000]= class 2: dead detector; data interpolated in L1B
- [1001]= class 3: solar zenith ≥ 86 degrees
- [1010]= class 4: solar zenith ≥ 85 and < 86 degrees
- [1011]= class 5: missing input
- [1100]= class 6: internal constant used in place of climatological data for at least one atmospheric constant
- [1101]= class 7: correction out of bounds, pixel constrained to extreme allowable value
- [1110]= class 8: L1B data faulty
- [1111]= class 9: not processed due to deep ocean or cloud
- Class 10-15: Combination of bits unused

    MOD09A1/Q1: Atmospheric correction bit=[12]/[30]

- [0]= class 0: Not Corrected product
- [1]= class 1: Corrected product

    MOD09A1/Q1: Adjacency correction bit=[13]/[31]

- [0]= class 0: Not Corrected product
- [1]= class 1: Corrected product

    MOD09Q1: Different orbit from 500m product, bit=[14]

- [0]= class 0: same orbit as 500m
- [1]= class 1: different orbit from 500m

    MOD09A1s: Cloud State bits=[0-1]

- [00]= class 0: clear
- [01]= class 1: cloudy
- [10]= class 2: mixed
- [11]= class 3: not set, assumed clear

    MOD09A1s: Cloud shadow bits=[2]

- [0]= class 0: no
- [1]= class 1: yes

    MOD09A1s: Land/Water Flag bits=[3-5]

- [000]= class 0: Shallow ocean
- [001]= class 1: Land
- [010]= class 2: Ocean coastlines and lake shorelines
- [011]= class 3: Shallow inland water
- [100]= class 4: Ephemeral water
- [101]= class 5: Deep inland water
- [110]= class 6: Continental/moderate ocean
- [111]= class 7: Deep ocean

    MOD09A1s: Aerosol Quantity bits=[6-7]

- [00]= class 0: Climatology
- [01]= class 1: Low
- [10]= class 2: Average
- [11]= class 3: High

    MOD09A1s: Cirrus detected bits=[8-9]

- [00]= class 0: None
- [01]= class 1: Small
- [10]= class 2: Average
- [11]= class 3: High

    MOD09A1s: Internal Cloud Algorithm Flag bits=[10]

- [0]= class 0: No cloud
- [1]= class 1: Cloud

    MOD09A1s: Internal Fire Algorithm Flag bits=[11]

- [0]= class 0: No fire
- [1]= class 1: Fire

    MOD09A1s: MOD35 snow/ice flag bits=[12]

- [0]= class 0: No
- [1]= class 1: Yes

    MOD09A1s: Pixel adjacent to cloud bits=[13]

- [0]= class 0: No
- [1]= class 1: Yes

    MOD09A1s: BRDF correction performed bits=[14]

- [0]= class 0: No
- [1]= class 1: Yes

    MOD09A1s: Internal Snow Mask bits=[15]

- [0]= class 0: No snow
- [1]= class 1: Snow

### MOD11A1

    MOD11A1: Mandatory QA Flags bits=[0-1]

- [00]= class 0: LST produced, good quality, not necessary to examine more detailed QA
- [01]= class 1: LST produced, other quality, recommend examination of more detailed QA
- [10]= class 2: LST not produced due to cloud effects
- [11]= class 3: LST not produced primarily due to reasons other than cloud

    MOD11A1: Data Quality Flag bits=[2-3]

- [00]= class 0: Good data quality of L1B in bands 31 and 32
- [01]= class 1: Other quality data
- [10]= class 2: TBD
- [11]= class 3: TBD

    MOD11A1: Emis Error Flag bits=[4-5]

- [00]= class 0: Average emissivity error ≤ 0.01
- [01]= class 1: Average emissivity error ≤ 0.02
- [10]= class 2: Average emissivity error ≤ 0.04
- [11]= class 3: Average emissivity error > 0.04

    MOD11A1: LST Error Flag bits=[6-7]

- [00]= class 0: Average LST error ≤ 1
- [01]= class 1: Average LST error ≤ 2
- [10]= class 2: Average LST error ≤ 3
- [11]= class 3: Average LST error > 3

### MOD11A2

    MOD11A2: Mandatory QA Flags bits=[0-1]

- [00]= class 0: LST produced, good quality, not necessary to examine more detailed QA
- [01]= class 1: LST produced, other quality, recommend examination of more detailed QA
- [10]= class 2: LST not produced due to cloud effects
- [11]= class 3: LST not produced primarily due to reasons other than cloud

    MOD11A2: Data Quality Flag bits=[2-3]

- [00]= class 0: Good data quality of L1B in 7 TIR bands
- [01]= class 1: Other quality data
- [10]= class 2: TBD
- [11]= class 3: TBD

    MOD11A2: Emis Error Flag bits=[4-5]

- [00]= class 0: Average emissivity error ≤ 0.01
- [01]= class 1: Average emissivity error ≤ 0.02
- [10]= class 2: Average emissivity error ≤ 0.04
- [11]= class 3: Average emissivity error > 0.04

    MOD11A2: LST Error Flag bits=[6-7]

- [00]= class 0: Average LST error ≤ 1
- [01]= class 1: Average LST error ≤ 2
- [10]= class 2: Average LST error ≤ 3
- [11]= class 3: Average LST error > 3

### MOD13A2

    MOD13A2: Mandatory QA Flags 1km bits[0-1]

- [00]= class 0: VI produced, good quality
- [01]= class 1: VI produced, but check other QA
- [10]= class 2: Pixel produced, but most probably cloud
- [11]= class 3: Pixel not produced due to other reasons than clouds

    MOD13A2: VI Usefulness Flag bits[2-5]

- [0000]= class 0: Highest quality
- [0001]= class 1: Lower quality
- [0010]= class 2: Decreasing quality
- [0100]= class 3: Decreasing quality
- [1000]= class 4: Decreasing quality
- [1001]= class 5: Decreasing quality
- [1010]= class 6: Decreasing quality
- [1100]= class 7: Lowest quality
- [1101]= class 8: Quality so low that it is not useful
- [1110]= class 9: L1B data faulty
- [1111]= class 10: Not useful for any other reason/not processed

    MOD13A2: Aerosol quantity Flags 1km bits[6-7]

- [00]= class 0: Climatology
- [01]= class 1: Low
- [10]= class 2: Average
- [11]= class 3: High

    MOD13A2: Adjacent cloud detected 1km bit[8]

- [00]= class 0: No
- [01]= class 1: Yes

    MOD13A2: Atmosphere BRDF correction performed 1km bit[9]

- [00]= class 0: No
- [01]= class 1: Yes

    MOD13A2: Mixed clouds 1km bit[10]

- [00]= class 0: No
- [01]= class 1: Yes

    MOD13A2: Land/Water Flags 1km bits[11-13]

- [000]= class 0: Shallow Ocean
- [001]= class 1: Land (Nothing else but land)
- [010]= class 2: Ocean Coastlines and lake shorelines
- [011]= class 3: Shallow inland water
- [100]= class 4: Ephemeral water
- [101]= class 5: Deep inland water
- [110]= class 6: Moderate or continental ocean
- [111]= class 7: Deep ocean

    MOD13A2: Possible Snow/Ice 1km bits[14]

- [0]= class 0: No
- [1]= class 1: Yes

    MOD13A2: Possible Shadow 1km bits[15]

- [0]= class 0: No
- [1]= class 1: Yes

### MOD13Q1

    MOD13Q1: Mandatory QA Flags 250m bits[0-1]

- [00]= class 0: VI produced, good quality
- [01]= class 1: VI produced, but check other QA
- [10]= class 2: Pixel produced, but most probably cloud
- [11]= class 3: Pixel not produced due to other reasons than clouds

    MOD13Q1: VI Usefulness Flag 250m bits[2-5]

- [0000]= class 0: Highest quality
- [0001]= class 1: Lower quality
- [0010]= class 2: Decreasing quality
- [0100]= class 3: Decreasing quality
- [1000]= class 4: Decreasing quality
- [1001]= class 5: Decreasing quality
- [1010]= class 6: Decreasing quality
- [1100]= class 7: Lowest quality
- [1101]= class 8: Quality so low that it is not useful
- [1110]= class 9: L1B data faulty
- [1111]= class 10: Not useful for any other reason/not processed

    MOD13Q1: Aerosol quantity Flags 250m bits[6-7]

- [00]= class 0: Climatology
- [01]= class 1: Low
- [10]= class 2: Average
- [11]= class 3: High

    MOD13Q1: Adjacent cloud detected 250m bit[8]

- [00]= class 0: No
- [01]= class 1: Yes

    MOD13Q1: Atmosphere BRDF correction performed 250m bit[9]

- [00]= class 0: No
- [01]= class 1: Yes

    MOD13Q1: Mixed clouds 250m bit[10]

- [00]= class 0: No
- [01]= class 1: Yes

    MOD13Q1: Land/Water Flags 250m bits[11-13]

- [000]= class 0: Shallow Ocean
- [001]= class 1: Land (Nothing else but land)
- [010]= class 2: Ocean Coastlines and lake shorelines
- [011]= class 3: Shallow inland water
- [100]= class 4: Ephemeral water
- [101]= class 5: Deep inland water
- [110]= class 6: Moderate or continental ocean
- [111]= class 7: Deep ocean

    MOD13Q1: Possible Snow/Ice 250m bits[14]

- [0]= class 0: No
- [1]= class 1: Yes

    MOD13Q1: Possible Shadow 250m bits[15]

- [0]= class 0: No
- [1]= class 1: Yes

### MCD43B2

    MCD43B2: Albedo Quality Ancillary Platform Data 1km bits[0-3]
    SDS: BRDF_Albedo_Ancillary

- [0000]= class 0: Satellite Platform: Terra
- [0001]= class 1: Satellite Platform: Terrra/Aqua
- [0010]= class 2: Satellite Platform: Aqua
- [1111]= class 15: Fill Value
- Classes 3-14: Not used

    MCD43B2: Albedo Quality Ancillary Land/Water Data 1km bits[4-7]
    SDS: BRDF_Albedo_Ancillary

- [0000] class 0: Shallow Ocean
- [0001] class 1: Land (Nothing else but land)
- [0010] class 2: Ocean and lake shorelines
- [0011] class 3: Shallow inland water
- [0100] class 4: Ephemeral water
- [0101] class 5: Deep inland water
- [0110] class 6: Moderate or continental ocean
- [0111] class 7: Deep ocean
- [1111] class 15: Fill Value
- Classes 8-14: Not used

    MCD43B2: Albedo Quality Ancillary Sun Zenith Angle at Local Solar Noon Data 1km bits[8-14]
    SDS: BRDF_Albedo_Ancillary

Returns integer value [0-90], 127 is Fill Value

    MCD43B2: Band-wise Albedo Quality Data 1km
    SDS: BRDF_Albedo_Band_Quality

bits[0-3][4-7][8-11][12-15][16-19][20-23][24-27]

- [0000]= class 0: best quality, 75% or more with best full inversions
- [0001]= class 1: good quality, 75% or more with full inversions
- [0010]= class 2: Mixed, 50% or less full inversions and 25% or less fill values
- [0011]= class 3: All magnitude inversions or 50% or less fill values
- [0100]= class 4: 75% or more fill values
- Classes 5-14: Not Used
- [1111]= class 15: Fill Value

## NOTES

In MOD09A1: It seems that cloud related info is not filled properly in the standard QC (MOD09A1 in this module) since version 3, State-QA 500m images (MOD09A1s in this module) should be used (see Vermote et al., 2008). MOD11A2 quality control (QC) bands do not have a FillValue (No-data) according to MODIS Land Products site. However, the metadata of the QC bands (i.e.: `gdalinfo QC_band`) shows `No-data=0`. This value is then transformed into GRASS NULLs when data is imported through r.in.gdal. Applying i.modis.qc on those QC bands will not give the expected range of values in the different QC bits. Therefore, before using i.modis.qc, the user needs to set the NULL value in QC bands back to zero (i.e.: `r.null map=QC_band null=0`) or just edit the metadata with GDAL utilities before importing into GRASS GIS. This is a known issue for MOD11A2 (8-day LST product), but other MODIS products might be affected as well.

## TODO

Add more daily products.

## REFERENCES

- MODIS Products
- Vermote E.F., Kotchenova S.Y., Ray J.P. MODIS Surface Reflectance User's Guide. Version 1.2. June 2008. MODIS Land Surface Reflectance Science Computing Facility. Homepage

## SEE ALSO

i.vi

## AUTHOR

Yann Chemin

## SOURCE CODE

Available at: i.modis.qc source code (history)

Accessed: Saturday May 09 11:20:19 2026

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