MOD09 (Surface Reflectance) User's Guide

MOD09 (Surface Reflectance) User’s Guide

MODIS Land Surface Reflectance Science Computing Facility

Principal Investigator: Dr. Eric F. Vermote

Web site: http://modis-sr.ltdri.org

Correspondence e-mail address: [email protected]

Prepared by E. F. Vermote and S. Y. Kotchenova

Version 1.1

March, 2008

Table of Contents

1. Product description ............................................................................................................................... 4

2. List of products ..................................................................................................................................... 4

3. Differences between Collection 4 and Collection 5 ............................................................................. 5

4. Data ordering (& browsing).................................................................................................................. 5

5. Data viewing tools ................................................................................................................................ 6

6. Data product granule ID ....................................................................................................................... 6

7. Data product grids................................................................................................................................. 7

7.1. MODIS sinusoidal grid.................................................................................................................. 7

7.2. Climate Modeling Grid (CMG) ..................................................................................................... 8

8. Data product structure........................................................................................................................... 9

8.1. Description and Science Data Sets (Collection 5)......................................................................... 9

8.1.1. MOD09GQ / MYD09GQ ....................................................................................................... 9

8.1.2. MOD09GA / MYD09GA ..................................................................................................... 10

8.1.3. MOD09Q1 / MYD09Q1....................................................................................................... 12

8.1.4. MOD09A1 / MYD09A1....................................................................................................... 13

8.1.5. MOD09CMG / MYD09CMG .............................................................................................. 14

8.2. Description and Science Data Sets (Collection 4)....................................................................... 16

8.2.1. MOD09GQK / MYD09GQK ............................................................................................... 16

8.2.2. MOD09GHK / MYD09GHK ............................................................................................... 17

8.2.3. MOD09Q1 / MYD09Q1....................................................................................................... 18

8.2.4. MOD09A1 / MYD09A1....................................................................................................... 19

8.2.5 MOD09GST / MYD09GST .................................................................................................. 20

8.3. Data product quality .................................................................................................................... 21

8.3.1. 250-m resolution QA ............................................................................................................ 21

8.3.2. 500-m and coarse resolution QA .......................................................................................... 22

8.4. Data product state flags ............................................................................................................... 23

8.4.1. 500-m and 1-km resolution data state QA (Collection 5)..................................................... 23

8.4.2. 1-km resolution data state QA (Collection 4)....................................................................... 24

8.5. Geolocation flags (Collection 5).................................................................................................. 25

8.6. Scan value information (Collection 5)......................................................................................... 26

8.7. Internal climatology (Collection 5) ............................................................................................. 27

8.8. Orbit and coverage (Collection 4) ............................................................................................... 28

9. Useful links......................................................................................................................................... 29

2

If there is something else you would like to see in the MOD09 User's Guide, please write to us at [email protected]

. We will be happy to consider your suggestions!

Notes:

a) A number of significant improvements have also been introduced into the AC algorithm, including the LUT-format modification for a more accurate interpolation of atmospheric parameters and the use of dynamic aerosol models and ocean bands for improved aerosol retrieval over land surface. A detailed description of these changes can be found at the MODIS Land Quality Assessment Web site

( http://landweb.nascom.nasa.gov/cgi-bin/QA_WWW/newPage.cgi

).

b) Please check the product availability on our Web site at http://modis-sr.ltdri.org

.

3

1. Product description

MOD09 (MODIS Surface Reflectance) is a seven-band product computed from the MODIS Level

1B land bands 1 (620-670 nm), 2 (841-876 nm), 3 (459-479), 4 (545-565 nm), 5 (1230-1250 nm), 6

(1628-1652 nm), and 7 (2105-2155 nm). The product is an estimate of the surface spectral reflectance for each band as it would have been measured at ground level as if there were no atmospheric scattering or absorption. It corrects for the effects of atmospheric gases, aerosols, and thin cirrus clouds.

2. List of products

Collection 4

Product Full Name

Surface Reflectance Daily L2G Global 250 m


Surface Reflectance 8-Day L3 Global 250 m


Surface Reflectance Quality Daily L2G Global 1km

Collection 5

Product Abbreviation

Terra Aqua

MOD09GQK

MOD09GHK

MYD09GQK

MYD09GHK

MOD09Q1

MOD09A1

MOD09GST

MYD09Q1

MYD09A1

MYD09GST

Product Full Name


Surface Reflectance Daily L2G Global 500 m and 1 km



Surface Reflectance Daily L3 Global 0.05Deg CMG*

*CMG – Climate Modeling Grid

Product Abbreviation

Terra Aqua

MOD09GQ

MOD09GA

MYD09GQ

MYD09GA

MOD09Q1

MOD09A1

MOD09CMG

MYD09Q1

MYD09A1

MYD09CMG

4

3. Differences between Collection 4 and Collection 5

The contents of MOD09 have been changed to meet the user's demand.

a) The Daily Surface Reflectance Quality product at 1-km resolution was incorporated into the Daily

Surface Reflectance product at 500-m resolution.

b) The Daily Surface Reflectance products at 500-m and 1-km resolution have new abbreviated names.

c) A new product called Global Daily Surface Reflectance at 0.05° resolution was created. This product is applied on a Climate Modeling Grid (CMG) for the purpose of being used in climate simulation models.

4. Data ordering (& browsing)

a) EOS (Earth Observing System) Data Gateway

The main source of data, a “place an order” database, a quick-start tutorial.

Link: http://edcimswww.cr.usgs.gov/pub/imswelcome/

b) LP DAAC (Land Processes Distributed Active Archive Center)

Useful information and links, ftp-access to a subset of MODIS land products.

Link: http://edcdaac.usgs.gov/main.asp

c) US Geological Survey (USGS) Global Visualization (GloVIS)

Access to selected MODIS land products with browse capability.

Link: http://glovis.usgs.gov/

d) MODIS Land Global Browse Images

5-km versions of selected product to enable synoptic quality assessment.

Link: http://landweb.nascom.nasa.gov/cgi-bin/browse/browse.cgi

e) Earth Science Data Interface (ESDI) at the Global Land Cover Facility

32-day composites, images in GeoTiff format, limited products.

Link: http://landcover.org/index.shtml

5

5. Data viewing tools

a) Imager (platform: Linux)

A software tool specifically designed by the MODIS LSR SCF for viewing surface reflectance suites.

Link: http://modis-sr.ltdri.org/MAIN_MODIS_SOFTWARE/IMAGER.html

b) HDFLook (platforms: SUN, AIX, SGI, Linux, MacOSX, Cygwin)

A multifunctional data processing and visualization tool for land, ocean and atmosphere MODIS data.

Link: http://www-loa.univ-lille1.fr/Hdflook/hdflook_gb.html

c) ENVI (platforms: Windows & Linux)

A software for the visualization, analysis, and presentation of all types of digital imagery.

Link: http://www.ittvis.com/envi/

d) HDF Explorer (platform: Windows)

A software environment where data are first viewed in a tree-like interface, and then optionally loaded and visualized in a variety of ways.

Link: http://www.space-research.org/

6. Data product granule ID

Example 1: MOD09GHK.A2006351.h18v06.004.2006353163945.hdf

MOD09GHK: product name (MODIS Terra Surface Reflectance Daily L2G Global 500 m)

A2000351: Acquisition year (2006) and Julian day (351) h18v06: tile ID (see MODIS sinusoidal grid)

004: Collection 4

2006353163945: Production year (2006), Julian day (353), and time (16:39:45)

Example 2: MOD09CMG.A2000338.005.2006332091104.hdf

MOD09CMG: product name (MODIS Terra Surface Reflectance Daily L3 Global 0.05Deg. CMG)

A2000338: Acquisition year (2000) and Julian day (338)

005: Collection 5

2006332091104: Production year (2006), Julian day (332), and time (09:11:04)

6

7. Data product grids

7.1. MODIS sinusoidal grid

The Earth's surface is divided into tiles (10° x 10°).

Figure 1. The MODIS sinusoidal grid with an example tile shown as a RGB-image produced from the

MODIS data acquired on December 3, 2006 over the US East cost. This product Granule ID is

MOD09A1.A2000337.h11v05.005.2006342055602.hdf.

7

7.2. Climate Modeling Grid (CMG)

The resolution of CMG is 0.05°. This grid is primarily used in climate studies.

Figure 2. An example of MODIS product based on the Climate Modeling Grid. The shown RGB-color image was produced from the MODIS data acquired on December 4, 2000. The product granule ID is

MOD09CMG.A2000338.005.2006332091104.hdf.

8

8. Data product structure

8.1. Description and Science Data Sets (Collection 5)

8.1.1. MOD09GQ / MYD09GQ

MODIS Terra/Aqua Surface Reflectance Daily L2G Global

250 m

Product description: MOD09GQ (MYD09GQ) provides

MODIS band 1-2 daily surface reflectance at 250-m resolution. This product is meant to be used in conjunction with the MOD09GA where important quality and viewing geometry information is stored.

Figure 3. An example of MOD09GQ surface reflectance product. The corresponding MODIS data were collected on

December 3, 2000 over the US territory (in particular, over

Alabama, Mississippi and Florida). Product Granule ID:

MOD09GQ.A2000339.h10v05.005.2006339053418.hdf.

Upper image: Band 2 (near-infrared ) surface reflectance shown on a gray scale. Lower image: A false-color RGB combination of bands 2, 1, and 1. Vegetation appears red, water appears blue, and clouds appears white. A land/sea mask has been used to remove deep ocean water which appears black.

Table 1. Science Data Sets for MOD09GQ / MYD09GQ.

Science Data Sets

(HDF Layers) (5)

Units

num_observations: number of observations within a pixel

250m Surface Reflectance Band

1 (620-670 nm)

None

Reflectance

250m Surface Reflectance Band

2 (841-876 nm)

Reflectance

250m Reflectance Band

Quality (see Table 11) obs_cov: Observation Coverage

(percentage of the grid cell area covered by the observation)

Bit Field

Percent

Bit Type

8-bit signed integer


16-bit signed

integer

16-bit unsigned integer


Fill

Value

Valid Range Scale Factor

-1 0 - 127 NA

-28672 -100 - 16000 0.0001

-28672 -100 - 16000 0.0001

2995 0 - 4096

-1 0 - 100

NA

(0.001)

0.0099999997

76482582

9

8.1.2. MOD09GA / MYD09GA

MODIS Terra/Aqua Surface Reflectance Daily L2G Global 500 m and 1 km

Product description: MOD09GA (MYD09GA) provides

MODIS band 1-7 daily surface reflectance at 500-m resolution and 1-km observation and geolocation statistics.

Figure 4. A MOD09GA RGB-image composed of surface reflectance measured by MODIS bands 1 (red), 4 (green) and 3 (blue) on December 6, 2000 over the US East coast.

Product granule ID:

MOD09GA.A2000340.h11v05.005.2006339102700.hdf

Table 2. Science Data Sets for MOD09GA / MYD09GA.

Data

Group

1 km


(HDF Layers (21))

num_observations_1km:

Number of Observations

State_1km: Reflectance

Data State (see Table 13 )

Sensor Zenith Angle

Sensor Azimuth Angle

Range: pixel to sensor

NA

Units

Bit Field

Degree

Degree

Meter

Bit Type Fill Value


-1


65535



-32767

-32767


65535

Valid Range

0 - 127

0 - 57335

0 - 18000

27000 - 65535

Scale Fac-

NA

NA

0.01

-18000 - 18000 0.01

25

tor

Solar Zenith Angle

Solar Azimuth Angle

Degree

Degree



-32767

-32767

0 - 18000 0.01

-18000 - 18000 0.01

gflags:

Geolocation flags

(see Table 15 )

Bit Field


255 0 - 248 NA orbit_pnt: Orbit Pointer none


-1 0 - 15 NA

***** ******************** ******** ********** ******** ********** *********

10

500 m num_observations_500m none


-1 sur_refl_b01: 500m Surface

Reflectance Band 1 (620-

670 nm)

Reflectance sur_refl_b02: 500m Surface


876 nm)



479 nm)



565 nm)



1250 nm)



1652 nm)



2155 nm)

Reflectance

QC_500m: 500m Reflectance Band Quality (see

Table 12)

Bit Field








-28672

-28672

-28672

-28672

-28672

-28672

-28672


787410671

0 - 127 NA

NA

-100 - 16000 0.0001

-100 - 16000 0.0001

-100 - 16000 0.0001

-100 - 16000 0.0001

-100 - 16000 0.0001

-100 - 16000 0.0001

-100 - 16000 0.0001

0 -

4294966019

Obs_cov_500m: Observation coverage

Percent


-1 0 - 100

(0.01)

0.00999999

77648258 iobs_res: Observation number q_scan: 250m scan value information (see Table 16) none

Bit Field



255

255

0 - 254

0 - 255

NA

NA

11

8.1.3. MOD09Q1 / MYD09Q1

MODIS Terra/Aqua Surface Reflectance 8-Day L3 Global 250 m

Product description: MOD09Q1 (MYD09Q1) provides

MODIS band 1-2 surface reflectance at 250-m resolution. It is a level-3 composite of MOD09GQ (MYD09GQ). Each

MOD09Q1 (MYD09Q1) pixel contains the best possible

L2G observation during an 8-day period as selected on the basis of high observation coverage, low view angle, the absence of clouds or cloud shadow, and aerosol loading.

Figure 5. An example of MOD09Q1 surface reflectance product. The corresponding MODIS data were collected in

December, 2000 over the US territory (in particular, over

Alabama, Mississippi and Florida). Product Granule ID:

MOD09Q1.A2000337.h10v05.005.2006342044337.hdf.


Table 3. Science Data Sets for MOD09Q1 / MYD09Q1



Units Bit Type Fill Value

250m Surface Reflectance

Band 1 (620-670 nm)

Reflectance 16-bit signed integer -28672

Valid Range

-100 - 16000

Scale Factor

0.0001


Band 2 (841-876 nm)

Reflectance 16-bit signed integer -28672 -100 - 16000 0.0001


Quality (see Table 11)

Bit Field


65535 0 - 32767 NA

12

8.1.4. MOD09A1 / MYD09A1


Product description: MOD09A1 (MYD09A1) provides MODIS band 1-7 surface reflectance at 500 m resolution. It is a level-3 composite of 500-m resolution

MOD09GA (MYD09GA). Each product pixel contains the best possible L2G observation during an 8-day period as selected on the basis of high observation coverage, low view angle, absence of clouds or cloud shadow, and aerosol loading.

Figure 6. A MOD09A1 RGB image composed of surface reflectance data measured by bands 1 (red), 4 (green) and

3(blue) in December, 2000 over the US East coast. Granule

ID: MOD09A1.A2000337.h11v05.005.2006342055602.hdf

Table 4. Science Data Sets for MOD09A1 / MYD09A1




Band 1 (620-670 nm)


Band 2 (841-876 nm)


Band 3 (459-479 nm)


Band 4 (545-565 nm)


Band 5 (1230-1250 nm)


Band 6 (1628-1652 nm)

Units

Reflectance

Reflectance

Reflectance

Reflectance

Reflectance

Reflectance

Bit Type







Fill Value

-28672

-28672

-28672

-28672

-28672

-28672

Valid Range

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

Scale

Factor

0.0001

0.0001

0.0001

0.0001

0.0001

0.0001


Band 7 (2105-2155 nm)

0.0001



Solar Zenith Angle

Bit Field

Degree

View Zenith Angle Degree

Relative Azimuth Angle Degree





4294967295

0

0

0

0 - 4294966531

0 - 18000

0 - 18000

-18000 - 18000

NA

0.01

0.01

0.01

500m State Flags (see Ta-

ble 13)

Day of Year

Reflectance

Bit field

Julian day




-28672

65535

65535

-100 - 16000

0 - 57343

1 - 366

NA

NA

13

8.1.5. MOD09CMG / MYD09CMG

MODIS Terra/Aqua Surface Reflectance Daily L3 Global 0.05Deg CMG

Product description: MOD09CMG (MYD09CMG) provides MODIS band 1-7 surface reflectance at

0.05-degree resolution. This product is based on a Climate Modeling Grid (CMG) for the purpose of being used in climate simulation models.

Figure 7. A MOD09CMG RGB-image composed of surface reflectance data measured by bands 1

(red), 4 (green) and 3 (blue) on December 7, 2000. The MODIS product granule ID is

MOD09CMG.A2000341.005.2006347161131.hdf.

14

Table 5. Science Data Sets for MOD09CMG / MYD09CMG.



Coarse Resolution Surface Reflectance

Band 1 (620-670 nm)


Band 2 (841-876 nm)


Band 3 (459-479 nm)


Band 4 (545-565 nm)


Band 5 (1230-1250 nm)


Band 6 (1628-1652 nm)


Band 7 (2105-2155 nm)

Coarse Resolution Solar Zenith Angle

Coarse Resolution View Zenith Angle

Coarse Resolution Relative Azimuth

Angle

Coarse Resolution Ozone

Coarse Resolution QA (see Table 12)

Coarse Resolution Internal CM (see

Table 17)

Averaged Number of Pixels

Coarse Resolution Brightness Temperature Band 20 (3.360-3.840 µm)




Coarse Resolution Granule Time

Units

Reflectance

Reflectance

Reflectance

Reflectance

Reflectance

Reflectance

Reflectance

Degree

Degree

Degree cm atm degrees K degrees K degrees K degrees K

HHMM unitless

Bit Field

Bit Field

Bit Type

Fill

Value

Valid Range

Scale

Factor








-28672

-28672

-28672

-28672

-28672

-28672

-28672




0

0

0


0


0


0


0


0

16-bit integer 0


0


0


0

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

0 - 18000

0 - 18000

-18000 - 18000

0 -255

0 - 40000

0 - 40000

0 - 40000

0 - 40000

0 - 2355

0 - 1073741824

1 - 8191

1 - 40

0.0001

0.0001

0.0001

0.0001

0.0001

0.0001

0.0001

0.01

0.01

0.01

400

100

100

100

100

1

NA

NA

NA

15

8.2. Description and Science Data Sets (Collection 4)

8.2.1. MOD09GQK / MYD09GQK

MODIS Terra/Aqua Surface Reflectance Daily L2G Global 250 m

Product description: MOD09GQK (MYD09GQK) provides MODIS band 1-2 daily surface reflectance at

250-m resolution. The best observations during a 24-hour period, as determined by overall pixel quality and observational coverage, are matched geographically according to corresponding 250-m Pointer Files

(MODPTQKM (see Section 9)). Quality information for this product is provided at three different levels of detail: for individual pixels, for each band and each resolution, and for the whole file.

Figure 8. An example of MYD09GQK surface reflectance product. The corresponding MODIS data were collected on May 26, 2004 over Brazil, South America. Granule ID:

MYD09GQK.A2004148.h12v09.004.2004151002653.hdf.

Upper image: Band 2 (near-infrared ) Surface Reflectance shown on a gray scale. Lower image: A false-color RGB combination of bands 2, 1, and 1. Vegetation appears red, water appears blue, and clouds appears white. A land/sea mask has been used to remove deep ocean water which appears black.

Table 6. Science Data Sets for MOD09GQK / MYD09GQK


(HDF Layers) (5)

Units Data Type

Fill

Value

Valid Range

Scale Factor

(divide by)

250m Surface Reflectance Band 1

(620-670 nm)

Reflectance 16-bit signed integer -28672 -100 - 16000 10000

250m Surface Reflectance Band 2

(841-876 nm)

Reflectance 16-bit signed integer -28672 -100 - 16000 10000

250m Reflectance Band Quality

(see Table 11)

Bit field 16-bit unsigned integer 2995

Orbit and coverage (see Table 18) Bit field 8-bit unsigned integer 15

Number of Observations NA 8-bit signed integer -1

0 - 4096

0 - 255

0 - 127

NA

NA

NA

16

8.2.2. MOD09GHK / MYD09GHK

MODIS Terra/Aqua Surface Reflectance Daily L2G Global 500 m

Product description: MOD09GHK (MYD09GHK) provides surface reflectance data at 250-m resolution for bands 1-2 and at 500-m resolution for bands 3-7. The best observations during a 24-hour period, as determined by overall pixel quality and observational coverage, are matched geographically according to corresponding 500-m

Pointer Files (MODPTHKM (see Section 9). Quality information for this product is provided at three different levels of detail: for individual pixels, for each band and each resolution, and for the whole file.

Figure 9. A MOD09GHK RGB-image composed of surface reflectance measured by bands 1 (red), 4 (green) and 3 (blue) on December 17, 2000 Sahara, Africa. Granule ID:

MOD09GHK.A2006351.h18v06.004.2006353163945.hdf

Table 7. Science Data Sets for MOD09GHK / MYD09GHK




Band 1 (620-670 nm)

Units

Reflectance

Data Type


Fill Value

-28672

Valid Range

-100 - 16000

Scale Factor

(divide by)

10000


Band 2 (841-876 nm)


Band 3 (459-479 nm)


Band 4 (545-565 nm)


Band 5 (1230-1250 nm)


Band 6 (1628-1652 nm)


Band 7 (2105-2155 nm)

Reflectance

Reflectance

Reflectance

Reflectance

Reflectance

Reflectance



Orbit and coverage

Bit field

Bit field

Number of Observations NA








-28672

-28672

-28672

-28672

-28672

-28672

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

787410671 0 - 4294967296

8-bit unsigned integer 15

8-bit signed integer -1

0 - 255

0 - 127

10000

10000

10000

10000

10000

10000

NA

NA

NA

17

8.2.3. MOD09Q1 / MYD09Q1


Product description: MOD09Q1 (MYD09Q1) provides band 1-2 surface reflectance at 250 m resolution. It is a level-3 composite of MOD09GQK (MYD09GQK). The best observations during an 8-day period, as determined by overall pixel quality and observational coverage, are matched geographically according to corresponding 250-m

Pointer Files (MODPTQKM (see Section 9)). Quality information for the MOD09Q1 product is provided at three different levels of detail: for individual pixels, for each band and each resolution, and for the whole file.

Figure 10. An example of MYD09GQK surface reflectance product. The corresponding MODIS data were collected in

May 2004 mostly over Brazil, South America. Granule ID:

MYD09Q1.A2004145.h12v10.004.2004157154243.hdf.


Table 8. Science Data Sets for MOD09Q1 / MYD09Q1



Surface Reflectance for band

1 (620-670 nm)

Surface Reflectance for band

2 (841-876 nm)

Surface reflectance 250m quality control flags (see Ta-

ble 11)

Units Data Type

16-bit unsigned

integer

Fill Value Valid Range

Reflectance 16-bit signed integer -28672 -100 - 16000

Reflectance 16-bit signed integer -28672 -100 - 16000

Bit field 65535 0-4294966531

Scale Factor

0.0001

0.0001

NA

18

8.2.4. MOD09A1 / MYD09A1


Product description: MOD09A1 (MYD09A1) is a composite of MOD09GHK (MYD09GHK). The best observations during an 8-day period, as determined by the overall pixel quality and observational coverage, are matched geographically according to corresponding 500-m Pointer Files (MODPTHKM (see

Section 9)). Quality information for the MOD09A1 product is provided at three different levels of detail: for individual pixels, for each band and each resolution, and for the whole file.

Figure 11. A MOD09A1 RGB-image composed of surface reflectance measured by bands 1 (red), 4 (green) and 3(blue) in May 2004 mostly over Brazil, South America. Granule ID:

MYD09A1.A2004145.h12v10.004.2004157154243.hdf.

Table 9. Science Data Sets for MOD09A1 / MYD09A1



Surface Reflectance for band 1

(620-670 nm)


(841-876 nm)


(459-479 nm)


(545-565 nm)


(1230-1250 nm)

Units

reflectance reflectance reflectance reflectance reflectance

Data Type-bit






Fill Value

-28672

-28672

-28672

-28672

-28672

Valid Range

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

-100 - 16000

Scale

Factor

0.0001

0.0001

0.0001

0.0001

0.0001


(1628-1652 nm)


(2105-2155 nm)

Surface reflectance 500m quality control flags (see Table 12)

Solar zenith

View zenith reflectance reflectance

Bit field

Degree

Degree





Relative azimuth

Surface reflectance 500m state flags (see Table 13)

Degree

Bit field



Surface reflectance day of year Julian Day 16-bit unsigned integer

-28672

-28672

-100 - 16000

-100 - 16000

32-bit unsigned integer 4294967295 0 - 4294966531

0

0

0

65535

65535

0 - 18000

0 - 18000

0.01

0.01

-18000 - 18000 0.01

0

0 - 366

0.0001

0.0001

NA

NA

NA

19

8.2.5 MOD09GST / MYD09GST

MODIS Terra/Aqua Surface Reflectance Quality Daily L2G Global 1 km

Product description: MOD09GST is a restructured version of the quality data in level-2 surface reflectance. It summarizes the quality of the MOD09 products, including atmospheric and other correction states. The product specifically contains information pertaining to cloud and cloud shadow, land and water designations, aerosols, and the data source of corrections performed on the file.

color cloud value land/sea value

magenta [undefined] [undefined] violet clear shallow yellow cloudy shallow green clear land red cloudy land white clear coastlines/shorelines coral cloudy coastlines/shorelines plum cloudy shallow inland water

MOD09GHK RGB-image blue clear continental/moderate sienna cloudy continental/moderate

Figure 12. The table above interprets the colors used to display the MOD09GST surface reflectance data state product over MODIS tile h08v06 covering northern Mexico on April 4,

2000.

Corresponding information from MOD09GST

Table 10. Science Data Sets for MOD09GST / MYD09GST



1km Reflectance Data State QA

(see Table 14 )

Orbit and coverage

Number of Observations

Units Data Type-bit

Bit field 16-bit unsigned integer

Bit field 8-bit unsigned integer

NA 8-bit signed integer

Fill Value Valid Range

65535

15

-1

0 - 65535

0 - 255

0 - 127

20

8.3. Data product quality

8.3.1. 250-m resolution QA

Table 11. 250-m surface reflectance data QA description (16-bit).

Bit

No.

Parameter Name

Bit

Comb.

00

01

0-1 MODLAND QA bits

10

Sur_refl_qc_250m

corrected product produced at ideal quality all bands corrected product produced at less than ideal quality some or all bands corrected product not produced due to cloud effects all bands

11 corrected product not produced due to other reasons some or all bands may be fill value [Note that a value of (11) overrides a value of (01)]. clear 2-3═ cloud state 00

01

10

11 cloudy mixed not set; assumed clear

1000 dead detector; data interpolated in L1B

1001 solar zenith >= 86 degrees

1010 solar zenith >= 85 and < 86 degrees

4-7 band 1 data quality four bit range

1100 internal constant used in place of climatological data for at least one atmospheric constant

1101 correction out of bounds, pixel constrained to extreme allowable value

1110 L1B data faulty

1111 not processed due to deep ocean or clouds

8-

11═ band 2 data quality four bit range

12

13 atmospheric correction performed adjacency correction performed

SAME AS BAND ABOVE

1 yes

0 no

1 yes

0 no

14-

15 spare (unused) - ---

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8.3.2. 500-m and coarse resolution QA

Table 12. 500-m and coarse resolution surface reflectance data QA description (32-bit).

Bit

No.

Parameter Name

0-1 MODLAND QA bits

Bit

Comb.

00

01

10

11

QC_500m / Coarse Resolution QA

corrected product produced at ideal quality -- all bands corrected product produced at less than ideal quality -- some or all bands corrected product not produced due to cloud effects -- all bands corrected product not produced for other reasons -- some or all bands, may be fill value (11) [Note that a value of

(11) overrides a value of (01)].

1000 dead detector; data interpolated in L1B

1001 solar zenith >= 86 degrees

1010 solar zenith >= 85 and < 86 degrees

2-5 band 1 data quality, four bit range

1100

1101 internal constant used in place of climatological data for at least one atmospheric constant correction out of bounds, pixel constrained to extreme allowable value


1110 L1B data faulty

1111 not processed due to deep ocean or clouds same as band above

10-13 band 3 data quality four bit range same as band above





30

31 atmospheric correction performed adjacency correction performed same as band above same as band above same as band above same as band above

1 yes

0 no

1 yes

0 no

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8.4. Data product state flags

8.4.1. 500-m and 1-km resolution data state QA (Collection 5)

Table 13. 500-m and 1-km resolution data state QA description (16-bit)

Bit No. Parameter Name Bit Comb.

state_1km

00 clear

01 cloudy

10 mixed

11 not set, assumed clear

1 yes

0 no

001 land

010

011 ocean coastlines and lake shorelines shallow inland water

10

11

12

13

00 climatology

01 low

10 average

11 high

00 none

01 small

10 average

11 high internal cloud algorithm flag

1 cloud internal fire algorithm flag

1 fire

MOD35 snow/ice flag

Pixel is adjacent to cloud

1 yes

0 no

1 yes

0 no

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15

14

15

10

11

BRDF correction performed

1 yes

0 no internal snow mask

1

0 snow no snow

8.4.2. 1-km resolution data state QA (Collection 4)

Table 14. 1-km Surface Reflectance data state QA Description (16-bit) for Collection 4.

Bits 10-16 contain different information in Collection 4 product compared to Collection 5 product.

PGE11 cloud algorithm flag

1 clear

0 cloudy

PGE11 fire algorithm flag

1 fire

12 MOD35 snow/ice flag

13-14 BRDF correction performed

1 yes

0 no

00 no

PGE11 snow algorithm flag

1

0 snow no snow

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8.5. Geolocation flags (Collection 5)

Table 15. 1-kilometer geolocation flags (16-bit).

Bit No.

0-2 fill

3

4

5

Description

Sensor range validity flag

Bit Comb.

state_1km

00 Fill

0 Valid

1 Invalid

Digital elevation model quality flag

0 Valid

1 Missing/inferior

Terrain data validity

0 Valid

1 Invalid

6 Ellipsoid intersection flag

0 Valid

1 Invalid

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8.6. Scan value information (Collection 5)

Table 16. 250-m scan value information description (8-bit).

Bit No.

0

1

Parameter Name Bit Comb. q_scan

1 yes missing observation in quadrant 4 [+0.5 row, +0.5 column]

0 no missing observation in quadrant 3 [+0.5 row, -0.5 column];

1 yes

0 no

2

3

4

5

6

7 missing observation in quadrant 2 [-0.5 row, +0.5 column]

1 yes

0 no missing observation in quadrant 1 [-0.5 row, -0.5 column]

1 yes scan of observation in quadrant 4 [+0.5 row, +0.5 column]

0 no

1 same scan of observation in quadrant 3 [+0.5 row, +0.5 column]

0 different


0 different


0 different

1 same

0 different

Note: The 250-m samples are for each of four quadrants within a 500-m cell. The first line/sample is in the upper left (north-west) corner of the image.

•

•

•

•

0 -- first 250m line (row), first 250m sample (column)

1 -- first 250m line, second 250m sample

2 -- second 250m line, first 250m sample

3 -- second 250m line, second 250m sample

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8.7. Internal climatology (Collection 5)

Table 17. Coarse resolution internal CM (15-bit).

Bit No. Description

0 cloudy

1 clear

4 snow

5 fire

7 dust

9 pixel is adjacent to cloud

10-11 cirrus

Bit Comb.

state

1 yes

0 no

1 yes

0 no

1 yes

0 no

1 yes

0 no

1 yes

0 no

1 yes

0 no

1 yes

0 no

1 yes

0 no

1 yes

0 no

1 yes

0 no

00 none

01 small

10 average

11 high

0 no salt pan

13 criteria used for aerosol retrieval

14 AOT (aerosol optical thinkness) has climatological values

1 yes

0 no

15 Unused - -

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8.8. Orbit and coverage (Collection 4)

Table 18. Orbit and coverage data set (8-bit) for Collection 4 (the orbit the observation came from and the observation coverage).

Bit No. Parameter Name Bit Comb. orb_cov_1

range: from 0 to 13 key: from 0000 (0) to 1011 (13)

4

6-7 scan half flag

000

001

0.0 – 12.5%

12.5 – 25.0%

Note: The orbit number is not the absolute orbit number but a relative orbit number in the file. In addition a flag is stored which distinguishes between observations which are in the top half of the scan (the first 5 1-km scan lines in the along track direction) and the bottom half of the scan (the last 5 1-km scan lines). The observation coverage is the area of intersection of observation footprint and cell divided by the area of the observation.

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9. Useful links

a) 250-m Pointer Files (MODPTQKM)

Link: http://edcdaac.usgs.gov/modis/modptqkmv4.asp

b) 500-m Pointer Files (MODPTQKM)

Link: http://edcdaac.usgs.gov/modis/modptqkmv4.asp

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