MODIS Land and HDF-EOSMODIS Land and HDF-EOS

HDF-EOS Workshop PresentationSeptember 20, 2000

Robert WolfeNASA GSFC Code 922, Raytheon ITSS

MODIS Land Science Team Support

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MODIS Land Science Team ProductsMODIS Land Science Team Products

• Goals :– operationally produce terrestrial remotely sensed products that may be

used by expert and non-expert community– establish a 10 year record that has continuity with precursor systems, e.g.,

AVHRR, and the future NPP and NPOESS VIIRS missions

• The MODIS products were developed primarily to serve the global change research community (MODIS has global, near daily coverage) and have many other potential applications

• The MODIS Land Science team was completively selected to developpeer-reviewed product generation algorithms (10 Principal Investigators, lead: Chris Justice, UVA)

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MODIS Land Product Overview (1/3)MODIS Land Product Overview (1/3)

• Radiation Budget Variables– Surface

Reflectance– Surface

Temperature and Emissivity

– Snow and Ice Cover

– BRDF and Albedo

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MODIS Land Product Overview (2/3)MODIS Land Product Overview (2/3)

• Ecosystem Variables– Vegetation Indices– Leaf Area Index

(LAI) and Fractional Photosynthetically Active Radiation (FPAR)

– Vegetation Production

– Net Primary Productivity (NPP)

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MODIS Land Product Overview (3/3)MODIS Land Product Overview (3/3)

• Land Cover Characteristics• Fire and Thermal

Anomalies

• Land Cover

• Vegetation Cover Conversion

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MODIS Production and DistributionMODIS Production and Distribution

• MODIS Land production commenced 02/26/2000

• Product checkout is underway, driven by instrument calibration, geolocation, algorithm code stability and data dependencies

• Land products Beta release from the DAACs began 08/04/2000

• Current products are for evaluation purposes

GSFC DAAC

Level 0 Instrument Data

NSIDC DAAC EDC DAAC

MODAPS

Level 1 Products

Ocean and Atmosphere

Products

Land Snow and Ice Cover Products

Land Non-cryospheric

Products

User Community

Level 1, Ocean and Atmos.

Products

User Community

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MODLAND GridsMODLAND Grids

• Fine resolution grids for the L2G, 3 and 4 products are based on two map projections: – Integerized Sinusoidal Grid (ISIN)– Lambert Azimuthal Equal-Area (LAEA) (polar grids) – Almost all of the fine resolution products will be made in the ISIN

• Exception: Sea-ice products are made in the in the LAEA projection with the grid centered at the north and south poles (EASI Grid implementation)

– Grid cell size varies by product and is either (approx.) 0.25 km, 0.5 km or 1 km – actual size depends on the projection

– Each grid is broken into non-overlapping tiles which cover approx. 10 x 10 deg. area

• Coarse resolution global Climate Modeling Grid (CMG) products are made in a geographic projection with grid cell sizes of 0.25 or 0.5 deg.

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ISIN GridISIN Grid

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HDF-EOS Usage (1/2)HDF-EOS Usage (1/2)

• Both swath and grid format

• 2d, 3d and some 4d SDS arrays• Global and SDS attributes

Type Interim Archive Total L2 Swath 1 5 6 ISIN 8 30 38 LAEA (Polar) 3 2 5 CMG (Geog.) 0 19 19 Total 12 56 68

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HDF-EOS Usage (2/2)HDF-EOS Usage (2/2)

• Subsetting/mosaicing– Collaborated with UAH in HEW development

– Used operationally for 24 Core Validation Sites and planned for Fluxnet sites

• Resampler– Collaborating with EDC/SDSM&T to develop resampler

– Could be used for DAAC services and end user

– L2 and L3 regridding support

• MODLAND developed QA Tools for Team– Extensions to IDL/ENVI and Unix command line

– Bit field handling, etc.

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Good things about HDF/HDF-EOSGood things about HDF/HDF-EOS

• Made collaboration easier between geographically distant scientists/developers– Self documenting file format allows easy exchange of

information between processes

• Standard method of representing geolocation

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HDF-EOS Gripes (1/2)HDF-EOS Gripes (1/2)

• Toolkit doesn't support all HDF objects and access types– Hybrid HDF and HDF-EOS approach used to create/read files– Also need to use SDP toolkit to manipulate metadata

• Subsettting on 3/4 dimensional arrays is difficult– ex. take bands 3 & 5 from 7 bands array (3d) and store

in 2 band array (3d)– downstream users need to which 2 bands were selected

• HDF Specific– No convention for support of bit fields– Performance depends on layout in 3 or 4 dimensional arrays

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HDF-EOS Gripes (2/2)HDF-EOS Gripes (2/2)

• Swath format does not support external geolocation files– workaround -- two geolocation arrays: one accurate 1

km external file and one 5 km internal array

– 5 km array takes up more space and not as accurate• Vendor support growing but still lacking

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For More InformationFor More Information

URL: http://modis.gsfc.nasa.gov/