EOS TerraMODIS Quality Assurance Overview

Joseph M Glassy,

Director, MODIS Software Development at NTSG

School of Forestry,

Numerical Terradynamics Simulation Group

University of Montana, Missoula Montana USA

Introduction

• Goals:– Summarize our SCF Quality Assurance

program (goals, protocols, interface to ECS)– Describe how QA/Validation information is

organized, formatted, and retrieved.– Introduce key Quality Assurance concepts and

techniques.– Invite feedback on how we can improve.

Quality Assurance, Validation,and Evaluation

• Distributed quality control measures integrated into a NASA operational mission is a relatively new approach (e.g. where SCF’s actively participate in QA beyond initial assignment).

• Quality Control measures divided into QA, evaluation, and a formal validation program.

Quality Assurance, Evaluation, and Validation

• Quality Assurance: near-real-time, tile and pixel level evaluation of tile products.

• Evaluation: reasonableness checks on trends towards “correctness” stopping short of saying outputs are “absolutely right”

• Validation: after-the-fact analysis (formal, global) using sparse point comparisons (FluxNet, Core Validation sites, campaigns like Safari 2000, etc) to “try” to assess absolute accuracy…

Quality Assurance

• Two emphases: routine and trouble-ticket driven• Two scopes: tile level (ECS metadata) vs. pixel

level (separate pixel QA, often as categorical scores)

• Tile level QA: mandated EOSDIS Core System fields as searchable metadata, to qualify data orders, use of tiles in specific analysis applications

• ECS Metadata :Object-Data-Lang./Parameter Value Lang (ODL-PVL) hierarchies.

Quality Assurance Data Flow

• Production at GSFC and/or MODAPS• Goal: SCF acquire(s) and analyze 5% of tiles• SCF check tile, pixel QA, then updates

SCIENCEQUALITYFLAG and explanation…• SCF posts QA evaluation back to LDOPE• LDOPE updates DB at Eros Data Center• User orders, receives tile(s) with updated QA

field(s).

QA VALIDSfor SCIENCEQUALITYFLAG

• Passed• Suspect• Failed• Inferred Passed• Inferred Failed• Being investigated• Not being investigated (default)

ECS Tile Level Metadata

• Appears in HDFEOS tiles as (3) file level character attributes:

• StructMetadata.0 – tile geolocation parameters• CoreMetadata.0 – user searchable key fields to

qualify Query/Orders and assessing usability in scientific analysis and field applications.

• ArchiveMetadata.0 – overlapping info, more for ECS/EDC use in organizing archives. (ignore)

CoreMetadata.0 Example

• ODL/PVL information is organized into a nested hierarchy of object “stanzas”

• QAPERCENTGOODQUALITY or,• QAPERCENTCLOUDCOVER may be helpful…• Example of a ODL/PVL stanza for LOCALGRANULEID

• :CoreMetadata.0 = "\n",• "GROUP = INVENTORYMETADATA\n",• " GROUPTYPE = MASTERGROUP\n",• "\n",• " GROUP = ECSDATAGRANULE\n",• "\n",• " OBJECT = LOCALGRANULEID\n",• " NUM_VAL = 1\n",• " VALUE = \"MOD15A1.A2000208.h18v04.002.2000322020100.hdf\"\n",• " END_OBJECT = LOCALGRANULEID\n",• "\n",• " OBJECT = PRODUCTIONDATETIME\n",• " NUM_VAL = 1\n",• " VALUE = \"2000-11-17T02:01:01.000Z\"\n",• " END_OBJECT = PRODUCTIONDATETIME\n",• "\n",

Embedded QA Bitfield Legend (via Noesys 2.0)

..all QA bitfields merged…

MODLAND_QC ALGOR_PATH

CLOUD_STATE

...vs. each QA bitfield separated…

CLOUD STATE (0=clear, 1=cloudy, 2=mixed, 3=not set)

QC N. Pixels Rel. Frequency

0 648401 45.028

1 404148 28.066

2 82511 5.730

3 304940 21.176

Quality Assurance Techniques

• Tile level analysis using visualization tools like HDFLook, ENVI/IDL, Noesys, HDF-Explorer

• Tile level statistical analysis & characterization• Multiple tile statistical characterizations, over time

periods• Reprojection/mosaic post-processing, to import

into GIS/RS environments, for formal comparison with other geo-spatial datasets.

Quality AssuranceTools Available

• Public domain: HDFLook (Lille,FR); Webwinds (JPL)

• Commercial: Noesys, ENVI/IDL, HDF-Explorer• Future: ERDAS Imagine, PCI EasiPACE, ArcInfo• Open source utilities: reprojtool.exe, qcbits.exe,

others as developed…• Ask your vendor to support HDF-EOS!

Quality AssuranceResources Available

• Consult MODIS Product User’s Guide and/or the product Abstract, available with orders at EDC

• Consult main NASA EOSDIS Core System metadata web site:

• observer.gsfc.nasa.gov/applied_tech/metadata

• Main MODIS Quality Assurance URL is:• http://modland.nascom.nasa.gov/QA_WWW/qahome.html