SeaDAS lab Jeremy Werdell - PowerPoint Presentation

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SeaDAS

lab

Jeremy WerdellSean BaileyNASA Goddard Space Flight CenterUMaine Ocean Optics Summer CourseJuly 10 – Aug 4 2017Acknowledgements: Aynur Abdurazik, Matt Elliot, Danny Knowles, & Don Shea

jeremy.werdell@nasa.gov

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by the end of this lab,

we hope you will …understand the organization & flow of satellite ocean color databe comfortable with SeaDAS & without fear of breaking itjeremy.werdell@nasa.gov

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SeaWiFS

Data Analysis System (

SeaDAS)http://seadas.gsfc.nasa.govhttp://oceancolor.gsfc.nasa.govimage analysis package for processing, displaying, analyzing, & QC’ing satellite ocean color data

what is

SeaDAS

?

jeremy.werdell@nasa.gov

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available for use with all NASA Ocean Biology Processing Group (OBPG) supported sensors: MODIS-Aqua & -Terra,

SeaWiFS

, OCTS,& CZCS, plus VIIRS, MERIS, HICO, OLI

general scientific imagery & data analysis package

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conceived of to fill a need in the post-CZCS, pre-

SeaWiFS

era when common tools did not exist to: - display satellite ocean color data - reproduce (& refine) the operational NASA productswhy SeaDAS?

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still uncommon for agencies to distribute source code to replicate operational satellite data processing

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SeaDAS: What’s in the box…

SeaDAS uses a module-based architecture

Modules/ToolsImage ViewFile ManagerLayer ManagerMask ManagerCollocation ToolMosaic ToolMap Projection ToolGeoCoding ToolStatistics ToolsMath Band ToolFilter Band Tool5

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It’s a big box …

NASA’s Ocean Biology Processing Group Science processing softwareCustom Data File Readers

(more than 15 specific satellites supported)Coastline and Land Mask ModuleBathymetry ModuleContour Line ModuleShip Track & SeaBASS Band (image) FiltersRGB ProfilesColor ManagerColor BarMap GridlinesInternal Help Pages

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lab organization

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morning lecture

: introduction & bookkeeping

afternoon lecture

: satellite data processing

instructor-led demonstrations on

:

- the

SeaDAS environment & visualizing data

- flags & masks - data analysis tools - satellite data processing - comparing satellite & in situ measurementsstudent exercises following each demonstration

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jeremy.werdell@nasa.gov

8has anyone used SeaDAS before?

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SEA SURFACE

TOP-OF-THE-ATMOSPHERE

the satellite views the

spectral light field

at the top-of-the-atmosphere

SATELLITE

PHYTOPLANKTON

1. remove atmosphere from total signal to derive estimate of light field emanating from sea surface

(remote sensing reflectance,

R

rs

)

2. relate spectral

R

rs

to C

a

(or geophysical product of interest)

3. spatially / temporally bin and remap satellite C

a

observations

satellite ocean color

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SeaDAS

infrastructuresource code (l2gen, l3bin, etc.) written in C & Fortran

same code used in production at GSFCjeremy.werdell@nasa.gov10

wrapper scripts written in Python (

modis_GEO.py

, etc.)

visualization GUI (graphical user interface) written in Java

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requirements

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satellite ocean color file formats

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HDF &

netCDF

http://www.hdfgroup.org

/

http://www.unidata.ucar.edu/software/netcdf

/

self-describing & machine independent file structure

layers of array-oriented data proceeded by global attributes that describe the data & provide metadata

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SeaDAS resources

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SeaDAS

Web site – online help & instructions

http://seadas.gsfc.nasa.gov

OceanColor

online forum –

SeaDAS

-specific boards

http://oceancolor.gsfc.nasa.gov

/forum/oceancolor/

forum_show.plSeaDAS 7 interactive help (buttons within the GUI)emailseadas@seadas.gsfc.nasa.govYouTube

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jeremy.werdell@nasa.gov

14lecture break

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Level 0

raw digital countsnative binary formatLevel 1A

raw digital countsHDF formattedLevel 1Bcalibrated reflectancesconverted telemetryLevel 2

geolocated

geophysical products for each pixel

ancillary

data

wind speed

surface pressure

total ozone

Reynolds SST

GEO

geolocation

radiant path geometry

ATT & EPH

spacecraft attitude

spacecraft position

MODIS data levels & flow

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SEA SURFACE

TOP-OF-THE-ATMOSPHERE

the satellite views the

spectral light field

at the top-of-the-atmosphere

SATELLITE

PHYTOPLANKTON

1. remove atmosphere from total signal to derive estimate of light field emanating from sea surface

(remote sensing reflectance,

R

rs

)

2. relate spectral

R

rs

to C

a

(or geophysical product of interest)

3. spatially / temporally bin and remap satellite C

a

observations

satellite ocean color

e

verything up to Level-1B

Level-2

Level-3

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common software for Level-2 processing of MODIS,

SeaWiFS, MERIS, & other sensors in a consistent mannersupports a multitude of product algorithms and processing methodologiesstandard productsevaluation productsuser defined productsrun-time selectionLevel-2 processing (l2gen)

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a

s data is processed by l2gen from Level 1 to Level 2, checks are made for different defined conditions

when certain tests and conditions are met for a given pixel, a flag is set for that pixel for that conditiona total of 31 flags can be set for each pixelthese l2gen processing flags are stored in the Level 2 data file as the "

l2_flags

"

product

t

he

storage method sets bits to 0 or 1 in 32-bit integers that correspond to each

pixel

Level-2 processing (l2gen)

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(flags in red are

masked during Level 3 processing)

Level-2 processing flagsjeremy.werdell@nasa.gov19

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nLw (443)

RGB Image

glintsediments

c

loud

a

dd

masking for high glint

a

dd

masking for

straylight

Level-2 flags & masks

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SEA SURFACE

TOP-OF-THE-ATMOSPHERE

the satellite views the

spectral light field

at the top-of-the-atmosphere

SATELLITE

PHYTOPLANKTON

1. remove atmosphere from total signal to derive estimate of light field emanating from sea surface

(remote sensing reflectance,

R

rs

)

2. relate spectral

R

rs

to C

a

(or geophysical product of interest)

3. spatially / temporally bin and remap satellite C

a

observations

satellite ocean color

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Level 3 binned

geophysical products averaged spatially and/or temporallysinusoidally

distributed, equal area binsLevel 3 mappedimages created by mapping and scaling binned productsuser-friendly, cylindrical equiangular projection

Level 2

geolocated

geophysical products for each pixel

Bin resolution 4.6

x

4.6 km

2

Mapped resolution0.042-deg0.084-degComposite PeriodsDaily8-dayMonthlySeasonalYearlyMission

MODIS Level-3 processing

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jeremy.werdell@nasa.gov

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p

rojection - any process which transforms a spatially organized data set from one coordinate system to

anothermapping - process of transforming a data set from an arbitrary spatial organization to a uniform (rectangular, row-by-column) organization, by processes of projection & resamplingbinning

-

process

of projecting

& aggregating

data from an arbitrary spatial

& temporal organization

to a uniform spatial scale over a defined time

range

Level-3 terminologyjeremy.werdell@nasa.gov23

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e

qual-area

- sinusoidal with equally space rows & number of bins per row proportional to sine of latitudeequal-angle - rectangular (Platte Carre) with rows and columns equally spaced in latitude and longitude

equal

-area

& -

angle projections are equivalent at the

equator

ocean color projections

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sinusoidal equal area projection

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bin file grid

map file grid

bin filesmultiple productsstored as floatsampling statistics includedmap filessingle productstored as scaled integerLevel-3 binned vs. mappedjeremy.werdell@nasa.gov

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Increasing Pixel Size

MODIS “bow-tie” effect

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o

ne MODIS scan at ~45 degrees scan angle

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t

wo MODIS scans showing overlap of pixels

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m

ultiple MODIS scans showing pixel overlap

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b

in boundaries overlaid on pixel locations

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o

cean coverage over time for binned files

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33lecture break

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acquiring ocean color data

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http://oceancolor.gsfc.nasa.gov/cgi/browse.pl

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BACKUP

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SeaDAS development timeline

conceived of in the mid-1990’s, referred to as “SeaPAK”renamed “SeaDAS” circa the launch of SeaWiFS in 1997

stimulated development of the ESA BEAM software package to visualize ENVISAT (MERIS) data products circa 2002awarded NASA Software of the Year in 2003built on an IDL (Interactive Data Language) infrastructure through June 2012 (version 6.4)recast as an integrated tool with the ESA BEAM software package in Spring 2013 (version 7)jeremy.werdell@nasa.gov36

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SeaDAS 7

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collaboration with BEAM (

Brockmann

Consult, Germany)

- look & feel of BEAM

- functionality & processing capabilities of

SeaDAS

6.4officially released in April 2013

you will have questions that I cannot answer – this is also ok

w

e will break something at some point today – this is ok

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BEAM & SeaDAS: Cross usability

File Inter-CompatibilityA file/session may be saved from SeaDAS

and loaded into BEAM*A file/session may be saved from BEAM and loaded into SeaDASPick One (then use the other when …)FEATURES: … it contains a feature you needBUGS: … it does not contain a bug impeding youHelpForum – check bothInternal Help – check bothVideos – Many SeaDAS YouTube videos are (indirectly or directly) applicable to BEAM* Some minor SeaDAS

specific added metadata could get lost.

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