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Auto/Semi-Automated processing

of ENVISAT ASAR imagery

of the Arctic Ocean

- Explore ArcGIS manual procedure

- Implement as a Python script

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XUELONG cruise during CHINARE-2010

from July 1 Xianmen to Sept 20 Shanghai

http://www.utsa.edu/LRSG/Arctic/index.htm

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XUELONG, crew, and staff

at Long-term Ice Station, Aug 17, 2010

http://www.utsa.edu/LRSG/Arctic/index.htm

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"Summer sea ice motion..." by Ron Kwok, JPL

Geophysical Research Letters, Vol 35, 2008

Jul Aug

2003

2004

Note: Longitude lines

added for 0, 90, 150,

180, and 270 degrees

Purple lines mark the

main region covered

during by the XUELONG

during CHINARE-2010

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"Summer sea ice motion..." by Ron Kwok, JPL

Geophysical Research Letters, Vol 35, 2008

Jul Aug

2005

2006

Note: Longitude lines

added for 0, 90, 150,

180, and 270 degrees

Purple lines mark the

main region covered

during by the XUELONG

during CHINARE-2010

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Background for CHINARE-2010

While the XUELONG icebreaker went by sea,

ENVISAT took SAR imagery from space

XUELONG saw sea ice from Jul 21 to Aug 28

160 ENVISAT ASAR images covering Jul 23 to

Sep 28, plus 6 missing or damaged images

Data for one image takes up 100 to 500 MB

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ENVISAT drawing

https://reader009.{domain}/reader009/html5/0408/

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Desired results

Automated process to create image rasters and

boundary polylines and put them into a geodatabase

Reasonable to handle ENVISAT ASAR datasets as fastas they are produced by the satellite

Average for Beaufort Sea (Arctic Ocean) only

16 daily datasets ~ 0.8 GB compressed data

Average for entire Arctic and Antarctic Oceans

80 daily datasets ~ 4 GB compressed data

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Step 1

Use web browser

Get ENVISAT ASAR data

In class: one dataset

Homework: multiple datasets

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>>> www.polarview.aq

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PolarView holds data only 1 month

Can filter by region

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Click an image to preview

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Can display list of images

Avg 16 daily datasets for Beaufort Sea

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Arctic Ocean - sample 24 hours

35 datasets

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Antarctic Ocean - sample 24 hours

28 datasets

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Select and download datasets

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Step 2

Uncompress and display original files

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ESA compressed the datafiles twice

Uncompress twice

Open the nested folders

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Original ASAR images are very dark

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Fix brightness/contrast

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All original files opened in ArcGIS

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Step 3

Convert ASAR image area to raster of a polygon

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Raster image pixel value: 16 bit range

Background/radar shadow data value = 0

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Reclassify Tool (Spatial Analyst)

R l d l 0

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Raster polygon data value = 0

Background/shadow data value = NoData

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Step 4

Convert raster polygon to a shapefile polygon

R t t P l T l (C i )

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Raster to Polygon Tool (Conversion)

(Note: Simply polygons off)

Sh fil l d t l 0

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Shapefile polygon data value = 0


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Step 5

Convert shapefile polygon to shapefile polyline

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Feature to Line (Data Management)

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Shapefile polyline created

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Files after creating image outline

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Step 6

Clip background, keep only ASAR image data

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Clip Tool (Data Management)


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All other pixels = original ASAR image

ArcMap clipped image and polyline

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ArcMap - clipped image and polyline

(Note: No spatial reference)

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Define Projection Tool (Data Management)

What happens if you select a different polar projection?

ArcMap clipped image and polyline

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ArcMap - clipped image and polyline

(With correct spatial reference)

Sample running of the script

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Sample running of the scriptImport required modules

Tar-zip inbox folder - F:/Chinare_2010_ASAR/TarZipInbox

Tar-zip done folder - F:/Chinare_2010_ASAR/TarZipDone

Working data folder - F:/Chinare_2010_ASAR/WorkingGeodatabase outputs - F:/Chinare_2010_ASAR/Arctic_ArcGIS_10.gdb

Coordinate system - WGS 1984 NSIDC Sea Ice Polar Stereographic North.prj

Start processing loop

Working on dataset 1 of 1 named WSM_SS_20110420_220800_4276_4

Extract from tarzip file to dataset folder

Move ASAR data up to the dataset folder

Original spatial reference - UnknownRedefine as - WGS 1984 NSIDC Sea Ice Polar Stereographic North.prj

Calculate statistics

Build pyramids

Reclassify 0 to NoData and positive to 0

Convert reclassified raster to polygon

Convert polygon to polyline

Use polygon to clip original raster

Build pyramids for clipped raster

Copy polyline to output geodatabaseF:/Chinare_2010_ASAR/Working/WSM_SS_20110420_220800_4276_4\WSM_SS_20110420_22080

0_4276_4_polyline.shp Successfully converted: F:/Chinare_2010_ASAR/Arctic_ArcGI

S_10.gdb\WSM_SS_20110420_220800_4276_4_polyline

Copy clipped raster to output geodatabase

Successfully converted: F:/Chinare_2010_ASAR/Working/WSM_SS_20110420_220800_427

6_4\WSM_SS_20110420_220800_4276_4_clip.tif To F:/Chinare_2010_ASAR/Arctic_ArcGIS

_10.gdb\WSM_SS_20110420_220800_4276_4_clip

Finish processing loop

Estimates for Beaufort Sea (Arctic Ocean)

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Estimates for Beaufort Sea (Arctic Ocean)

Average 16 daily datasets on PolarView

Downloading time not included

Processing time 80 minutes

Mac laptop with 1.8 GHz processor, running Windows 7

All data stored on external SSD via USB 2.0 connection

Approximate data sizes MB

Compressed dataset from PolarView 800 Uncompressed ASAR datafile (GeoTIFF) 2320

All ArcGIS working files after processing 3360

Image boundary and clipped raster 960

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Questions?

Documents

L11_Python2