Using Open Source Programming with Satellite Imagery

Claire Porter

Polar Geospatial Center

University of Minnesota

1. Electro-optical high-resolution commercial satellite imagery

2. PGC’s open source approach: GDAL and Python

3. Applications to other datasets

high-res imagery

• High-resolution Commercial Satellite Imagery in ice-covered regions

– 0.5m – 4m resolution

– 1 to 8 electro-optical bands

– Passive sensors

– High temporal resolution

high-res imagery

Fuel Cache

Imagery ©2011 Digital Globe, Inc.

overland traverses

Imagery ©2012 Digital Globe, Inc.

field camp monitoring

icebreaker operations

1000 m Imagery ©2012 Digital Globe, Inc.

Icebreaker

McMurdo Station

landing site reconnaissance

landing site reconnaissance

100 m

geologic mapping

Imagery ©2012 Digital Globe, Inc.

emperor penguin census

Imagery ©2012 Digital Globe, Inc.

weddell seal counts

elevation from stereoscopic images

feature tracking

200m

imagery challenges

• Challenges of the imagery

– Organization

• Over 500,000 images in polar regions

• Cataloging and space requirements

– Format

• Basic spatial location – not terrain corrected

• Uncorrected DN values

• 16 bit

• NITF format

open source tools

• GDAL and Python

• Open source and freely available

• Large user base, well established and well maintained

– GDAL

• Libraries and standalone utilities

• Built with C++

• Becoming incorporated into other GIS packages

• Both raster and vector libraries

• Very good coordinate system support

• Bindings to Python, Ruby, Java, .NET, Perl, etc.

– Python

• GDAL Python bindings include Numpy/Scipy

• Benefits of GDAL with intuitive Python language

open source tools

• What you can do:

– Organization

• Query rasters and vectors for geometry and metadata

• Write info to a spatial database or vector format

• Rename and archive imagery

– Manipulation

• Orthorectify, project, and manipulate imagery

• Stack bands, pan-sharpen, mosaic, or subset multiple images

• Run the package on a linux cluster for batch processing

• Easily schedule cron jobs for repeat updates

imagery catalog

• Example 1: PGC imagery catalog

imagery processor

Input Image DEM (optional)

gdalwarp : orthorectify with RPCs

gdal_translate and gdal_merge or VRT: rescale and stretch

RPCs (if external)

VRT

Reflectance Info

gdal_translate: write to output format

Output Image

gdaladdo: compute pyramids (if geoTiff)

• Example 2: PGC image orthorectification script

radiometric correction

radiometric correction

Imagery Copyright Geoeye, Inc.

radiometric correction

mosaics

GDAL script by Dan Stahlke, GINA Imagery Copyright 2011 Digital Globe, Inc.

pan-sharpening

GDAL script by Dan Stahlke, GINA Imagery Copyright 2011 Digital Globe, Inc.

pan-sharpening

other applications

• Mosaics, Reprojection, and Subsetting: Rapidice.org