92 research outputs found
In-Flight CCD Distortion Calibration for Pushbroom Satellites Based on Subpixel Correlation
We describe a method that allows for accurate inflight calibration of the interior orientation of any pushbroom camera and that in particular solves the problem of modeling the distortions induced by charge coupled device (CCD) misalignments. The distortion induced on the ground by each CCD is measured using subpixel correlation between the orthorectified image to be calibrated and an orthorectified reference image that is assumed distortion free. Distortions are modeled as camera defects, which are assumed constant over time. Our results show that in-flight interior orientation calibration reduces internal camera biases by one order of magnitude. In particular, we fully characterize and model the Satellite Pour l'Observation de la Terre (SPOT) 4-HRV1 sensor, and we conjecture that distortions mostly result from the mechanical strain produced when the satellite was launched rather than from effects of on-orbit thermal variations or aging. The derived calibration models have been integrated to the software package Coregistration of Optically Sensed Images and Correlation (COSI-Corr), freely available from the Caltech Tectonics Observatory website. Such calibration models are particularly useful in reducing biases in digital elevation models (DEMs) generated from stereo matching and in improving the accuracy of change detection algorithms
Co-Registration of Optically Sensed Images and Correlation (COSI-Corr): an Operational Methodology for Ground Deformation Measurements
Recent methodological progress, Co-Registration of
Optically Sensed Images and Correlation, outlined here, makes it
possible to measure horizontal ground deformation from optical
images on an operational basis, using the COSI-Corr software
package. In particular, its sub-pixel capabilities allow for accurate
mapping of surface ruptures and measurement of co-seismic
offsets. We retrieved the fault rupture of the 2005 Mw 7.6
Kashmir earthquake from ASTER images, and we also present
a dense mapping of the 1992 Mw 7.3 Landers earthquake of
California, from the mosaicking of 30 pairs of aerial images
The 2001 M_w 7.6 Bhuj earthquake, low fault friction, and the crustal support of plate driving forces in India
We present a source model for the 2001 M_w 7.6 Bhuj earthquake of northwest India. The slip distribution suggests a high stress drop (~35 MPa) and, together with the depth distribution of aftershocks, that the entire crust is seismogenic. We suggest that the active faults have an effective coefficient of friction of ~0.08, which is sufficient for the seismogenic crust to support the majority of the compressive force transmitted through the Indian lithosphere. This model is consistent with the midcrustal depth of the transition from extension to compression beneath the Ganges foreland basin where India underthrusts southern Tibet. If the coefficient of friction were the more traditional value of 0.6, the lithosphere would be required to support a net force roughly an order of magnitude higher than current estimates in order to match the observed depth of the neutral fiber
Monitoring Earth Surface Changes from Space
This report gives an overview of the activities which have been undertaken as part of the
technical follow-on to the large study âMonitoring Earth Surface Changes from Spaceâ. In addition to the
support provided by the Keck Institute for Space Studies, these activities have been supported by
matching funds from the Gordon and Betty Moore Foundation, from UAE and Kuwait, and from the
MDAP NASA program.
Activities were organized under five different themes, each lead by a different PI:
1- Optical Image Time-Series (PI: Sebastien Leprince). These activities aim at developing
techniques to analyze optical images acquired by different imaging systems and at different times
to look at general landscape evolution (evolutions due to tectonic activity, glacier flow,
landslides, sand dunes migration, etc.). They also aim at building a framework for large scale
processing to look at global changes.
2- SAR Time-Series Analysis (PI: Mark Simons). These activities aim at developing techniques to
analyze radar image time series, in particular via interferrometric techniques. These activities
involve close interactions with JPL via the ARIA project (PI: Susan Owen).
3- Seismic Waves Imaging (PI: Pablo Ampuero). These activities aim at developing techniques for
seismic inversion with dense measurement in time and space, such as measurement that would be
provided by a space seismometer. These activities involve close interactions with JPL, which
received a matching R&TD funding to investigate the development of a space optical
seismometer (PI: David Redding).
4- Sub-surface Imaging (PI: Essam Heggy). These activities involve close interactions at testing the
possibility of an Earth orbiting Ground Penetrating Radar (GPR). Within the scope of this project,
only airborne applications will be sought after, with study for space applications.
5- Science Applications (PI: Mike Lamb). These activities involve taking advantage of the
techniques developed by the other groups. It also drives the technical developments and foresees
the external visitor program.
We detail below these activities. Each sub-section has software products, publications, and/or conference
posters/talks as outcome. All publications and presentations in international meetings are listed again at
the end of the report together with a few other publications produced by collaborators who have
participated in the KISS study but did not receive funding from us. Regarding the âseismic waves
imagingâ project, we have explored different designs and mission concepts for a 4 m-class Seismic
Imager Geostationnary satellite system. We are currently working on estimating the cost and preparing a
draft GSI Mission Whitepaper
Gazing at the Solar System: Capturing the Evolution of Dunes, Faults, Volcanoes, and Ice from Space
Gazing imaging holds promise for improved understanding of surface
characteristics and processes of Earth and solar system bodies. Evolution of
earthquake fault zones, migration of
sand dunes, and retreat of ice masses
can be understood by observing
changing features over time.
To gaze or stare means to look
steadily, intently, and with fixed
attention, offering the ability to probe
the characteristics of a target deeply,
allowing retrieval of 3D structure and
changes on fine and coarse scales.
Observing surface reflectance and 3D
structure from multiple perspectives
allows for a more complete view of a
surface than conventional remote
imaging. A gaze from low Earth orbit
(LEO) could last several minutes
allowing for video capture of dynamic
processes. Repeat passes enable
monitoring time scales of days to years.
Numerous vantage points are available during a gaze (Figure 1). Features in
the scene are projected into each image frame enabling the recovery of dense
3D structure. The recovery is robust to errors in the spacecraft position and
attitude knowledge, because features are from different perspectives. The
combination of a varying look angle and the solar illumination allows recovering
texture and reflectance properties and permits the separation of atmospheric
effects. Applications are numerous and diverse, including, for example, glacier
and ice sheet flux, sand dune migration, geohazards from earthquakes,
volcanoes, landslides, rivers and floods, animal migrations, ecosystem changes,
geysers on Enceladus, or ice structure on Europa.
The Keck Institute for Space Studies (KISS) hosted a workshop in June of
2014 to explore opportunities and challenges of gazing imaging. The goals of the
workshop were to develop and discuss the broad scientific questions that can be
addressed using spaceborne gazing, specific types of targets and applications,
the resolution and spectral bands needed to achieve the science objectives, and
possible instrument configurations for future missions.
The workshop participants found that gazing imaging offers the ability to
measure morphology, composition, and reflectance simultaneously and to
measure their variability over time. Gazing imaging can be applied to better
understand the consequences of climate change and natural hazards processes,
through the study of continuous and episodic processes in both domains
Influence of camera distortions on satellite image registration and change detection applications
Applications such as change detection and digital elevation model extraction from optical images require a rigorous modeling of the acquisition geometry. We show that the unrecorded satellite jitter during image acquisition, and the uncertainties on the CCD arrays geometry are the current major limiting factors for applications requiring high accuracy. These artifacts are identified and quantified on several optical satellites, i.e., SPOT, ASTER, QuickBird, and HiRISE
Surface displacements in the September 2005 Afar rifting event from satellite image matching: Asymmetric uplift and faulting
Combining subâpixel analysis of SPOT4 images with InSAR measurements, we generate 3D surface displacements for the September 2005 rifting event on the Dabbahu Segment in the Afar valley. The axis of rifting in the event is shifted to the east of the geomorphic rift. The horizontal displacements reveal 6 m of extension, and vertical displacements show asymmetric uplift of the flanks of the dike. Simple forward modelling indicates this asymmetry is due to the dike dipping 80° to the west towards the geomorphic rift. The boundary between eastward and westward displacements aligns with the transition between uplift and subsidence on the east in the north part of the segment, but on the west in the south. Normal faulting is not required on both sides of the instantaneous rift. Eastâdipping normal faulting on the west side of the instantaneous rift aligns with a westâdipping normal fault in the topography
Deformation during the 1975â1984 Krafla rifting crisis, NE Iceland, measured from historical optical imagery
We measure the displacement field resulting from the 1975â1984 Krafla rifting crisis, NE Iceland, using optical image correlation. Images are processed using the COSI-Corr software package. Surface extension is accommodated on normal faults and fissures which bound the rift zone, in response to dike injection at depth. Correlation of declassified KH-9 spy and SPOT5 satellite images reveals extension between 1977â2002 (2.5 m average opening over 80 km), while correlation of aerial photos between 1957â1990 provide measurements of the total extension (average 4.3 m opening over 80 km). Our results show âŒ8 m of opening immediately north of Krafla caldera, decreasing to 3â4 m at the northern end of the rift. Correlation of aerial photos from 1957â1976 reveal a bi-modal pattern of opening along the rift during the early crisis, which may indicate either two different magma sources located at either end of the rift zone (a similar pattern of opening was observed in the 2005 Afar rift crisis in East Africa), or variations in rock strength along the rift. Our results provide new information on how past dike injection events accommodate long-term plate spreading, as well as providing more details on the Krafla rift crisis. This study also highlights the potential of optical image correlation using inexpensive declassified spy satellite and aerial photos to measure deformation of the Earth's surface going back many decades, thus providing a new tool for measuring Earth surface dynamics, e.g. glaciers, landsliding, coastal erosion, volcano monitoring and earthquake studies, when InSAR and GPS data are not available
Revisiting Past Earthquakes and Seismo-Volcanic Crises Using Declassified Optical Satellite Imagery
Recent development of the user-friendly software package âCo-registration of Optically Sensed Images and Correlationâ
(COSI-Corr), which allows for automatic and precise ortho-rectification, co-registration, and sub-pixel correlation of pushbroom satellite and aerial images, has enabled Earthâs surface dynamics to be accurately monitored using optical imagery [1]. This technique compares two images of the Earthâs surface that were acquired at different times, and estimates any potential pixel shifts between them with an accuracy typically better than 1/10 of the pixel size. Correlation of both satellite and aerial images has been successfully used to identify coseismic ground ruptures and quantify fault offsets during large earthquakes [2]â[4], as well as monitoring sand dune migration, landsliding, ice flow [5] [6], and volcanic activity [7] [8]. In this study, we demonstrate that recently declassified US spy satellite images can be used to measure ground deformation resulting from seismotectonic and volcanic events using optical sub-pixel correlation. KH-9 Hexagon satellite images, with a swath size of 250Ă125 km, were acquired by the US government between 1971 and 1980, and are available for purchase from the United States Geological Survey (USGS) at small cost ($30 per image). During this period, around 29,000 images were acquired globally [9], providing a comprehensive record of the Earthâs surface at 6â9m resolution
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