Transcript FRINGE99 meeting (10

The LANDMAP project for the Automated
Creation and Validation of multi-resolution
orthorectified satellite image products and a
1” DEM of the British Isles from ERS tandem
SAR interferometry
Landmap: creation of base map data from space
Kamie Kitmitto
MIMAS, Manchester Computing, UK
Jan-Peter Muller, Alec Walker , Jeremy Morley , Joel Barnes,
Ryan Keenan, Paul Cross, Ian Dowman, Karl Mitchell, Sanjay Rana
University College London, UK
Kumar Chugani
Selektra Limited
Andy Smith
Phoenix Systems, Kingston-upon-Thames, UK
Neil Quarmby
IS Ltd.
http://www.landmap.ac.uk
DEPARTMENT OF GEOMATIC ENGINEERING
Overview
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LANDMAP objectives
Context
UK national archive of satellite data for education
LANDMAP deliverables
GIS for optimal scene selection & GPS QC
LANDMAP IfSAR-DEM production system
Accuracy assessment of IfSAR-DEM
Status and future prospects
DEPARTMENT OF GEOMATIC ENGINEERING
LANDMAP Objectives
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Creation of a set of base image maps of the British Isles
through orthorectification of the national Higher
Education satellite archive, current and future
ERS Tandem multi-pass SAR interferometry to create
– 3rd party royalty free 1” (≈25m) DEM to be used for orthorectification
– Orthorectified SAR products to be used as a base map for LANDSAT &
SPOT geocoding
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All processing to be fully automated and independent of
ANY external copyrighted data-sets so that it can be
applied anywhere in future using any satellite data
– “dead reckoning” : no need for Ground Control
– Use of GLOBE-DEM to provide phase flattening
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Development of national IfSAR processing facilities for
UK Higher Education for large-scale projects
DEPARTMENT OF GEOMATIC ENGINEERING
Example LANDMAP multi-sensor tiepointing
DEPARTMENT OF GEOMATIC ENGINEERING
Context
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Topography required both for georadiometric correction
of satellite data and scientific applications such as
improving hydrological modelling
ERS Tandem IfSAR could be used to create global
topography at grid-spacings down to 1” (≈30m) almost
everywhere except tropical forests & water bodies
ERS Tandem IfSAR can also be used to densify existing
30” (~1km) and future 3” SRTM DEMs and with
multiple passes can achieve accuracies up to 1m Zrms
ERS Tandem IfSAR-DEMs can be used to fill in gaps
from SRTM 3” (~100m) above 60º and improve accuracy
Many applications require changes in the land surface
topography (e.g. aviation, telecomms) which differential
IfSAR could provide using IfSAR-DEMs
DEPARTMENT OF GEOMATIC ENGINEERING
UK National Archive of Satellite Data for
Education
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National coverage of remote sensing satellite data acquired to
support teaching, learning and research across all sectors of
Higher Education
Existing level 1 SPOT panchromatic (182 scenes) and LANDSAT-5
data (35 scenes) from 1980s currently not used by non-RS
specialists due to difficulty in relating these to other data with
geographical co-ordinates
Acquisition of 1999/2000 archive of LANDSAT-7 scenes to relate to
census data
ESA kindly agreed to acquire additional ERS Tandem ascending
(nigh time) coverage during Autumn 1999 to fill gaps & to
complement LANDSAT-7 data
Raw SAR data provided through InfoTerra from DERA Space.
DEPARTMENT OF GEOMATIC ENGINEERING
LANDMAP Deliverables
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Output datasets (satellite data in both strip and mosaic formats)
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1” (30m) Digital Elevation Model product (WGS84 and GB National Grid)
Kinematic GPS profiles for quality assessment of DEM and geocoded products
Orthorectified archive of ERS-SAR amplitude and phase coherence data-strips
Orthorectified archive of LANDSAT 30m & 15 m PAN and SPOT 10m data
Mosaic of orthorectified IfSAR, LANDSAT & SPOT products
Multi-sensor satellite data in various fused formats
Output Services
– Quality Assurance of geometric properties all of the above products
– GIS layer masks and cut-lines showing origin of DEM and image products
– Web based training materials on use of ERS-IfSAR data for mapping and
interferometry
– Integrated set of software tools, a guide to best working practice, and a
streamlined work flow for the processing of remote sensing satellite data
– End of project workshop/seminar (RSPS Conference 12-14 September 2001 DTI
Conference Centre, London)
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National automated System/Procedures and resources on MIMAS for
IfSAR-DEM and orthorectification of satellite imagery using ortho IfSAR
phase coherence as base map
DEPARTMENT OF GEOMATIC ENGINEERING
GIS for Optimal Scene selection
and GPS quality control data
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Planning ERS tandem data selection needed to optimise
– the longest possible strip length (data acquisition time period)
– same season with a clear preference on Autumn/Winter (“leaf-off”)
– best possible IfSAR imaging geometry determined by the perpendicular interantennae/spacecraft distance
– Limited budget for ERS data acquisitions
– 3 phases/passes for DEM: descending, ascending, gap-fillers
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DESCW metadata ingested into ARC/INFO GIS
GIS spatial handling facilities employed to select best strip data for
subsequent processing
GIS employed with 3rd party digital road data to select optimal
routes for kinematic GPS transects for IfSAR-DEM quality
assessment as well as planimetric quality assessment of satellite
orthoimage products
DEPARTMENT OF GEOMATIC ENGINEERING
ERS Tandem data selection for 4 Passes
(daytime, night-time, “gap-fillers”) to
maximise coverage & imaging geometry
1st pass coverage
2nd pass coverage
DEPARTMENT OF GEOMATIC ENGINEERING
ERS Tandem data selection for 4 Passes
(daytime, night-time, “gap-fillers”) to
maximise coverage & imaging geometry
3rd pass coverage
4th pass coverage
DEPARTMENT OF GEOMATIC ENGINEERING
GIS was also employed to select optimal routes for
Kinematic GPS profiling to assess the quality of
Individual strips, their overlap, the final merged
results from the 3 phases and orthorectification
DEPARTMENT OF GEOMATIC ENGINEERING
LANDMAP IfSAR-DEM
production system
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LANDMAP IfSAR-DEM processing uses Phoenix Systems
PulSAR™ for SAR focussing and InSAR Toolkit™ for
interferogram/phase coherence for ERS SAR strips
Strip processing developed to minimise number of
individual scenes to be processed (e.g. 82 to 13 for 1st pass)
Precision orbital elements (PRCs) used from D-PAF
Coarse 30” (1km) DEM from CEOS-GLOBE and DTED0
used to correct for inaccuracies in PRCs & to enable “dead
reckoning” without control points
Low phase coherence mask used to eliminate water features
which cause problems for phase unwrapping
All output products in geoTIFF format for subsequent use
in GIS, standard image display and processing software
DEPARTMENT OF GEOMATIC ENGINEERING
GLOBE-DEM import
PulSAR focusing
Orbit & registration analysis
DEM reprojection
SAR image co-registration
Master | Slave
GLOBE-DEM
(SAR co-ords.)
SAR ortho & phase adjust
Interferogram/coherence
Phase unwrapping
Height interpret+ortho
Geocode
IfSAR DEM
On MIMAS Irwell each 5-scene strip takes 3-7 days to process, creating 30GB of data, employing 5% of the CPUs,
0.9gb of RAM. Each Pass creates around 500gb of data products, all of which are backed up onto DLT4000
DEPARTMENT OF GEOMATIC ENGINEERING
LANDMAP 1st Pass DEM
1st Pass gaps filled by
GLOBE-DEM
Pseudocolour IfSAR DEM at 30” (Descending ERS data)
DEPARTMENT OF GEOMATIC ENGINEERING
First-pass Phase Coherence
N.B. Large areas
With PC>50%
Lower phase
Coherence over
Scotland & Wales.
No apparent relationship
to height difference with
OS® PANORAMA®
DEPARTMENT OF GEOMATIC ENGINEERING
Accuracy assessment of IfSAR-DEM
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Assessment of IfSAR-DEM accuracy
– 3rd party DEMs such as the OS® PANORAMA 50m DTM
– comparison of hydrological networks derived from IfSAR-DEM cf. existing
blue line (e.g. IH MLF )
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Assessment of planimetric and elevation accuracy through
2 special dedicated 2 week campaigns to collect kinematic
GPS around British Isles
ITE Monks Wood land cover map is also being used for
assessment of accuracy
EA laser altimetric DEMs being employed for detailed
understanding of what level the heights represent in canopy
Best accuracy appears to be around 2.5m Zrmse vs. IH-OS
50m DEM (further details in Walker, Muller, Naden,
IGARSS99) but more typically 8-14m Zrmse vs. kGPS
DEPARTMENT OF GEOMATIC ENGINEERING
Factors affecting Accuracy of IfSAR-DEM
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Surface level for scattering centres which are often
assumed as the top of observable canopy affected by tree
cover, depth of penetration, tower obstacles
Atmospheric effects due to time delay effects from water
vapour variability
Phase unwrapping artefacts
Planimetric accuracy due to PRC and timing errors
Artefacts in the GLOBE DEM which cannot be
corrected by ERS-1 RA as there are insufficient density
of such points in the UK
Phase coherence effects due to land cover and local
surface wind/water conditions (little, if any evidence
found for correlation with height differences)
DEPARTMENT OF GEOMATIC ENGINEERING
Accuracy assessment of IfSAR-DEM :
Kinematic GPS showing the effects of
canopy tops cf. kGPS road surface
DEPARTMENT OF GEOMATIC ENGINEERING
Accuracy assessment of IfSAR-DEM :
Atmospheric artefacts detected by
comparison with OS® PANORAMA
IfSAR-OS
Red-PC
G/B- IfSAR-OS
N.B. Severe artefacts in Eastern Scotland
but very few other regions. These will be
removed using multipass fusion.
DEPARTMENT OF GEOMATIC ENGINEERING
Accuracy assessment of IfSAR-DEM :
Phase unwrapping artefacts
MCFU (original)
InSAR (original)
MCFU/InSAR
N.B. MCFU/InSAR produces tile artefacts due to the local adjustment wrt GLOBE which will
be eliminated using multi-pass combinations
DEPARTMENT OF GEOMATIC ENGINEERING
IfSAR DEM - KGPS
DEPARTMENT OF GEOMATIC ENGINEERING
Panorama DEM - KGPS
DEPARTMENT OF GEOMATIC ENGINEERING
DTED DEM - KGPS
DEPARTMENT OF GEOMATIC ENGINEERING
IfSAR/LIDAR
Comparison
DEPARTMENT OF GEOMATIC ENGINEERING
Planimetric accuracy
OSCAR road lines, 1:50,000 map derived (Crown Copyright 1999) in Green,
kGPS trails in Blue superimposed on SAR amplitude image
DEPARTMENT OF GEOMATIC ENGINEERING
Excellent results for IfSAR-OS® height
differences where there are no atmospheric
effects or problems with dropped lines
N.B. Most areas
with height
differences ≤9m
and much of the
low lying areas with
∂Z≤1m
DEM as of 6th of
March 2001.
DEPARTMENT OF GEOMATIC ENGINEERING
Status and Future Prospects
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Final DEM completed by 3rd April 2001
Orthoimage creation will now proceed with ERS
Imagery
LANDSAT 5 & 7 and SPOT will follow - May 2001
Public Web page to introduce techniques and to deliver
DEMs & metadata using a “point-and-click” interface
based on ArcIMS and OpenGIS Web Mapping testbed
under development, due by Q3/ 2001
Final LANDMAP products due for release Q3/ 2001
URL: http://www.landmap.ac.uk
DEPARTMENT OF GEOMATIC ENGINEERING