DEPARTMENT OF GEOMATIC ENGINEERING The LANDMAP project for the Automated Creation and Validation of...

DEPARTMENT OF GEOMATIC ENGINEERING

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 interferometryLandmap: creation of base map data from space

Kamie KitmittoMIMAS, 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, UKKumar ChuganiSelektra Limited

Andy SmithPhoenix Systems, Kingston-upon-Thames, UK

Neil QuarmbyIS Ltd.

http://www.landmap.ac.uk


Overview

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


LANDMAP Objectives 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

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

Development of national IfSAR processing facilities for UK Higher Education for large-scale projects


Example LANDMAP multi-sensor tiepointing


Context 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


UK National Archive of Satellite Data for Education

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.


LANDMAP Deliverables Output datasets (satellite data in both strip and mosaic formats)

– 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) National automated System/Procedures and resources on MIMAS for

IfSAR-DEM and orthorectification of satellite imagery using ortho IfSAR phase coherence as base map


GIS for Optimal Scene selection and GPS quality control data

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 inter-

antennae/spacecraft distance– Limited budget for ERS data acquisitions– 3 phases/passes for DEM: descending, ascending, gap-fillers

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


ERS Tandem data selection for 4 Passes (daytime, night-time, “gap-fillers”) to

maximise coverage & imaging geometry

1st pass coverage 2nd pass coverage


ERS Tandem data selection for 4 Passes (daytime, night-time, “gap-fillers”) to

maximise coverage & imaging geometry

3rd pass coverage 4th pass coverage


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


LANDMAP IfSAR-DEM production system

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


GLOBE-DEM import

DEM reprojection

PulSAR focusing

Orbit & registration analysis

SAR image co-registration

Master | Slave

SAR ortho & phase adjustInterferogram/coherence

GLOBE-DEM(SAR co-ords.)

Phase unwrapping

Height interpret+ortho

Geocode IfSAR DEMIfSAR 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


LANDMAP 1st Pass DEM

Pseudocolour IfSAR DEM at 30” (Descending ERS data)

1st Pass gaps filled byGLOBE-DEM


First-pass Phase Coherence

N.B. Large areasWith PC>50%Lower phase Coherence over Scotland & Wales.No apparent relationship to height difference withOS® PANORAMA®


Accuracy assessment of IfSAR-DEM

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 )

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


Factors affecting Accuracy of IfSAR-DEM

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)


Accuracy assessment of IfSAR-DEM : Kinematic GPS showing the effects of

canopy tops cf. kGPS road surface


Accuracy assessment of IfSAR-DEM : Atmospheric artefacts detected by comparison with OS® PANORAMA

N.B. Severe artefacts in Eastern Scotlandbut very few other regions. These will beremoved using multipass fusion.

Red-PCG/B- IfSAR-OS

IfSAR-OS


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 willbe eliminated using multi-pass combinations


IfSAR DEM - KGPS


Panorama DEM - KGPS


DTED DEM - KGPS


IfSAR/LIDAR Comparison


Planimetric accuracy

OSCAR road lines, 1:50,000 map derived (Crown Copyright 1999) in Green, kGPS trails in Blue superimposed on SAR amplitude image


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.

Excellent results for IfSAR-OS® height differences where there are no atmospheric

effects or problems with dropped lines


Status and Future Prospects

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 The LANDMAP project for the Automated Creation and Validation of...

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