high resolution land- cover modelling with plÉiades …
TRANSCRIPT
Mark ThompsonGeoTerra Image
HIGH RESOLUTION LAND-
COVER MODELLING WITH
PLÉIADES IMAGRY AND
DEM DATA IN SUPPORT OF
FINE-SCALE LANDSCAPE
THERMAL MODELLING
37th ISRSE Conference Pretoria, South Africa, 05 2017
Authors:
Mr Mark Thompson, GeoTerra Image, South Africa
Ms Lungile Moyo, GeoTerra Image, South Africa
Dr Corné Eloff, Airbus, South Africa
Mr Thinus Prinsloo, Pinkmatter Solutions, South Africa
Mr Neels Brink, DENEL Dynamics, South Africa
37th ISRSE Conference Pretoria, South Africa, 05 2017
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INTRODUCTION
Using detailed land-cover data to
determine thermal landscape signatures …
Thermal signatures used as a navigation
aid by sensors onboard autonomous aerial
vehicles …
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INTRODUCTION
Land-cover classes converted into thermal
units to match navigation sensor
requirements…
37th ISRSE Conference Pretoria, South Africa, 05 2017
Airbus Channel Partner Conference – 11/5/2016
INTRODUCTION
0.5m resolution Pléiades imagery
used to generate high detail land-
cover and terrain data…
37th ISRSE Conference Pretoria, South Africa, 05 2017
Data generated from Tri-Stereo
Pléiades imagery for enhanced
relief representation and metric
accuracy…
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INTRODUCTION
Why? …
… using satellite data to simulate
landscape thermal radiance is significantly
cheaper than in-situ field measurements …
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STUDY AREA
Complex mix of land-cover, land-use
and terrain variation…
37th ISRSE Conference Pretoria, South Africa, 05 2017
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PLEIADES TRI-STEREO TERRAIN DATA
Tri-stereo data uses 3 x views compared
to conventional stereo which uses 2 x
views…
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• combination of 2 x oblique & 1 x
nadir views of the terrain…
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PLEIADES TRI-STEREO TERRAIN DATA
Tri-Stereo provides enhanced 3D
modelling, especially in areas of high, local
relief variation, in both natural and man-
made landscapes…
37th ISRSE Conference Pretoria, South Africa, 05 2017
Tri-Stereo approach ‘minimises’ data loss in
stereo ‘loss’ areas…
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Stereo collection over very steep areas
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View 1 View 2
Over large mountainous areas, where slopes are very high,
some « hidden » surfaces may remain
Front telescope
Rear telescope
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“3-stereo” collection over very steep areas
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View 2 (nadir)View 1 View 3
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“tri-stereo” impact over steep areas
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Tri-stereo
Stereo only
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“tri-stereo” benefits: Melbourne
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DEM from images 1 + 2
Merge of the 3DEMs
Melbourne:3D-wise,
a difficult area.
Hidden areas
extent (in red) are
reduced by approx.
75% when using 3
images
DEM from images 1 +3
DEM from images 2+3
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PLEIADES TRI-STEREO TERRAIN DATA
High detail 1m resolution DSM and (derived) DTM
output, with ≤ 1.5m vertical and horizontal
accuracies …
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MODELLING THE TRI-STEREO TERRAIN DATA
Challenges:
37th ISRSE Conference Pretoria, South Africa, 05 2017
• Heterogenous landscape
• Thick vegetation
• Housing and infrastructure
• Waterbodies
• Mountains and lowlands
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MODELLING THE TRI-STEREO TERRAIN DATA
Further challenges:
37th ISRSE Conference Pretoria, South Africa, 05 2017
• Large study area: 385 km2 extent
• requires 2 x tri-stereo acquisitions
• with 6 days acquisition difference
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MODELLING THE TRI-STEREO TERRAIN DATA
4 data processing steps:
37th ISRSE Conference Pretoria, South Africa, 05 2017
4. Product generation Cycle
3. Orthorectification Cycle
2. Reference PAN Cycle
1. DEM Extraction Cycle
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MODELLING THE TRI-STEREO TERRAIN DATA
37th ISRSE Conference Pretoria, South Africa, 05 2017
DEM Extraction Cycle:
Aim is to generate high geometric precision
0.5m DSM from which equivalent quality
DTM can be extracted.
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Tri-Stereo generated DSM and derived DTM
37th ISRSE Conference Pretoria, South Africa, 05 2017
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MODELLING THE TRI-STEREO TERRAIN DATA
Reference PAN Cycle:
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Aim is to generate 0.5m high geometric
precision PAN reference images for future
MS data orthorectification…using the DTM /
DSM and external local ortho-photography
for ground control.
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MODELLING THE TRI-STEREO TERRAIN DATA
Orthorectification Cycle:
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Aim is to generate comparable orthorectified
images (all views, all tri-stereo datasets), with
equivalent geometry and radiometric
properties.
Orthorectification model now uses reference
PAN image instead of local ortho-photo data
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MODELLING THE TRI-STEREO TERRAIN DATA
Product Generation Cycle:
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1. PAN sharpened MS orthorectified image
2. Top-of-Atmosphere corrected
3. Full study area image mosaic
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Final PAN Sharpened Pléiades ortho-image
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MODELLING THE TRI-STEREO TERRAIN DATA
37th ISRSE Conference Pretoria, South Africa, 05 2017
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GENERATION OF LAND-COVER / USE DATA
Object rather than pixel-based landscape
segmentation and classification for best
object boundary delineation.
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GENERATION OF LAND-COVER / USE DATA
Detailed LCLU data required to enable ID of
thermally equivalent thematic info classes.
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• Going beyond normal LCLU detail…
• Roof material and colour
• Road markings and material type
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GENERATION OF LAND-COVER / USE DATA
Landscape segmentation based on PAN
sharpened imagery, since DTM exhibited local
object-edge gradient degradation…
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Structural “gutter-lines” not
always represented as sharp
edges …
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GENERATION OF LAND-COVER / USE DATA
2m DTM threshold used to separate
ground from above ground features.
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Separate, object-based classification of
ground and above-ground features, using
spectral & height characteristics…
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GENERATION OF LAND-COVER / USE DATA
37th ISRSE Conference Pretoria, South Africa, 05 2017
Airbus Channel Partner Conference – 11/5/2016
GENERATION OF LAND-COVER / USE DATA
37th ISRSE Conference Pretoria, South Africa, 05 2017
Airbus Channel Partner Conference – 11/5/2016
GENERATION OF LAND-COVER / USE DATA
Externally sourced spatial masks used to
assist with separation of objects with similar
spectral & height characteristics…
37th ISRSE Conference Pretoria, South Africa, 05 2017
Buffered road centre-line
mask used to separate
white road markings from
similar light coloured
road-edge kerbstones.
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GENERATION OF LAND-COVER / USE DATA
Finally, shadowed areas identified and
removed for land-cover classification
consistency…
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DSM Terrain Data
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Hill-shaded DSM Terrain Data
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Separation of 2m above ground objects
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Identification of all shadow areas
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Land-cover versus original PAN sharpened
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Land-cover with and without shadows
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CONVERSION OF LCLU TO THERMAL UNITS
Aerial navigation sensor relies on thermal
landscape representations…
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• convert LCLU classes into thermal
equivalent units.
• LCLU categories matched to thermo-
dynamic materials database
• unclassified PAN image used to generate
pixel-level conversion template
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Comparison of PAN, Land-cover & Thermal
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PAN Land-cover Thermal units
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CONVERSION OF LCLU TO THERMAL UNITS
Thermodynamic modelling can simulate any
time of day (incl. variable shadow extent)
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Airborne camera effects (motion, noise,
blur) added for final navigation dataset.
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