Characterization of Croatian Minefields using Satellite Radar Image Time Series Analysis.
SPRINT project results
N. Milisavljevic – D. Closson
V. Lacroix (presenter)
Royal Military Academy, Belgium
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Outline
1. SPRINT project
2. AOI & image database
3. Radar image processing
4. Data fusion – first level
5. Data fusion – second level
6. Examples
7. Validation
8. Conclusions
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
SPRINT project
AcronymSPaceborne Radar INterferometric Techniques for Humanitarian Demining Land Release
SPRINT aims at differentiating human-induced effects/activities affecting the Earth surface from the natural ones by exploiting combinations of amplitude and phase changes of space-borne radar signals
The goal: to provide a new layer of information towards determining whether mine suspected areas are hazardous indeed or not
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
AOI & image database
Source: M. Bajić, Operations with Advanced Intelligence Decision Support System for Suspected Area Asessmentin Croatia and Bosnia and Herzegovina, Workshop “Merging Mine Action Technology and Methodology”,GICHD, Geneva; 6-8.09.2010
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
AOI
Source: M. Bajić, Operations with Advanced Intelligence Decision Support System for Suspected Area Asessmentin Croatia and Bosnia and Herzegovina, Workshop “Merging Mine Action Technology and Methodology”,GICHD, Geneva; 6-8.09.2010
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
AOI
Suspected hazardous and confirmed hazardous areas shown in hatched and crosshatched red polygons (data from 2009) - 4km x 4km grid.
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Radar image database
GOSPIC
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Radar image processing
Source: Sarmap, SBAS tutorial, 2013.
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
42 ERS + 40 Envisat (1992‐2010)
Source: ESA
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Amplitude & coherence
Monday 03 Jun 13
Amplitude T0Phase T0
Amplitude T1Phase T1
Coherence T0-T1
Black = surface changes
Minefield Buffer
Radar image processing
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Radar image processing
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Data fusion – first level
• Four data sources: ERS coherence data stack, ERS amplitude data stack, Envisat coherence data stack and Envisat amplitude data stack
• Firstly, data within each of these stacks are combined and classified using multi‐temporal signature analysis, where pixels with similar signatures are grouped together
• Thus, at the output of this level, we have unsupervised classification result for each of the data sources:
– ERS coherence
– ERS amplitude
– Envisat coherence
– Envisat amplitude
• These classification results are inputs for the second level
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
All vs. selected data
Acquisition dates for all ERS data, selected ERS, all Envisat data and selected Envisat data
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Data fusion – second level
Combination strategies
ERS intensityERS coherence Envisat intensityEnvisat coherence
coherence combination intensity combination
coherence and intensity combination
Envisat combinationERS combination
ERS coherence Envisat coherenceERS intensity Envisat intensity
ERS and Envisat combination
all data used:
1
2
selected data used:
3
4
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Example
• Visual observation:
– Suspected minefield contains mainly grass, crops and urban part
– Buffer around it contains trees, grass, crops and an urban part
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
ERS coherence unsupervised classification results
• If all coherence data are used: • If only selected coherence data are used:
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
ERS intensity unsupervised classification results
• If all intensity data are used: • If only selected intensity data are used:
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Envisat coherence unsupervised classification results
• If all coherence data are used: • If only selected coherence data are used:
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Envisat intensity unsupervised classification results
• If all intensity data are used: • If only selected intensity data are used:
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Recall of level 2 fusion
Combination strategies
ERS intensityERS coherence Envisat intensityEnvisat coherence
coherence combination intensity combination
coherence and intensity combination
Envisat combinationERS combination
ERS coherence Envisat coherenceERS intensity Envisat intensity
ERS and Envisat combination
all data used:
1
2
selected data used:
3
4
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
ERS coherence classification
IntensityCoherence
Low High
Low
High
ERS intensity classification
Envisat intensity classification
Envisat coherence classification
An example of the summary: Combination coherence and intensity strategy
(using all data)
1
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
ERS intensity classification
Envisat intensity classification
ERS coherence classification
Envisat coherence classification
ERSEnvisat
L ML MH H
L
ML
MH
H
IntensityCoherence
Low High
Low L ML
High MH H
the tables show the color codes used for intermediate results (upper table)and for the final output (lower table)
Combination ERS and Envisat strategy (using selected data)
4
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Validation (1/4)
Example of the fortification objects, remnants of war marked with arrows, triangles or circles visible on the aerialimage that was acquired in April 2009 at the MSA community of Gospić (© Milan Bajić)
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Validation (2/4)
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
orientation point of the mine recordreconstructed position of the minefieldbunker linecover for infantry and artilleryabandoned roaddestroyed house
trenchpassage under the railwaynatural objects arranged for fiery actiondrywallbridges and gangwaysheliportshallow draftsabandoned surfaces
safe roadsurface in use
house in useroad in usetruck with bees
Validation (3/4)
5th Mine Action Technology Workshop, Pretoria; June 20, 2014
Brown= reconstructed minefield positionGreen = surface usedPurple = pathway usedRed = various levels of danger (dark is the highest)
ERS using all data
Monday 03 Jun 13
Validation (4/4)
ERS using selected data
Monday 03 Jun 13
Envisat using all data
Monday 03 Jun 13
Envisat using selected data
Monday 03 Jun 13
Conclusions
SPRINT showed the technical feasibility of processing stacks ofradar images to produce useful information to the MSA reduction issue.
The example chosen - Gospic region - is relevant because CROMACanalyzed this area in great detail in 2008-2010. It was thereforechallenging to provide new and relevant information to them.
The validation of the work carried out by Prof Milan Bajic allows us tobuild up future projects towards an operational tool for SGR (Sentinel-1data collection).
In the near future, Sentinel-1 SAR (C-band) images will be provided forfree by the EU-ESA owing to the Copernicus project. The resolution willbe better than ERS and Envisat (5 m vs 20m); the revisit time 11 days(and then 6 days when 2 satellites) vs 35 days.
Free software such as POLSARPRO already allow the users toprocess such type of data.
5th Mine Action Technology Workshop, Pretoria; June 20, 2014