oblique aerial imagery for nma some best...
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Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
F. Remondino1, I. Toschi1, M. Gerke2, F. Nex2, D. Holland3, A. McGill4,
J. Talaya Lopez5, A. Magarinos5
1 3D Optical Metrology (3DOM) unit, Bruno Kessler Foundation (FBK), Trento, Italy
Email: <remondino><toschi>@fbk.eu, http://3dom.fbk.eu
2 University of Twente, Faculty of Geo-Information Science and Earth Observation (ITC),
Department of Earth Observation Science, The Netherlands
Email: <m.gerke><f.nex>@utwente.nl
3 Ordnance Survey, Southampton, UK – Email: [email protected]
4 Ordnance Survey, Dublin, Ireland – Email: [email protected]
5 ICGC, Spain – Email: <julia.talaya><antonio.magarinos>@icgc.cat
OBLIQUE AERIAL IMAGERY FOR NMA
– SOME BEST PRACTICES –
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
EuroSDR & oblique aerial imagery
EuroSDR is an organization composed of
European NMCAs/NMAs and research
organizations of most EU member states
EuroSDR is following the development of oblique
aerial cameras since 2013, when a research
activity was created to:
NM
CA
s
Researc
h O
rg.
+
continuously update its members on the developments in this technology
explore more deeply the potential of oblique imagery
investigate performances of hardware and software solutions
provide practical and cost-effective methodologies for mapping agencies
underline substantial technical and operational benefits
provide clear statements and best practices
Oblique research activity of EuroSDR is couple to the ISPRS Scientific
Initiative on “Multiplatform Photogrammetry” – see presentation on Saturday
16/Jul/2016: 10:30am-12:00pm, room Club B
Gerke, M., Nex, F., Remondino, F., Jacobsen, K., Kremer, J., Karel, W., 2016: Orientation of
oblique airborne image sets - Experiences from the ISPRS/EuroSDR benchmark on multi-
platform photogrammetry
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Oblique imagery and cameras
First recorded aerial photo in the US (1860) by J.W. Black and S. King in
Boston (USA) was an oblique shot from a balloon
In the two World Wars, oblique were used for inspection & reconnaissance
In the “analogue times” too expensive technology
Almost 10 years ago: Pictometry system
Nowadays different systems available
A “returned” technology / system
Source: Wikipedia
USGC-9
Zeiss twin RMK Leica DRC30
Vexcel Osprey’
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
General classification of oblique digital cameras
Current oblique aerial systems
single swiping camera
VisionMap
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
General classification of oblique digital cameras
single swiping camera
2 cameras
Zeiss twin RMK
IGI Dual
DiMAC
Current oblique aerial systems
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
General classification of oblique digital cameras
single swiping camera
2 cameras
3 cameras
3x Fairchild K-17 Bagley 3-lens (1920)
3x Jena LMKDLR-3K
Current oblique aerial systems
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
General classification of oblique digital cameras
Zeiss (1930)
NPO KSI
single swiping camera
2 cameras
3 cameras
4 cameras
Rolleimetric AIC x4
Current oblique aerial systems
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
General classification of oblique digital cameras
Fairchild T-3A (1930’s)
Leica RCS30
single swiping camera
2 cameras
3 cameras
4 cameras
5 cameras
Microsoft/Vexcel Osprey
Current oblique aerial systems
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
General classification of oblique digital cameras
Schiempflug (1904)
NPO KSI single swiping camera
2 cameras
3 cameras
4 cameras
5 cameras
Multiple cameras
9-lens Fairchild Octoblique Midas (2015)
Current oblique aerial systems
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Fan (static or sweeping) vs Maltese Cross configuration
- IGI Dual Cam
- A3 Visionmap- Track‘Air MIDAS
- IGI Penta DigiCam
- Hexagon/Leica RCD30
- Pictometry / BlomOblique
- Microsoft/Vexcel Osprey
Current oblique aerial systems
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Maltese Cross configuration
One vertically pointing camera + 4 oblique cameras
pointing to the four cardinal directions
Modular (i.e. varying angles) vs fixed
Small vs medium vs large format camera sensors
RGB + NIR (in the nadir)
Wide vs narrow angle lens
Larger image block (more strips, more overlap, more
redundancy)
Current oblique aerial systems
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Image block comparisons
ADS80
coverage
RCD30
coverage
RCD30 Oblique
(PentaPod)
coverage
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Oblique aerial systems - Open research issues
handling of occlusions, scale and radiometric changes
correct and fast identification of homologues points, in particular across
viewing directions
automatic AT with well distributed tie points
direct geo-referencing
use of relative orientation among the oblique views
processing time
redundancy / overlap exploitation
fusion of point clouds coming from different viewing directions (and with
different accuracy & resolution)
automation in interpretation, especially for complex architectures
etc.
→ Most of these issues were tackled
within the EuroSDR research activity
on oblique aerial cameras
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
EuroSDR & oblique aerial imagery
Main participant of the EuroSDR “oblique research activity”:
FBK Trento, Italy
ITC / Twente University, The Netherlands
Ordnance Survey (OS) UK
Ordnance Survey (OS) Ireland
Institut Cartogràfic i Geològic de Catalunya (ICGC), Spain
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
EuroSDR & oblique aerial imagery
Performances of existing hardware and software (benchmark)
Needs for using oblique flights / images wrt standard nadir
acquisitions
Advantages of oblique datasets
Lesson learnt from internal experiences
Limitations of the oblique pipeline wrt the standard nadir solution
Visions
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Needs for using oblique flights
Nadir flights for:
update of topographic maps,
production of orthophotos,
creation of national-wide DSMs/DTMs,
generation of Building Height Attribute, etc.
Oblique flight for:
3D object extraction and modeling,
improve realistic appearance of (3D) geo-products,
improve urban mapping,
reduce occlusions,
improve reliability and redundancy
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Advantages of oblique datasets
Production of 3D vs 2.5D point clouds
Reduced occlusions
Derivation of 3D topographic layers / info directly from 3D point clouds
(no need for stereo restitutions)
Measurements on building façades and, generally, in narrow streets
Better modeling of man-made and complex objects (sheers,
overhangs, canopies, underpasses, etc.)
Territory identification and interpretation for more efficient evidence-
based decision making process
In general, improve the quality of the geo-product offered by NMAs
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Lesson learnt from internal experiences
Better performance with 80x80 overlap configuration and GSD in the
order of 6-7cm (Maltese cross configuration / cameras)
Reducing overlap to the usual 60x60 or 60x40 produce noisier
correlation and higher occlusions → need for larger overlap, so
blocks!
Parallelization (no Cloud) is very mandatory to speed up processing
(an oblique block is ca 10 times larger than a nadir block)
Covering large areas requires high amount of flight hours so
illumination conditions should be carefully considered
Tridicon (3DCom/Hexagon) suite seems to be the most effective
solution to generate 3D building models out of dense point clouds
25 sq. km @ 7cm GSD #images flight time
60x40 conf. with large format camera < 400 < 1h
80x80 conf. with oblique camera > 6000 > 3h
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Limitations
Medium format cameras (with Bayer filter) have an apparent
resolution smaller than the nominal flight GSD. Using synthetic
targets an effective resolutions of 1.98xGSD (R), 1.32xGSD (G) and
2.21xGSD (B) were obtained
Current off-the-shelf workflows for image processing, aerial
triangulation (AT), dense point cloud and 3D data generation have
important room for improvement
Often manual intervention for subdividing blocks and facilitate AT
procedures is requested
Although DIM produce more dense and complete point clouds, true-
orthos suffer of DIM results, thus DTM still primary source
Image block size and management
Tools for 3D building generation from dense point clouds normally do
not consider points of the façades
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Visions
Soon oblique will be a common source for 3D urban areas and to
create high resolution 3D datasets
New algorithms and solutions will improve data processing
performances and results
Oblique imagery will facilitate the complete automatization of
LOD2-3 building extraction based on multi-view algorithms
Oblique will increase user’s expectation wrt current and standard
products (e.g. true-ortho, quality 3D textured building models, etc.)
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Oblique camera systems are definitely back and a promising
solution for mapping purposes
Different systems available, new coming out soon on the market
Oblique airborne images will probably become a standard
complementary to traditional large format nadir images
Oblique will not replace traditional nadir acquisitions (urban areas)
Many possible applications: map update, 3D city modeling,
inspection, interpretation, footprint identification, 3D cadastre, real
estate, etc.
NMAs are slowly thinking to adjust their production pipeline to cope
with oblique datasets
Oblique requires a new approach in the photogrammetric and
production pipeline
Data acquisition (flight plan) + Data processing (convergent, huge point clouds,
etc.) + 3D restitution / Automated interpretation
Conclusions (1/2)
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
Additional costs of oblique flights (especially additional flight lines)
might be compensated by additional outcomes and benefits
Benefit offered by oblique imagery are not yet compelling enough to
result in a commitment to operational use of oblique flights
The images volume in a project increases dramatically affecting image
management, AT, dense matching, storage and archive operations
Very dense, accurate and detailed point clouds but then?
New solutions to derive structured information out of unstructured point clouds
Large polygonal models (e.g. GoogleEarth) are not useful for NMAs if not only
for visualization
Conclusions (2/2)
versus
Fabio Remondino - OBLIQUE AERIAL IMAGERY for NMA
THANK YOU!
F. REMONDINO, I. TOSCHI, M. GERKE, F. NEX, D. HOLLAND,
A. MCGILL, J. TALAYA LOPEZ, A. MAGARINOS