a case study of pleiades tri-stereo imagery:

A Case Study of Pleiades Tri-Stereo Imagery:

Nadezhda Malyavina, Head of Racurs Production department

September 2013, Fontainebleau, France

accuracy assessment, interpretability, 3D modeling potential.

Petr Titarov, Software developer, Racurs

Elena Kobzeva, Chief Engineer, Technology 2000

13th International Scientific and Technical Conference

From Imagery to Map: Digital Photogrammetric Technologies

A Case Study of Pleiades Tri-Stereo Imagery

Pleiades imagery orientation accuracy assessment

3D modeling of urban area (the city of Yekaterinburg)

Creating and updating topographic maps using Pleiades imagery

Contents

Pleiades imagery orientation accuracy assessment

Pushbroom imagery orientation models

Test dataset description

Pleiades imagery orientation accuracy

Rigorous, rational polynomial (RPC) and universal pushbroom models

Pleiades Tri-Stereo product and ground points set

Orientation accuracy of single Pleiades images, stereopairs and the triplet

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RPC adjustment: affine refinement

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Pleiades Tri-Stereo Imagery

Parameters Images

Image ID DS_PHR1A_201306010719183 _ SE1_PX_E060N56_0920_01800

DS_PHR1A_201306010719416 _ SE1_PX_E060N56_0920_01876

DS_PHR1A_201306010719523 _ SE1_PX_E060N56_0920_01876

Imaging date and time 2013-06-01 07:19:53.4 2013-06-01 07:20:16.6 2013-06-01 07:20:27.4

Viewing angle along track 10.1° -2.7° -8.5°

Viewing angle across track 1.4 ° 1.9° 2.1 °


Pleiades Tri-Stereo Imagery – Bundle Product

Pan Image, GSD 0.7 m

MS Image, GSD 2.8 m

The images were pan-sharpened using PHOTOMOD

Pan Image, GSD 0.7 m Pan Image, GSD 0.7 m

MS Image, GSD 2.8 m MS Image, GSD 2.8 m


Ground points set

Ground coordinates accuracy: 0.2-1.0 m RMSE

Points measurements in the images accuracy: 1 pixel

Pleiades imagery orientation accuracy assessment: methodology

Scheme #

GCPsnumber

Orientation model Objective

I 0 RPC Supplied RPC accuracy assessment

II 0 RPC + shiftAssessment of accuracy achievable using supplied RPC and tie points (but no ground control)

III 1 RPC + shift Assessment of accuracy achievable with RPC and a single ground control point

IV 4 RPC + affine Assessment of accuracy achievable with RPC and the typical ground control point configuration, applying affine refinement

V 4 RPC + shift To compare the efficiency of affine and shift RPC refinements

VI 10 RPC + shiftTo find out if the accuracy improves with increasing the number of ground control points in the case of applying shift RPC refinement

VII 10 RPC + affineTo find out if the accuracy improves with increasing the number of ground control points in the case of applying affine RPC refinement

VIIIall

availableRPC + shift Assessment of the best achievable accuracy in the case of applying shift RPC refinement

IXall

availableRPC + affine Assessment of the best achievable accuracy in the case of applying affine RPC refinement

X 4 Affine Assessment of accuracy achievable with the affine universal model and a minimal set of ground control points, and comparison with orientation with RPC (the ground control points set was the same as in Schemes III and IV).

XI 10 Parallel-perspective Assessment of accuracy achievable with the various universal models and comparison with orientation with RPC (the ground control points set was the same as in Schemes V and VI).

XII 10 DLT

XIII 10 Affine

Pleiades imagery orientation accuracy: single images

Image phr1a_p_201306010719533_sen_624609101-001

Scheme GCPs count Orient. model GCP RMSE, m GCP MAX, m CPs count CP RMSE, m CP MAX, m

I 0 RPC - - 33 3.1 4.9

III 1 RPC+shift 0.0 0.0 32 1.0 2.3

IV 4 RPC+affine 0.4 0.5 29 1.0 1.9

V 4 RPC+shift 0.6 0.8 29 1.0 2.0

VI 10 RPC+shift 0.7 1.0 23 1.1 1.9

VII 10 RPC+affine 0.7 1.0 23 1.0 1.9

VIII 33 RPC+shift 1.0 2.2 0 - -

IX 33 RPC+affine 0.9 2.3 0 - -

X 4 affine 0.0 0.0 29 2.6 4.2

XI 10 par.persp. 0.8 1.3 23 2.2 3.9

XII 10 DLT 1.2 1.7 23 1.9 3.0

XIII 10 affine 1.6 2.4 23 1.8 3.4

Pleiades imagery orientation accuracy : single images

Image phr1a_p_201306010720166_sen_624610101-001


I 0 RPC - - 38 3.9 4.6

III 1 RPC+shift 0.0 0.0 37 0.8 1.5

IV 4 RPC+affine 0.1 0.2 34 0.7 1.7

V 4 RPC+shift 0.3 0.4 34 0.7 1.5

VI 10 RPC+shift 0.6 0.9 28 0.7 1.3

VII 10 RPC+affine 0.5 0.8 28 0.7 1.3

VIII 38 RPC+shift 0.6 1.4 0 - -

IX 38 RPC+affine 0.6 1.2 0 - -

X 4 affine 0.0 0.0 34 4.5 7.6

XI 10 par.persp. 2.0 4.1 28 2.5 4.4

XII 10 DLT 0.8 1.2 28 1.5 3.0

XIII 10 affine 2.8 4.8 28 2.8 5.7

Pleiades imagery orientation accuracy : single images

Image phr1a_p_201306010720273_sen_624611101-001


I 0 RPC - - 38 4.2 5.4

III 1 RPC+shift 0.0 0.0 37 0.9 1.8

IV 4 RPC+affine 0.1 0.2 34 0.8 2.1

V 4 RPC+shift 0.3 0.3 34 0.8 2.1

VI 10 RPC+shift 0.5 0.9 28 0.7 1.8

VII 10 RPC+affine 0.5 0.8 28 0.7 1.9

VIII 38 RPC+shift 0.7 1.8 0 - -

IX 38 RPC+affine 0.6 1.7 0 - -

X 4 affine 0.0 0.0 34 6.6 11.3

XI 10 par.persp. 2.8 5.8 28 3.7 6.3

XII 10 DLT 1.9 2.6 28 2.3 4.7

XIII 10 affine 3.9 6.5 28 4.0 7.9

Pleiades imagery orientation accuracy: single images

Conclusions:

Planimetric accuracy of supplied RPC was RMSE 3.1-4.2 m (the specification is CE90 = 8.5 m).

The accuracy of 0.8-1.0 m RMSE (i.e. rather close to the limit set by the measurements accuracy) was achieved with a single GCP, applying shift refinement to the supplied RPC model.

The accuracy of 0.7-1.0 m RMSE was achieved with 4 GCPs, applying either shift of affine RPC refinement.

Further increasing the number of GCPs did not improve the accuracy.

The orientation accuracy achieved with universal methods varied over a wide range and was significantly worse than one achieved with RPC and bias removal.

Pleiades imagery orientation accuracy: the triplet

Triplet orientation without tie points

Scheme GCPs count

Orient. model GCP RMSE, m

GCP MAX, m

CPs count

CP RMSE, m

CP MAX, m

dS dZ dS dZ dS dZ dS dZ

I 0 RPC - - - - 38 3.8 2.2 4.9 4.9

III 1 RPC+shift 0.0 0.0 0.0 0.0 37 0.8 2.3 1.3 5.3

IV 4 RPC+aff. 0.1 0.1 0.1 0.1 34 0.8 2.0 2.0 4.3

V 4 RPC+shift 0.3 1.6 0.5 2.1 34 0.7 2.1 1.5 4.4

VI 10 RPC+shift 0.6 1.4 1.1 2.5 28 0.7 2.3 1.4 4.9

VII 10 RPC+affine 0.5 1.5 1.0 2.7 28 0.8 2.4 1.8 5.0

VIII 38 RPC+shift 0.7 2.2 1.4 5.9 0 - - - -

IX 38 RPC+affine 0.6 2.1 1.2 6.1 0 - - - -

X 4 affine 0.0 0.0 0.0 0.0 34 13.5 51.4 36.9 125.6

XI 10 par.persp. 2.5 11.5 5.5 23.7 28 3.4 13.7 7.3 34.3

XII 10 DLT 0.9 3.1 2.2 6.1 28 1.9 19.1 4.9 49.3

XIII 10 affine 2.4 10.3 5.1 21.4 28 3.5 12.9 7.2 30.1


Triplet orientation with tie points

Scheme GCPs count

Orient. model

GCP RMSE, m GCP MAX, m CPs count CP RMSE, m CP MAX, m


II 0 RPC+shift - - - - 38 3.6 2.2 4.5 5.7

III 1 RPC+shift 0.2 0.6 0.2 0.6 37 0.7 2.2 1.4 5.6

IV 4 RPC+affine 0.1 0.1 0.1 0.1 34 0.8 2.0 2.0 4.3

V 4 RPC+shift 0.3 1.6 0.5 2.2 34 0.7 2.1 1.5 4.7

VI 10 RPC+shift 0.6 1.4 1.1 2.4 28 0.7 2.3 1.4 5.4

VII 10 RPC+affine 0.6 1.4 1.1 2.4 28 0.7 2.3 1.4 5.2

VIII 38 RPC+shift 0.6 2.1 1.2 5.0 0 - - - -

IX 38 RPC+affine 0.6 2.0 1.1 5.0 0 - - - -

X 4 affine 0.0 0.0 0.0 0.0 34 8.0 38.0 19.3 67.8

XI 10 par.persp. 4.5 28.7 9.5 64.2 28 5.0 31.9 12.6 95.2

XII 10 DLT 3.6 30.5 7.4 67.3 28 4.5 34.6 11.1 106.2

XIII 10 affine 4.5 30.9 9.5 70.5 28 5.4 33.8 13.6 105.8


Using supplied RPC and no GCPs, the achieved planimetric accuracy was 3.6 m RMSE in the case of involving tie points and 3.8 m without them; the vertical accuracy was 2.2 m in both cases. So involving tie points in the adjustment procedure did not significantly improve the accuracy;

Involving GCPs made the difference between adjustment with and without tie points insignificant.

The accuracy of 0.7-1.0 m RMSE was achieved with 4 GCPs, applying either shift of affine RPC refinement. Using a single GCP and applying shift RPC refinement, the planimetric accuracy of 0.7-0.8 m and the vertical accuracy of 2.2-2.3 m were achieved. Increasing GCPs number to 4 allowed improving the results but not significantly, the vertical accuracy became of 2.0-2.1 m.

Further increasing the number of GCPs did not improve the accuracy.

The universal methods are not suitable for stereoscopic (three dimensional) processing of Pleiades imagery.

Conclusions:

Pleiades imagery orientation accuracy: stereopairs vs. the triplet

Triplet orientation (maximum B:H=0.37)

Scheme GCPs count

Orient. model



I 0 RPC - - - - 25 3.6 2.0 4.5 4.9

III 1 RPC+shift 0.0 0.0 0.0 0.0 24 0.8 2.2 1.2 5.3

IV 4 RPC+affine 0.1 0.1 0.1 0.1 21 0.7 2.0 1.1 4.3

V 4 RPC+ shift 0.3 1.6 0.5 2.1 21 0.7 1.9 1.4 4.0

VI 10 RPC+ shift 0.6 1.3 1.2 2.1 15 0.6 2.2 0.9 4.3

VII 10 RPC+affine 0.5 0.6 0.8 1.2 15 0.7 2.1 1.2 4.4


Forward + backward stereopair orientation (B:H=0.37)

Scheme GCPs count

Orient. model



I 0 RPC - - - - 25 3.5 1.9 4.5 4.3

III 1 RPC+ shift 0.0 0.0 0.0 0.0 24 0.8 2.2 1.3 4.9

IV 4 RPC+affine 0.1 0.2 0.2 0.2 21 0.7 2.0 1.1 4.7

V 4 RPC+ shift 0.3 1.7 0.6 2.0 21 0.7 1.9 1.4 3.6

VI 10 RPC+ shift 0.7 1.3 1.2 2.2 15 0.6 2.2 1.0 3.9

VII 10 RPC+affine 0.5 0.7 0.8 1.1 15 0.7 2.1 1.3 4.0


Forward + nadir stereopair orientation (B:H=0.25)

Scheme GCPs count

Orient. model



I 0 RPC - - - - 25 3.3 2.6 4.2 7.7

III 1 RPC+shift 0.0 0.0 0.0 0.0 24 0.8 2.8 1.4 7.8

IV 4 RPC+ affine 0.0 0.6 0.0 0.8 21 0.7 2.2 1.2 6.4

V 4 RPC+shift 0.4 1.6 0.5 2.5 21 0.7 2.2 1.3 6.3

VI 10 RPC+shift 0.6 1.5 1.0 2.4 15 0.7 2.7 1.3 6.7

VII 10 RPC+ affine 0.5 1.0 0.8 1.6 15 0.7 2.5 1.4 6.5


Nadir + backward stereopair orientation (B:H=0.11)

Scheme GCPs count

Orient. model



I 0 RPC - - - - 25 4.1 3.5 4.9 9.4

III 1 RPC+shift 0.0 0.0 0.0 0.0 24 1.0 3.0 1.7 8.0

IV 4 RPC+ affine 0.2 1.8 0.3 2.5 21 0.7 3.4 1.5 10.1

V 4 RPC+shift 0.4 2.7 0.6 4.0 21 0.7 3.3 1.2 8.8

VI 10 RPC+shift 0.6 2.4 1.0 4.6 15 0.7 3.3 1.4 8.0

VII 10 RPC+ affine 0.5 2.2 0.7 4.3 15 0.7 2.9 1.5 7.8


Conclusions:

The accuracy of orientation of the triplet and of the forward+backward stereopair (i.e. the stereopair with the largest base-to-height ratio) was approximately the same.

The accuracy of triplet orientation was slightly better than one of the stereopairs which included the nadir image (so the stereopairs had lower base-to-height ratio).

Mapping and 3D modeling of urban areas

Creating 3D models

Deriving DEM

Generating orthoimagery

3D modeling of urban area

Assessment of suitability for topographic maps creating and updating

Interpretability assessment

Assessment of objects positioning accuracy

Drawing contour lines

Creating 3D models using PHOTOMOD: deriving DEM

Creating 3D models using PHOTOMOD: generating orthoimagery

Creating 3D models using PHOTOMOD: 3D vectorization

Creating 3D models using PHOTOMOD: automatic 3D modeling

PHOTOMOD. Object texturing

PHOTOMOD. Model texturing using close-range imagery

PHOTOMOD. Import of “special” objects

PHOTOMOD. Creating 3D model of the city of Yekaterinburg

Interpretability assessment

Source dataset:

Pleiades orthoimagery, 0.5m, RGB Worldview-2 orthoimagery, 0.5m, RGB

A3 orthoimagery, 0.1m, RGB Topographic interpretation samples set WV-

2, GE-1 and Ikonos Scanned topographic plans of scale 1:500,

contour interval 0,5 m; Vector topographic maps of scale 1:10 000 ,

contour interval 2 m

Interpretation results

Imagery Number of recognized objects

Images only

Add. Info

Field ve-rification

Not re-cognized

Pleiades 103 92 21 20

WV 2 106 90 19 19

A3 126 78 15 14


Source dataset:

Pleiades stereopair (9º and -11º), 0,5 m, PAN

Pleiades orthoimagery 0.5m, RGB

WV2 orthoimagery, 0.5m, RGB A3 orthoimagery 0.1m, RGB as

reference data

PHOTOMOD. Comparing different types of objects

Single-storey private houses Multistory city buildings

Pleiades A3 Pleiades A3

Interpretability analysis

1.5 m - wide ledges are indiscernible

Shape and size of multistory buildings are reconstructed correctly

It is impossible to tell residential buildings from nonresidential ones

Some architectural forms may be missing (the ledges are shown on one side of the building and missing on the other)


Parameter WV2 ortho Pleiades ortho Pleiades stereo

Number of measurements 371 366 371

Mean error, m 1.3 1.5 0.9

Maximum error, m 4.0 5.4 3.5

Error distribution – vector map of scale 1: 2 000

Error distribution – vector map of scale 1 : 5 000

35%

40%

25% 35%

40%

25%

58%33%

9%

85%

15%

1%

81%

17%

2%

97%

3%

0-0,4 mm

0.4-08 mm

larger than 0.8 mm

0-0,4 mm

0.4-08 mm

larger than 0.8 mm

PHOTOMOD. Drawing contour lines

Contour lines verification using reference data

Vector topographic maps of scale 1:10 000, contour interval 2 m

Contour lines derived from the Pleiades stereopair

Topographic mapping and 3D modeling of urban areas

The 3D model created is geometrically accurate and discrete, so it is possible to access separate objects, to set attribute values for them and to perform 3D measurements - in other words, to produce geospatial databases. The model can be used for visualization and for 3D city planning. Stereoscopic measurements ensure better accuracy and interpretability than ones performed in single images, while using tri-stereo imagery reduces “blind zones”.

Pleiades images are suitable for creating and updating topographic maps of scale up to 1: 10000. If additional sources of data are available and field verification is possible, it is possible to create and update 1 : 5 000 scale maps of moderate-sized inter-settlement areas.

Accuracy and interpretability of Pleiades imagery are comparable to ones of WordView-2.

Conclusions:

Acknowledgement

RACURS and TECHNOLOGY 2000

express their gratitude to

ASTRIUM GeoInformation Services

for the Pleiades Tri-Stereo Imagery Product over the city of Yekaterinburg

A Case Study of Pleiades Tri-Stereo Imagery

Thank you for attention !

a case study of pleiades tri-stereo imagery:

Documents

images accuracy

ground coordinates accuracy

best achievable accuracy

rpc formulae

rational polynomial

affine universal model

mms image

efficiency of affine