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TECHNOLOGICAL BOUNDARY OF ACCURACY OF ORTHORECTIFICATIONOF IKONOS AND QUICK-BIRD BASED ORTHOPHOTOMAPS

R.LACH, C.MISIUN, L.SKRZYPCZYK

pp. 216 – 230 XII th Conference of Polish Society of Photogrammetry and Remote Sensing, Bialobrzegi,Poland, June 2002, ISBN 83-917952-0-9

Robert LACH,rlach@techmex.com.pl ,

+48 605 695 064 mobile+48 22 560 82 24 direct phone+48 22 560 82 00 secretary+48 22 560 82 30 fax

DISCLAIMER

As it appears a lot of information noise; this article was submitted for review

to specialists of SPACE IMAGING LLC .

Precision Plus orthophotomaps production in Poland, some remarks of production

orthorectification of IKONOS imagery with usage of Rational Polynomial Coefficiencies

files for area of 30 000 km² for the needs of Integrated Administration and Control

System of European Commission in Poland

Description of the project refers to acquiring of archive imagery of SI EURASIA and

new collection of area of Poland from 2003 year. SI EURASIA passed us information

from 52 uncuccessful METEOSAT passes and 16 succesful IKONOS passes.

Text of this article have been writtenin 2002 year. Disclaimer and

comment on the first page wereadded in 2003 and 2004 prior to

World Congress of ISPRS inIstanbul.

My contact data are different thenthey were in 2002

Thereforecurrent contact data are :Robert LACHGEOSPACE-PLrobertlach00@gmail.com+48 500 739 777 mobile phone

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As there appears a lot of "information noise" in Poland as to possible ortorectification of VHR data,

the authors wish to share the results of their work - they have performed all by themselves and that

refers to fully domestic production of satellite ortophotomaps prepared for over 3,169 km² in 2002 -

with both the Polish and international photogrammetric family.

There had appeared international publications referring to the problem several years before IKONOS

and then QUICK BIRD systems were launched and they were often full of speculations as to expected

accuracy of ortophotomaps. After IKONOS was launched, there appeared another tide of

publications in reference to self-dependent attempts to orthorectify the Carterra GEO products,

which could hardly be successful due to lacking access to the mathematical model of IKONOS sensor1

- despite their correct mathematical approach with application of precise model to orthorectification

(rational polynomial coefficiences). The error results in RMSE terms used to range to 3-4 m.

Application of the IKONOS sensor model, implemented, for the first time upon consent of

SPACE IMAGING Inc., by ERDAS,

a collection of images for Poland with not exceeding deviation of 180 from nadir,

fulfilling of strict requirements of SPACE IMAGING INC2. as to accuracy of the control

points measurement (GCPs.) with application of GPS technology,

application of Digital Elevation Model (characterised with accuracy of height delimitation of

2-3 m) to the orthorectification process,

made it possible to produce orthophotomaps with the RMSE value below 1 m. Production of the

ortophotomaps has been realised in full by a Polish team : Baltyckie Centrum Systemow Informacji

Przestrzennej [the Baltic Centre for Spatial Information Systems] thanks to logistic technological and

financial support of the TECHMEX S.A. and an open-minded position of Space Imaging Eurasia.

A short introduction to the VHR systems competition

A delayed start of that prognosticated era of VHR satellites, which began with placing

IKONOS 2 system on the orbit in 1999, has been more and more dynamically advanced.

However, the users' expectations as to the quality of VHR satellite data have not been satisfied

yet by the EROS satellite system the information content of which hardly differs from the

KOSMOS system KVR-1000 data functioning on the Polish market. Launching the Quick

Bird system in October 2001 will advance origination of the VHR imagery market, not earlier,

however, than in the perspective of 2-3 years from 2002 on as at that time the systems are

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expected to start their real competition as far as their archives of metropolitan cities areas are

concerned. Efficient use of the VHR satellite system does not depend on resolution itself but

on the access to the wanted data on the market first of all. Meanwhile, the archives of images

of Poland that are available in Internet - of the Digital Globe's Quick Bird system - show that

on September,17th 2002 there are only 57 images characterised with less than 20% cloud

cover. In consideration of the speed of growth of archive of the IKONOS system with the

capacity to register large areas of interest (AOI) growing even up to four times bigger than

that of Quick Bird (Kurczynski, Wolniewicz) as well as the process of establishing of the

Polish archive of IKONOS system for 3 years now - the fact of disproportion between the

archives of IKONOS and of Quick Bird in Poland is not to be wondered at. Meanwhile,

SPACE IMAGING Inc. started constructing IKONOS BLOCK II system that, in 2004, is

going to have resolution of 40 cm and it seems that in two years time IKONOS and IKONOS

BLOCK II joint collection capacity will be at least 6 times of Quick Bird.

DEM produced from the IKONOS stereopair and the ortophotomap of Presision Plus

class as the first in Poland.

Having heard a lot of "information noise" in Poland as to the fact whether VHR imageries can

give a product as precise as to make the RMSE value smaller than 1 m and - having had no

access to the sensor model yet - in 2001we purchased Precision Plus orthophoto from SPACE

IMAGING Inc. We acted on behalf of the Municipality of Bytom that placed an order with us

to perform a detection of changes by comparing ortophotomaps of 1997 and 2001. SPACE

IMAGING Inc. requested us to measure only GCPs (ground control points) only and produced

a Numerical Terrain Model from the IKONOS stereogram with 6 meters post spacing (using a

Stereo Analyst module of ERDAS Inc.) and they next sent us imagery material after it was

ortorectified. The report on ortorectification process showed value of RMSE = 0.9 m. After

the ortophotomap sent by SPACE IMAGING Inc. was overlapped over the ortophotomap of

Bytom, performed in Poland by OPGK Olsztyn) on the basis of aerial photos from 1997, the

two ortophotomaps visually fitted together and only the radiometry of IKONOS' imageries

distinguished itself with more "lively' colours than the ortophoto taken from the PHARE

program aerial photographs. In the course of technical acceptance of the product in the GIS

unit of Bytom Municipality there cadastral data were overlapped onto the IKONOS

orthophotomap. Result, shown below proves that cadastral data (earlier created with

application of DGPS measurements asr fitting together with the IKONOS-based orthophoto.

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[the ortophotomap of October 2001 showing the borders of lands and building contours in

Bytom. Scale 1: 3,500, RMSE value of 0.9m]

IKONOS DATA ORTORECTIFICATION TESTS

An independent ortorectification of the Carterra GEO data with an IGM (Image

Geometry Model) model

Having carried out those tests and purchased the programming for independent

ortorectification of the IKONOS imageries from ERDAS Inc., we decided to perform

ortophotomaps of Precision Plus class by ourselves. On March 8 2002, Mr. Murat Erciyes,

President of SPACE IMAGING EURASIA had a meeting with the authorities of the National

Office of Geodesy and Cartography and Mr. Aleksander Bentkowski - President of Agency for

Restructuring and Modernisation of Agriculture. Tests of the IKONOS system that were to

include testing different kinds of land - from almost a flat one to those of big height variety -

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were decided to be carried out. The Polish Presidents of GUGiK (General Surveyors Office)

and ARMA (Agency for Restructuring and Modernisation of Agriculture) did hope to receive

so accurate a product that might satisfy both the IACS accuracy requirements and the accuracy

requirements for modernisation of the cadastral system with application of photogrammetric

technologies. Shortly speaking, the question consisted in performance of ortophotomaps of the

biggest possible accuracy - even of 1:5,000 scale. Additionally, the purpose of testing was also

to check whether, in the course of one passage, the system would register several adjacent

stripes of photographs in order to optimise the way of collection of IKONOS . On April 4

2002 SPACE IMAGING EURASIA registered images of 1150 sq. km of the Nowy S¹cz

administrative district area that had been chosen due to big overheights there (the lowest point

in the district is 200 m high and the highest - 1200m).

DETERMINATION OF ACCURACY of APPLIED DIGITAL ELEVATION MODEL.

The D.E.M. delivered by external partner was applied for ortorectification. Two D.E.M.s

were compared from the area surrounding Debrzno in the administrative district of Czluchów

– and are shown below. This DEM. was compared with the one performed for Debrzno from

the photographs of PHARE LIS 9206 program in SoftPlotter v.1.3. The area of about 36 sq.

km surrounding Debrzno was examined. The area is diversified as to the relief, the differences

in height being from 135 m to 178 m.

DEM delivered by external source on the left, DEM created from serial photogrammetric photos

( 1: 26 000 scale) on the right

Digital Elevation Model provided by external partner was converted to ASCI file. Resulting file was

imported into Microstation package. Blue lines of DEM sections were defined in 500 meters intervals

on from each other. Profiles were generated in Microstation. Test was executed on 3739 points ,

placed in 20 meter distances, grouped in 13 profiles. Each profile included 200 measured points.

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Rozk³ad procentowy ró¿nicwysokoœci

47%

29%

14%

9%

1%

0%

0 - 1m

1 - 2m

2 - 3m

3 - 5m

5 - 10m

>10m

Results :RMSE 2.65NSSDA 5.20

Max. odchyłka 20.24Min. odchyłka -6.68

0 - 0,5m 10451 0 - 1m 18622 1 - 5m 17373 5 - 10m 704 >10m 68

Accuracy of determination of z coordinate was better than one meter for 50 % of compared z

points as shown above. Preliminary test proved that 96 % of points of checked sample have z

accuracy – better than 5 meters.

Test No.2.

The same DEM sample was checked again in different way. Tested DEM with 20 meter post

spacing was converted from original file to ACSI format file. ASCI file was imported to

ERDAS IMAGINE 8.5.v. Sample DEM was compared with DEM produced from aerial

PHARE program photos, but these DEMs were delivered in different coordinate systems.

After unification of projections and coordinate systems both files were compared, where each

z values from one DEM file were substracted from z values of second DEM file. Test was

executed for DEM 165 248 points with 20 meter post spacing.

Results :

RMSE 1.91NSSDA 3.75Max. odchyłka 15.24Min.Odchyłka

-19.86

0 - 0,5m 415641 0 - 1m 765712 1 - 2m 482303 2 - 3m 230864 3 - 5m 148425 5 - 10m 23086 >10m 211

Three classes of determination of z accuracy (green, light yellow and orange), within range of

1-3 meters errors form 92 % of checked DEM sample.

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Test No.3.

The aim of the test was to determine differences of location of analysed terrain details for

photos orthorectified on the basis of one and the other DEM. Two orthorectification processes

were run, using different DEMs. Later differences between resulting images were measured in

ERDAS IMAGINE, after orthorectification in the same software environment.

Results :

Orthorectification of IKONOS scenes begun for several different landscapes after these initial

DEM tests. Several different test areas were selected from almost flat to mountain-type area.

We also wanted to test ability to register IKONOS imagery in different modes of collection,

including collection of each individual scenes, two-image strips collection, three image-strips

collection and four image-strips collection. These ways of collecting were applied during

testing process to 4 TEST AREAS.

TEST AREA 1 - Krasnik

First image of Krasnik village was acquired from Space Imaging Inc archive, since at the

beginning of testing process SI EURASIA did not have imagery for southern area of Poland,

characterized by large number of very small farms. Therefore we have purchased scene from

SI Inc archive , collected with viewing angle of less than 18 º angle from nadir, delivered to us

together with rpc files. (GeoOrthoKit)., registered on June 3rd of 2001. Number of GCPs was

determined on the basis of former findings of IKONOS orthorectification. MSPM program of

Ashtech was used for analysis of number of satellites and their geometric configuration.

Project of location of GCPs was prepared and 4 points of national POLREF network were

selected as tie points. (numbered 1701, 1802, 1803 and 2808). Twelve (12) points were

basic DEM Compared DEM RMSENr

PróbkiX Y X Y różnica H dX dY 22 dYdX

1 3510473.42 6003560.43 3510473.70 6003560.43 0.63 -0.28 0.00 0.283 3512706.63 6002257.10 3512706.49 6002257.52 0.46 0.14 -0.42 0.44

16 3508956.00 6001406.41 3508956.35 6001406.77 0.56 -0.35 -0.35 0.502 3512819.75 6002610.88 3512818.77 6002611.02 1.18 0.98 -0.14 0.996 3513496.60 6002775.67 3513497.25 6002775.28 -0.94 -0.65 0.39 0.76

13 3511764.34 6003508.14 3511763.96 6003508.14 0.99 0.37 0.00 0.3715 3509259.43 6001342.26 3509259.23 6001341.65 -1.08 0.20 0.61 0.647 3512790.99 6002125.73 3512791.69 6002125.16 -2.14 -0.70 0.57 0.908 3512028.98 6002205.98 3512029.28 6002206.14 -2.06 -0.30 -0.16 0.34

12 3511673.58 6003466.58 3511673.10 6003466.58 1.99 0.48 0.00 0.4810 3508671.23 6001889.33 3508673.11 6001890.01 3.01 -1.88 -0.67 2.0011 3511502.19 6003257.71 3511501.80 6003257.94 3.20 0.38 -0.23 0.454 3513389.03 6002851.19 3513392.44 6002850.05 -4.31 -3.41 1.14 3.609 3511971.94 6002026.77 3511970.87 6002028.32 4.03 1.07 -1.55 1.89

14 3511848.81 6005095.52 3511847.67 6005094.00 4.09 1.14 1.52 1.905 3513609.47 6002833.79 3513619.61 6002831.06 -18.43 -10.14 2.73 10.50

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measured using static method on the basis of reference points on 2002-03-20, using 4 GPS

Ashtech Z-XII and Ashtech Z-Surveyor receivers. Tropospheric correction was applied for

standard meteo conditions. Minimal elevation angle was set for 15 º. Rigorous eualization of

network was realized with usage of FILLNET program of Ashtech. Results were achieved in

WGS-84/ERTF’89.

B & L coordinates received were transformed from WGS-84 system to Krasowski 1942

(Pulkovo) on the basis of 4 common points of POLREF network .

Orthorectification was performed with usage of ERDAS IMAGINE 8.5.version with

application of OrthoBase module. Used DEM had 20 meter post spacing. Results achieved at

control points 12 CGPs were checked and then, after removing of worst point were

recaltulated again on 11 GCPs. Obtained result is shown on next page in the form of window

from part of ERDAS Imagine orthorectification report.

RESULTS ACHIEVED : RMSE received for 1 IKONOS scene = 0.8661 m

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TEST AREA 2 – Gostynin

Two image strips were collected on April, 7th , 2002 for area of relatively flat Gostynin area (central-

northern part of Poland ) of total area of 583 km².

20 meter post spacing DEM was used for orthorectification. GCPs were collected in similar way,

remembering about fulfilling strict accuracy requirements of SPACE IMAGING Guidelines for CGP

collection . These guidelines require to collect CGPs for most precise orthorectification with

planimetric accuracy better than 20 cm and “z” accuracy better than 60 cm.

RESULTS ACHIEVED :(for particular image strips)

image id 1: RMS Errors for 28 GCPs: x: 0.2952

y: 0.2603

total: 0.3936

image id 2: RMS Errors for 24 GCPs: x: 0.2922y: 0.3295

total: 0.4404

image id 3: RMS Errors for 23 GCPs: x: 0.3117y: 0.4108

total: 0.5157

TEST AREA 3 – Nowy Sacz County

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Three image strips were collected on April, 4th, 2002 for Nowy Sacz County, for 1150 km²,

during one IKONOS pass over the area. Nowy Sacz county is located in the south of Poland,

bordering with Slovakia . It was most difficult area for orthorectification, since difference in hight at

the territory of the county are larger than 1000 m. Lowest point has 200 meters above the sea level,

the highest has more than 1200 m . Six images were orthorectified in one block, with usage of 53

GCPs. First stage of work was orthorectification of panchromatic imagery. GCPs causing greatest

errors were rejected. Next stage of work lead to creation of pseudo-natural color composition and

orthorectification of multicpactral data. Last phase of work was merging of panchromatic and

multispectral imagery with application of PCA method.

RESULTS ACHIEVED :Image accuracy for control and check points for each scene:image id 1: RMS Errors for 13 GCPs: x: 0.8224

y: 1.1841total: 1.4416

image id 2: RMS Errors for 9 GCPs: x: 0.7305y: 0.7736

total: 1.0640image id 3: RMS Errors for 10 GCPs: x: 1.0780

y: 0.9510total: 1.4375

image id 4: RMS Errors for 10 GCPs: x: 0.9687y: 0.7371

total: 1.2173image id 5: RMS Errors for 7 GCPs: x: 0.6371

y: 1.4884total: 1.6191

image id 6: RMS Errors for 6 GCPs: x: 0.0000y: 0.0000

total: 0.0000

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Total image RMSE = 1,2866 m

All works related to image collection, delivery to Poland, GCP collection,orthorectification, mozaicking took only two weeks.

Resulting orthorectified naighbouring scenes. Please notify this is not a mozaicked orthoimagery, but

only set of two orthorectified scenes. Border between scenes may be observed in the forest area in the

southern part of image (at its centre). Currently cadastral records existing for part of the county are

overlapped over IKONOS orthophoto.

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TEST AREA 4

Drawsko Pomorskie area

Four adjacent IKONOS strips, results in review by Military Intelligence Directorate

of Polish Army General Staff

CONCLUSIONS:

1. Registration of IKONOS imagery should be taken at 18o deviation angle from nadir

to produce ortophotomaps of RMSE <= 1 m,

2. Measurement accuracy of GCPs should - according to the technical instructions of SPACE

IMAGING Inc. and SPACE IMAGING EURASIA - be better than 20 cm (x and y) and better

than 60 cm vertically to make the summary error of measurement and point determination not

exceed 0.5 m (x,y) and 1 m (z)

3. Application of Terrain Numerical Model and post spacing of 20 metres as well as height

determination accuracy of 2-3 metres makes possible the domestic production of Precision

Plus class ortophotomaps where RMSE error is better than 90 cm.

4. The mode of registration of a bigger area (3 or 4 stripes of photographs one after another) in

the course of one route of the satellite (Objects: Nowy Sacz and Drawsko Pomorskie), tested

in 2002, shows the optimum way of registering the area of Poland.

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5. The ortophotomaps already produced do satisfy both the accuracy requirements of the

European Union (EC Directive No 1593/2000) in reference to construction of ortophotomaps

and Land Parcel Identification System within the Integrated System of Administration and

Control as well as geodetic-cartographic regulations referring to the accuracy of the

ortophotomaps for the cadastral purposes for scale 1: 5000

Literature

Kaczynski R., Ewiak I., Ren Wei Chun, Yang Ming Hui, 2001 "Evaluation of Panchromatic IKONOS

Data for Mapping, Geodesy and Cartography", Vilnius, Vol. XXVII, No 4, pp 157-160

Bruno Biagini, Riccardo Nasini, 22-23 March 2002, EURIMAGE European Resellers Meeting, Roma

Zdzislaw Kurczynski, July 2002, Wies³aw Wolniewicz "VHR satellite imagery systems" Part I pp 18

- 22 GEODETA

Zdzislaw Kurczynski, Wieslaw Wolniewicz "VHR satellite imagery systems" Part II What is the

pixel below 1 m" pp 26 - 30 GEODETA, August 2002

Ryszard Preuss, Zdzislaw Kurczyñski "Conception of production of a ortophotomap of Poland for the

purposes of identification of land parcels - LPIS" pp 6 - 10 GEODETA, August 2002

Jan Konieczny, September 2002 "National System of Identification of Farms and Stock, the Polish

IACS and LPIS, Quickly, Properly, Cheaply ?" pp 8 - 11, GEODETA

Robert Lach, Murat Erciyes, September 2002 "Our Movement Now" pp 12 - 14, GEODETA

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Tao C. Vincent, Yong Hu, Steve Schnick, 2002 "Photogrammetric Exploitation of IKONOS imagery

using the Rational Function Model", ASPRS Congress, Washington

Olivier Leo, Guido Lemoine, Jacques Stakenborg, 2001 "Discussion Paper on Land Parcel

Identification System v. 1.4.< Ispra, Italy

European Council Regulation No 1593/2000 of 17 July 2000.

1 (T. Toutin, Ph. Cheng, R. Kaczynski)

2 QA-042, Rev D, 11/28/00, GCP Specifications, Space Imaging proprietary