By Eng. Zahraa Mohamed Abd Al-Rahman - Home | AAG · 2010. 6. 29. · Page 1 By. Eng. Zahraa Mohamed Abd Al-Rahman. Assessment Of Egyptian Satellite (EGYPT SAT-1) Images For The Production

ByEng. Zahraa Mohamed Abd Al-Rahman

Assessment Of Egyptian Satellite (EGYPT SAT-1) Images For The

Production and Updating Of 1:25000 Planimetric Maps

[email protected]

Importance of Digital Mapping

• Digital mapping has a great importance in theplanning, improvement, and developmentprocesses.

• Many areas in Egypt are not covered bytopographic maps of relatively large scalemaps, and they are difficult to obtain.

• Hence, it is essential to investigate the potentialof using various techniques for producing andupdating these maps, including SatelliteRemote Sensing.

• Digital city maps can be produced usingvarious techniques including:– Field Surveying: is an accurate production

technique, however it is expensive and timeconsuming.

– Digital Photogrammetry: is the most adopted worldwide technique for city maps production and isfaster than field surveying.

– Remote Sensing : is the science and art of acquiringinformation (spectral, spatial, and temporal) aboutmaterial objects, area, or phenomenon, withoutcoming into physical contact with the objects, orarea.

Digital Maps Production Techniques

It becomes a suitable alternative tool for digital city

map production in Egypt , either in a planimetric mode

using single (mono) images (x,y) or in a topographic

mode using stereo images (x, y, z) .

Why Remote Sensing?

• Launching and operation of a series of threesatellites:− Egypt Sat-1 Launched successfully on April 17,

2007.

− Egypt Sat-2 Planned to be launched in 2012.

− Desert Sat Planned to be launched in 2017.It used at observation of Egyptian Deserts.

The Egyptian Space Program

The Egyptian Space Program

Egypt sat 1Egypt sat 2Desert Sat

Spatial Resolution=7.8 mSpatial Resolution=5.4 mSpatial Resolution=2.5 m

• The objective of the three satellites is to provide

images for Egyptian land which is necessary

necessary for the purpose of comprehensive

peaceful development of Arab countries.

Objectives of Egypt’s Space Program

• Egypt SAT-1 is the first Egyptian satellite forRemote Sensing.

-It is an international collaborative project ofNARSS, Total cost is about 20 Million Dollars.

-It can capture images for any location in Egypt.

-Tilting capability (35 deg) so it can covers Salom,Alamen,..we can get a Stereoscopic Imaging

-It can be used for many purposes, including theproduction and updating of maps

Egypt Sat-1 Remote Sensing Satellite

Egypt Sat-1 Photos During Construction Phase



Egypt sat

Egypt Sat-1 Photo at launching site

• It was launched on a Dnepr-1 by a Russian ejector fromCosmodrome Station in Baikonur from Kazakhstan


• Egypt has a Ground controlstation for its satellites nearCairo.

• Data receiving stations in Aswanat the extreme south of Egypt.

Ground Station & Control Centers

Egypt sat1 can cover Arab countries, and Africa.

Aswan Receiving Station Coverage

• Transferring technology of making satellites toEgypt.

• To be used for scientific researches.• Determination of the mineral and water sources.• Observation of different phenomena like pollution

of beaches, limitation of the green area,observation of informal settlement area,…

• Studying headwaters of Nile.

Applications of Egypt SAT-1

Egypt Sat-1 Spacecraft General Layout

• Egypt Sat-1 satellite has two onboard sensors:– Multi-Band Earth Imager (MBEI):

4 Spectral bands in the visible range:• 0.50 - 0.59 µm• 0.61 - 0.68 µm• 0.79 - 0.89 µm• 0.50 - 0.89 µm (panchromatic)– Instrument mass = 26 kg

– Infrared Earth Imager (IREI): Invisible range• Spectral band: 1.55 - 1.7 µm

– Instrument mass = 14 kg

– Spatial resolution at nadir: 39m (cross-track)x 46m (along- track)

Sensor Characteristics of Egypt SAT-1

• It has:− Swath width for MBEI is 46km− Swath width for IREI is 55km− Instrument type for both sensors (MBEI and

IREI )is Pushbroom imager


IREI instrument in its test frame


• Orbit Characteristics:• Egypt SAT-1 operates in sun-synchronous orbit• Inclination of 98.1 degree with equator• It rotates around the earth sphere each 98 min• It rotated nearly 15 times per day 4 times of these

rotations are above ground stations.• Orbit Height: is 668 K.M above Earth surface

• Platform Characteristics:• Weight: 165 KILOGRAMS

Characteristics of EGYPT SAT-1

Objectives• Assessing the suitability of the Egypt SAT-1

satellite mono imagery for the production &updating of 1:25000 Planimetric city maps.

• Testing the effect of the number and distributionof ground control points, with various 2-Dpolynomial rectification models on the accuracyof the resulting EGYPT SAT-1 rectified imageryand digital maps .

• Evaluation of the requirements, resources, andtime consuming for the production of 1:25000scale maps.

Experimental work

1- Data Acquisition:A Satellite image covering the study area wasacquired (panchromatic and multi-spectral) . Mediumscale maps were also taken for the same study areain vector GIS format .

Experimental Work Setup

Satellite Image


Raster InformationNumber of Bands

3

Cell Size (X,Y) 7,8

FormatERDAS Imagine

Pixel Depth 8 Bit

Spatial Reference: WGS 1984 UTM - ZONE 36N

Case Study Area:Zamalek & Dokki

Used Map for the same study area


2- Ground Control Points (GCP’s):A total number of 20 GCP’s were acquired from thedigital map for sharp and well defined features. Thecorresponding Egypt sat1 image points were alsomeasured .


Ground Control Points (GCP’s) marked on Map



The same Ground Control Points (GCP’s) marked on Satellite image

Radiometric & Geometric Correction Techniques

EGYPT SAT-1 satellite images have been Radiometrically

processed to enhance the image interpretation quality to

the maximum extent. Then they are Geometrically

processed to minimize the distortions.

3- Experimental Work:Based on the built in 2-D transformation model in theARCGIS software , several transformations (2-DRectification Models) were used with the objective oftesting the effect of number and distribution of GCP’sas well as the effect of different mathematical modelson the resulting rectified satellite images .


Experimental Work

According to recent research, the best rectification model is proved

to be the second order polynomial function

This model is given by 2 following equations:

Where:xi,yi: the image coordinates of point iXi, Yi: the map or (Ground Control Points) coordinates(a1, a2, b1, b2,…: Coefficients of Transformation Function


Effect of the Number of the GCP’s:• Each case was performed with a different

number of well distributed GCP’s distrustedacross the EGYPT SAT-1 image.

• GCP’s starts with 10 points as a minimumrequired number, 15 points and 20 points,respectively. We used 1st, 2nd, 3rd orderpolynomial for each case.

• The resulting total RMSE were calculated atboth the GCP’s and the 20 constant C.Ppoints.

Ground Check Points


4- Analysis of Results:

Assessment of results is based on the discrepancies

in RMS errors of the GCP’s and a C. P.


(RMSE)X RMS error in the X direction

(RMSE)Y RMS error in the Y direction

n The number of ground check points (CP)

i Check point number

XRi The X residual for CPi

YRi The Y residual for CPi

Accuracy Assessment

TRMSE Total RMS error(RMSE) x RMS error in the X direction(RMSE) Y RMS error in the Y directionn The number of ground check points (CP)i Check point number XRi The X residual for CPiYRi The Y residual for CPi

Accuracy Assessment

Comparison between the Correction Methods

Number of ground control points

Used polynomial Control points Check points

10 GCPs First order 13.8 20.2

Second order 8.1 13.8

Third order 8.2 18.9

15 GCPs First order 8.8 18.4Second order 7.8 13.0

Third order 7.7 15.020 GCPs First order 8.9 10.9

Second order 8.3 9.4

Third order 8.2 10.6

The following figure shows the effect of increasing number ofthe Control Point on the resulting RMS using variousmathematical models.

Comparison Between the Correction Methods BY Using GCP’s To Asses the accuracy

Third order

Second order

First order

Numbers of Points

8.2 7.7

8.1 7.8

13.8

8.28.3

8.8

0

2

4

6

8

10

12

14

16

10 15 20

8.2

First Order

SecondOrder

ThirdOrder

18.420.2

10.913.8 13

9.410.6

18.9

15

0

5

10

15

20

25

10 15 20Numbers of Points

The following figure shows the effect of increasing number of thecontrol point on the resulting RMS Check Points using variousmathematical models

Comparison Between the Correction MethodsBY Using Check Points To Asses the Accuracy

5- Final OutputThe Egypt sat1 image has been geo-referenced.Then, the final output map with a scale of 1:25000 isproduced and compared with the original map of thesame area to assess the final results.


Rectified EGYPT-SAT 1 Image

Original Map of Scale 1:25000

Production & Updating of Digital Maps

• The necessity of updating the maps is a must for anycountry to be able to maintain and develop itsresources and serve various sectors by using ARCGIS software.

• The rectified Egypt SAT-1 image is displayed on thecomputer screen and converted to vector format.

• Vectorization is done manually on the screen and theoutput is stored on different layers with appropriatefeatures representation (points, line, and areas).

Digitization of Egypt SAT-1Satellite Imagery

River Nile

Urban Area

Green Area

Center LineMain Road

Bridges

Special Places

Map Key

• Revision process includes finding errors, locatingmissing data, and checking features and layerpresentation

• Errors are then corrected and missed spatial data are added

• Data are verified visually on screen, where eachlayer is given different color during comparison

Quality Assurance

Production of 1:25000 Digital Map From Rectified Egypt-Sat1

River Nile

Urban area

Green area

Center lineMain road

Bridges

Map Key

Time Requirement

• The time requirement for 1:25000 mapsproduction from EGYPT SAT-1 image iscalculated during the production process of thevector maps for the study area.

• It is found that the time needed for fulfilling thework is about 90 hours for a populated areawith dimensions of 4.6 x 7 km (32 Squarekilometers).

Based on the results obtained in the research and theanalysis concerning assessing the suitability of EGYPTSAT-1 satellite imagery for updating and production of1:25000 Planimetric city maps, the following conclusionscan be stated:

Conclusions

1. Image rectification geometry showed good andacceptable results for EGYPTSAT-1 satellite imagery,satisfying map accuracy standard requirements.

Conclusions

2. Results showed that using second order polynomial

With 20 well distributed GCP’s is the best model

resulted with a total RMSE of 9.4 meters at the check

points. The results satisfies the requirements of the

1:25000 Planimetric map accuracy standard.

Conclusions

3. Egypt SAT-1 can be titled to capture 3-D images, or re-capture images for location within periods less than16 days so it can be product stereo image and so it beproduct topographic maps.

4. A total number of 20 GCP’s and 20 ground checkpoints were used in the experiments after beingacquired from the existing available maps. If thesepoints had been acquired using GPS, the cost wouldbe extremely high . Thus, using GCP’s from 1:25000maps to rectify EGYPT SAT-1 images and producing1:25000 Planimetric map is proved to be efficient &cheap.

Conclusions

6. Assessing accuracy based on residuals at GCP’sused for the rectification process could be completelymisleading. It is extremely unacceptable to baseaccuracy on residuals at Ground Control Pointsinvolved in the transformation & rectification process.It is standard practice to keep reasonable number ofwell disturbed points only as check points.

7. The time requirement for 1:25000 maps productionfrom EGYPT SAT-1 image is about 10 days for apopulated area with dimensions of 4.6 x 7 km (32Square kilometers). This time is estimated for low-experience operator and it might be decreased if thework is done by more experienced operator.

Some recommendations for future research anddevelopment work:1.More research is recommended in the area ofmathematical modeling of geometric and physicalconditions of EGYPT SAT-1 imagery as well as geometricmodel restitution based on rigorous treatment andcomparing the obtained results with those obtained fromthe commercially available software package.

Recommendations

Some recommendations for future research anddevelopment work:

2.Most of the studies dealing with the satellite imagery have

been so far in The 2-D planimetric space. With the exception

of SPOT 3-D case, very limited studies deal with high

resolution imagery in the 3-D spatial space. So, it is

recommended that more research must be performed in

this area of research.

Recommendations

Some recommendations for future research anddevelopment work:

3.We recommended to use EGYPT SAT-1 for production and

updating Planimetric city maps because its achieved the

best results and we can get this data for free.

Recommendations

THANK YOU!

[email protected]

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By Eng. Zahraa Mohamed Abd Al-Rahman - Home | AAG · 2010. 6. 29. · Page 1 By. Eng. Zahraa Mohamed Abd Al-Rahman. Assessment Of Egyptian Satellite (EGYPT SAT-1) Images For The Production

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