2007 Urban Remote Sensing Joint Event

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Change Detection Analysis for Urban Development in Bucharest-Romania, using High Resolution

Satellite Imagery

Ionut Sandric, Bogdan Mihai, Ionut Savulescu, Bogdan Suditu, Zenaida Chitu

University of Bucharest, Faculty of Geography Bucharest, Romania

sandric@geo.unibuc.ro

Abstract— The evolution of Bucharest during the last 40 years

showed spectacular changes, as a result of the socialist urban

policy. The paper investigates the leading transformation of the

urban structures, comparing declassified intelligence imagery

(2002) CORONA KH 7 (0.60-1.20m spatial resolution) from 1966

and IKONOS pansharpened image from 2002 (1m spatial

resolution). We tried to use an image segmentation algorithm to

automatically classify the changes in urban structures. Poor

results were obtained as a result of the image geometry, altered

radiometry and blur “band stripes” induced by the scanning

process of the original film. Imagery interpretation and field

observations were applied on three case studies: Palace of

Parliament, the so called “People’s House”, Titan district, Piata

Sudului-Berceni area, superposing on the most transformed

areas. A large area of old houses disappeared especially on the

place of the huge Palace of Parliament where half of the

historical centre was replaced by block of flats, some old

churches disappeared or moved etc. Big block of flats quarters

appeared on fallow ground to the edge of Bucharest, some of

them, like Titan district, had replaced the old small houses

districts.

I. INTRODUCTION

Urban development of Bucharest during socialist

regime has had similar evolution, but still different features.

The demographic “boom” of the town (passing 58 thousand in

1831, 340 thousand in 1912, 1 million inhabitants in 1948 and

2 million inhabitants in 1992) generated the increase of the

built-up area together with the socialist industrialization. In

2002 the population was of about 1.996 million but the trend

is now a positive one. A particular feature was the evolution of

urban structures after the big Earthquake in March 1977. Most

of old building area, especially in the centre was destroyed or partly damaged. After 1980, the dictatorship rule put its

imprint also on the city development. The socialist urban

policy “made possible” the rase from the ground of old

specific small houses and the building of new big block of

flats, in the centre and around the downtown urban structures

These particular features of the urban development of

the Capital of Romania can be modeled using high resolution

satellite imagery. For a long time, historical air photos for

Bucharest have had a secret character (and some of them still

have) and a sparse coverage in space and time

Since 1995 and 2002 the declassification of

CORONA intelligence imagery have covered a gap in the

spatial knowledge of natural and social phenomena, making

possible a lot of comparative approaches [2,3,4,11,12]

Different similar contributions in the international literature, and especially those related to the urban structures

development issues, tried to use the potential of intelligence

imagery [9,13,14]. The temporal resolution of this data and its

spatial resolution, made possible an interpretation of the urban

features since 1961. For Eastern European countries and

especially for the former Soviet Union states this data are

available since the declassification begun in February 1995

and continued in 2002 [6,13,14,19]. The CORONA imagery

covers the period of the beginning of the socialist urban

transformations, when new urban districts with block of flats

appeared to the edge of the former structures (mediaeval and

modern). Although the use of CORONA imagery is a real advantage for land recognition and urban development, there

are not so much papers on urban issues, but a lot of works

from archeology, and especially in desert sites [4, 6, 7, 16].

Some papers refer to desert vegetation [1], flood hazards [7],

environment [2]

International contributions integrating change

detection for urban structures are quite numerous. They

integrates rather medium resolution data like LANDSAT or

SPOT 3, 4 imagery [10,14, 17], but during the last years the

use of high resolution satellite imagery has increased,

especially with the launch of IKONOS, QuickBird, OrbView and SPOT 5, focused on natural hazard short impact [3,7] and

on brand new urban structures [5]

II. MATERIALS AND METHODS

A. Image features

The potential of CORONA imagery is increasing in

the framework of change detection studies. Historical imagery can be easily compared with high resolution imagery like

IKONOS and Quick Bird, OrbView, SPOT 5, because of their

2007 Urban Remote Sensing Joint Event

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almost equal spatial resolution. This makes possible visual

interpretation [3, 4, 5, 13, 14] with ground control and validation, but according to our information without automatic

object-oriented classification. This is caused by the oblique

view of most of CORONA imagery and the low spectral

resolution. Other important deficiency of CORONA imagery

for object-oriented classification is the scanning errors which

often alternately appear as “blur stripes” (Fig. 1).

Figure 1. “Blur stripes” effect on CORONA image, affecting the quality of

data. The white line shows the limits between “blur stripes” areas and the original quality of the image

The CORONA image was acquired on July, 12, 1966

by the KH 7 high resolution camera (Lanyard sensor), spatial resolution 0.6-1.2 m. This is a summer scene, superposed on

the peak of the vegetation season. Interpretations are

influenced by the big density of tree canopies, within the parks

and the gardens. The main problem appears along the streets,

where trees make a sinuous limit between the road and the

pedestrian area. The image is almost oblique, and this feature

influences the interpretation and the data extraction and in

sometimes in the case of the highest buildings, like for

example the block of flats (the number of floors can be easily

estimated). A big advantage is the lack of cloud cover, not a

frequent feature for CORONA images.

The IKONOS image is a pansharpened mosaic dated January, 22, 2002 covering a rectangular area of about 12x17

km, superposed on 75% of the Bucharest metropolitan area.

This is obtained from two consecutive scenes of about 11x11

km, superposed in a transversal direction and taken from the

same orbit. This is a real advantage because there is a real

continuity in terms of radiometry and they can be

geometrically corrected and co-registered. The area coverage

contains the most transformed built-up areas, the city centre as

well as some of the largest areas with block of flats (built

during socialist period) and the industrial districts. Cloud

coverage is of about 20%, but there are only clouds of low

altitude, thin and transparent. Although the image acquisition time is in January, there is no snow, because of a warm

weather in that period, more likely caused by global warming.

The lack of leafy surfaces of deciduous tree, canopies, helped

very much the process of image analysis, interpretation and

data extraction, and in the same had a drawback on image

analyses for land-use and land-cover change detection. The

CORONA image is a summer image and the IKONOS image

is a winter image. This made, despite the temporal resolution,

the interpretation of green areas and their evolution to be made

under uncertainty

B. Image processing

The images were georeferenced in stereographic

“Stereo 70” projection (the national grid of Romania), datum

Dealul Piscului 1970. Twenty ground control points,

homogenously spatially distributed, were acquired on an image

by image basis. The reference images were the topographical

maps 1:10000 scale. A rms error of less than 2.5m was obtained and a polynomial transformation with nearest

neighbor resample method [2] was applied. No

orthocorrection was applied. The differences of altitude within

the study area are not so important (less than 15-10 m)

An image segmentation algorithm was used to

automatically classify the changes in urban structures. Our

option was the supervised texture segmentation algorithm

developed by Arco Luccier [12] and implemented in Parbat

software [18]. Poor results were obtained as a result of the

image geometry, altered radiometry and “blur stripes” induced

by the scanning process of the original film

III. RESULTS

A. Socialist urban policy

Since 1970, the housing policy in Romania was

closely linked to the accelerated “systematization,

modernization and civilization” programme.

The Territorial and settlement planning programme had as final goal: “the development with two coordinates of

economic efficiency with social criteria” and the graduated

disappearance of the town-village inequalities”, and also

between center and periphery. In 1972, the Xth Congress of

the communist party considered this as strategically important

for Romania. The Law 58/1974, regarding the territorial and

settlement systematization brought new principles for the land

use, for the building density having as a final goal the

reduction of the settlement built-up area perimeter (potential

development area).

The same period it was allowed to build in the outer

residential areas. The Decree 545/1958 limited the residential built-up area and restricted the spatial development beyond the

legal limit established by the master plan map. In 1950 some

villages were included in the Bucharest administrative

territory (Fig. 2). New buildings with flats appeared inside the

2007 Urban Remote Sensing Joint Event

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Figure 2. Administrative and residential areas typology in Bucharest

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potential built-up area, dividing the former parcels. The house

density increased. Two-floor individual buildings were allowed in especially designated areas and within the big

block of flats districts. They recommended 6-10 floors block

of flats. The next decade, housing policy was focused almost

exclusively on blocks of flats. The reconstruction plan was

based on the 1956 urban master plan. This period blocks of

flats appeared in Ferentari, Vatra Luminoasa and Bucurestii

Noi (‘’The New Bucharest’’) districts, but the number of flats

within was limited [15].

Since 1959 the main policy was to built much more,

faster and cheaper. For efficiency reasons, the two floored

building model was abandoned The “efficiency” in urban land use policy was

spatially translated through the restriction for family houses

building. In the Article number 30 of the above mentioned

law, it was written that “the land within the built-up area

perimeter of towns and villages can be obtained only through

legal heritage, and their sale on legal base documents is

forbidden”. According to this document, the access of citizens

from other areas interested to buy the eventually fallow

grounds became impossible. The restriction to buy grounds or

houses in the peripherical areas was taken simultaneous with

the process of the future designated demolition areas [15].

Since 1975, the formula of the big blocks of flats ensembles was considered to be the most adequate to the

Romanian realities. This became a key role factor for the

economic and social reconstruction of towns. During the 60s

the blocks of flats building was done only on fallow grounds,

in the intermediary and in the outer areas of Bucharest. In the

next decades, these replaced, after demolitions, less clean

urban structures or houses without an architectural value [15].

Imagery interpretation and field observations were

applied on three case studies: Palace of Parliament, the so

called “People’s House”, Titan district, Piata Sudului-Berceni

area, superposing on the most transformed areas. These areas are considered to be relevant for the changes that happened

between 1966 and 2002 and include almost all the urban

structures featuring the city

1) Palace of Parliament (People’s House)

The Bucharest downtown represents the first urban

settlement on this place, attested in 1459 A.D., by the Prince

Vlad Tepes (‘’the empailer’’). Around the Princerly Court, the

urban districts flourished during in different periods, between

the 18th and the 19th century because of handicrafts and

commerce. The houses developed around churches and

orthodox monasteries which represented the spiritual centre of the district (the parish’ communities).Today’s Bucharest has

more than 300 churches, mainly from the medieval and

modern periods. Street network developed in a natural way, in

a complicated system but converging towards the churches. In

March 1977, after a big earthquake (7.4 degrees on Richter

scale) a lot of old houses and churches were seriously affected

and some of them were demolished because of practical

reasons. This was a turning point in the history of Bucharest. Most building, some of them of historical value (merchant’s

houses, landlord’s houses inns etc.) were destroyed or were

repaired quite late. The main loss was the demolition of more

churches in the central area; some of them damaged some of

them not. The area around the People’s House (The Palace of

Parliament) was totally rased from the ground. Streets with

houses, gardens, old trees and churches disappeared. An

interesting situation featured the Mihai Voda church (former

monastery dated since 1589-1591, founded by the Prince

Mihai Viteazul). Because of its historical and cultural value,

this building moved from its primary place on the edge of a Dambovita River upper terrace to a new position to the terrace

top (on a distance of 600 m) (Fig.3 and 4).

The old city center of Bucharest was almost

completely demolished and replaced by “The new Civic

Centre” area. This was done in two stages:

• 1984-1987: total demolition of the areas of interest,

street network designing, urban modeling and building. The

old city center urban structure of Bucharest can be seen on

CORONA image before the first stage of demolition (Fig. 3).

• 1987-1989: a selective demolition of the areas

designed for the building of different constructions and

residential buildings; during this period, the costs for demolition increased in terms of money and time and the big

project had decreased (Casa Poporului or the ‘’People’s

house’’, the Unirii Avenue etc.). The result appeared alter

1989 when “islands” from the old Bucharest preserved behind

the communist buildings of the Civic Centre [15].

2) Titan area

The biggest part with block of flats was built during

the 60s and the 70s, among the big residential ensembles (so

called “the dormitory districts”). These appeared in the

neighborhood of the big industrial districts, mostly on fallow grounds, to the outskirts of the city (Balta Alba, Drumul

Taberei, Pajura etc.). Other block of flats districts were built

alter the demolition of former villages around the city, like

Dristor, Dudesti, and partly Berceni, Titan, Crangasi etc. The

primary street network of the demolished structures was

conserved in the design process of the new districts. For

example in the area of Ramnicu Sarat Boulevard southwards

from the Dristor residential district, the block of flats were

built to the end of the 60s and superposes on the main street of

the former Cioplea village (Fig. 5 and 6). The big ensembles

of Balta Alba and Titan had been developed, during 60s and

70s, around the old settlements nuclei, the first one from mediaeval times and the second one from modern ages. They

“covered” afterwards these old structures of settlements.

Remnant features from the old structures cannot be found in

today’s shape of these districts [15]

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Figure 3. CORONA image, 1966. The present day building configuration of Palace of Parliament overlayed on former urban structures

Figure 4. IKONOS image, 2002. Main old street network overlayed on actual urban structures

2007 Urban Remote Sensing Joint Event

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Figure 5. CORONA image. Area of Ramnicu Sarat Boulevard

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Figure 6. IKONOS image. Area of Ramnicu Sarat Boulevard

IV. DISCUSSION

The best results were obtained using visual interpretation and not object oriented analysis. The oblique

view angle of the CORONA imagery makes the visual

interpretation difficult and tedious. Special attention must be

given to shadow areas and tree canopies, which on summer

images poses real problems. The “blur stripes” induced by

scanning process require special attention. The rms error of

2.5 meters for each image hasn’t raised any problems. The

recent high resolution satellite imagery, IKONOS, QuickBird,

OrbView, SPOT 5, are more suited to object-oriented analysis

but, have the disadvantage of temporal resolution. Similar

results were obtained in other studies [3, 5, 13, 14] from Eastern Europe and Asia, and the main method was based on

visual interpretation and analysis. The results can easily

integrated in a GIS system. They can be used for further urban

analysis and spatial development, as an important part in

calculating the prior probability for “weight of evidence”

models applied in future urban planning.

V. CONCLUSIONS

CORONA satellite imagery offers a big advantage,

acting like a time windows to past. The declassification of

intelligence satellite imagery made possible to scientist from

various research fields to better understands the spatial and temporal evolution of different phenomena

The so called “Little Paris” during the interwar

period is a very interesting town. The transformation started in

December 1989 stopped the socialist urban development. The

new evolution, marked at the beginning by uncertainty, started

from a complex urban structure typology, which can explain a

long urban history (impossible to be rased from the ground by

any regime)

This study is just one aspect from various issues

regarding the evolution of Bucharest during the last 40 years

and the future development as a European Capital. Further research is required

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