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1.1. Objectives of the project
1.2. Expected results
1.3. Test areas description
1.4. Data/software used

The transition in the past years in the Republic of Bulgaria from a centralized planned economy to a market-oriented economy negatively affected the land tenure and agricultural production. As a consequence of land redistribution, thousands new privately owned farms have been created and the majority of former state and cooperative farms have disappeared. During the transitional period for a large part of the country the central and regional authorities have had no updated information concerning new land uses, new plot sizes or information on how large are the areas not cultivated at present. These areas are the most sensible for degradation.

Being aware of the possibilities of Remote Sensing (RS) and Geographical Information Systems (GIS) technologies as tools for land cover and land use inventory and monitoring, the Bulgarian Ministry of Agriculture and Forestry requested FAO technical assistance for strengthening the Bulgarian Aerospace Agency (BASA) capacity in this field through a joint study in selected parts of the country.

The FAO Technical Cooperation Project TCP/BUL/8922 “Strengthening Capacity in Agricultural Development through Remote Sensing and GIS” was elaborated jointly by FAO and Bulgarian experts and initiated its activities in June 1999.

1.1. Objectives of the project

The Project has two kinds of objectives: the immediate and the medium term objectives.

The immediate objectives of the project were:

The achievement of these urgent immediate objectives created the basis for fulfilling the medium term objectives that were:

1.2. Expected results

The Project had specific outputs expected to be produced during its implementation.

They can be summarized as follow:

Methodology developed for the three test areas and field-tested will enable

BASA to expand the study to the other parts of the country.

Two kinds of land cover maps are expected:

The information on land cover extracted from satellite data interpretation was merged into a GIS with the relevant information on soils and land degradation, thus generating a unique database for agricultural planning.

1.3. Test areas description

Montana test area
Sofia test area
Plovdiv test area
Sandanski test area

Three distinct test areas, representative of the agricultural production of the country, were studied and mapped at 1:50 000 scale (Figure 1), namely:

1. Danube Plain, district of Montana
2. Sofia Intermountain Plain, Sofia district
3. Plovdiv area
Further, the Sandanski test area, in the lower reaches of the Strouma Valley, was mapped at 1:5 000 scale.

The test areas were visited in June 1999 for a first rapid assessment of their characteristics and selection of the most appropriate satellite data.

Montana test area

Fig. 1. Location map

A - Montana area
B - Sofia Intermontane Plain
C - Plovdiv area
D - Sandanski area
The Montana test area is situated in the western part of the Danube Plain. It is approximately bounded by the Danube River on the north and by the Stara Planina Mountains on the south and west (highest peak - Mt. Botev, 2372 m above sea level) and eastwards, by the Skut River.

The majority of the landforms of the test area have a predominantly plain-hilly character with an average altitude of 30 m. The topographic surface has a clearly expressed north-northeast slope, which determines the major direction of the drainage. The most important rivers here are Lom, Tzibritza, Ogosta and Skut, which are tributaries of the Danube River, and belong to the Black Sea watershed basin. They have well-formed asymmetric valleys with steep western, and gentle eastern slopes. Together they dissect a wide plateau. On the north, along the Danube River several alluvial terraces occur in the floodplain.

The average annual precipitation is about 560-580 mm, which is significantly lower than the values for the rest of the country.

The potential natural vegetation includes mainly xerophytes and forest-steppe species with oak, field elm, and some grass representatives. Along the Danube and its tributaries alluvial lowlands, where the level of the water table is relatively high, hydrophytous vegetation is present with forests of white willow and poplar.

The low altitude, relatively dry continental climate and xerophytous vegetation are the factors determining the processes of origin and distribution of the major soil types, which are Chernozems and Kastanozems. From the north to the south, in connection with increase of the precipitation and the influence of the forest vegetation, Luvic Chernozems and Luvisols occur. In the area of lowlands of the Danube River and near the major tributaries, alluvial and organic soils occur.

Main crops within this test area are winter wheat, winter barley, maize and sunflower. River valleys are covered with meadows, vegetables and spring crops.

Sizes of fields are diversified and they range from small family fields of vegetables to several dozen of hectares, which are covered with wheat and maize. Fields, which at present are not cultivated, occupy some part of former agricultural lands.

Sofia test area

Sofia test area belongs to the chain of the intermountain plains situated between the southern slopes of the Stara Planina Mountains and the northern slopes of the Sredna Gora Mountains. The Sofia Plain (540 m above the sea level) is separated in its western side from the Burelska Plain by the Aldomirovski Hills. Eastward the Negushevski Hills separate it from the Saranska Plain. The highest peaks of the surrounding mountains are: Mt. Murgash (1687 m) on the north and Mt. Chernivrah (2290 m) on the south.

The major river of the plain is the Iskar River, which originates in the Rila Mountains and flows into the Danube River. The Iskar River and its tributaries form the drainage system of the plain. The southern parts of the Vitosha Mountains (which are included in the test area) are drained by the Strouma River.

The Sofia Plain is, geologically, a graben. Its bottom is filled up with Pliocene sediments (clays, sands, pebbles and marls) of considerable thickness, covered with alluvial sediments.

The average annual precipitation is 600 mm with the maximum in May-June.

The natural potential vegetation of the Sofia plain consists of mezophytous forests with a predominance of oak and field elm. Nowadays large areas of these formations are replaced by agricultural lands and by mezophytous grass vegetation. The southern slopes and dryer places are occupied by xerophytous formations with oak and the higher slopes by durmast forests.

The major soil types of Sofia Intermountain Plain are Vertisols, Chernozems, Cambisols and Fluvisols. In the mountains Lithosols, Cambisols and Luvisols are dominant.

Arable lands are cropped mainly by vegetables, sunflower and winter wheat. Small areas not cultivated at present occur. Sizes of fields are diversified, the majority of which are small and medium in size.

Several industrial plants located within the vicinity of Sofia occupy large areas and are hazardous for the environment. These factories also have a negative influence on soils and plants.

Plovdiv test area

Plovdiv test area is situated in the eastern part of the Gornotrakiiska lowland. This lowland is located in-between the Rodopi Mountains (highest peak - Mt. G. Perelik, 2191 m above sea level) to the south, and the Sredna Gora Mountains (highest peak - Mt. Bogdan, 1604 m above sea level) to the north. Eastward this area is widely open towards the Black Sea. The Rodopi and Sredna Gora Mountains close the Gornortakiiska lowland to the west.

The average altitude of the lowland is about 160 m. The slope is from the northwest to the southeast direction. It is predominantly a gentle slope, which determines the meandering of the major river, the Maritza River. This river is associated with well expressed, low and wide, in some places swampy, flood plain terraces. Maritza River and its tributaries form the drainage system in the lowland. They are part of the Aegean watershed basin.

The average values for the annual precipitation vary between 450 and 600 mm.

The main types of soils present here are Vertisols, Planosols and Luvisols. Eutric, Dystric and Calcaric Fluvisols are connected with Quaternary alluvial sediments. The soils of the lowland are generally moist and rich in humus.

Because of the predominantly agricultural character of the lowland, only very small areas with natural vegetation have been preserved. Some of them are situated along the rivers where, due to the high level of the water table, natural formations of hydrophytous grass and forest vegetation like reed, willow, poplar and alder are developed. In Chromic Cambisols, situated on the hilly surfaces of the lowland, remains of the relatively xerophytous forest vegetation (species of hornbeam, oak and field elm) can be found.

Under the centrally planned economy Gornotrakiiska lowland was an area of intensive irrigation with a large production of rice. Nowadays just a few irrigation canals of the former dense irrigation system are still operating.

The Plovdiv test area is almost entirely covered by arable lands, meadows and pastures. The main crops are: winter wheat, sunflower and vegetables. A few hundred hectares of rice fields still exist.

After the redistribution of the land during the last years, the majority of the fields are of small to medium size.

Sandanski test area

The area of Sandanski is situated in the southern part of the Strouma Valley, where the Strouma River comes out from the Kresna pass and the riverbed becomes wider. The area borders on Pirin Mountain to the north and east, Malashevska Mountain to the west and Belasitza Mountain to the south, where the town of Petrich is also situated. The exact test area lies northwest from the town of Sandanski (including part of the city) and covers an area of 6.25 sq km. The town is situated at an altitude of 224 m above sea level in the southwestern foothills of the Pirin Mountains in the valley of the Sandanski Bistritsa River, which is a tributary of the Strouma River. The relief is hilly.

The area of Sandanski has the lowest annual rainfall in Bulgaria (400 mm) and almost no foggy days. The air is remarkably clean and free of pollution.

The major soil types are Fluvisols and Cambisols.

Mainly vegetables, maize and tobacco cover arable lands. The warm climate permits production of three crop yields in one year. Medium size fields of cabbage are present. The soil and the steep relief are very suitable for vineyards, which are the most common permanent crop in the area. Two types of cultivation of vineyards are used (large size fields with 2-2.5 m distance of rows, small private fields with 1-1.5 m distance of rows). Some orchards also occur.

1.4. Data/software used

Three kinds of data were used for this project:

1. satellite data,
2. topographic and thematic maps,
3. descriptive data.
The necessary satellite data was selected and acquired after visits to the three test areas. The main criteria for selection of satellite data were:

After examination of the list showing satellite images available for Bulgaria, five Landsat Thematic Mapper and Enhanced Thematic Mapper images were ordered. Landsat Thematic Mapper images were preferred due to the availability of three infrared spectral bands, which are important for interpretation of vegetation. Spatial resolution of multispectral images (30 × 30 m) is very suitable for land cover mapping at the scale 1:50 000. Panchromatic images acquired by the new Landsat 7 Enhanced Thematic Mapper have a spatial resolution of 15 × 15 m. It is possible to increase spatial resolution of colour composites by merging multispectral (30 × 30 m) and panchromatic (15 × 15 m) images. These new data (1999) were used for the Plovdiv area.

For the Plovdiv test zone a radar image ERS-2-SAR.GEC was also acquired. This image was used to test its usefulness for discrimination of vegetation cover and landforms.

For the Sandanski area IKONOS very high resolution (1 × 1 m) data were acquired, permitting mapping at 1:5 000 scale.

A list of the satellite data is given in Table 1. All data are of good quality and in digital format.

Table 1: Satellite data used in the study

Test Area

Satellite System


Acquisition Date

Spatial Resolution

Montana area

Landsat-5 TM



30 m

Landsat-5 TM



Sofia Intermountain Plain

Landsat-5 TM



30 m

Plovdiv area

Landsat-5 TM

183/30-31 floating


30 m

Landsat-7 ETM

183/30-31 floating


15-30 m

Landsat-5 TM

183/30-31 floating


30 m





12.5 m

Sandanski area




1 m pan-sharp

As a reference and auxiliary materials, 14 sheets of topographic maps at the scales 1:50 000, 1:25 000 and one at 1:5 000, covering the mentioned test areas have been purchased from the Topographic Service. These maps have analogue (paper) format. Scanning of these maps was done by BASA. Civil edition of topographic maps has no geographical coordinates, only a kilometric grid is marked. This gave some problems during the different stages of satellite image geometric correction and elaboration of land cover maps.

Some Thematic maps such as: soil maps, geological maps, geomorphologic maps and maps of vegetation, were available in the archive of BASA and were consulted when needed.

Table 2: Topographic and thematic maps used in the study

Montana area

Sofia area

Plovdiv area

Sandanski area

Topomaps - scale
1:50 000















Topomaps - scale
1:25 000


Large scale
topomap - scale
1:5 000


State Soil digital maps of Bulgaria - scale 1:10 000 and scale 1:50 000

Geological map of Bulgaria - scale 1:500 000

Vegetation map of Bulgaria - scale 1:600 000

Geomorphological map of Bulgaria - scale 1:600 000

Hydrological map of Bulgaria - scale 1:500 000

Descriptive data were also used, such as climatic data giving information about precipitation, temperatures and differentiation of vegetative period.

Analysis and interpretation of the satellite data were carried out in the BASA facilities, using ERDAS 8.3.1 digital image processing software and ArcView 3.2 software for the GIS tasks.

GPS technologies were used for field checking and verification of the results.

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