Remote Sensing for Decision-Makers Series N. 21
Pilot study in Bulgaria
This series, produced by the FAO Environment and Natural Resources Service, is intended for such decision-makers as heads and division directors of national and international organizations and administrations, as well as for project managers, planners and policy-makers of development institutions. Its aim is to present new possibilities of using remote sensing and geographic information system (GIS) techniques to aid planning for, and management of, renewable natural resources in agriculture, forestry and fisheries. This issue is specifically intended for decision-makers concerned with land cover mapping and land management.
Land cover maps constitute necessary tools for development planning and management of the territory. Furthermore, land cover maps depicting the current reality are essential in countries where, due to political changes, rapid dynamic phenomena have taken place, resulting in a complete restructuring of the agricultural and other sectors, as in the case of Bulgaria.
The scale of such maps should be large enough to provide detailed information; however, it should allow for regional assessment, statistics and subsequent planning. The 1:50 000 scale is the most suited for this exercise.
For optimal use, land cover maps should be in digital format, which allows easy updating, and associated with a GIS including other information such as soil units, erosion features and provincial/municipal boundaries. The resulting database is an essential tool for decision-making in land management.
Methodological approach
Remote sensing covers all techniques related to the analysis and use of data from environmental and earth resources satellites (such as Meteosat, NOAA-AVHRR, Landsat Thematic Mapper (TM), SPOT and ERS-SAR) and from aerial photographs.
The main function of remote sensing is to map and monitor the earth's resources. Compared with traditional survey techniques, satellite remote sensing is accurate, timely and cost-effective.
The term "geographic information system" is currently applied to computerized information storage, processing, analysing and retrieval systems that have hardware and software specifically designed to cope with geographically referenced spatial data and corresponding attribute information. Spatial data are commonly in the form of maps depicting topography, water availability, soil types, forests and grasslands, climate, geology, population, landownership, administrative boundaries, infrastructure (highways, railways, electricity or communications systems), etc. The capability of combining different maps in a single operation, known as "overlaying", is one of the most important GIS functions, together with modelling and site selection.
The operational availability of high-resolution satellite imagery, namely Landsat TM, SPOT, Soyouz, ERS-SAR, RADARSAT and others, opens up new possibilities for investigating and monitoring natural resources. Compared with information acquired by traditional methods, these data offer a number of advantages:
Vineyards and their appearance on Landsat TM (interpretation key)
Three large areas in different regions of Bulgaria were selected by the FAO Project TCP/BUL/8922 as representative of the agricultural production of the country. An operative methodology for the preparation from recent satellite data of land cover maps specially devised for agricultural applications, was tested and finalized. The most recent Landsat TM data, cloud-free and acquired over the test areas according to the local crop calendar, were used.
The land cover was classified according to the FAO Land Cover Classification System (LCCS), a comprehensive, standardized a priori classification system, created for mapping exercises and independent of the scale or mapping method. The classification uses a set of independent diagnostic criteria that allow correlation with existing classifications and legends. The system could therefore serve as an internationally agreed reference base for land cover. The methodology is applicable at any scale and is comprehensive in the sense that any land cover identified anywhere in the world can be readily accommodated.
As a result, 14 land cover maps at 1:50 000 scale were completed for a total area of 5600 km2. The map legend includes the 49 land cover classes which were identified for the three study areas. The methodological approach indicated in the figure is described in the FAO technical paper: Preparation of land cover database of Bulgaria through remote sensing and GIS, Environment and Natural Resources Working Paper No 6.
Soil types and erosion features, obtained from traditional sources, were linked to each land cover mapped unit as attributes into a GIS system. This resulted in a comprehensive database, which provides useful information for agriculture, forestry and urban development planning, for environment protection, and for many other applications. The data collected in the database allow for different kinds of spatial analyses, which are necessary in land management. As the database has been developed using ArcView, a common GIS software package, it will be easy to combine the database with other data sets, existing or in preparation, for a variety of different applications.
The flexibility and accuracy of satellite mapping were demonstrated by using a different kind of satellite data, which is more expensive but offers the possibility of mapping at a large scale (1:5 000). For an area of particular interest, IKONOS very high-resolution satellite data (1 m - pan sharp) were used successfully to:
State of vineyards for part of the Sandanski region, using IKONOS very high-resolution data acquired in August 2000
Example of a land cover map 1:50 000 scale
Costs and delivery times
Cost (US$/km2) |
Time (months) |
|
Acquisition of satellite data: |
||
Landsat |
2.9 |
1.5 |
Image processing and interpretation |
0.5 |
1. |
Ground survey |
0.5 |
1.5 |
GIS/Database preparation |
0.8 |
2 |
Map preparation |
0.2 |
0.5 |
Total |
4.9 |
6 |
Acquisition of satellite data: IKONOS |
24.0 |
1 |
Note: Landsat data were purchased for more than one agricultural season; IKONOS was used only for a small area. | ||
Advantages of land cover maps and associated database
Conclusion
The pilot study in Bulgaria demonstrated the accuracy, flexibility and cost-effectiveness of satellite remote sensing, coupled with LCCS methodology, for land cover mapping. The preparation of a database adds further value to the exercise. The above approach is now implemented in many countries worldwide. Project undertaken by the Bulgarian Aerospace Agency (BASA), assisted by FAO Environment and Natural Resources Service, in the framework of project TCP/BUL/8922 "Strengthening Capacity in Agricultural Development through Remote Sensing and GIS".
The Remote Sensing for Decision-Makers Series can be obtained from:
Environment and Natural Resources Service
Sustainable Development Department
Food and Agriculture Organization of the United Nations
Viale delle Terme di Caracalla, 00100 Rome, Italy
Tel.: (+39) 06 57055583; fax: (+39) 06 57053369
e-mail: [email protected]
A list of the issues available in this series is given on the Internet:
www.fao.org/sd/EIdirect/EIre0072.htm
The designations employed and the presentation of material in this brochure do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authority, or concerning the delimitation of its frontiers or boundaries.
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