Global Administrative Unit Layers - Characteristics

Characteristics

The GAUL always maintains global geographic layers (in shapefile format) with a unified coding system at the levels of country, first administrative (e.g. regions), and second administrative (e.g. districts). In addition, when data is available, it provides layers on a country-by-country basis down to third, fourth and lower levels. The target beneficiary of the GAUL data is the UN community, universities, and other authorized international and national institutions/agencies. Data might not be officially validated by authoritative national sources and can not be distributed to the general public. A disclaimer should always accompany any use of the GAUL data.

Because the GAUL works at global level, controversial boundaries can not be ignored. The approach of the GAUL is to maintain disputed areas in such a way to preserve national integrity for all disputing countries.

The coastline of the GAUL is mostly compliant with the coast of the International Boundary map delivered by the UN Cartographic Section except for some countries (e.g. Viet Nam, India, Bangladesh, etc.) where it has been updated according to the satellite images (e.g. Landsat ETM). For future releases of the GAUL, the process of updating the coastline will go on, country by country, through a comparison with the satellite images.

The GAUL keeps track of administrative units that have been changed, added, or deleted in the past. Changes implemented in different years are recorded in the GAUL on different layers. For this reason the GAUL product is not a single layer but a group of layers, named the GAUL Set. The GAUL project does not implement changes dated before 1990.

GAUL codes are numeric and unique for all administrative units at any of the administrative hierarchical level. Any GAUL code is independent from the codes of its higher administrative levels. GAUL codes assigned to administrative units of a given country are not necessarily sequential numbers. The main benefit of the GAUL Coding System is that changing in the codes of an administrative unit might not imply a change of codes of the correspondent units at lower levels. This means that the effort to maintain the links between thematic data and associated administrative units is reduced to a minimum.