A slightly more general concept considers that a sampling frame is a tool that allows the identification and access to the elements of the population, even if an explicit list does not exist.
The French Teruti survey[6] chose in the 1960's an approach based on a systematic sample of clusters of points.
The Italian AGRIT survey has explored different approaches, comparing segment and point methods.
[7] The Joint Research Centre of the EC has conducted a large number of studies on area sampling frame methodology and area frame surveys for agricultural, forestry, environmental and human settlement studies.
[5][11] Validation of thematic maps produced by satellite image analysis has become one of the main application fields of area sampling frames[12]