The methodology used is ultimately designed to estimate the coverage of year-round safe improved water points of a certain territory. One drawback of water point maps is that they are only as accurate as the underlying data collected, so that there is a need to define reliable but simple indicators as the basis of the monitoring framework. Clearly, the core sector indicator is water supply coverage, and in rural areas, access to water is normally defined by establishing a ratio of the maximum distance and number of people served by each water point. Three different possibilities exist when defining access:   In order to accurately assess the number of people served using distance as a criterion (no. 2) the spatial distribution of population is required, and this is problematic in the majority of cases. Despite the progress made with satellite free access images, many rural areas are still not covered with sufficient precision. On the other hand, due to periodic sociological census undertaken in nearly all countries, population distribution in administrative structures is usually quite well documented. Thus, first above-mentioned criterion is the most commonly used. With this information, the percentage of access to water in an area is estimated, and first indicator of access can be defined as Improved Community Water Point Density, which is equal to the number of Improved Community Water Points per 1,000 inhabitants. A certain area would have access if its density of water points per 1,000 inhabitants is above the national threshold, and percentage of people not served in an area would be proportional to the lack of water points available compared to that threshold. However, to further improve Improved Community Water Point indicators is simple since information on functionality for each water point is also collected during the survey. Non-functionality is an important obstacle to access to rural water supply, and in sub-Saharan Africa averages around 35%. Consequently, Functional Community Water Point Density can be used as more accurate access indicator. If water quality and seasonality issues are taken into consideration, other 'access' indicators can be defined, as shown in following Table. In addition to safe water supplies, basic sanitation and hygiene also have significant impact on household health. Provision and use of sanitation isolates contaminated faeces from the environment, and therefore the consistent use of the facility, not its mere existence, is likely to lead to health and environmental improvements. However and in much the same way as with water supply, care is needed to define an acceptable form of excreta disposal. A wide range of technologies is used, particularly for settings where low-cost solutions are required, and relevant research conducted elsewhere concluded that all types of facility can be operated hygienically.