This part of ISO 5667 provides guidance on the design of sampling programmes and the choice of instrumentation and techniques for the sampling of the quality of wet deposition. It does not cover measurement of the quantity of rain. This part of ISO 5667 does not cover dry deposition or other types of wet deposition such as mist, fog and cloudwaters, since their measurements are still at research stages. However, their importance should be noted, since research results suggest that, in some cases their loading can be comparable with, or exceed, wet precipitation. Therefore, wet precipitation data alone are rarely sufficient for calculating total loadings. The main objectives are outlined in 1.1 and 1.2. 1.1 Control of local emissions Determination of loadings (i.e. mass/area/time) by wet deposition to a particular ecosystem requires information on emissions, transformation and transport of pollutants from point or area sources. This information, together with assessment of the relative loadings from distant and local sources, when combined with studies on the effects of the pollutant on the ecosystem, can be used to arrive at acceptable emission control regulations. 1.2 Long range transport of airborne pollutants Determination of temporal and spatial variations in the constituents of precipitation on a regional scale requires that the stations which are selected are representative, and are remote from local point or area sources.