The SO₂ data and notification service intents to monitor SO₂ emissions worldwide, with a focus on SO₂ emitted by volcanoes during eruptions. To provide detailed maps and to easier locate SO₂ emissions, a set of regions has been defined as indicated in the map above and in the menu map on the left. The pull-down menu on the left lists the centre coordinates of the regions.

The regions as plotted on the above map and on the menu map are 30 by 30 degrees. To facilitate following the motion of SO₂ from one region into another, the regions used in the analysis are 5 degrees wider on either side, so that the regions overlap one another: the maps show regions of 40 by 40 degrees.

Two special regions have been defined for the polar areas: the north (south) polar region covers all latitudes above (below) 60 degrees latitude, and thus overlap with the top (bottom) row of rectangular regions.

Since these default regions overlap, a given volcano can appear in more than one region. About half the volcanoes is located in two regions, some 45 in four regions.

Selecting a region from the menu on the left leads to a webpage which shows the volcanoes in that region that have erupted since the year 1800, as listed on the website of the Global Volcanism Programme (GVP). The page futher tells in which of the regions defined by the GVP the volconoes are found.

 
Note that the Submarine volcanoes (with summits below sealevel) are not considered very important here, as it is very unlikely that their SO₂ emissions can be detected.

The plots shown on these pages are made with the program IDL. As can be seen for example near the left and right axis of the world graph above, IDL has some problems correctly colouring the continent Antarctica. The boundaries of the countries drawn on the region maps are the political boundaries from 1993.