Physiographic Units Level 3 1:250,000 Ireland (ROI) ITM

The term Physiography can be described as a blending of “physical" and "geography". Physiographic Units show Ireland’s physical landscape divided into categories such as ‘Bedrock plain’ and ‘Flat to undulating sediments’. Areas are grouped based on bedrock geology (solid rock at or below the land surface), Quaternary (largely Ice Age) sediments and geomorphology (landforms). Digital Elevation Models (DEMs) and Aerial photography are also used. Three maps were made, each giving a different level of detail. The Level 1 map has 7 categories. These show bedrock landscapes at different heights above sea level such as mountains (more than 300 m), hills (100 to 300 m) and plains (less than 100 m). Sediment (sand, gravel and soil) landscapes are grouped by slopes, such as rolling (gentle hills), hummocky (small lumpy hills) and flat. The Level 2 map has 16 categories. These show bedrock landscapes with different texture (how rough or smooth it is) or rugosity (how wrinkly it is), depending on the bedrock type (e.g. granite bedrock evolves into rounded mountains or hills). Sediment (sand, gravel and soil) landscapes are grouped by the type of geological process shaping them eg (Drumlin and ribbed moraine topography). The Level 3 map has 29 categories. This is the most complex and further categorises in a similar way to level 2. Areas were mapped at scales ranging from 1:30,000 to 1:100,000 (1cm on the map relates to 1km). The map is designed to be used at 1:250,000 scale (1cm on the map relates to 2.5km). It is a vector dataset. Vector data portray the world using points, lines, and polygons (areas). This data is shown as polygons. Each polygon has a unique identifier and its landscape category.