Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P STYLE="margin:0 0 0 0;"><SPAN>LiDAR (Light Detection and Ranging) is a remote sensing technology, i.e. the technology is not in direct contact with what is being measured. From satellite, aeroplane or helicopter, a LiDAR system sends a light pulse to the ground. This pulse hits the ground and returns back to a sensor on the system. The time is recorded to measure how long it takes for this light to return.</SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN><SPAN>Knowing this time measurement scientists are able to create topography maps.</SPAN></SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN>LiDAR data are collected as points (X,Y,Z (x & y coordinates) and z (height)). The data is then converted into gridded (GeoTIFF) data to create a Digital Terrain Model and Digital Surface Model of the earth. This LiDAR data was collected between May 2010 and May 2011.</SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN /></P><P STYLE="margin:0 0 14 0;"><SPAN><SPAN>Digital Terrain Models (DTM) are bare earth models (no trees or buildings) of the Earth</SPAN></SPAN><SPAN><SPAN>’</SPAN></SPAN><SPAN><SPAN>s surface.</SPAN></SPAN></P><P STYLE="margin:0 0 14 0;"><SPAN><SPAN>Digital Surface Models (DSM) are earth models in its current state. For example, a DSM includes elevations from buildings, tree canopy, electrical power lines and other features.</SPAN></SPAN></P><P STYLE="margin:0 0 14 0;"><SPAN><SPAN>Hillshading is a method which gives a 3D appearance to the terrain. It shows the shape of hills and mountains using shading (levels of grey) on a map, by the use of graded shadows that would be cast by high ground if light was shining from a chosen direction.</SPAN></SPAN></P><P STYLE="margin:0 0 14 0;"><SPAN>This data shows the hillshade of the DTM.</SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN>This data was collected by Transport Infrastructure Ireland. All data formats are provided as GeoTIFF rasters. </SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN>Raster data is another name for gridded data. Raster data stores information in pixels (grid cells). Each raster grid makes up a matrix of cells (or pixels) organised into rows and columns. </SPAN><SPAN>TII</SPAN><SPAN> data has a grid cell size of 2 meter by 2 meter. This means that each cell (pixel) represents an area of 2 meter squared.</SPAN></P></DIV></DIV></DIV>
Service Item Id: 9e332de4a4264b779c9dbb5d1f0d1149
Copyright Text: Contains Irish Public Sector Data (Geological Survey Ireland & Transport Infrastructure Ireland) licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence.