Ráith Gráinne is named after the legendary princess Gráinne, who fled from Tara and from Fionn mac Cumhaill with her lover Diarmait úa Duibhne. It is a barrow (about 60m in diameter) consisting of a central mound surrounded by a ditch and external bank. In the centre are the remains of what may be another, small barrow. By combining geophysical and topographic data it has been possible to demonstrate that the slight prominence in the north-eastern side is actually the central burial mound of an earlier ring-barrow that was incorporated into Ráith Gráinne. It too encompasses a small barrow into its north-eastern quadrant suggesting that this was an accepted custom at the time.
To the northeast of Ráith Gráinne are the remains of up to four extremely low-profile sites which can be seen when the sun is low on the western horizon.
FLI-MAP 400; an aerial LiDAR survey system, was initially designed to survey infrastructural assets such as roads, railways and electricity supply networks. The sensor system mounted beneath the main helicopter fuselage consists of:
- FLI-MAP 400; an aerial LiDAR survey system, was initially designed to survey infrastructural assets such as roads, railways and electricity supply networks. The sensor system mounted beneath the main helicopter fuselage consists of:
- Three 150 kHz LiDAR sensors (7◦ forward, nadir and 7◦ aft);
- Scanning angle 60◦
- Accuracy (relative) Horizontal 5 cm, Vertical 3 cm
- Multiple returns 4
- Two RTK GPS receivers – provide accurate location in used in conjunction with RTK base stations;
- Inertial Navigation System (INS)- continuously track the position, orientation, and velocity of the helicopter;
- Digital imaging (11 megapixel) and digital video capture
Resulting data sets include first return (DSM) and last return point (DTM, bare earth) models
Post-processing was completed in Geomagic Studio 2012 software: individual scans are edited, aligned, before a final surface is generated using global registration, fusion, and a small objects filter algorithm.. For dissemination purposes a 3D version of the model was generated using simplification, retopologisation and texturing processes utilising Autodesk Mudbox and 3DS Max.