DEM: Digital Elevation model - any digital representation of any kind of elevation. Lidar can produce multiple DEMs in one pass DSM: Digitial Surface Model - the elevation map produced with primarily "first return" data. That is, a digital map of the first thing that the laser reaches. This usually includes objects like treetops, buildings, … Continue reading LiDAR in its Many Forms (DEM, DSM, DTM)
simply geology
Ground Penetrating Radar (GPR): An Image of the Near-Surface
Introduction Ground Penetrating Radar (GPR) is a powerful tool that can help us understand what lies beneath the surface. GPR works by sending high-frequency electromagnetic waves into the ground and measuring the reflections that bounce back. The frequency of these electromagnetic waves is in the same general range of frequencies used by cell phones. The … Continue reading Ground Penetrating Radar (GPR): An Image of the Near-Surface
Electrical Resistivity Tomography (ERT) Geophysics
What is ERT? Electrical Resistivity Tomography (ERT) is a geophysical technique that uses electrical currents to image the subsurface. Don't let the name intimidate you, let's break it down: Electrical: an electrical field is passed through the ground (and measured along the way) Resistivity: we are interested in knowing how different materials "resist" that current … Continue reading Electrical Resistivity Tomography (ERT) Geophysics
Riley J. Balikian 
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