Medium altitude airborne Geiger-mode mapping LIDAR system

Abstract

Over the past 15 years the Massachusetts Institute of Technology, Lincoln Laboratory (MIT/LL), Defense Advanced Research Projects Agency (DARPA) and private industry have been developing airborne LiDAR systems based on arrays of Geiger-mode Avalanche Photodiode (GmAPD) detectors capable of detecting a single photon. The extreme sensitivity of GmAPD detectors allows operation of LiDAR sensors at unprecedented altitudes and area collection rates in excess of 1,000 km 2 /hr. Up until now the primary emphasis of this technology has been limited to defense applications despite the significant benefits of applying this technology to non-military uses such as mapping, monitoring critical infrastructure and disaster relief. This paper briefly describes the operation of GmAPDs, design and operation of a Geiger-mode LiDAR, a comparison of Geiger-mode and traditional linear mode LiDARs, and a description of the first commercial Geiger-mode LiDAR system, the IntelliEarth™ Geospatial Solutions Geiger-mode LiDAR sensor.

Scanning, Multibeam, Single Photon Lidars for Rapid, Large Scale, High Resolution, Topographic and Bathymetric Mapping

“…The 1064 nm wavelength is sometimes touted as having several natural advantages including: (1) a factor of 3 lower solar background; (2) generally higher reflectances from natural surfaces such as soil/dry vegetation (25% vs. 15%) and green vegetation (65% vs. 10%); (3) slightly better atmospheric transmission; and (4) no frequency conversion losses in laser power which are typically on the order of 40% to 50% [2,15]. The 532 nm wavelength benefits from: (1) the availability of relatively mature and inexpensive, high efficiency array detectors and narrowband spectral filters; (2) detector dark count contributions to background noise are typically much lower in the visible spectrum; and (3) good transmission in water columns which allows solid land topography and bathymetry to be performed by a single instrument at a single wavelength as in Figure 13.…”

“…Later generations included the medium altitude Airborne Lidar Research Testbed (ALIRT), and the High Altitude Lidar Operations Experiment (HALOE) [13,14]. More recently, DARPA transferred GMAPD technology from MIT/LL to commercial entities, and Harris Corporation has introduced the first commercial GM system, The IntelliEarth™ Geospatial Solutions Geigermode Lidar Sensor [15].…”

“…In contrast, detected surfaces must be separated by 7.5 m or 240 m to be seen by an actively or passively quenched GMAPD respectively. Furthermore, each GMAPD in the array, as currently implemented in the Harris system, has only one measurement opportunity per imaging cycle although Harris claims that future asynchronous readout integrated circuits (ROICs) will enable multiple Time of Flight (TOF) measurements per APD per cycle [15]. While this would greatly enhance GM lidar performance, the detection rates within the small FOV of a given APD will still be limited by the longer quenching times.…”

“…Receiver Recovery Times: As just discussed, the SPL pixel recovery time of 1.6 nanoseconds (sometimes referred to as "deadtime" or "blanking loss" [15]) is limited not by the detector but by the timing receiver, whereas current GMAPD recovery times are typically in the range of 50 to 1600 nanoseconds depending on whether the Single Photon Avalanche Diodes (SPADs) making up the array are actively or passively quenched. This implies that SPLs can detect, within the same pixel, objects which are separated by only 0.24 m in range.…”

Characterizing 3D City Modeling Projects: Towards a Harmonized Interoperable System

“…Along with advancements in data acquisition (e.g., [13]), 3D reconstruction [3], and applications [2], 3D city models have become common geospatial data assets for cities. A comprehensive study by [14] already identified over one thousand 3D city models worldwide.…”