NASA's Airborne Topographic Mapper (ATM) trajectory and camera data for the Arctic Spring and Fall campaigns 2019

The Airborne Topographic Mapper (ATM) was a suite of lidar and camera systems developed and used by NASA for observing the Earth’s topography for several scientific applications, foremost of which was the measurement of changing Arctic and Antarctic ice sheets, glaciers and sea ice.This particular data set is used in a publication by Studinger et al., (submitted) that developed methods for estimating water depths of supraglacial lakes using stereophotogrammetry and Structure from Motion (SfM). This archive serves as a supplement for that publication. The publication focuses on two supraglacial lakes in Kalaallit Nunaat (Greenland) that are referred to as Lake Central West (CW) and Lake North West (NW). Trajectory/camera pose files The trajectory data used for image processing of Lake CW and Lake NW are assembled from three navigation data streams that all contain the Global Positioning System (GPS) time as the common reference for synchronization: 1) 10 Hz GITAR (GPS Inferred Trajectories for Aircraft and Rockets), 2) 200 Hz SBET (Smoothed Best Estimate of Trajectory), and 3) 2 Hz ATM’s auxiliary data (AUX). The general workflow is summarized in the diagram below. Details are described in Studinger et al., (submitted). A Jupyter notebook tutorial is available that shows how the DGPS antenna phase center positions can be converted into camera focal plane positions (convert DGPS antenna phase center to camera focal plane positions). The resulting trajectory or camera pose files are formatted as ASCII text files for input into the Ames Stereo Pipeline's (ASP) cam_gen module (cam_gen format). To map image pixels captured with the camera’s sensor to locations on the earth’s surface requires accurate knowledge of the camera system’s intrinsic optical parameters and extrinsic pose parameters. These parameters are used in transformation matrices that convert pixels from sensor coordinates to the camera coordinate system and eventually to a geodetic world coordinate system that locates pixel locations on the surface of the earth. This is accomplished by repeat passes over airport ramps flown at different altitudes and orientations with precisely surveyed Ground Control Points (GCPs). For this publication, calibration flights were conducted over two airfields: Texas Gulf Coast Regional Airport (KLBX) and NASA's Wallops Flight Facility (KWAL). We use built-in methods in Agisoft’s Metashape to determine a set of camera parameters consistent with the GCPs. The resulting camera files are in Tsai ASCII format for ASP (https://stereopipeline.readthedocs.io/en/latest/pinholemodels.html#tsai). Thule Air Base ramp pass CAMBOT image mosaic The publication also uses a natural-color image mosaic that was assembled from 16 CAMBOT (Continuous Airborne Mapping By Optical Translator) L1-B images acquired during a calibration pass over the ramp at Pituffik Space Base in northwest Greenland (formerly Thule Air Base). The sequences of images was acquired during an overpass on 9 September 2019. The geolocated image mosaic spans 1240 × 300 m and is in GeoTiff format with 15×15 m pixel resolution.