The "OpenGPS" receiver is a GFZ-developed research instrument focusing on the scientific exploitation of reflected GPS signals. Its hardware and software concept is based on the "OpenSourceGPS" project initiated by C. Kelley in 2001 .
The "OpenGPS" hardware utilizes the single frequency GPS module "Superstar II" (manufatured by CMC Electronics, now NovAtel) with GP2015/GP2021 chip set (Zarlink, formerly Mitel Semiconductor) whose processing and memory units were removed. A custom-designed interface logic allows the host CPU to directly access the registers of the 12 channel hardware correlator GP2021 via the PCI interface. The receiver board runs in a standard PC equipped with a real time operating system RTAI-Linux (www.rtai.org).
The "OpenGPS" receiver software is based on the GPL-licensed "OpenSourceGPS" software and has been extended according to specific requirements for GPS reflectometry. It features the following characteristics:
During the last decade the "OpenGPS" receiver has been used successfully in a number of measurement campaigns [2, 3].
 Kelley, C.: Internet-based open source software for learning about GPS, GPS Solutions, 6, 201-205, doi:10.1007/s10291-002-0026-2, 2002.
 A. Helm: Ground-based GPS altimetry with the L1 OpenGPS receiver using carrier phase-delay observations of the reflected GPS signals, Scientific technical report STR08/10, Deutsches GeoForschungsZentrum, 2008.
 A. Helm et al., Detection of coherent reflections with GPS bipath interferometry, unpublished, http://arxiv.org/abs/physics/0407091
 G. Beyerle and F. Zus (2017): Open-loop GPS signal tracking at low elevation angles from a ground-based observation site. Atmos. Meas. Tech., 10, 15-34. doi:10.5194/amt-10-15-2017
 Beyerle, Georg (2016): Ground-based GPS observations at low elevation angles using
open-loop signal tracking. GFZ Data Services. doi:10.5880/GFZ.2016.1.1.002