Tech Talk

Harris Corp. Completes Space Qualification Testing of Hosted Payload for Global Aircraft Tracking System

March 11, 2014By

Harris Corporation has achieved a key milestone under a five-year contract with Aireon LLC that will create the first global satellite-based aircraft tracking system. The announcement was made during the SATELLITE 2014 Conference and Exhibition, held March 10-13 at the Washington Convention Center in Washington, D.C. The company’s Automatic Dependent Surveillance-Broadcast (ADS-B) 1090 Extended Squitter receiver payload has been successfully... read more

The Kinematic GPS Challenge: First Gravity Comparison Results

March 14, 2012By

By Theresa Diehl The National Geodetic Survey (NGS) has issued a “Kinematic GPS Challenge” to the community in support of NGS’ airborne gravity data collection program, called Gravity for the Redefinition of the American Vertical Datum (GRAV-D). The “Challenge” is meant to provide a unique benchmarking opportunity for the kinematic GPS community by making available two flights of data from... read more

This article is tagged with , and posted in Algorithms & Methods, Opinions, Survey News, Tech Talk

A Comparison of Lidar and Camera-Based Lane Detection Systems

February 3, 2012By

By Jordan Britt, David Bevly, and Christopher Rose Nearly half of all highway fatalities occur from unintended lane departures, which comprise approximately 20,000 deaths annually in the United States.  Studies have shown great promise in reducing unintended lane departures by alerting the driver when they are drifting out of the lane. At the core of these systems is a lane... read more

This article is tagged with , and posted in GNSS, Tech Talk

On-Site Geo-Referencing of 3D Static Terrestrial Laser Scans

June 29, 2011By

By Jens-André Paffenholz This blog presents an efficient procedure for directly geo-referencing static 3D laser scans. This is a worthwhile way to obtain the required transformation parameters from the local sensor-defined coordinate system to a global system. Therefore, a multi-sensor systems (MSS) is designed with a phase-measuring laser scanner and 3D positional sensors (see Figure 1). By means of at least... read more

This article is tagged with , and posted in Augmentation & Assistance, Tech Talk

Where Time and Space Meet

November 1, 2010By

Increasing availability and performance of state-of-the-art navigation sensors motivates the need for a highly accurate reference system commonly referred to as a time-space position information (TSPI) device. The Advanced Navigation Center at the Air Force Institute of Technology is working with the Air Force Flight Test Center to develop a next generation time-space position information (TSPI) system to be used for test and evaluation of modern navigation devices. read more

This article is tagged with and posted in Aviation, Tech Talk

Integer ambiguity validation: Still an open problem?

July 30, 2007By

By Sandra Verhagen High-precision Global Navigation Satellite System (GNSS) positioning results are obtained with carrier phase measurements, once the integer cycle ambiguities have been successfully resolved. The position solution is obtained in four steps: 1. Float solution:least-squares, discarding integer nature. 2. Integer solution: real-valued float ambiguities mapped to integer-valued ambiguities.Examples of integer estimators (Teunissen, 1998a): • Integer Least-Squares: optimal, requires... read more

This article is tagged with , and posted in Algorithms & Methods, Tech Talk

Antenna-induced biases in GNSS receivers May 17, 2007

May 17, 2007By

By Inder Jeet Gupta It is well known that the phase center of a GNSS antenna can vary with the satellite direction. This phase center movement leads to aspect dependent carrier phase and code phase biases in the satellite signal. For precise geo-location, one needs to characterize the antenna-induced carrier and code phase biases over the upper hemisphere. In the... read more

This article is tagged with , and posted in OEM, Tech Talk

GPS Transmitter Frequencies

January 16, 2007By

Why are the two GPS Transmitter frequencies (1575.42 and 1227.6 MHz) coherently selected integer multiples of 10.23 MHz master clock? Question posted on CANSPACE on October 30, 2006, by Sivaraman Ranganathan. The document defining the GPS signal, IS-GPS-200, states that “The carrier frequencies for the L1 and L2 signals shall be coherently derived from a common frequency source within the... read more

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