The POS system collects vehicle position, velocity, attitude, track, speed, and dynamics from a moving vehicle. This data can be used to create centerline maps and to calculate geometric data such as curvature, grade, and cross-slope. The POS also provides motion compensation information to other sensor systems onboard the data collection vehicle. The system incorporates the Applanix POS LV unit and includes an Inertial Measurement Unit (IMU), dual GPS receivers, and other data acquisition sensors such as a DMI and GAMS (GPS Azimuth Measuring Subsystem) for superior position accuracy.

Features

• Integrated DMI/GPS/Inertial sensors
• Robust and precise position and orientation measurements
• Accurate data from a vehicle traveling at highway speeds up to 70 mph/112kmph
• GPS data linked to photolog images (latitude, longitude and elevation location)
• Continuity of all data and data accuracies during GPS dropouts
• No motion artifacts, even under the most severe conditions
• No gyro spin-up time
• Self-calibrating for rapid deployment
• 200 Hz real-time true data rate
• Compact Inertial Measure Unit (IMU) in protective housing

Dual GPS Receiver/Antennas The system features dual GPS receivers and antennas. The GPS antennas are securely mounted on the roof of the vehicle. POS requires at least one integrated GPS receiver for accurate positioning. However, the system comes with two receivers. The position difference between the two antennas serves as a heading sensor, improving heading accuracy and reliability. The system uses raw GPS observables from the receiver to aid the inertial data, allowing the system to derive useful aiding data from even a single visible satellite.

Inertial Measurement Unit (IMU) The IMU is the primary sensor used to measure position and orientation differences. It outputs raw data representing 3-axis acceleration and angular rotation of the vehicle. These observations are blended with raw GPS observables and distance traveled data to derive the position and orientation solution.

Distance Measurement Instrument (DMI) DMI generates a linear reference tag for each point and functions as an additional required aiding sensor for the POS by outputting pulses representing incremental revolutions of the wheel. DMI information provides a measure of the vehicleÕs linear distance traveled, and is used to constrain errors in vehicle velocity and displacement. Distances are accurate to within +/- one-thousandth (0.001) mile per mile, and displaying the distance in miles to four decimal places.

Real-time Differential GPS The POS uses the OmniSTAR differential GPS (D-GPS) system to provide real-time corrections to vehicle positioning data. OmniSTAR maintains a network of permanent base stations located throughout the continental United States. These base stations, which are located at fixed, known locations, track all GPS satellites above 5 degrees of elevation. The base stations compute pseudo-range corrections for each satellite it is tracking at an interval of 600 milliseconds. The corrections from each station are then uploaded to a geo-stationary satellite where they are broadcast out over the coverage area.

The receiver unit in each POS vehicle uses the correction message, which contains corrections from all of the bases stations across the continent, and positional data acquired from the positional unit, to both calculate an optimized set of corrections for pseudo-range errors and to localize atmospheric errors.

Extended blackout is rare since the correction signal is satellite-based and the POS is capable of enduring the loss of the DGPS signal for extended periods of time without serious degradation of positional accuracies.

Output

The system produces two files per route direction: a binary format raw data file containing full position information, and a text file containing position information corresponding to each photolog frame. Fields include date, time, latitude and longitude (in decimal degrees), elevation (in meters above GPS ellipsoid) and frame number. The data can be exported to Access-compatible database tables.

Road geometric data can be calculated from the standard output fields using the Curve and Grade Viewer. Curve and grade data is reported in accordance with the HPMS standard. Length, starting point, degree of curvature or radius length, percent grade, curve classification, and grade class is provided for each segment of the route.

Software

Applanix Controller The Applanix Controller displays the status of GPS data from the POS unit during data collection. The vehicle position, velocity, dynamics, attitude are displayed, as well as the status of GPS satellites in communication with the system.

GPS Viewer The GPS Viewer displays plots of GPS data collected with the system. Multiple traces can be overlaid on one another, and they can be magnified for quality inspection. Numerical data is shown for each point, along with curve, grade, heading, pitch, and roll data.

Optional Software

• Curve and Grade Viewer
• Roadview 6
• Roadview Explorer
• Roadview Player

Purchase Options

Customized systems and data collection service packages are available.