Processing Options

Some basic processing options are shown in the main NavLab window:

• Multi-pass: processing is typically performed in the forward and reverse directions. Multi-pass will enable processing in the forward and reverse directions several times each and all results will be combined.

• Precise files: Precise files are clock and ephemeris products produced by NovAtel. Typically, it's beneficial to download precise files.

• Enable AR: This enables PPP-AR (Precise Point Positioning with Ambiguity Resolution). PPP-AR uses refined ephemeris and clock bias correction products to improve GNSS processing results when differential GNSS is not available (i.e. when a reference station is not used during processing). This feature requires an NRT license (see Tools->Licensing).

Additionally some advanced options are available in the Advanced Options window:

Alignment method: Alignment method determines how an initial heading/yaw value is estimated:

• Auto: allow the software to select between static and kinematic.

• Kinematic: Align kinematically. This is the most common method, and is supported by all IMUs.

• Static: Align statically. This method is only supported by high performance IMUs, such as the IMU-32, 52, and 60.

Minimum alignment velocity: When aligning kinematically, this parameter can be used to restrict alignment to some minimum lateral speed. This is ideal for preventing prematurely aligning, such as during taxiing or takeoff.

Enable Doppler Velocities: Vehicle velocity can be estimated using GNSS doppler information. Noisy GNSS doppler information can degrade trajectory processing, however this is uncommon.

Ionospheric processing: Ionospheric processing, also referred to as dual frequency processing, improves trajectory solutions when baseline lengths (distance between GNSS reference station and lidar system) are long (> 7 km), however with very short baselines, results are typically best without ionospheric processing. When set to automatic, NavLab will enable/disable Ionospheric processing automatically based on the discard tolerance set below.

Discard tolerance: Discard tolerance is the baseline distance below which Ionospheric processing will be disabled if Ionospheric processing is set to Automatic.

Criteria for accepting new fixes: This controls how frequently re-fixing of carrier phase ambiguities occurs. When set to Default, re-fixing occurs somewhat frequently, using the default A-RTK settings. This is ideal with mobile and pedestrian data, and may also improve airborne data. If set to On-engage only, ambiguities will be fixed at the beginning of processing, and will only be re-fixed in the event of a high PDOP.

Quality acceptance criteria: This controls the maximum quality factor accepted when re-fixing carrier phase ambiguities. The lower the quality factor number, the lower the RMS error of the epoch, and the lower the probability of an incorrect fix.

Constellations to use: Select which GNSS satellite constellations to use during processing. Only disable a constellation if there is a known issue with that constellation in the acquired data.

PVA file: PVA files can be used for importing external vehicle position updates.