# 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](https://docs.phoenixlidar.com/spatialexplorer-8-and-9/user-interface/toolbars/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.