5.4 Map Fusion Processing

Hardware Requirements

Map Fusion is more computationally demanding than single-scan processing. Verifying hardware before starting a long fusion job prevents a failure at hour 30 of a 65-hour run.

Project Setup

Setting up a fusion project correctly at the start prevents configuration errors that require restarting the entire job.

Configuration

The configuration settings for a fusion job control how the algorithm handles SLAM optimization, RTK data, and the alignment computation. The defaults are appropriate for most projects. The settings below are the ones you need to understand when the defaults are not the right choice.

Quality Setting

Fast, Standard, and Slow settings control algorithm depth and iteration count. Standard is the recommended starting point for fusion projects. If the first attempt at Standard fails or produces misalignment, switch to Slow before troubleshooting collection. If RAM is the constraint, Medium Quality (Standard) reduces memory consumption relative to Slow at a modest accuracy trade. For large projects at or above 150 minutes total, use Medium Quality to avoid processing failures on machines with 96 GB or less of RAM.

SLAM Mode

Three options are available. None produces the highest accuracy and should be used when collection technique was sound and there are no known drift problems. Robust is the default balanced setting, it handles moderate drift and degraded environments better than None at a slight accuracy trade. Narrow Scene is for tunnels and mine galleries specifically; it should not be applied to standard indoor projects.

Loop Closure

Enable Loop Closure when the scan route within any segment included intentional loop paths back to the initialization area. Loop Closure distributes accumulated error across the whole trajectory rather than allowing it to concentrate at the end of the route. If the route was mostly linear with limited loop opportunities, Loop Closure has less effect and can be left at default.

RTK Data Handling

Auto is the default. In Auto mode, LixelStudio applies RTK data where it is valid and ignores it where it is not. Disabled forces the processor to treat all segments as having no RTK. Use Disabled only if RTK data is known to be corrupt or if you intentionally want a relative-coordinates-only output. Do not disable RTK as a troubleshooting step without understanding that doing so removes global coordinates from the entire fused result.

Reference Map Selection

If your fusion project includes segments with different accuracy levels, for example, one segment with excellent RTK and several without, designate the highest-quality segment as the reference map. Other segments align to it. The reference segment should be the one with the most reliable individual SLAM quality and the strongest RTK or control point anchoring.

Processing Phases

Map Fusion processing runs in three sequential phases. Understanding what each phase does helps you interpret progress indicators and diagnose where a failure occurred.

Quality Review

After processing completes, review the fused result before exporting. A quality review that takes 15 minutes catches problems that would waste hours of downstream work in Revit or AutoCAD.

Segment Boundary Inspection

Navigate to each segment boundary, the area where two segments join, and inspect the geometry. A well-aligned fusion shows seamless continuation of geometry across the boundary. Misalignment shows as a step, doubling of surfaces, or geometry that does not line up between the two sides of the boundary. If misalignment is visible, the connection at that boundary needs to be investigated before the result is used.

Accuracy Report and RMSE

Review the accuracy report generated after processing. The RMSE values at each control point connection show how closely the algorithm achieved the theoretical alignment. High RMSE at a specific connection indicates a problem with that segment pair's connection data, poor overlap, a control point with inconsistent position between takes, or an RTK validity issue.

Coverage Completeness

Verify that the fused output includes data from all segments and that there are no unexpected gaps at the transition zones. A segment that failed during individual SLAM optimization may be absent from the fused result, the final dataset will be missing the territory that segment was supposed to cover.

Export

The fused result exports from LixelStudio as a single dataset. The format selection follows the same decision logic as single-scan exports.