Section 1

Georeferencing Method Selection

This decision must be made before leaving the office. It cannot be added or changed after the scan is complete.

Method

When to Use

Requires

Key Limitation

None

Internal documentation, visual output only, no coordinate deliverable required

Nothing additional

No real-world coordinates. Cannot be placed in a GIS or used for high-accuracy deliverables.

RTK

Outdoor projects and indoor scans within approximately 100 m of a sky-visible entry point

RTK module, active NTRIP connection, Fixed status confirmed before scanning

Cannot initiate fix indoors. A fix carried in from outside provides absolute coordinates for approximately 100 m of interior scan path. Does not constrain SLAM drift on long scans without supplemental GCPs.

PPK

Remote sites with no CORS network, obstructed sky, or where RTK fix is unreliable

Base station, RINEX files, base coordinate

Base station must be within 5 km. Requires post-processing. Cannot confirm accuracy until after the scan.

GCP only

Indoor projects, underground, GPS-denied environments

Surveyed point coordinates, physical markers placed before scanning, CSV file

Markers must be placed before the scan. Points must be marked in LixelGO during scanning. Cannot be added after the fact.

Hybrid (RTK + GCP)

Large outdoor projects, high-accuracy deliverables, spanning indoor and outdoor areas

RTK module + surveyed GCPs at max 100 m intervals

Most demanding to execute but most robust result. RTK corrects coordinate frame; GCPs constrain drift accumulation.

Section 2

RTK: Status and Minimum Requirements

RTK Status Indicators

Single

No corrections applied. GPS-only position. Not valid for georeferenced scanning under any circumstances.

Float

Receiving corrections but solution not yet fixed. Not valid for scanning. Wait for Fixed. Do not begin scanning with Float status. The coordinate data embedded in the scan will not meet accuracy requirements.

Fixed

Centimeter-level corrections applied. Valid for scanning. This is the only status at which RTK data is reliable for absolute coordinate output.

RTK Minimum Validity Thresholds

RTK data collected below these thresholds may process, but with compromised accuracy. All thresholds must be met for a reliable georeferenced result.

Requirement

Threshold

Notes

Satellite status

Fixed only

Float and Single are not valid for reliable coordinate conversion.

Available satellites

More than 10

GPS, GLONASS, BDS, and Galileo all contribute. More constellations improve fix reliability.

Movement while Fixed

More than 10 m

Trajectory bounding box must exceed 10 m. A short in-place loop does not satisfy this requirement.

Valid RTK data points

More than 100

Visible in LixelStudio after upload. Verify before processing.

Accuracy verification scan

Over 100 m, not straight

Fixed status throughout. Required for formal accuracy verification.

RTK corrects the coordinate frame but does not constrain SLAM drift. A long outdoor scan with RTK and no GCPs will have an accurate coordinate origin but may accumulate geometric drift across the extent of the scan. For large projects, supplement RTK with GCPs at 100 m intervals to prevent drift from compounding.

Section 3

PPK: Minimum Requirements

PPK Minimum Thresholds

Base station to rover distance: less than 5 km. Keep baselines under 2 km for optimal accuracy. Longer baselines degrade the PPK solution quality.
Scan area coverage must exceed 10 meters of open ground visible to the sky. A GPS-denied scan with no outdoor segment cannot produce PPK output.
Valid PPK data points after processing: more than 100. Displayed in LixelStudio after upload. Check this before processing. Below 100 means the PPK solution is unreliable.
Base station RINEX: continuous, gap-free logging at 1-second intervals or finer throughout the entire scan window. Gaps in the base station record cannot be patched in post-processing.
Antenna tilt: within 20 degrees of vertical throughout the scan. The PPK antenna on the L2 Pro must remain near vertical during field collection.

PPK is not inherently less accurate than RTK. Both process the same GNSS observations. RTK does it in real time; PPK does it afterward with the full dataset available. In practice, PPK can achieve equivalent or better accuracy than RTK when baseline distances are short and RINEX data is clean.

Section 4

GCP Placement Rules

GCP Type Reference

GCP1 (Absolute): Carries known, surveyed real-world coordinates. Applied in LixelStudio, it aligns the scan to a real-world coordinate system and corrects IMU leveling error. Required when the project deliverable needs absolute coordinates.
GCP2 (Relative): Uses XGRIDS sticker targets with no absolute coordinate requirement. Functions as an internal anchor constraining SLAM drift and improving internal consistency. Use when relative accuracy matters but georeferencing is not required.
The same physical sticker target can be either type. The difference is whether a surveyed coordinate is attached in LixelStudio.

Spacing Limits

L2 Pro: maximum 100 m between any two GCPs. Reduce spacing in feature-poor or complex environments.
K1: maximum 50 m between any two GCPs. The K1's shorter range makes it more sensitive to drift accumulation.
PortalCam (Map Fusion): minimum 3 points, at least 10 m apart, in an L-shaped distribution.

Placement Distribution Rules

Points cannot be collinear. Three or more points on a single straight line provide correction in only 1 axis. Distribute points so they form a three-dimensional network, not a line.
Points must be evenly distributed, not clustered. A cluster of control points in one area of the site with none elsewhere provides poor constraint across the scan extent.
Place points at scan boundaries and at zone transitions (floor changes, building entries, areas where coverage paths cross).
Each point must be visitable during the scan. Place markers where the scanner can approach and dwell within 1 to 2 meters for a clean mark.

Point names are case-sensitive and must match exactly. The name in your CSV coordinate file must match character-for-character what you type in LixelGO when marking the point during the scan. A single uppercase-to-lowercase difference is enough to cause the point to fail in processing.

Section 5

Control Point Marking Procedure

K1 and L2 Pro: Marking in LixelGO

Write all point names on paper before going to site. Type them from that written list into both the coordinate CSV file and LixelGO. Do not invent names in the field while scanning.
Approach the marker and stop with the scanner within 1 to 2 meters of the target.
Tap the control point button in LixelGO and enter the exact point name.
Hold the device stationary for at least 5 seconds after submitting the mark. Moving immediately after submission risks a poor quality mark.
Resume scanning after the confirmation appears.
After the last control point, continue scanning for at least 15 seconds and walk a small loop before ending the session. This gives SLAM additional constraint context around the final control point.

PortalCam: Shared Points for Map Fusion

For PortalCam Map Fusion, shared control points must be physically visited in each scan session that needs to connect to others.
Device placement at the same physical location across different scan sessions must be approximately consistent in position and orientation. The device does not need to be in the exact same spot, but the viewing angle and distance to the marker should be similar.
Mark each shared point in the LCC Scan app during every session where it needs to be used.

Section 6

Coordinate System Quick Reference

You do not need a surveying background to configure coordinate systems in LixelStudio, but you do need these 4 terms.

Term

What It Means for XGRIDS Processing

Ellipsoid

The mathematical Earth model used as a reference surface. WGS84 is the global GPS standard. GRS80 is used by most modern national systems. The RTK module records in whatever ellipsoid your CORS network transmits. Know which one before processing.

Datum

A specific realization of a coordinate system defined by an ellipsoid and control points. WGS84 and NAD83 use the same ellipsoid but are different datums. Coordinates in the same area can differ by over 1 meter depending on which datum is used.

Projection

The transformation that converts geographic coordinates (latitude/longitude) into flat planar coordinates (Easting/Northing). LixelStudio outputs projected coordinates. You must specify the target projection. UTM, State Plane, and national systems all have their own definitions.

Helmert transformation

Required when your RTK source datum differs from your output target datum. Uses 7 parameters (3 translations, 3 rotations, 1 scale factor). Parameters must come from an authoritative geodetic authority for your specific region. Do not guess these values.

Section 7

Critical Warnings

No recovery Georeferencing cannot be added after the scan. RTK must be configured and active before recording begins. GCPs must be placed in the physical space and marked during the scan. A project delivered without georeferencing cannot be corrected without re-scanning the site.
Processing failure Mismatched GCP names cause silent processing failure. The name in your CSV file must match exactly what you typed in LixelGO, including case. A mismatched point is silently discarded in LixelStudio. You will not get an error, you will just get a result without that control point applied.
Warning Float is not an acceptable substitute for Fixed. Scanning with RTK in Float status embeds unreliable position data into the scan file. The coordinate conversion in LixelStudio will produce a result, but the accuracy of that result is not centimeter-level and cannot be verified after the fact.
Warning RTK does not constrain SLAM drift on long scans. RTK corrects the coordinate frame. It does not prevent drift from accumulating across the trajectory. On scans exceeding several hundred meters, use GCPs at 100 m intervals in addition to RTK.
Warning RINEX gaps in the base station record cannot be recovered in post-processing. If the base station stopped logging at any point during the scan window, the PPK solution for that time period will be degraded or absent. Monitor base station status during the scan.
Warning Neither RTK nor GCPs compensate for poor scanning technique. A hybrid-georeferenced scan with no loop closures and excessive speed will still produce a drift-affected result, just one with absolute coordinates attached to it. Georeferencing and scanning technique are separate concerns. Both must be correct.
Warning GCPs on a single straight line provide correction in only 1 axis. 3 collinear points are not a valid control network. Distribute points in a three-dimensional network across the scan extent.

Module 4 Quick Field Guide