4.5 Control Point Marking During Scanning
Control points must be marked correctly during the scan session or they produce no benefit in processing. The procedure differs by device. The naming convention is the same for all of them, and a single naming error at the marker renders that point useless regardless of how accurately it was surveyed.
Naming Convention
Point names are case-sensitive. The name you type in LixelGO at the marker must match the name in your coordinate CSV file exactly, character by character, including capitalization. There is no fuzzy matching, no autocorrection, and no warning at processing time if the names differ. If they do not match, that point is simply ignored.
Naming Rules
Valid Names
GCP01
A1
CP003
NORTH01
Invalid or Mismatched Names
GCP 01, no spaces
gcp01 when CSV has GCP01
GCP-01, no special characters
CP 3 when CSV has CP003
Write your point names on paper before going to site. Type them from that list into both the coordinate CSV and LixelGO. Do not invent names in the field while scanning, inconsistency between the list in your head and what you type is the most common cause of control point failures in processing.
K1 and L2 Pro Workflow
For the K1 and L2 Pro, marking a control point requires placing the device on the ground at the target position. The device must be stationary when the mark is recorded.
Walk Around the Sticker Before Placing the Device
Circle the target sticker once or twice with the scanner active before placing it on the ground. This scans the sticker from multiple angles and gives LixelStudio the geometry it needs for automatic target detection during accuracy verification. Do not skip this step, placing the device immediately on a sticker that has not been scanned from any standing angle produces a poorly-covered target.
Set the Device Down Gently on the Marker
Place the scanner on the sticker target slowly and steadily, centering it as accurately as possible over the marked position. Avoid any sudden contact with the ground, jarring the device at the moment of placement introduces positional error at that control point that cannot be corrected in post-processing.
Add the Control Point in LixelGO
While the device is stationary on the target, open the control point interface in LixelGO and type the point name exactly as it appears in your coordinate CSV. Confirm the entry. Wait for the success confirmation before moving.
Lift the Device Slowly and Continue Scanning
Pick up the scanner slowly and steadily. Violent or sudden movement immediately after marking affects the accuracy of that point. After lifting, remain in the vicinity of the marker for a few seconds or circle it once to scan additional surrounding geometry before moving on.
PortalCam Workflow
The PortalCam control point procedure differs because the device is mounted on a tripod rather than placed directly on the ground. The requirements for app and firmware versions are specific: LCC Scan version 1.2.0_p1 or later and firmware version V3.2.3-20251104 or later are required for control point functionality.
Deploy the PortalCam on Its Tripod at the Control Point Location
Set up the tripod stably at the control point position. Choose locations with good ambient lighting, clear texture in the surrounding area, and unobstructed open space. Avoid corners, dark alcoves, and areas directly adjacent to mirrors or glass.
Add the Control Point in LCC Scan
In LCC Scan, open the control point marking interface and type the point name. Hold the device stationary for at least 5 seconds after submitting the mark. The extended hold time is a PortalCam-specific requirement that ensures sufficient scan data is collected at the stationary position.
Circle the Point After Marking
After the hold period, walk the PortalCam in a circle around the control point location to capture surrounding geometry from multiple angles. This produces a more complete point cloud around the marker and improves target detection reliability in LixelStudio.
For shared control points used across multiple PortalCam maps in a Map Fusion workflow, the device placement at the same physical location across different scan sessions needs to be approximately consistent: position difference less than 0.5 m, orientation within 20 degrees, and height difference within approximately 10 cm. Exact repeatability is not required, but gross inconsistency between sessions degrades fusion quality.
Marking for RTK Accuracy Verification
When using RTK and verifying accuracy against target stickers, the marking procedure is different from GCP marking. For RTK accuracy verification, you do not need to place the device on the ground at the target. Walking around the sticker while scanning is sufficient to capture it for accuracy verification purposes. The device does not need to be stationary.
The sticker still needs to be scanned properly for LixelStudio's automatic target detection to work. Walk around it at close range, within half a meter, and ensure it is clearly visible in the scan path before moving on.
Ending a Session After the Last Control Point
If the last action before ending the scan session is marking a control point, do not end the recording immediately. Wait at least 15 seconds after the control point confirmation before stopping the session. Ending too quickly after a mark means the point carries insufficient scan data around it, LixelStudio may not recognize it as a valid control point.
The 15-second rule is a minimum. After the last control point, if the project permits, continue scanning for 20 to 30 seconds and walk a small loop nearby before ending. This provides the scan with additional closing geometry and ensures the last marked point has full coverage in the dataset.
©2026 Alpine Reality Capture LLC • XGRIDS Pro Guide™