XGRIDS Pro Guide™ / Module 7: Advanced PortalCam

7.4 Map Fusion Collection Strategy

PortalCam joins multiple scan segments into one model using on-device fusion points. Three points in an L at every seam is the whole game, and it is decided in the field, not at the workstation.

Section 1

How PortalCam Connects Its Scans

Map Fusion stitches several PortalCam segments into one model in LCC Studio, for a site too large for a single battery or session. PortalCam connects those segments through fusion points: spots you mark on the ground during the scan.

A fusion point is a spot you mark on-device at a known physical location. When the same-named point appears in two neighboring segments, LCC Studio uses it to lock those segments together. Get the points right and fusion is reliable. Skip them, place too few, or name them inconsistently, and the segment drops out with no error.

The one rule that governs every PortalCam fusion. Every segment must connect to at least one neighbor through matching fusion points in a shared overlap zone. A segment with no matching points is excluded from the result. Fusion points cannot be added after the scan, so this is decided before you start walking, not after.

Section 2

Plan the Limits Before You Scan

Every limit below is a field-planning decision. Exceed one and the fusion fails at the workstation, after the crew has left the site.

Limit
Specification
Segments per job
Up to 10.
Combined capture
Up to 200 minutes total across all segments in one job.
Time per segment
LCC Studio sets no per-segment time limit, provided the job stays inside the two caps above.
Recommended capture length
30 minutes or less per capture. XGRIDS advises against going longer in any mode, fusion segments and single scenes alike, because longer captures tend to produce drift and layering artifacts. This is the number that should drive your segment plan.
Device capture ceiling
60 minutes. A firmware limit on one recording, independent of battery state. It shares its number with the 60-minute battery runtime for an unrelated reason.
Workstation memory
64 GB reconstructs up to 30 minutes of capture reliably, with risk of failure past 45. 128 GB reaches 60 minutes, with risk past 90. This is the limit that actually fails jobs.
Alpine working target
12 to 15 minutes per segment. What to plan to, rather than any of the ceilings above.
Device compatibility
Every segment must come from the same device model. PortalCam segments fuse only with other PortalCam segments.
Overlap per seam
Aim for about 50 ft (15 m) of shared coverage. Never drop below 33 ft (10 m). Overlap is the connection bridge, not the whole segment.

Plan to 12 to 15 minutes and none of the rest of the table ever comes into play. The software caps are generous: ten segments and 200 combined minutes leave a lot of arithmetic room, and there is no per-segment clock at all. What actually decides segment length is the 30-minute capture guidance and the memory in the machine that will process the job.

Do not let two segments overlap almost completely. If one segment's coverage sits entirely inside another's, LCC Studio cannot work out how they relate and the fusion fails. Each segment has to cover some unique ground of its own.

Keep the whole job inside a two-hour lighting window. Capture all segments within about two hours and avoid scanning across major lighting changes, such as a sunny-to-cloudy shift or lights switching on and off. The fusion matches appearance as well as geometry, so a big lighting change between segments weakens the connection.

Section 3

Fusion Point Connection Visual

This is a plan view, looking straight down at the site. Each colored box is one segment's coverage. The connection lives in the overlap zone, where both segments record the same three fusion points in an L.

Two Segments, One L-Shaped Trio Both segments record the same three points in an L. That shared L is the only link. Overlap ~50 ft (15 m) Segment A holds fp01, fp02, fp03 Segment B holds fp01, fp02, fp03 fp02 fp01 fp03 ≥33 ft ≥33 ft walk a full circle around each point ✓ Connected: one fused model One shared L-trio ties both segments together Three points, spaced ≥33 ft (10 m) apart, in an L. Not a line, not two points.
Section 4

Place and Name the Fusion Points

Fusion points are a PortalCam feature you set on-device during the scan. They require current PortalCam firmware and a current LCC Scan app; older builds do not offer the feature. You place them with the PortalCam on its built-in tripod, and you place at least three at every seam.

Where the three points go

The L-Shaped Trio
  • At least three points per seam, arranged in an L. Two points set one line and the third, off to the side, fixes the twist. Three points in a straight line do not, so spread them into an L.
  • Spaced at least 33 ft (10 m) apart. Points bunched together barely constrain the fit. Give each leg of the L real length.
  • Inside the overlap zone, on rich, stable geometry. Corners, columns, equipment, and door frames give the fusion something to lock onto. Avoid low light, stairs, narrow corridors, and reflective surfaces.
  • Visible and reachable on the return visit. You will place the same points again from the next segment, so pick spots you can walk back to and stand at cleanly.

How to place one point

  1. Set the PortalCam on its tripod at the spot, stable, in an open, well-lit area with clear texture and an unobstructed view.
  2. In LCC Scan, choose Add Control Point, set the Type to Map Fusion, and give it a Name you will reuse for the matching point in the next segment.
  3. Walk one full circle around the point so the scanner captures a complete cloud around it. This single habit does the most to steady the fusion.
  4. Wait before you move on. Do not power the device off within 5 seconds of adding a point, or the point file can be lost.

Fusion point names are case-sensitive and must match exactly across segments. A point named fp01 in one segment and FP01 in the next reads as two different points. The connection fails silently, with no error, and the segment drops out of the result. Decide the naming scheme before the crew starts and hold to it.

Pro Tip

Keep names short and lowercase with no spaces or symbols, like fp01, fp02, fp03. Simple names are faster to type on-device while scanning and they sidestep the case-mismatch failure entirely. When you re-place a point in the next segment, getting back to roughly the same spot is enough: within about 1.6 ft (0.5 m), the same facing within 20 degrees, and about the same height within 4 in (10 cm).

Section 5

The Field Collection Sequence

Each segment follows the same rhythm: initialize, scan the coverage area with standard PortalCam technique, then place the L-trio in the overlap zone before you stop. The trick that makes the seam line up is walking the L in reverse on the next segment.

  1. Plan the seams before you arrive. Sketch the segments on a floor plan and mark where each pair will connect. For a three-segment job you need two seam locations: one shared by segments 1 and 2, one shared by segments 2 and 3.
  2. Initialize segment 1. Set the PortalCam down in a feature-rich spot with the front camera facing a clean, static area. Complete the standard initialization before you pick it up.
  3. Scan the coverage area. Use standard PortalCam technique: multi-height passes, a serpentine path, bidirectional coverage, and loop closures, at no more than 1.6 ft/s (0.5 m/s) and slower indoors. See 7.2 Advanced Scanning for the full method.
  4. Place the L-trio in the overlap zone. Before ending the segment, set three fusion points in an L along the boundary you will share with the next segment. Name them fp01, fp02, fp03 and circle each one.
  5. End segment 1, then initialize segment 2. Start the next segment inside that same overlap zone.
  6. Walk the L in reverse and re-place the matching points. Retrace the L-path from the previous segment and drop points with the exact same names, fp01, fp02, fp03, at the same physical spots. This reverse walk is what makes the two segments agree.
  7. Continue into new ground. After re-placing the shared points, scan onward into the area segment 1 did not cover. At the next seam, continue the sequence with fp04, fp05, fp06, and so on.
Pro Tip

Sketch the segment plan before the first scan: mark each segment, each overlap zone, and each L-trio with its point names on a site plan or a phone photo. Almost every fusion failure traces back to a seam that was never captured or a name that did not match.

Section 6

Process in LCC Studio and Check the Seams

Fusion happens back at the workstation, but a bad seam almost always traces to the field, not the software.

  1. Create the project. In LCC Studio, click Create, select Map Fusion, and import the captured segments. LCC Studio reads the fusion point names and matches them across segments.
  2. Check the memory estimate before you commit. LCC Studio predicts the memory the job will need and shows it. A red Estimated Memory reading means the combined capture is too large for this machine, and the fix at that point is to drop Reconstruction Quality to Standard, add memory, or split the work. Starting anyway ends in an out-of-memory failure hours later.
  3. Start, and do not interrupt. LCC Studio processes each segment, then aligns them on the shared points. A large fusion runs long. Full processing steps and hardware requirements are on Module 9: LCC Studio.
  4. Inspect every seam in the viewer. Walk each boundary between segments. A doubled, stepped, or offset seam means the overlap or the L-trio at that seam fell short. That segment must be rescanned; it cannot be corrected in post.

Still misaligning after a clean-looking field capture? Work through 7.5 Connection Troubleshooting. The usual culprits are too little overlap, a trio placed in a line instead of an L, a lighting change mid-job, or a case-mismatched point name.

Section 7

Naming Your Segments

Name segments so building, floor, and segment read at a glance. A pattern like BuildingName_Floor_SegmentLetter sorts correctly and stays unambiguous when the files load into LCC Studio.

Examples: MainLibrary_FL1_SegA, MainLibrary_FL1_SegB, MainLibrary_FL2_SegA. Keep names under 30 characters to avoid Windows path-length issues, and use no spaces or special characters.

Segment names and fusion point names are two different things. Segment names keep your files organized. Fusion point names are what LCC Studio matches to connect segments, and those are the case-sensitive ones from Section 4. Both benefit from a simple scheme decided before you scan.

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