Projection and Coordinate System Setup

Overview

Incorrect projection configuration is one of the most common causes of point cloud display issues in VisionLidar. This guide covers how to set up coordinate systems correctly, and how to diagnose and resolve common projection-related problems.

Understanding Coordinate Systems in VisionLidar

VisionLidar uses two projection settings when opening or converting a project:

If Source and Destination match, no transformation is applied. If they differ, VisionLidar reprojects the data on import.

Step-by-Step: Setting Up a Project with the Correct Projection

When Creating a New Project

1. Go to File → New Project

2. In the project creation dialog, add your LAS/LAZ files

3. In the Projection field, select the coordinate system that matches your scan data

4. If you need to work in a different system, set the Destination Projection accordingly

5. Proceed with project creation

When Converting Files (File Conversion Tool)

1. Go to Tools → File Conversion

2. Add your source files

3. In the Parameters tab, enable Use Projection / Conversion

4. Set the Source Projection to match the original file coordinate system

5. Set the Destination Projection to the target system

6. Click OK to convert

Common Pitfalls and How to Avoid Them

Pitfall 1: Local Grid vs. Projected Coordinate System

Many clients (especially in Quebec and France) work with local grid systems or custom projections not available in standard EPSG databases.

Symptom: Point cloud loads but is displaced from expected geographic position, or does not align with other datasets.

Resolution:

• Confirm the exact EPSG code for the client's coordinate system from their survey metadata

• If the system uses a custom local grid, the client may need to provide a custom projection definition

• Common Quebec systems: NAD83 / MTM zone 7 (EPSG:32187), NAD83 / MTM zone 8 (EPSG:32188)

Pitfall 2: Large Coordinate Values Causing Rounding Errors

LAS files with large X/Y values (e.g., full UTM or MTM coordinates like 5,000,000 m North) can cause floating-point precision issues, leading to jagged or incorrectly rendered point clouds.

Symptom: Point cloud appears with "jitter" or geometric noise that disappears when zoomed in.

Resolution:

• Use File Conversion → Parameters → Modify the Origin to subtract a local offset from the coordinates

• This reduces large absolute coordinates to smaller values, improving floating-point precision

• The offset can be documented and reapplied when exporting back to the original system

Pitfall 3: US Survey Feet vs. International Feet vs. Metric

LAS files from US clients may be in US Survey Feet or International Feet rather than meters. Confusing these units results in a point cloud that is correctly shaped but at the wrong scale.

Symptom: Point cloud appears very small or very large compared to expected dimensions; measurements are off by a factor of ~0.3048 or ~3.281.

Resolution:

• In AI / Classify LAS, always set the correct Unit of Measure (Metric, US Foot, or Feet) before running batch classification

• In File Conversion, use the Use Projection / Conversion option to convert to metric if the client wants to work in meters

• Confirm the unit with the client before processing

Pitfall 4: Missing or Undefined Projection in Source Files

Some LAS files have no projection defined in their header, or have an incorrect EPSG code.

Symptom: VisionLidar cannot detect the projection automatically and prompts for manual entry, or loads data at the wrong location.

Resolution:

1. Ask the client what coordinate system was used during acquisition

2. Manually assign the correct EPSG code in the Source Projection field

3. If the client doesn't know the projection, check the scanner manufacturer's export settings or the acquisition report

Projection and GeoJSON Export

A known issue exists where GeoJSON exports may have coordinate shifts depending on the projection configuration (VLW-1951).

Symptom: GeoJSON exported from VisionLidar opens in QGIS or ArcGIS at a slightly offset position.

Resolution: Escalate to Support and reference VLW-1951. Provide the client's EPSG code and a sample export.

Projection in File Conversion: Quick Reference

Spherical Image Projection

When importing spherical images, the Source Projection in the Spherical Images upload dialog must match the coordinate system used in the position file (TXT/CSV).

Common issue: Images load but appear far from the point cloud.

Resolution: Verify the position file units and CRS match the project's coordinate system. If the images use a different CRS, enable Projection and Conversion in the Upload Images dialog and set Source/Destination accordingly.

Escalation

If a projection issue cannot be resolved with the steps above, provide the following when escalating:

• The EPSG code(s) of the source and target projection

• The scanner make/model and acquisition software used

• A sample LAS/LAZ file (or the LAS header information)

• A description of the observed displacement or error