Sodex Mobile: Best Practices for scanning with SDX-PocketScan

Overview

Sodex Mobile is an iOS app that turns an iPhone Pro with LiDAR into a professional 3D scanner. When used with the SDX-PocketScan RTK receiver, it can deliver centimeter level accuracy. Sodex Mobile visualizes the point cloud while you scan and uses high precision GNSS with optional NTRIP corrections to georeference your scan.

Good results depend on the right setup and correct movement technique. This guide explains how to move and how not to move while scanning.

Before you start scanning

Device and hardware

• Use a supported iPhone Pro model with LiDAR
• Attach the SDX-PocketScan RTK receiver to the back of the phone
• Make sure the RTK receiver is powered and connected

Why this matters

• Sodex Mobile relies on the SDX-PocketScan receiver to achieve centimeter accuracy

GNSS fix and status tiles

• Start the app in an open area with a clear view of the sky
• Open the scan screen and check the status tiles
• Wait for a stable high precision GNSS state before you begin scanning

Recommended practice

• Do not start moving until GNSS is stable
• If you are close to buildings, trees, or machines, move to a clearer area first
• Maintain an RTK-Fix for optimal scan accuracy

Starting a scan

Stand still and initialize

When you tap the record button to start a scan:

• Stand still for the first few seconds
• Wait until you see the first points forming in the live point cloud view
• Confirm there are no warnings before you begin moving

Why this matters

• The LiDAR and tracking system need a stable start to establish a reference frame
• Moving immediately can introduce early drift

How to hold the phone

• Hold the phone steady at chest height
• Do not hold it too close to your body because you can block GNSS signals
• Keep the phone at roughly a 45 degree downward angle

How to enter the planned route

• After initialization, for any scan that will continue in a straight line or sweeping pattern, first approach the planned line from the side for about 5 m, ideally at a 90 degree angle, before continuing along the main route
• This short side approach helps the app stabilize before the main capture path begins

Movement pattern

Keep a consistent scanning angle

• Hold the phone at roughly a 45 degree downward angle
• Avoid pointing straight down or straight ahead for long periods

Why this works

• This angle captures both the ground and vertical features
• Feature-rich scenes improve iPhone tracking and reduce drift

Walk slowly in one direction

• Walk forward at a calm pace in one direction
• Keep the phone stable with no fast motion and no sudden acceleration
• If the app warns that you are moving too fast, slow down immediately

Why this works

• Less device motion helps maintain stable tracking and cleaner point clouds
• Consistent movement reduces the risk of drift over the trajectory

• 

Optional: Sweeping

• If you use sweeps, keep them small, slow, and smooth
• Do not paint quickly or change direction abruptly
• Before you begin the sweep pattern, first approach the planned line from the side for about 5 m after initialization, ideally at about a 90 degree angle
• Do not use sweeping as a substitute for route planning

Follow a planned route

Plan your path before you press record. The goal is to cover everything with clean, predictable movement and consistent phone orientation.

• For LiDAR processing, do not loop back to touch up areas you already scanned
• For LiDAR processing, do not walk the same line twice within one scan
• For LiDAR processing, do not scan the same edge from both directions within one scan
• For photogrammetry processing, include the overlap and backtracking that the workflow needs

How to capture larger areas

Option 1: Snake route
Cover the area using a continuous snake route: walk one long strip, make a smooth turn at the end, then walk the next strip parallel to the first and continue.

Option 2: Split into multiple scans
For very large sites, split the job into multiple smaller scans by zone. This avoids overly long trajectories and reduces the risk of drift. Upload all scans and process them in SDX-Cloud as needed.

Key principle: route planning must match the intended processing method.

Maintain a moderate walking speed

• Move at a calm walking pace
• Avoid sudden accelerations and stops

Why this matters

• Moving too fast can distort the point cloud and cause tracking issues
• If you see a warning about speed, slow down

Avoid large orientation changes

• Keep the device orientation stable
• Do not rotate the phone wildly or change tilt rapidly
• If you need to change direction, turn your whole body smoothly instead of whipping the phone around

Use GCPs for photogrammetry processing

• If a GCP is visible in the device field of view, sweep over it 2-3 times to improve GCP detection
• Keep these passes slow and controlled
• Continue the normal route after the GCP has been covered clearly
• For broader GCP guidance, see Sodex Mobile - How to work with and measure up GCPs

How to scan stockpiles

Stockpiles are often used for volume evaluation. To get reliable results, you need clean coverage of the full pile shape toe to crest and a clear boundary at the base.

Recommended route

• Do a single loop around the stockpile at a steady distance
• Keep the phone at a steady angle and pace and avoid fast painting motions
• While walking, move your arm up and down to capture the whole slope

Common mistakes to avoid

Do NOT move too rapidly

• Avoid fast pivots, abrupt turns, and rapid movements
• If you need to turn around, do it slowly and smoothly

Do not hold the phone against your body

• Keep the device in front of you
• Maintain separation from your torso so the receiver has a clear view of the sky

Do not capture fingers or your own shadow

• Do not place your fingers in front of the camera or let them cover part of the camera view
• Avoid capturing your own shadow, especially when the scan will be processed with photogrammetry
• Repeatedly capturing fingers or your own shadow can lead to errors during photogrammetry processing

Do not use the wrong backtracking pattern for the intended processing

• Match the route to the intended processing method before you start the scan
• Do not fix missed LiDAR spots by walking back through them in the same scan
• If the scan is intended for photogrammetry, include the required overlap and repeated visibility

Better alternative

• Finish the scan, then start a second scan for a missed LiDAR section
• When scanning larger areas, use a snake route or split into multiple smaller scans

No rapid painting motion

• Do not wave the phone around quickly
• Sweeps should be slow and controlled, like a smooth camera pan

Avoid poor scanning conditions when possible

• Very featureless areas can increase drift
• If the phone is held too horizontal and only sees ground, tracking can drift
• Reflective surfaces such as standing water can degrade results
• Moving objects can introduce artifacts

Recommended practice

• Ensure the scanned area is feature rich with vertical objects, curbs, corners, equipment, or trees
• Keep the 45 degree angle so the scanner captures more context and not only ground
• Maintain RTK-Fix throughout the scan for best accuracy

Related Articles

• How to download Sodex Mobile
• Turn on SDX-PocketScan and connect to Sodex Mobile App
• Getting started: Sodex Mobile
• SDX-Cloud: How to Create a Device User (SDX-PocketScan)
• SDX-Cloud: How to Add an SDX-PocketScan Device
• Sodex Mobile: Lidar vs Photogrammetry processing
• Sodex Mobile - How to work with and measure up GCPs