Sodex Mobile - How to work with Ground Control Points

Summary

This article gives you an overview of how to work with Ground Control Points (GCPs) in Sodex Mobile together with the SDX-PocketScan receiver, the SDX-Pole Antenna, and a compatible pole. It is the entry point for the available mobile GCP workflows and helps you choose the right path before you move into workflow-specific instructions.

Introduction

Ground Control Points help you anchor field data to known positions and improve the reliability of processed results. In the current Sodex Mobile workflow, GCPs are captured and organized in layers that synchronize with SDX-Cloud and SDX-CAD.

You can use GCPs in three main ways: capture them directly after a scan, reuse an existing point layer as the GCP source for a scan upload, or use a point layer as the default project GCP set for future work. This article stays intentionally high level so you can understand when each workflow fits your job.

Prerequisites

• You have access to the correct project in Sodex Mobile.
• You have an SDX-PocketScan receiver, an SDX-Pole Antenna, and a compatible pole with a 5/8-inch thread.
• The SDX-PocketScan receiver is powered on before it is inserted into the SDX-Pole Antenna.
• The external GPS antenna is unplugged before you insert the SDX-PocketScan receiver into the SDX-Pole Antenna.
• You have visible Ground Control Points available on site.
• If you want to reuse previously measured points, the project already contains a suitable point layer.
• You use at least 3 GCPs for processing. Sodex recommends at least 5 so you still have fallback points if one point is not clearly visible.
• Your GCPs are distributed with at least 10 m between them where the site layout allows it.
• If you want to capture GCPs directly for a scan before upload, the connected device uses a Mapping Pro license.

Step-by-step instructions

1. Understand the three available GCP workflows

1. Open the project in Sodex Mobile where you want to work with Ground Control Points.
2. Decide whether you want to capture GCPs for one scan, reuse an existing point layer for a scan upload, or use a point layer as the default project GCP set.
3. Use the overview below to choose the workflow that matches your field task.

Expected result: You know which GCP workflow fits your current job before you start capturing or uploading data.

2. Workflow overview: Capture GCPs directly after a scan

Use this workflow when you create an SDX-PocketScan scan and then capture the Ground Control Points specifically for that scan before upload. When this option is selected, the app starts background processing without uploading immediately, keeps the scan in an intermediate state where GCPs are still missing, and blocks upload until the required GCPs are available.

When you scan a site that will use GCPs, pass over each GCP 2–3 times during capture so the marker is clearly visible in the scan data.

3. Workflow overview: Reuse an existing point layer for a scan upload

Use this workflow when your Ground Control Points were already measured and stored as points in a layer. During scan upload, you can select those existing points as the GCP source for the scan instead of measuring them again immediately after capture.

4. Workflow overview: Use a point layer as the default project GCP set

Use this workflow when you want to build a reusable project-level Ground Control Point setup. In this case, a point layer is used as the project's default GCP source so it can support future SDX-PocketScan scans or drone flights in the same project.

5. Prepare the hardware and layer setup before any GCP workflow

1. Mount the SDX-Pole Antenna on a compatible pole with a 5/8-inch thread.
2. Turn on the SDX-PocketScan receiver.
3. Unplug the external GPS antenna if it is still connected.
4. Insert the powered-on SDX-PocketScan receiver into the SDX-Pole Antenna.
5. Open the correct project in Sodex Mobile.
6. Make sure the required point layer already exists if you plan to reuse measured points, or create the layer you want to use for capture.
7. Complete tilt compensation before you capture points with the pole workflow.

Expected result: Your hardware setup is ready and you can continue with the workflow that matches your use case.

Bright or glowing GCPs in outdoor capture

In some outdoor capture conditions, Ground Control Points and road markings can look unusually bright or glowing in the captured images. This usually happens when strong sunlight comes from behind you or slightly above you during scanning.

This is a light reflection effect in the camera image. It does not by itself mean that scan photogrammetry processing will fail.

There is no app setting to remove this during capture. If this appears regularly in your outdoor work, a clip-on lens hood can help reduce the effecte if you experience problems during photogrammetry processing.

Limits and notes

• At least 3 GCPs are required for successful processing.
• Sodex recommends using at least 5 GCPs so you have fallback points if one point is not clearly visible.
• For larger areas, you may need more GCPs, sometimes up to 10.
• Distribute GCPs at least 10 m away from each other where site conditions allow.
• If GCPs are applied to a scan, each GCP should be scanned 2–3 times by swiping over it during capture.
• If a previously captured point is reused as a GCP, the physical marker must not have moved since the point was measured.
• GCPs are organized in layers in the current mobile workflow.
• This article is an overview page and does not replace the detailed workflow-specific instructions.

Related articles

• Connect to the SDX-Pole Antenna in Sodex Mobile
• Create a survey in Sodex Mobile
• Ground Control Points in SDX-Cloud
• Introduction to Ground Control Points
• Setup Ground Control Points to enhance your project's accuracy