Pipeline Survey from the Ground with RTK

Cities across China are replacing aging gas pipelines, and the work has created a large volume of outdoor inspection and as-built survey tasks. The renovated lines are different from the buried pipes they replace. Most are risers and overhead runs fixed along building walls in residential areas and industrial parks, surrounded by tall buildings and trees. Every elbow and joint needs a reliable coordinate, because deformation or displacement that goes unrecorded becomes a safety risk over time. This article looks at how two CHC Navigation receivers, the CHCNAV i85 and the CHCNAV ViLi i100, let a crew complete a pipeline survey from the ground.

Elevated gas pipelines mounted on a building wall — The surveying site features gas pipelines running along a building wall, with elevated elbows and joints that require ground-based surveying.

Why Above-Ground Pipelines Are Hard to Survey

A conventional pipeline survey places a pole on each point. That works for a valve at ground level and fails for a pipe several meters up a wall. Three problems come up on almost every site:

Height. Elbows and joints on overhead runs are out of reach. Measuring them directly means carrying and climbing a ladder again and again, which is tiring and exposes the crew to falls.
Signal blockage. Pipes are fixed close to walls, so the point to be measured sits where tall buildings block the sky. An RTK receiver placed there struggles to hold a fixed solution, and coordinates can jump.
Access. Some pipes cross planted strips and green belts. Walking in to place a pole damages the planting.

For the organization that manages the network, the coordinates are the product. Inspection records, hazard follow-up and renovation sign-off all depend on them being accurate.

Laser Measurement with the i85: Aim, Do Not Climb

The i85 carries a laser rangefinder alongside its GNSS and IMU sensors. The operator stands in a safe position, aims at the pipe elbow and records the point without touching it. The laser rangefinder measures distances of up to 150 meters, with accuracy of up to 3 cm at 5 meters, supported by IMU compensation.

This changes where the receiver has to be. It can stay in a spot with a better view of the sky while the laser reaches the point beside the wall, so the obstructed position is measured without standing in it. The same applies to pipes inside green belts, which are measured from the path.

Surveyor using an i85 receiver to survey elevated gas pipelines from the ground. — A surveyor uses the CHCNAV i85 Laser IMU-RTK GNSS receiver to measure pipeline points from different ground positions, whether targeting elevated points with a laser or surveying across vegetation around buildings, without needing to access the pipeline directly.

Vi-LiDAR on the ViLi i100: Photograph, Then Pick the Points

The ViLi i100 takes a different route to the same goal. Its Vi-LiDAR contactless survey function works much like taking a photo with a phone: the operator photographs the pipe, then selects the points to measure on the image. Several points can be picked from a single photo, and their 3D coordinates are returned together, which suits a run of pipe with many fittings close to one another.

The ViLi i100 is also built for the narrow gaps between buildings where satellite positioning is weakest. The SFix 2.0 engine delivers positioning accuracy of 5 cm within 20 meters in GNSS-denied areas, supported by a LiDAR sensor capable of capturing 860,000 points per second. A surveyor can walk from an open area into a tight passage and keep measuring.

A Pipeline Survey in Three Steps

Step	What the crew does
1. Prepare	Power on in an open area and initialize RTK.
2. Measure	With the i85, aim the laser at the pipe point and record it. With the ViLi i100, photograph the pipe and pick the points on the image.
3. Export	Export the data in a standard format from the LandStar field software and load it into the pipeline GIS.

Once in the GIS, the same coordinates serve three jobs: updating routine inspection records, tracking hazards through to rectification, and verifying as-built results after renovation.

Choosing Between the Two Methods

Situation on site	Better fit	Why
Single points high on a wall or across a green belt	i85, laser measurement	One aim and one reading per point, from a distance
A run of pipe with many fittings close together	ViLi i100, Vi-LiDAR	Several points picked from one photo
Narrow gaps between buildings with little sky view	ViLi i100, SFix 2.0	Positioning is held where satellite signals are blocked

Beyond Gas Pipelines

Nothing in this workflow is specific to gas. The same ground-based approach applies wherever pipes and conduits run above ground or close to buildings: electrical conduit routes, municipal networks, and pipelines inside campuses and industrial plants. In each case the crew stays on the ground, the points are measured without contact, and the results go straight into the asset records.

If you are deciding which receiver suits your sites, our guide to choosing a GNSS receiver for your survey site compares the range by working conditions, and our surveying and engineering solutions page covers the wider equipment set.

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About CHC Navigation

CHC Navigation (CHCNAV) develops advanced mapping, navigation, and positioning solutions designed to increase productivity and efficiency. Serving industries such as geospatial, agriculture, machine control and autonomy, CHCNAV delivers innovative technologies that empower professionals and drive industry advancement. With a global presence spanning over 140 countries and a team of more than 2,200 professionals, CHC Navigation is recognized as a leader in the geospatial industry and beyond. For more information about CHC Navigation [300627.SZ], please visit: https://geospatial.chcnav.com/about/overview

Surveying Elevated Gas Pipelines from the Ground