Question: How can I maintain high-accuracy positioning abilities in RTK-denied locations?
Answer: Traverse into the RTK-denied area with a GNSS receiver, TruPulse® rangefinder, and MapStar® TruAngle® II to position assets via Laser GIS®.
LaserGIS System with a Trimble receiver, TruPulse 200i laser rangefinder, MapStar TruAngle II encoder, and a tablet.
Our traverse workflow helps you easily position hard-to-reach assets, often located in tight urban alleys, parking garages, or underneath a dense canopy. The hardware involved allows you to overcome RTK signal issues while achieving better accuracy than GNSS alone could offer. After starting with a known azimuth derived from GNSS or other control points, the MapStar TruAngle’s turned angles provide azimuth measurements with ±0.1° accuracy. TruPulse rangefinders capture distance measurements with accuracy up to ±4 cm (1.6 in).
This modular workflow uses the LaserSoft® MapSmart® app to integrate any brand of GNSS receiver. Collect only the points you need to map, add attribute data, and export ready-to-use files right from your tablet or mobile device. If you’d like to add this workflow to your app, our SDK for the TruPulse lasers and TruAngle II allows for easy integration.
Below is a step-by-step breakdown of how it’s done. After that, you can find an instructional video and typical accuracy data. First, let’s get familiar with some key terms that help describe the process.
Hidden Asset: Any object or specific point that needs to be positioned within an RTK-denied environment. Some common examples include gas or water meters, valve markers, and other access points or property indicators.
Backsight Point (BP): Your first location. This requires a GNSS signal and a clear line of sight to your Occupy Point.
Occupy Point (OP): Your second location. This requires a GNSS signal and a clear line of sight to your Backsight Point and nearby hidden assets.
Control Point (CP): Any additional location, often within the RTK-denied environment, with a clear line-of-sight to your previously used location and nearby hidden assets. A GNSS signal is not required.
CP1 requires a clear line of sight back to your OP. CP2 requires a clear line of sight back to CP1. CP3 requires a clear line of sight back to CP2, and so on.
LaserGIS® System (LGIS): The mapping bundle used for this method, which includes a GNSS receiver, a TruPulse rangefinder, a MapStar TruAngle II encoder, and the LaserSoft MapSmart app for data collection. Typically, users mount their hardware onto a survey pole.
Before you get started, measure instrument heights for your GNSS receiver and TruPulse rangefinder. Log the values in your data collection app or mapping program.
1) Occupy a convenient Backsight Point (BP) and log its position with your GNSS receiver. You might want to use a specific object, like a sign or post. If nothing is available, station a reflective target at the BP before moving to your Occupy Point (OP).
2) Station your LaserGIS System (LGIS) at the OP and log its position with your GNSS Receiver. The workflow captures a Reference Azimuth between your OP and the BP.
3) Use your TruPulse rangefinder to put the BP target into your rangefinder’s crosshairs. Fire the LGIS to align it with the Reference Azimuth.
You can now use your rangefinder to collect coordinate data for hidden assets within sight of your OP. Keep your LGIS steadily stationed at the OP, sight in on a hidden asset, press the fire button, and repeat as needed. Asset locations will populate your map file as a new point each time you press the fire button.
4) If you have more hidden assets to map, station a reflective target at your first Control Point (CP1). Keep your LGIS stationed at the OP and aim ahead to CP1. Put the reflective target into your rangefinder’s crosshairs and press the fire button to log CP1 on your map file.
5) Station a reflective target at your OP and move your LGIS to CP1. Aim back at the OP, put the reflective target into your rangefinder’s crosshairs, and zero your encoder. This establishes a new reference azimuth.
6) Use your rangefinder to collect coordinate data for hidden assets within sight of CP1.
7) If you have more hidden assets to map, station a reflective target at your second Control Point (CP2). Keep your LGIS stationed at CP1, aim ahead to CP2, put the reflective target into your rangefinder’s crosshairs, and fire to log CP2 on your map file.
8) Station a reflective target at CP1 and move your LGIS to CP2. Aim back at CP1, put the reflective target into your rangefinder’s crosshairs, and zero your encoder. This establishes a new reference azimuth.
9) Use your rangefinder to collect coordinate data for hidden assets within sight of CP2.
Continue traversing with additional control points until all hidden assets in the RTK-denied area have been positioned onto your map file.
The video below breaks down each step with visuals that complement your understanding of the workflow. Our LaserSoft MapSmart app is the featured data collection software. Please reach out if you want our Traverse Workflow added to your app. Contact info@lasertech.com to receive our SDK.
The typical accuracy for this workflow depends on your hardware and the distances between your LaserGIS Traverse System and each asset. Here are the typical accuracies to expect when using current hardware:
LaserGIS System Hardware: TruPulse 200x laser rangefinder and MapStar TruAngle II angle encoder
Typical Accuracy: 4cm/2in to targets at a 50m/150ft distance 8cm/3in accuracy to targets at a 100m/300ft distance
LaserGIS Traverse System Hardware: TruPulse 200i or 360i and MapStar TruAngle II
Typical Accuracy: 8cm/3in to targets at a 50m/150ft distance 15cm/6in accuracy to targets at a 100m/300ft distance
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