How accurate is the tilted measurement taken with Trimble R12i?

GNSS tilted measurement has introduced the possibility of performing topographic surveys very productively. However, not all users of this technology seem to trust this feature, so it is important to delve into the accuracies that Trimble R12i achieves using this technique.

 

SELECTED SCENARIO

An infrastructure scenario is chosen for the topographic representation. The objective is to achieve a digital model, understanding that GNSS offers a discrete methodology for coordinate determination.

 

Fig 1. Selected scenario

 

The survey is developed representing the breaklines of the different elements that make up this infrastructure work.

 

Fig 2. Topographic survey

 

Fig 3. Topographic survey

DIGITAL MODEL

A digital model is developed through triangulation using the different points along with the breaklines for correct triangle orientation:

Fig 4. Digital model

 

TOPOGRAPHIC SURVEY ANALYSIS

Basically, a topographic representation was made using breaklines. The elements at ground level were surveyed conventionally, however, the highest part was established productively by conveniently inclining the pole.

 

Fig 5. Topographic representation

 

In the following graph, it is possible to analyze the influence of tilt on the precision of coordinate determination. The abscissa axis shows the different points ordered according to their tilt, expressed on the right ordinate axis. As can be seen, the points are ordered according to their tilt (gray points), which are grouped into two sets. The first points have less than 10° of tilt, which indicates that they were practically determined with the pole vertical, while the second set shows points whose tilt is above 50°.

In the first group of points, it can be seen that the vertical accuracy (orange points) is approximately double the horizontal accuracy. On the other hand, for points determined with a tilt greater than 50°, the horizontal and vertical accuracies are equalized to a value close to 3 cm.

 

 Fig 6. Influence of tilt on the accuracy of coordinate determination

 

Conclusions

Tilted measurement allows for the determination of positions with a topographic grade, being fully compatible with a series of activities that benefit in terms of productivity and safety from the use of this technique.

 

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