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TruPulse® 360: Ensuring Quality GPS Laser Offsets

 

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A customer exploring current technology for GIS data capture was interested in using a TruPulse 360 combined with GPS. They wanted to know how the procedure worked, what kind of accuracy they could achieve and if there was any increase in efficiency in the field. This paper will describe what the results were in each of these areas of performing Laser Offsets with a GPS for feature location.

The Site

A test course was set up in a local park consisting of 21 features scattered about a parking area of ~ 5 acres (Figure 1). They ranged from sewer & water objects flush to the ground to trees, light poles and signage. The ground was relatively flat with a few small swales for drainage. The 21 objects were surveyed in with an optical total station creating a set of known coordinates to compare the laser data to. It is assumed these points are within 1” relative accuracy.

 

The Work Flow

A Laser Offset is a mapping technique whereby one occupies a single position with a GPS and derives a coordinate for that spot. Then Distance, Inclination and Azimuth are measured to a remote feature with the TruPulse 360 by sighting on the object and firing the system. This data is then applied to the GPS position, the coordinates of the remote feature are calculated and it is placed on the map. Thus, from a single location, all features that are in view can be mapped by simply measuring to them with the laser. Some important tips for field procedure with the TruPulse 360 were used on this test and are as follows:

 

 

 

 

 

 

 

 

 

The Results

The table below shows the distance away each feature was from the measurement point and the amount its position varied from the control data measured with the total station.

 

 

Observations

Conclusions

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