Surveying with the Leica Total Station (TCR1105)

Surveying with the Leica Total Station (TCR1105)

Total stations are electronic optical distance-measuring instruments used in modern land surveying to record topographic and man made features (they are also sometimes used by other interest groups such as archaeologists, engineers and others). Total stations have evolved from theodolites (precision instruments for measuring angles in horizontal and vertical planes) and in one-sense can still be considered as an electronic theodolite integrated with a distance meter in order to calculate slope and distances to particular points and capable of diverse mapping and spatial position measuring tasks.

Total stations combine a number of technologies to achieve remarkable accuracy and reliability.  The first, an extension of traditional transits and theodolites, is the ability to register very fine angular divisions. The error of radial measurements increases with distance from the measuring device. The angular precision for common theodolite instruments ranges from 20 seconds of arc to less than 1 second of arc.

Surveying with the Leica Total Station (TCR1105)To provide some idea of how well positional accuracy is conserved over distance with these levels of angular precision, a rule of thumb is that 1 second of arc is about 1 cm error over a 2000 m distance, so the maximum angular error of a 1 second of arc Total station would be 1 cm when measuring a point that is 2 km away from the instrument. A 10 second of arc instrument would achieve the same accuracy at a distance of 200 m. Therefore total stations increase the range of a survey while maintaining precise positional accuracies.

The second, more novel aspect of total stations is that they measure the distance to the target point with an infrared laser emitted by an EDM (electronic distance measuring device) and reflected back with a prism held vertically above the actual point of interest. The actual accuracy is determined by the wavelength of the infrared light used, and errors can range from as little as 1 mm plus 1 ppm to around 5 mm plus 5 ppm. Thus, at 2,000 m, a distance error would vary from 3 mm to 15 mm over this range of accuracies. The total distance that the EDM can measure depends on a number of variables, including atmospheric conditions, quality of the EDM, and the number of prism reflectors used as targets over top of the destination points.

Total stations produce the same basic spherical measures as optical survey instruments; horizontal and vertical angles and a radial distance measure. Total stations differ, however, by collecting additional data and then calculating additional measurements. Most importantly, most total stations are capable of simultaneous trigonometric conversion of spherical survey coordinates to Cartesian orthogonal spatial measurements (usually east, north, and altitude). The coordinates of the setup position of the total station can also be inputted by the user (or found within a data register) and consistently offset from the measured points. This allows all measurements to be taken with reference to a single datum, eliminating the need to manually adjust the data from different local datums to the overall site grid.Surveying with the Leica Total Station (TCR1105)

Computational abilities go far beyond simple transformations, and most total stations carry a number of useful other programs in their memory for various other survey techniques. For instance, with the free station function, a total station can be setup over top of an unknown point and it can calculate the current unknown position after several measurements are recorded to a couple of known points.

Some newer models of total stations now even have GNSS (Global Navigation Satellite System) interfaces built into them that allow precise measurements without virtually having to know the coordinates of any known points. The GNSS / total station combination allow the device to calculate the location of the instrument with GPS satellites and then use that spatial information along with the total station tools to measure and calculate spatially referenced values for the other unknown points.

The Leica TPS1100 Professional Series was designed to provide practical solutions to make surveying processes simple, efficient and productive. They include a wide variety of practical, automated functions to achieve the highest degree of efficiency within the shortest period.

This document features the Leica total station model TCR1105 and was created to provide a brief overview of the survey instrument as well as provide important operational instructions for some of its basic functionality and practical uses. Some of the sections will provide step by step instructions through all the necessary actions to get certain tasks completed and some of the other sections will be slightly broader and intended for more informational purposes. For some of the other tasks that total stations can be used for we recommend that you refer to the brief instrument user guide or the manufacturer’s web site.

Surveying with the Leica Total Station - equipment

Equipment

Included with the TCR1105 unit are several pieces of hardware used in the calibration, set up and maintenance of the Total Station device (note: various TCR1105 units or other total station models may not have the exact items that we have shown below).Surveying with the Leica Total Station - equipment

The contents in our TCR1105 case are displayed in the photo above, clockwise starting with top left corner are; basic user manual, TCR1105 total station unit and 2 batteries, target plate, computer serial cable, flash card, car charger, AC power cord, battery charger, lens cover, weather cover, height meter (measuring tape and customized plastic hook), and various allen hex keys.

Other equipment used in the operation of the unit are displayed in the photo on the left and include a survey grade tripod, reflective survey prisms and aluminum poles with height measurement labelled and built in level bubbles to mount the prisms onto. The reflective survey prisms can also be used with survey grade tripods (shown below) when mounted on tribrachs.


Click here for more information from surveying with the Leica Total Station (TCR1105) or refer to our Leica Total Station user guide available for download.