**Leica TDA5000 - Short Range Performance Tests**

**using Corner Cube and Tooling Ball Reflectors**

*Reinhard Gottwald, Ivan Müller, Michaela Obrist*

*FHBB Basel Institute of Technology, Switzerland*

*Dept. of Surveying & Geoinformation Systems*

**1. INTRODUCTION**

In Fall 1996 Leica Inc. introduced the successor to the famous
T2000/TC2002 instruments family - the TPS5000. Today the following high
precision instruments are available :

\- TM5000 Motorized Theodolite

\- TDM5000 Motorized Total-Station

\- TDA5000 Motorized Total-Station with *A*utomated *T*arget
*R*ecognition System

> (ATR)

\- TM5100 Motorized Theodolite with panfocal telescope (T3000)

The most important specifications are \[ 5 \] :

![](media/image1.emf){width="2.252083333333333in"
height="2.859722222222222in"}*Angle Measurements*

Standard deviation according

to DIN 18723 (HZ & V) 0.2 mgon

*Drives*

motorized, positioning

accuracy (HZ & V) 0.2 mgon

*Range-Finder* *(EDM)*

Standard deviation 1 mm + 2ppm

*Special Axyz-communication interface*

Fig.1 Leica TDA5000

This paper summarizes the results of EDM and ATR test measurements using
a variety of special Leica glass reflectors within a distance range of
up to 40 m. The following types of reflectors were used :

Table 1 Type of Glass Reflector Prisms used for the test Measurements

  ----------------------------------------- ------------------ -----------------------------
  **Reflector**                             **Abbreviation**   

  Leica standard geodesy prism                                 GPR1

  1.5\" Corner Cube Reflector                                  TBCC15

  0.5\" Tooling Ball Corner Cube Reflector                     TBCC05

  0.5\" Tooling Ball Prism Reflector                           TBPR05
  ----------------------------------------- ------------------ -----------------------------

![](media/image2.emf){width="1.101388888888889in"
height="1.3395833333333333in"}

![](media/image3.emf){width="1.1305555555555555in"
height="1.3298611111111112in"}

Fig. 2 1.5\" Corner Cube 0.5\" Tooling Ball 0.5\" Tooling Ball

Reflector Corner Cube Refl. Prism Reflector

TBCC15 TBCC05 TBPR05

Additional tests with different types of retro tape targets have also
been performed, but are not finished yet \[ 4 \]. These results will be
published in the German Surveying Magazine 'AVN' in early 1998.

**2. Range finder (EDM)**

Most of the Measurements were performed with two TDA5000 instruments
(No. 437735/FHBB and No. 437742/Leica PMU). Due to the results of the
integral short range performance test (see 2.3) additional measurements
were made with a TDM5000 (No. 437722/Leica PMU).

2.1 Shortest measuring Distance

Table 2 Shortest measuring distance

  ----------------------------------------- -----------------------------
  **Reflector**                             **Shortest measuring distance
                                            \[m\]**

  GPR1                                      \~0.9

  TBCC15                                    \~0.9

  TBCC05                                    \~6.0

  TBPR05                                    \~4.0
  ----------------------------------------- -----------------------------

2.2 Offset Correction

This correction was determined by using a 'Rüeger'-type of calibration
baseline with unknown distances. The 5 baseline-points were marked with
Kern forced centering tripods.

Fig.3 Configuration of the Rüeger-type calibration baseline

Table 3 Offset Correction c

  ------------ -------- ------------ ------------ -- ------------ ---------------- --
                        **Offset                                                   
                        Correction                                                 
                        c**                                                        

  Instrument            GPR1         TBCC15          TBCC05       TBPR05           

  Type         No.      \[mm\]       \[mm\]          \[mm\]       \[mm\]           

  TDA5000      437735   -0.46 ± 0.08 +33.81 ±        +33.92 ±     +28.98 ± 0.30    
                                     0.12            0.16                          

  TDA5000      437742   -0.07 ± 0.10 +34.30 ±        not determ.  +28.57 ± 0.30    
                                     0.11                                          
  ------------ -------- ------------ ------------ -- ------------ ---------------- --

2.3 Integral Short Range Test

These test measurements were carried out on the Interferometer Baseline
at Basel Institute of Technology.

![](media/image5.emf)

Fig. 4 Interferometer Baseline (Configuration: \'Absolute Distance
Comparison\')

The reflector of the Interferometer-System (hp5526a) and the reflector
of the EDM are mounted on a sliding carriage with a cogged belt drive
and a microcomputer controlled step-motor device. To carry out an
absolute distance comparison between the interferometer and the EDM, the
distance from the vertical axis of the EDM and the interferometer
reference point is known to about 0.02 mm. The whole setup is described
more in detail in \[ 1 \].

![](media/image6.emf){width="5.967361111111111in"
height="3.0909722222222222in"}

Fig. 5 Part-sectional view of the Interferometer Baseline

The following diagrams show typical results (differences between the
nominal values (interferometer) and the actual EDM-values) of the
baseline measurements :

![](media/image7.emf)

Fig. 6.1 Close Range Performance - GPR1

The scattering of the differences \'Nominal - Actual Values\' is more or
less accidental. The maximum scattering amplitude is approximately ± 0.3
mm. All tested instruments are performing within the manufacturers
sepcifications.

![](media/image8.emf)

Fig. 6.2 Close Range Performance - TBCC15

*TDA5000* Both tested instruments show a typical cyclical behavior. The
maximum amplitude is approximately ± 0.4 mm, the length of a cycle
period is 3 m (EDM modulation frequency: 50 MHz).

*TDM5000* There is no significant change in behavior compared with the
GPR1 measurements.

![](media/image9.emf)

Fig. 6.3 Close Range Performance - TBCC05

*TDA5000* This test was performed only with instrument No. 437735. It
shows a significant cyclic behavior. The oscillation is decadent. The
amplitude is decreasing (1. Cycle: 6 mm, 2. Cycle 3 mm, 3. Cycle 1.6
mm).

*TDM5000* Up to 10 m measuring distance there seems to be also a cyclic
behavior. The maximum amplitude of the oscillation is approximately 1
mm.

![](media/image10.emf)

Fig. 6.4 Close Range Performance - TBPR05

*TDA5000* Both tested instruments show a significant cyclic behavior.
Both oscillations have the same phase relationship. The oscillation is
decadent. The amplitude is decreasing :

No. 437735 No. 437742

1\. Cycle 6.0 mm 4.0 mm

2\. Cycle 2.5 mm 1.6 mm

3\. Cycle 1.1 mm 0.5 mm

*TDM5000* There is no significant cyclic behavior. The maximum
differences according to the interferometer are ± 0.5 mm.

*Attempt at an explanation*

It is well known that interferences between the transmitting and the
receiving signal on the one hand and the use of peripheral rays on the
other hand may cause cyclic errors. The manufacturers of EDM are
reducing or eliminating these effects by constructive (optical) and/or
electronical countermeasures.

Fig. 7 Front lens area of the TDA5000 telescope. (Left: Dimensions,
Right : during a

> distance measurement)

A main difference in the optical system of the TDM5000 and the TDA5000
is the integrated ATR optics (see Fig. 7, left). The diameter of the ATR
front lens is approximately 8 mm. The EDM transmitting signal is located
slightly eccentric (left telescope side, face 1; see Fig. 7, right). The
center of the EDM signal is covered by the ATR optics.

> \- There might be a possibility of signal reflections at the ATR
> optics. This might cause interferences between the transmitting and
> the receiving signal
>
> \- The diameter of the TBCC05 and TBPR05 prism is 8 mm
>
> \- Measurements to the TBCC05 and TBPR05 prism have to be made in the
> \'Reflex Tape Mode\' with a high intensity of the transmitting signal.
> This might cause problems in the signal adjustment of the receiving
> signal (boomerang effect ?)

*Recommendation*

\- Avoid using 0.5\" Reflectors for precise distance measurements

\- If you need to use 0.5\" reflectors, avoid distances below 15 m

\- Take into account, that the accuracy of your measurements is reduced

**3. Automated Target Recognition System (ATR)**

The Automated Target Recognition System (ATR) enables an automated
acquisition of reflective targets (glass prism). Therefore an infrared
beam (IR laser diode) is emitted through a special coaxial optical
system (see Fig. 7). If there is a reflective target within the ATR
field of view, the signal is reflected back to the telescope. The
reflected signal is projected on to a CCD camera which is built into the
telescope. Using image processing algorithms, the instrument is moved to
a nearly correct position. Vertical and horizontal offsets between the
line of sight and the center of gravity of the reflected light are
calculated and taken into account to obtain the correct horizontal and
vertical angle measurements. A detailed description of the functionality
and the performance of the ATR is given in \[ 2 \] and \[ 6 \].

3.1 Shortest measuring distance

Depending on the type of Reflector the ATR is operational down to
distances between 2.8 m (GPR 1) and 4.0 m (TBCC05). Due to the results
of the repeatability tests (see 3.3), the ATR should not be used on
distances beyond 5.0 m.

3.2 Reflector Alignment

The tests were carried out for an object distance of 10 m. Based on
these test results (see Fig. 8), we recommend aligning the reflector
better than ±15° to the line of sight of the ATR.

3.3 Repeatability

These tests were carried out for a distance range between 3.0 m and 40 m
either with \'manual\' pointing or \'automated\' pointing using the ATR.

![](media/image12.emf)

Fig. 8 ATR / Reflector Alignment

Fig. 9 Absolute transversal Deviation (\'manual\' pointing versus ATR)

**4. Conclusion**

The TDA5000 is a highly accurate measuring system. The manufacturers
specifications (EDM, ATR) could be proved within the tested distance
range for the standard geodesy triple-prism GPR1.

The 1.5\" Corner Cube Tooling Ball reflector (TBCC15) can be used
without a major loss of accuracy. 0.5\" Tooling Ball Reflectors (TBCC05,
TBPR05) cause a significant cyclic error (EDM). They should not be used
for accurate measurements and not below an object distance of about 15
m.

The ATR system performs well independently of the type of glass
reflector. It should not be used below an object distance of 5 m.

**5. REFERENCES**

\[ 1 \] R. Gottwald, *Das Messlabor der Abteilung Vermessungswesen an
der Ingenieurschule beider Basel -* *Ein Ausbildungsprojekt*, Vermessung
Photogrammetrie Kulturtechnik (93) 11/95, pp. 670 - 674

\[ 2 \] R. Haag, G. Bayer, M. Zimmermann, R. Scherrer, *Vermessen mit
der automatischen Feinzielung des* *TCA1800 von Leica*, Vermessung
Photogrammetrie Kulturtechnik (95) 7/97, pp. 466 - 471

\[ 3 \] I. Müller, M. Obrist, *TDA5000 - Untersuchung der Automatischen
Zielerfassung und des* *elektronischen* *Distanzmessers im Nahbereich*.
FHBB semester project work 1997 (unpublished)

\[ 4 \] I. Müller, M. Obrist, *Leica Axyz-STM mit TDA5000 im
verfahrenstechnischen Anlagenbau,* FHBB Dissertation 1997 (in
preparation, unpublished)

\[ 5 \] Leica. *T3000/T3000A/TM5000/TDM5000 Precision electronic
theodolites*. Leica leaflet U1-300-0EN - VIII.96

\[ 6 \] Leica. *TPS1000 Total Stations - Automated Target Recognition
ATR1, Performance and Calibration,* Leica Product Information
(Preliminary Version 2.20) 02/97