TPS1100 Professional Series

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TPS1100 Professional Series
A New Generation of Total Stations from Leica Geosystems
Karl Zeiske
May 1999
L
MADE TO MEASURE
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Summary
This report describes the main components of the
new generation of total stations, a further development
of the successful TPS System 1000 series. The
angle-measuring system, the measurement of distance
without the use of a reflector, the automatic
target recognition and the flexible coding are all dealt
with in detail.
The application of new technologies and the implementation
of the wishes of customers across the
globe have led to appreciable improvements in the
operating concept and in the functionality. The resulting
expansion of the range of applications, and the
simplification of procedures, have made it possible to
improve productivity substantially.
1. Overview
The new generation of total stations has been developed
from the successful TPS System 1000 series,
from which it has adopted the most successful features.
Much has been improved, and the functionality
expanded, on the basis of input from customers all
over the world. As a result of new technologies, the
instruments have become smaller and lighter and the
measuring procedures have been accelerated.
The existing operating concept, involving the large
eight-line display and the clear, systematically-arranged
keyboard, has been retained. Years of experience
with the TPS1000 instruments have enabled the
user guidance and the operation to be clarified and
simplified yet further.
Fig 1: Motorized total station with automatic target
recognition and EGL electronic guide light
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The improved automatic target recognition system
allows higher-speed tracking than was possible with
the TPS1000 instruments.
For the first time, an electronic total station includes
not only the established infrared distancer which
measures to prisms and reflector tapes, but also a
distancer for reflectorless measurement and in which
the emitter projects a visible laser beam.
Other new features are the use of camcorder batteries
as the power supply, the endless fine drives even with
the instrument models which are not motorized, and
the laser plummet permanently in the vertical axis as
a standard feature. The spot brightness of this laser
plummet is adjustable, so that the instrument can be
set up over the ground point quickly and conveniently,
irrespective of the ambient conditions.
Many versions of the instrument are available. The
user can choose the most appropriate of them:
TC….. Classical total station
TCM….. Motorized total station
TCR….. Total station with reflectorless
distancer
TCRM….. Motorized total station with
reflectorless distancer
TCA….. Motorized total station with automatic
target recognition
Each of these versions is produced at four different
levels of accuracy (angle-measuring accuracy in
accordance with DIN 18723 and ISO 12857).
Type 1101 1.5” , 0.5 mgon
Type 1102 2” , 0.6 mgon
Type 1103 3” , 1.0 mgon
Type 1105 5” , 1.5 mgon

2. Measuring angles
In the static, absolute circle-scanning system used,
the coded graduations of a glass circle are read
optoelectronically (fig. 2).
Fig. 2: The circle-scanning principle
Unlike most absolute angle-measuring systems on
the market, where the position has to be decoded
from several parallel tracks, the circle carries only one
graduation track, the code of which continually alters
and contains all of the positional information. This
code is read by means of a linear CCD array and an 8bit
A/D converter, and supplies the approximate
position with an accuracy of around 0.3 gon.
Determining the positions of the centres of the individual
code lines on the array, and then using an
appropriate algorithm to find the mean, produces the
fine measurement. A minimum of ten code lines must
be captured in order to determine the position. In
general, however, a single measurement involves
around 60 code lines, improving the interpolation
accuracy, the redundancy and the reproducibility. The
principle of this angle-measuring system is applied to
all Leica theodolites and total stations.
The value measured for the horizontal direction is
corrected before being displayed or recorded. The
correction is calculated from the following parameters,
as a function of the vertical angle measured:
- the latest collimation error and tilting-axis error to
be determined and stored in the instrument
- the momentary component of the vertical-axis tilt,
transverse to the line of sight.
The vertical angle is corrected by the amount of the
stored index error and by the component of the
vertical-axis tilt in the direction of the line of sight. A
tilt sensor monitors both components of the verticalaxis
tilt. Fig. 3 shows the principle of a tilt sensor, in
which a liquid mirror forms the reference horizon.
1 - Reticle on prism
2 - Oil surface
3 - Deviating prism
4 - Imaging lens
Fig. 3: Tilt sensor
5 - Image of the reticle
6 - CCD linear array
7 - Illuminator (LED)
The reticle (1) located on the prism is illuminated (7),
and is imaged (5) on the linear CCD array (6) by way
of the imaging lens (4) after double reflection at the
liquid surface (2). The triangular line pattern of the
reticle makes it possible to capture both tilt components
by means of just one unidimensional receiver.
Longitudinal tilt alters the spacing between the differently-oriented
lines; transverse tilt shifts the centre of
the entire line pattern along the CCD array.
This arrangement enables the tilt sensor to be made
so small that ideally it could be placed centrally over
the vertical axis. The liquid mirror would then be
displaced from its horizontal position only very
slightly, even during rapid rotation of the alidade.
Also, the tilt measurement can no longer be affected
by other factors such as the temperature-related
deformation of the theodolite standard.
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3. Measuring Distance
Two coaxially-measuring distancers are incorporated
into the TCR instruments (fig. 4). Both distancers
operate on the well-known phase measurement
principle.
The infrared laser beam for measuring distances to
prisms and reflector tapes has a wavelength of
780nm, a range of 3000 metres with a single prism,
and an accuracy of 2mm + 2ppm. The visible red laser
beam has a wavelength of 670nm and measures
distances of up to 80 metres with an accuracy of 3mm
+ 2ppm without using a reflector.
Fig. 4: Optical design of a total station measuring without reflector
The unambiguity of the distance measurement up to
12km is assured by a special frequency system. Its
base is a frequency of 100MHz, corresponding to a
measuring scale of 1.5m.
The “Long Range“ measuring mode can be engaged
for long distances. With it, the red laser beam can
also be used to measure to prisms at a distance of
between 1000 metres and 5000 metres.
A keystroke will switch between the two distancers
immediately and at any time. The correct zero-point
correction (additive constant) is set automatically.
This combination of two distancers in a single total
station, achieved now for the first time, offers great
advantages where the points to be measured are
4
Reflector, target
Laser for
reflectorless
measurement
Laser for
reflectorsupported
measurement
accessible only with difficulty or not at all, for example
on frontages, during control measurements on
steel constructions, and in determining lengths of
conduits. The visible red laser beam can also be
switched on permanently for marking target points,
e.g. for profile surveys in tunnels or for indoor surveys.
At a distance of 50 metres the laser dot has a
size of approximately 1cm x 2cm.
Receiver
diode
Motor
Graded filter / internal light path
Telescope of total station

4. Automatic target recognition
4.1 The Principle
Automatic target recognition (ATR) is incorporated
into the telescope in the same manner as is the EDM.
An infrared laser beam is projected coaxially into the
telescope axis by means of optical components and
emerges from the main objective. A beam splitter
separates the reflected beam of the ATR from the
EDM beam and from the visible light, and guides it to
the receiver (the video sensor).
Special hardware adds the intensities of the elements
of the video sensor in rows and in columns, resulting
in two “projections”. The centres of these are determined
by a processor and are then transformed into a
horizontal and a vertical angle of correction with
regard to the visual line of sight. These angle corrections
are used to correct the values relating to the
visual line of sight, as measured by the circle-scanning
system.
4.2 Fine pointing
Three sequentially-running processes characterize the
fine pointing: the search process, the targeting process
and the measuring process.
After the coarse manual pointing of a prism, the fine
pointing with the help of ATR is completely automatic.
ATR first checks whether the coarsely-targeted
prism is located within the field of view of the telescope.
If it cannot detect the prism, it commences a
search procedure involving a continuous spiral movement
of the telescope. The speed of this scan is
selected so that there are no gaps between the individual
images in the area scanned. The telescope
stops moving as soon as the prism has been detected.
When using the ATR measuring technique, it is not
necessary to target the prism centrally in order to
determine the horizontal direction and the vertical
angle. Nevertheless Hz and V angle corrections are
determined during the subsequent targeting process
when the motor moves the telescope so that it points
to the centre of the prism within the predetermined
tolerance limits.
There are two reasons for this: firstly, so that the user
can confirm the correct automatic targeting by visual
observation and secondly, so that a distance can be
measured at the same time. ATR requires one prism
for target identification and so, to simplify operation,
the ATR angle measurement has been coupled to the
triggering of a distance measurement.
During the measuring procedure, angle corrections
are redetermined, the horizontal and vertical angles
are corrected appropriately, and the distance is
measured or the target-point coordinates are calcu-
lated. Fig. 5 shows the sequence of an ATR measurement
procedure.
The measuring accuracy of ATR in its standard setting
corresponds to the angle-measuring accuracy of the
corresponding instrument model. If a distancemeasuring
mode different from the standard one is
selected, the accuracy of the ATR measurement
adapts to the accuracy class of this measuring mode.
In, for example, the distance-measuring mode “Fast“,
this shortens the measuring time and enables the
measurement to be carried out on unstable, handheld
reflectors at close range.
When ATR is used for measuring, there is no need to
focus the telescope or to fine-point the target, and so
the speed of measurement is increased enormously
and the precision, which is independent of the observer,
remains constant.
4.3 Tracking the target
Tracking is essentially an automatic control system,
or feedback loop (fig. 6). The theodolite drive, the
control range, consists of two axes each with a servomotor,
a transmission and a circle-scanning system.
The ATR is a measuring system, which supplies not
only the actual values, but also the deviation between
actual and required values and the horizontal and
vertical corrections from the electronic or optical line
of sight. The automatic control system is intended to
minimize the deviations, irrespective of the speed and
acceleration of the target. The deviations are read off
at the video rate; from them, the circuit determines
the currents needed by the motor in order to attain
the set goal.
This procedure runs continuously throughout the
tracking phase. If contact with the target is lost, e.g. if
the reflector carrier passes behind an obstacle, the
tracking process is interrupted. The values that then
become effective instead of the deviation values are
based on a movement model, which assumes the
horizontal and vertical speeds of the reflector carrier
to be constant. These speeds are derived from the
filtered movement before loss of contact. Filtering
serves to eliminate superimposed frequencies such
as the vertical component of walking. Because the
model is just an approximation of the movement, it is
applied only for a period of a few seconds.
If measurements are triggered parallel to the tracking
process, the course of the moving target can be
determined. The time synchronization of the individual
sensors of the total station has a considerable
influence in this application. The measuring systems
are integrated for different periods, and so the true
time at which they are determined has to be established
and then interpolated or extrapolated to a
common point in time.
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Fig. 5: The sequence of an ATR measurement
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Fig. 6: Feedback loop of target tracking
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5. Remote control
The remote-control system RCS1100 is an additional
option for all Leica total stations. It is particularly
efficient in conjunction with instruments that have
automatic target recognition. The controller, battery,
radio modem and antenna of the RCS1100 form a
compact unit, which fits easily to a reflector pole (fig.
7). The display and keyboard of the controller are
identical to those of the total station, and so all instrument
functions, including the applications programs,
can be called up from the target area.
Fig. 7: RCS1100 remote control system
The remote control system makes it easier to capture
important additional information at the target area in
particular, and offers great advantages during stakeout.
After a measurement, the path difference from
the reflector to the point to be set out is calculated
and is displayed on the controller. This facilitates and
accelerates the stakeout procedure, and also enables
the accuracy of the stakeout to be inspected directly
from the target area.
The EGL electronic guide light provides additional
help during stakeout; it is a flashing light source,
which can be built into any telescope housing (fig. 1),
and enables the reflector carrier to be aligned with the
line of sight of the instrument.
6. Software
The entire software for the TPS1100 instruments can
be roughly divided into three groups:
- The systems software for controlling all basic
functions of the total station
- The comprehensive library of applications programs
- The LEICA SurveyOffice, PC programs package for
communication between instrument and computer.
6.1. System software
The system software controls all measurement
functions, the display and the recording. For each
dialogue in the display (e.g. measuring, data management,
calibration etc.), the function keys are occupied
by the appropriate relevant function. This ensures
ideal user guidance along with quick and easy operation.
All measurement sequences, and the functions which
can be called from the various dialogues, are logically
arranged. They can also be configured and so
matched to individual user requirements.
In the measuring dialogue, three different display
templates can be defined; a keystroke switches
between them so that the user has an overview of all
important data.
Five different recording templates can be defined
quite independently of the display templates. 12
items of data in any sequence can be recorded in any
one measuring block. There is a choice between data
formats containing either 8 or 16 characters per data
word.
All data can be stored on PCMCIA memory cards in
various files, or can be exported via the RS232 interface
to an external computer. Up to 60 files can be
managed; they can be given any name. A distinction
is made between measurement files for storing
measurements, files with fixed-point coordinates,
and code lists.
Code lists with additional information for the postprocessing
of measurement data can be imported
directly through the keyboard into the instrument, but
it is preferable to compile code lists on a PC with the
program “Codelist Manager” from the Leica Survey
Office and then to import this into the instrument.
For standard coding, the appropriate code is selected
from the list and then stored in a separate code block.
A code block can contain a code and up to eight
additional items of information. If no code list has
been stored in the instrument, code blocks can also
be entered manually via the keyboard and stored.
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Rapid coding (“Quick-Code”) is a special function
with which a keystroke triggers a measurement, after
which the measurement block and the corresponding
code block are recorded automatically. To do this, a
single-digit or two-digit number must be allocated to
each code as a quick-code abbreviation when the
code list is compiled with the “Codelist Manager” PC
program. After the point has been targeted, it is
enough to enter this number using the numeric
keyboard. This action triggers a distance measurement,
and stores the complete measurement block in
accordance with the recording template selected and
with the associated code block from the code list. The
user can decide whether the measurement block or
the code block should be the first to be stored.
Point-related codes, and also up to eight attributes,
can also be recorded along with each measurementdata
block. The input is directly through the measurement
dialogue. The precondition for this is that the
point code and the attribute are defined both in the
display and in the recording template.
6.2. Applications programs
To deal with the most important tasks in surveying,
the following applications programs are incorporated
into all instruments:
Horizontal-circle orientation and height transfer
Resection
Free-station survey
Setting out (stakeout)
Computation of tie distance
Remote height
The user can load the following optional programs at
any time:
Reference line
Area computation
Hidden points
Sets of angles
Traverse
Local resection
Road stakeout
File Editor
COGO functions
Auto Record (acceleration of mass point surveys)
Face Scan for TCRM instruments
DTM stakeout
Leica offers GEOBASIC, a modern development
environment within which users can develop their
own individual applications programs.
Printed in Switzerland. Copyright Leica Geosystems AG, Heerbrugg, Switzerland, 1999
712705en - V.99 - RVA
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6.3. LEICA SurveyOffice
The LEICA SurveyOffice is a PC software package
with the following functions:
- Exchange of data between instrument and PC
- Creation of code lists universally usable in the
TPS300 instruments, the TPS1100 instruments and
the new GPS500 system
- Loading and deleting systems software and applications
programs and related display texts in various
languages.
Leica Geosystems AG
Geodesy
Heinrich-Wild-Strasse
CH-9435 Heerbrugg
Switzerland
Phone +41 71 727 3131
Fax +41 71 727 4702
www.leica-geosystems.com