Topic: Total Stations

Almost every land surveyor in the modern world will at some point use a Total Station instrument in their daily surveying work.  However, if you ask a land surveyor about the history of the Total Station, very few can tell you.   In fact, you may be surprised to know how recent the advent of Total Station happened.

Early History of Total Stations

The total station was introduced in 1968 by Zeiss Instruments and was named the Elta 46 and for the first time distance and angle measurements could be recorded by one instrument. The total station is a transit integrated with an EDM, electronic distance meter, which can read slope distances from the instrument to a particular point of land. This combination gives the surveyor the capability of retrieving data related to the coordinates of the reflector in the device.

A total station (TS) is also known as a total station theodolite (TST)which is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure both vertical and horizontal angles and the slope distance from the instrument to a particular point, and an on-board computer to collect data and perform triangulation calculations. Over time, the Total Station has evolved into a more robotic instrument used by land surveyors and with this evolution has come greater productivity. Robotic or motorized total stations allow the operator to control the instrument from a distance via remote control. This eliminates the need for an assistant staff member as the operator holds the retroreflector and controls the total station from the observed point. These motorized total stations can also be used in automated setups knows as Automated Motorized Total Station (AMTS).

One of the first things you learn in Surveying School is the differences and similarities between Total Stations and Theodolites.

A theodolite /θiːˈɒdəlaɪt/ is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but they are also used extensively for building and infrastructure construction, and some specialized applications such as meteorology and rocket launching. It consists of a moveable telescope mounted so it can rotate around horizontal and vertical axes and provide angular readouts. These indicate the orientation of the telescope, and are used to relate the first point sighted through the telescope to subsequent sightings of other points from the same theodolite position. These angles can be measured with great accuracy, typically to milliradian or seconds of arc. From these readings a plan can be drawn, or objects can be positioned in accordance with an existing plan. The modern theodolite has evolved into what is known as a total station where angles and distances are measured electronically, and are read directly to computer memory. In a transit theodolite, the telescope is short enough to rotate through the zenith, otherwise for non-transit instruments vertical (or altitude), rotation is restricted to a limited arc. The optical level is sometimes mistaken for a theodolite, but it does not measure vertical angles, and is used only for levelling on a horizontal plane.

The theodolite became a modern, accurate instrument in 1787, with the introduction of Jesse Ramsden's famous great theodolite, which he created using a very accurate dividing engine of his own design. The demand could not be met by foreign theodolites owing to their inadequate precision, hence all instruments meeting high precision requirements were made in England. Despite the many German instrument builders at the turn of the century, there were no usable German theodolites available. A transition was brought about by Breithaupt and the symbiosis of Utzschneider, Reichenbach and Fraunhofer. As technology progressed, in the 1840s, the vertical partial circle was replaced with a full circle, and both vertical and horizontal circles were finely graduated. This was the transit theodolite. Theodolites were later adapted to a wider variety of mountings and uses. In the 1870s, an interesting waterborne version of the theodolite (using a pendulum device to counteract wave movement) was invented by Edward Samuel Ritchie. It was used by the U.S. Navy to take the first precision surveys of American harbors on the Atlantic and Gulf coasts.

Zeiss Theodolite patents

2552893Theodolite scale reading system, Conway D Hillman, Allister L Baker, 1950-06-08 -
2837956 Theodolite having scale reading means,  Schneider Wilhelm, Carl Zeiss AG, 1954-07-26 - improved reading of vertical angle bubble
2837956 Theodolite having scale reading means, Schneider Wilhelm, Carl Zeiss AG, 1954-07-26 -
2911877 Geodetical instruments, Drodofsky Martin, Carl Zeiss AG, 1957-02-08 -

HP Total Station & related Patents

3619058 Distance Measuring Apparatus, William R. Hewlett and Gregory Justice, Nov. 9, 1971, -
3900259 Time Interval Phase Detection in Distance Measuring Apparatus, Claude M. Mott and Richard J. Clark, Aug. 19, 1975
4335306 Surveying instrument, HP Inc, 1979-10-29, - HP 3820A total station
4789874 Single channel encoder system, Mark W. Majette, William J. Walsh, John A. Wickeraad, 1987-07-23, -
5774074 Multi-track position encoder system, Eugene A. Cooper, Steven B. Elgee, HP Inc, 1997-01-21, - 2-track angle encoder for printer platens
PS at one time HP/Agilent made a very precise absolute angle encoder, but the above 2 patents are not for what I was looking for.

Practically every major land surveying equipment manufacturer carries a branded Total Station.  Over the years, systems for Angle Measurement and Data Collection have evolved in sophistication.   Most total station instruments measure angles by means of electro-optical scanning of extremely precise digital bar-codes etched on rotating glass cylinders or discs within the instrument. The best quality total stations are capable of measuring angles to 0.5 arc-second. Inexpensive "construction grade" total stations can generally measure angles to 5 or 10 arc-seconds.

Measurement of distance is accomplished with a modulated infrared carrier signal, generated by a small solid-state emitter within the instrument's optical path, and reflected by a prism reflector or the object under survey. The modulation pattern in the returning signal is read and interpreted by the computer in the total station. The distance is determined by emitting and receiving multiple frequencies, and determining the integer number of wavelengths to the target for each frequency. Most total stations use purpose-built glass prism (surveying) reflectors for the EDM signal.

A typical total station can measure distances up to 1,500 meters (4,900 ft) with an accuracy of about 1.5 millimeters (0.059 in) ± 2 parts per million.

Reflectorless total stations can measure distances to any object that is reasonably light in color, up to a few hundred meters.

The coordinates of an unknown point relative to a known coordinate can be determined using the total station as long as a direct line of sight can be established between the two points. Angles and distances are measured from the total station to points under survey, and the coordinates (X, Y, and Z; or easting, northing, and elevation) of surveyed points relative to the total station position are calculated using trigonometry and triangulation.

To determine an absolute location, a total station requires line of sight observations and can be set up over a known point or with line of sight to 2 or more points with known location, called free stationing.[3][4]

For this reason, some total stations also have a Global Navigation Satellite System receiver and do not require a direct line of sight to determine coordinates. However, GNSS measurements may require longer occupation periods and offer relatively poor accuracy in the vertical axis.