Introduction to the Wild T4

The Wild T4 is world renowned as the ultimate in surveying theodolites, it is the largest and most precise micrometer theodolite ever made. Circle readings are read directly to 0.1 arc second horizontally and 0.2 arc second vertically, these circle reading can be estimated to 1/2 that interval.  The large base, scope, and levels combined weigh 132 pounds (57kg), the telescope assembly has to be removed from the base and packed separately for transportation.

Manufactured by the Wild Heerbrugg Ltd. Company in Switzerland, the T4 was used for angle measurements of the highest accuracy.  It was most commonly used to establish astronomical latitude and longitude of geodetic points by observing the stars, but was also used for geodetic astronomy, determination of the deflection of the vertical by astronomical observations; as a stationary instrument in observatories, for 1st order triangulation, tunnel staking and similar precise applications. 

Dr. Heinrich Wild brought his revolutionary ideas into the scope of astronomic-geodetic measurements, this type of theodolite is known as the "broken telescope" type.  It is so called because the light that enters the telescope is reflected, or "broken" by a first surface mirror set at 45° at the intersection of the instrument axis.  The image formed in the telescope is viewed through an eyepiece placed at one end of the trunnion axis which allows comfortable sighting to zenith, because the eyepiece and “impersonal micrometer” is always at eye level.  Readings of both the horizontal and vertical circles are made with an optical coincidence micrometer giving the mean of the readings on each side of the circle.  Its powerful telescope with 2 interchangeable eyepieces has a 60 and 80 power magnification, an inverted image, and there is no focus since the optics are permanently fixed on infinity. 

The T4 is capable of determining the longitude to ~ 0.015 second of time (~ 0.23 second of arc), latitude to ~ 0.2 second of arc and the azimuth to ~ 0.3 second of arc.  Accessories of equally high precision were also available for use with the T4, such as a chronograph, a chronometer and a time signal receiver.  The eyepiece micrometer of the T4 can be attached directly to a chronograph during longitude determinations.

The T4 Universal Instrument

The Wild T4 was first produced in 1941 and this “old style” model continued in production until 1966.  Production began on the “new style” T4A in 1968 and ended in 1975.  Some modified T4A’s were produced for the Defense Mapping Agency in the period 1977 to 1981, these modified T4A’s incorporated digital cameras as a substitute for the optical eyepiece.  A total of 357 T4’s were produced during the period 1941 to 1970, it is estimated less than 100 new style T4’s were produced in the years after 1970 (which includes 12 modified T4A’s).

T4 Specifications:

Horizontal circle readings 0.1 second of arc, vertical circle readings 0.2 second of arc

Objective lens diam. 2.4 inches (60 mm, old style), 2.8 inches (70 mm, new style)

Magnifying power (70 old style.  60 & 80, new style) inverted image telescope with a focal length of 22.7 inches (578 mm)

Telescope Length 21.2 inches (540 mm), shortest sight distance approx. 300 feet

Horizontal circle diameter 9.4 inches (240 mm), vertical circle 5.3 inches (135 mm)

Sensitivity of the vertical circle index level, 2" per 2 mm

(0.2” can be obtained by using the coincidence “split” bubble).

Sensitivity of hanging level, 1" per 2 mm

Sensitivities of  the two Horrebow-Talcott levels are 1.5” per 2 mm

Heinrich Wild

Born November 15, 1877 at Mitlödi GL, Switzerland, died December 26, 1951 at Baden, Switzerland.

Heinrich Wild and his development of modern Theodolites

On the first day of September 1902, a 24-year-old Swiss surveyor stood behind his theodolite on the summit of 10,686-foot-high Dent du Midi, a prominent peak in the Bernese Alps overlooking the great bend of the Rhone to the southeast of Lake Geneva. It had taken nearly three hours to adjust his instrument in preparation for the observations he had come to make, oblivious to a gathering thunderstorm. Before he had time to complete his painstaking triangulation, snow was blowing all around him and, for all practical purposes, the day was a total loss.

Most surveyors would have cursed the rotten weather as they trudged, step after weary step, back down the mountain and into the late summer warmth of the valley, but not Heinrich Wild (pronounced veeld). Since 1899 he had been surveying for the Swiss Federal Topographic Survey in Berne, and he was only too familiar with weather on Alpine mountain tops. He could live with the weather, if only he had a better theodolite.

The annoying incident atop Dent du Midi started him thinking about building better survey instruments. There must be a way, he reasoned, to change the design of the critical conical standing axis and screw microscopes, which until then had to be regulated and calibrated with each setup, wasting precious time needed for observation. In his imaginative mind new ideas were soon taking shape.

First he found a technique of simultaneously reading the circle at two diametrically opposite graduations in one eyepiece, for which he took out his first patent on January 5, 1907. Next he patented a military range finder, which he had designed in response to a competition.

Looking for a manufacturer for his inventions, he approached the firm of Carl Zeiss in the German city of Jena. Zeiss had not made any surveying instruments up to that time, but appreciated the brilliant designs of the young inventor. With an offer to head a newly established branch in their firm, Heinrich Wild moved his family to Jena in the spring of 1908.

In Jena he built his first precision level. The level had an inner focusing lens, allowing for a telescope of constant length that increased the pointing accuracy and made it rustproof. It also had a reversible tubular level. The halved images at both ends of its bubble could be brought into coincidence via a system of prisms by turning a tilting screw, a revolutionary idea that has since been adopted by the entire instrument industry. In 1911, Wild designed a theodolite in which the images of the two diametrically opposite circle graduations appeared on top of each other in one reading microscope. He was also already experimenting with an automatic level based on a mercury horizon.

World War I and military service in the Swiss artillery interrupted his work at Zeiss. At war's end he returned to Jena, and in 1920 he produced the Zeiss Th1 theodolite.

Zeiss Th1 theodolite (the Th1 was designed by Heinrich Wild and produced by Carl Zeiss, Jena)

The following are improvements in this form of the instrument:

1. Changing over of the images of the horizontal and vertical circles by means of a changeover prism.

2. Bringing the eyepiece of the microscope immediately alongside that of the telescope.

3. Greatly increased precision of graduation and reading of the circles, rendering the instrument capable of replacing theodolites of twice its size of the old form.

   A further improvement deserving of special mention is the new Arrangement for attaching the instrument to its tripod. Wild moved the point of suspension of the plumb-bob into the plane of the feet of the leveling screws, thus permitting of the instrument being leveled without disturbing the centering over the station-point.

But postwar Germany was a poor place to raise a family with nine children, and Wild returned to Switzerland. In Heerbrugg, Wild together with two partners, Dr. Robert Helbling from Flums and Jacob Schmidheiny from Heerbrugg formed the “Heinrich Wild, Werkstätte für Feinmechanik und Optik, Heerbrugg in April of 1921. On December 21, 1923, the first two models of the famous T2, destined to become one of the great surveying instruments of all time, left the plant.

The rapid development of aerial photography and associated equipment, much of it developed by Wild in Heerbrugg, helped to spread the name of Wild throughout the surveying world.  The company grew from a modest 30-man work force in 1923 to 260 by the end of 1930, with sales representatives in 27 countries. Also in 1930, the Federal University of Technology in Zurich bestowed on him the honorary degree of Doctor of Technical Sciences.

Unfortunately for his enterprise, the beginning of the Great Depression put severe stress on the management of the young firm, causing Wild to quit the company late in 1932.

Free from the pressure of running a production plant, Wild became a free-lance designer and inventor. In 1935 he received a contract from the Swiss manufacturer Kern & Co. to design a new theodolite. The result was first the DK2, then the DKM3, featuring a mirror-lens telescope with an erect image and a focal length of 430 mm. The new design was adapted to the DKM2 and finally the midget DKM1.  All these instruments had several new features in common: Leveling cams which turn on a horizontal axis for precise leveling, very stable, high precision ball bearing vertical axis, glass circles with two concentric graduations (double circle principle), powerful, short telescopes, fully transitable, an overall very compact and rugged lightweight design. All these features are still typical of today's Kern theodolites as confirmed by the two theodolites DKM1 and DKM3 which, 40 years after their creation, are still a mainstay in our present manufacturing program, even though several improvements were added in the course of time.  Kern has been taken over from Wild in 1988 and closed down there plant in 1991.

Wild's association with Kern ended only with his death in 1951. Until the end, he experimented with and invented new and ever more precise surveying and mapping instruments. The surveying profession owes Wild for the tools that make the present standards of accuracy and efficiency possible. Three giants of the precision instrument industry—Zeiss, Wild Heerbrugg and Kern—owe their success in large part to the brilliant ideas of this surveyor turned inventor.  Today it  Leica Geosystems is the successor of Wild and Kern, and Trimble is the successor of Spectra, Zeiss, Geotronics.

The company name was changed to Wild Heerbrugg in 1954, Leitz Wetzler was acquired in 1986, Kern was acquired in 1988, and the company merged with Cambridge Instrument Company forming Leica in 1990.

The snowstorm on Dent du Midi had blotted out the view on that distant 1902 September day, yet it gave impetus to genius that has greatly improved our vision into the world we measure.