1962 Wild Heerbrugg T2 theodolite

1962 Wild Heerbrugg T2 theodolite
Figure 1: 1962 Wild Heerbrugg T2 theodolite
This Wild Heerbrugg T2 universal instrument was part of a large donation to my collection together with a 1969 Wild T2E theodolite, a 20th c. Askania Tu400 theodolite, a 1951 Wild N2 level, a 1960s Jenoptik Koni 007 level, a 1960s Zeiss Opton Ni 2 level, a 1956 geodetic sextant, and various accessories.

Provenance
The above mentioned group of instruments once was part of the set of instruments used by the field organisation TGTW of the Survey Department (Meetkundige Dienst, 'MD' in short) of Rijkswaterstaat (part of the Dutch Ministry of Infrastructure and the Environment, responsible for the design, construction, management and maintenance of the main infrastructure facilities in the Netherlands).

The department was closed in the early 2000s and in 2008 the instruments were donated to my collection.

Development1
The Wild T2 was first produced in 1926. The archetype Wild T2 in my collection was the third modification of the first model. The instrument shown here was the third model T2 produced, which was produced between 1956 and 1968, and dates from 1962. Two years later it would be followed by the Wild T2E in my collection.

Accuracy2
This Wild T2 universal instrument is equipped with glass circles (90mm diameter horizontal and 70mm diameter vertical) and a optical reading mechanism. The T2 does not have a compensator for the vertical index, a coincidence vial is used instead (see figure 6). With 70mm diameter the vertical circle of this third model T2 is substantially larger than that of the archetype model T2, while the horizontal circle remained the same.

This T2 has centesimal circles divided down to 20c (0.20gon) intervals, can be read using a micrometer directly to 2cc and estimated to at least 1cc (see figure 11 and figure 12). The circles are illuminated by two distinctive rotating mirrors; one directly on the secondary axis and one at the base of the instrument (see figure 7 and figure 8).

The Wild Heerbrugg T2 from the other side.
Figure 2: The Wild Heerbrugg T2 from the other side.
Alternatively the circles can be illuminated by electric lights, but sadly enough the instrument came without them.

Production
The first T2's were produced in 1926. Up to 1970 a total of 38,800 were made and many more thereafter.3 Here in the Netherlands the T2 has been the most popular instrument among surveyors for many decades and probably every surveyor educated here in the second half of the 20th century has worked with it.

According to the Ahrend Prijscourant 22 of 1962 a "T2 in metalen stolp, met optisch lood ... elektrische verlichting zonder statief, 400g..." ("T2 in metal cover, with optical plumb ... electrical lighting without tripod, 400g") would have cost fl.3,630.-.4

The instrument
This Wild T2 came complete with its steel container and lens cap. It is centesimally divided. The telescope has a magnification power of 30 times. The inverted field of view shows four stadia hairs with a multiplication factor of 100 (see figure 9).

Centring can be done using an optical plummet, which has a normal cross-hairs for the purpose (see figure 10).

Externally there are only two differences with the 1969 Wild T2E; the peep sight on the telescope (see figure 5, it is no longer featured on the later model) and the sliding (instead of turning) locking mechanism of the tribrach (see figure 3 and figure 4).

Internally the presentation of the coincidence reading method of the circles and the interval of the micrometer differ from the later model (see figure 11 and figure 12).

Notes

[1]: See the theodolite overview page at the Virtual Archive of Wild Heerbrugg.
[2]: Wild Heerbrugg, Wild T2: Universal Theodolite, Instructions for Use, (Heerbrugg, 1968), p.10.
[3]: See the Products: Quantity at the Virtual Archive of Wild Heerbrugg.
[4]: Ahrend, Prijskoerant 22 Meten, (1962), pp.20-21.

If you have any questions and/or remarks please let me know.

The Wild T2 with its container and lens cap.
Figure 3: The Wild T2 with its container and lens cap.
 
This Wild theodolite features the final type of tribrach attachment method.
Figure 4: This Wild theodolite features the final type of tribrach attachment method.

Coarse aiming is done with a peep sight and bead.
Figure 5: Coarse aiming is done with a peep sight and bead.
 
The vial for the vertical circle.
Figure 6: The vial for the vertical circle.

The vertical circle is illuminated with a rotatable mirror.
Figure 7: The vertical circle is illuminated with a rotatable mirror.
 
The horizontal circle is illuminated with a rotatable circle.
Figure 8: The horizontal circle is illuminated with a rotatable circle.

The telescope has an inverted view and four stadia hairs.
Figure 9: The telescope has an inverted view and four stadia hairs.
 
The optical plummet shows straight forward cross-hairs.
Figure 10: The optical plummet shows straight forward cross-hairs.

The upper block shows two diametrically opposite parts of the gon divided circle.
Figure 11: The upper block shows two diametrically opposite parts of the gon divided circle.
 
At left the horizontal scale reads 337.4766gon, at right the vertical scale reads 107.4520gon.
Figure 12: At left the horizontal scale reads 337.4766gon, at right the vertical scale reads 107.4520gon.

This and next figure show the same reading at two ends of the micrometer, this one at 399.9999 gon.
Figure 13: This and next figure show the same reading at two ends of the micrometer, this one at 399.9999 gon.
 
Here it shows the same reading at the other end of the micrometer, 0.0000 gon.
Figure 14: Here it shows the same reading at the other end of the micrometer, 0.0000 gon.

Surveyor's crosses Geodetic Sextants Theodolites Total Stations Levels Standards Tools Firms
19th C. SDL 1919 K&E 1926 Zeiss RThII 1924 Zeiss Th1 1929 Wild T2 1937 Wild T3 (astronomic) 1939 Wild T3 (geodetic) 1943 CT&S Tavistock 1948 Wild T1 1952 Wild RDH 1956 Wild T0 1961 Wild T1A 1961 Wild MIL-ABLE T2 1962 Wild T2 1963/76 Wild T2 - DI3S 1963 Wild RDS 1966 Kern DKM2 1969 Wild T2E 1976/79 Wild T2 mod - DI4 1990 Wild T2 mod - Di1000 20th c. Askania Tu400