With a generous donation by my family for my birthday in 2010 I could make this long lasting wish come true; adding a T3 to my collection. A search on the internet initially resulted in two instruments in the US, but both were incomplete, lacking the additional oculars that were supplied by default to each of them.

Making inquiries on the matter at the Virtual Archive of Wild Heerbrugg resulted in an offer by Jürg Dedual for this very early T3. Being from 1937 (see figure 18) the instrument was the best theodolite of its time that Wild produced and in quality only matched by instruments like the Parkhurst theodolite by K&E and the geodetic version of the Tavistock theodolite by Cooke, Troughton & Simms (the Wild T4 would not be produced until 1941¹). The Parkhurst theodolite at the US Coast and Geodetic Survey was finally replaced by the T3 in 1952.² Since 1957 here in the Netherlands first order triangulation was exclusively done using T3s which had replaced the Wanschaff theodolites that were used in the period 1879 – 1937.³

According to the 1933 Wichmann catalogue No. 30/L T3's were sold - together with the container, accessories and a tripod - for RM3005,- (RM = Reichs Mark or German Mark), which would have been approximately US$715.50 at the time, roughly US$73,900.- or €53,500.- in 2009.⁴ This was twice as much as a Wild T2 (US$369.-) and almost four times the price of the K&E Preliminary Survey Transit 5129N (US$205.-) in my collection.

Together with the Carl Zeiss ThI and archetype Wild T2 the T3 was one of the first theodolites to feature glass circles (135mm diameter horizontal and 90mm diameter vertical) and an optical reading system, after Heinrich Wild's Zeiss ThI. The T3 does not have a compensator for the vertical index, a large coincidence level (see figure 10) with a settling accuracy of 0.5" is used instead.⁵

Like this one the majority of the T3's had sexagesimal circles (divided in degrees) and can be read down to 0.2" and estimated to 0.1" or better (see figure 13). Centesimal T3 have been made as well, especially for the Dutch government (see below).

The accuracy of the direction reading is given as 0.5".⁵ Reading the circles is something to get used to as the micrometer scale of this early model is divided in 60 mayor intervals spanning 2' in total, while being numbered 0-60 (see figure 13). The mayor intervals are subdivided into 10 parts each, making each division 0.2".

When reading the micrometer scale the figure found has thus to be multiplied by 2 in order to get the actual arc minutes and seconds (see figure 13). Later models would still be divided in the same way, but were numbered 0'-00" to 2'-00" making the multiplication unnecessary. Even though the instrument has not been maintained for a long period of time and being shipped from Switzerland it still showed a horizontal index error of only 4" and a vertical index error of just under 2" when I first tested it.

This section is identical to the same section of the geodetic T3.

Up to 1970 only 6,860 T3s were produced by Wild (compared to the 38,800 T2s for the same period this was a limited production).⁶ The T3 was only used in small quantities here in the Netherlands.

The first T3 probably entered the Netherlands when the Bijhoudingsdienst der Rijksdriehoeksmeting (Maintenance Division of the Dutch Trigonometry Department) received one on loan for three months from Wild-Heerbrugg in 1931.⁷ The instrument was found to be equal in quality to the Wanschaff theodolites used until then, but saved time and money as observations could be done without assistance and circle readings while keeping ones stance (for which it was no longer necessary to create large structures around the instrument).⁷

Having great practical and economical advantages, in December the following year it was decided to purchase one T3 for second order measurements.⁸ Up to at least 1937 this T3 remained the only one and was exclusively used by the survey crew of land surveyor Meertens, while the other crews still used the Wanschaff's.⁹ Based on the serial numbers another T3 was purchased a decade later. These early T3's were sexagesimal instruments. In order to speed up the calculations - which at the time were done using calculators of Brunsviga and Marchant, like the Brunsviga Models D13 R/2 and 13ZK and the Marchant Pin Wheel¹⁰ - the instruments were sent back to Swiss to have them modified to the centesimal system.¹¹

Soon after other institutes and companies in the Netherlands started using T3s as well, but so far I have traced only seven of them; at least two were used at the University of Delft (serial no's 26595 and 33172) and still remain in their collection. The 26595 is a T3R (Recording) on which it was possible to mount a camera on the tube to photograph the circles, allowing interpretation afterwards using a microscope.¹² At least another two were owned by GrontMij and sold when they became redundant (one of which with serial no 82980 is in the collection of a colleague) and at least three (but possibly four or even five) were used by the Dutch triangulation division Rijksdriehoeksmeting of the topographical department Kadaster (two instruments with serial numbers 18815 and 74314 still remain in the collection of the Kadaster Bedrijfsmuseum, for the 74314 see picture 23 on their web site).^13,14

In contrast the Wild T2 was one of the most popular instruments among land surveyors here in the Netherlands in that period and were used probably in their hundreds.¹⁵

This T3 came complete with its original container, all three oculars, lamps, and metal lens cap (see figure 3 and figure 6). The three oculars allow to use the instrument with varying magnifications of 24x, 30x and 40x (see figure 7). The one showed here is sexagesimal divided (so in degrees, minutes and seconds), while the geodetic Wild T3 in my collection is centesimal divided (400 divisions in a full circle).

Another major difference with the geodetic T3 is the reticle. Where the geodetic T3 lacks stadia hairs this astronomical T3 is invested with them, probably for timing purposes during astronomical observations (see figure 8).

Another difference is the electricity connector which differs from the usual shape known from Wild instruments. As the connector has the same paint as the rest of the instrument it may have been changed on request by the owner.

Judging a minute speck in the objective glass and some scratches on the joke it has had a rough life in the field. Upon arrival the instrument was not even correctly assembled, by which the yoke had about a millimetre play with the base. The play was removed by tightening the T-shaped prism carrier (see figure 19, figure 20 and figure 21). This on itself however caused the horizontal circle to be out of focus as in the hollow axis of the prism carrier a lens system is mounted that now moved upwards with it.

The prism carrier was removed again several times to get the internal focussing in the correct position by a trial-and-error procedure. After a few hours the focus was correct again and now the instrument works as it should.

[1]: Although the Wild Heerbrugg web site shows a date up to 1940 I received a snippet from the Wild Serial Number Book from J. Dedual of the Virtual Archive of Wild-Heerbrugg showing its actual manufacturing year. For the earliest T4 see their theodolites section

[2]: See the Wild T3 section at NOAA Celebrates 200 Years of Science, Service, and Stewardship.

[3]: See Geodetic Work in the Netherlands, Report Presented at the Twelfth General Assembly of the International Association of Geodesy at Helsinki, 1960, p.1. Also see Jaarverslag 2008, Nederlandse Commissie voor Geodesie, p.4.

[4]: Calculated using:

• Historical Dollar-to-Marks

Currency Conversion Page.

MeasuringWorth.com to correct for inflation using GDP Per Capita (the "average" per-person output of the economy, which tells how "affordable" this would be to the average person).

[5]: Wild Heerbrugg, Wild T3, Instructions for Use, (Switzerland, 1983), p.6.

[6]: See the Products: Quantity page of the Wild Heerbrugg archive.

[7]: Verslag van de Rijkscommissie voor Graadmeting en Waterpassing aangaande hare Werkzaamheden over het Jaar 1931, p.4.

[8]: Verslag van de Rijkscommissie ... over het Jaar 1932, p.4.

[9]: Verslag van de Rijkscommissie ... over het Jaar 1937, p.4.

[10]: Z. Klaasse, Inventaris Bedrijfsmuseum Kadaster, Deel 2. e.Ruilverkaveling, f.Schepen, g.Consignatie van Effecten aan Toonder, h.Inventarissen van Archieven en Meubilair, i.Landmeetkundige Instrumenten, j.Tekenmateriaal en Kantoorbenodigdheden., (Apeldoorn, 2010), pp.125-127.

[11]: With thanks to former employee Ton Zijderveld for his memories on this matter.

[12]: With many thanks to J. Dedual of the Virtual Archive of Wild-Heerbrugg for explaining this to me.

[13]: Z. Klaasse, Inventaris Bedrijfsmuseum Kadaster, Deel 2. e.Ruilverkaveling, f.Schepen, g.Consignatie van Effecten aan Toonder, h.Inventarissen van Archieven en Meubilair, i.Landmeetkundige Instrumenten, j.Tekenmateriaal en Kantoorbenodigdheden., (Apeldoorn, 2010), p.70.

[14]: Ministerie van Volkshuisvesting en Ruimtelijke Ordening, '2.Rijksdriehoeksmeting', in: G.J. Bruins W.A. Claessen, Serie Landmeetkundig Perspectief Dienst van het Kadaster en de Openbare Registers, (1979), pp.31,34. According to former Kadaster employee Jan Stehouwer several T3s were sold to Rijksdriehoeksmeting employees when they became redundant and as the Rijksdriehoeksmeting had five cars for the transport of surveyors and instruments it is possible that there were even five (given the policy that each car had a theodolite). In addition to that the first survey exclusively done with multiple T3s was done in 1956, which is earlier than the second surviving T3 in their collection. According to Ton Zijderveld they used three T3's in the 40s and had army cars to transport them. These cars were replaced by four Fords in 1952 and would therefore accomodate four instruments.

[15]: All firms I worked with had at least one or two of them and so do most collectors I know. At the survey department of Rijkswaterstaat each land surveyor had one in his car and around 2001 I witnessed some 40 of them (all old model) being made redundant in one large clean-up.