1984 Kern E1 electronic theodolite

The Kern E1 electronic theodolite with DM503 EDM.
Figure 1: The Kern E1 electronic theodolite with DM503 EDM.
I was given this total station in 2009. Based on the manual the instrument was made around 1984 by the Swiss company Kern & Co.

The instrument shown here was one of the first total stations, an instrument capable of measuring horizontal and vertical angles as well as slope distances and storing these in an electronic memory device (the first total station was the 1968 Reg Elta 14 from Zeiss, but that stored the data on paper tape1).

The Kern E1 basically is an electronic theodolite with a detachable distance meter (in this case the DM503, see figure 3), not a fully integrated total station like the 1980 Wild TC1. The E1 was introduced in the early 1980s while the attached DM503 distance meter was introduced in June 1983.2 Before that Kern produced non-electronic theodolites like the Kern DKM2.

Provenance
The Kern E1 was once bought by the Dutch Governmental Survey Department (Meetkundige Dienst) and was mainly used for beach surveys in the south western part of the Netherlands. Given the low inventory number "Kern 2" it was one of the first acquired by them (see figure 7).

Accuracy
Being an electronic theodolite the E1 can be used in sexagesimal degrees (360 divisions in a full circle) and gon mode (400 divisions in a full circle) by flipping a switch (see figure 8), while decimal degrees and military units (6400 divisions in a full circle) were available as an option.

The instrument has a compensator for the vertical scale and has an angular resolution smaller than 0.3" (arc seconds, 0.0001 gon) and can be read down to 3" (0.001 gon). The instrument's accuracy is 2" (0.0006 gon, see figure 14).

The Kern E1 - DM503 combination from the other side.
Figure 2: The Kern E1 - DM503 combination from the other side.
A quick field test - taking 20 distances to a fixed prism at 8.75 meters distance - revealed an accuracy for the distance meter of 0.002m (1σ, 68%). The manufacturer specified the accuracy as "±3mm + 2mm/km".2 Horizontal and vertical distances are automatically calculated and the latter are corrected for refraction (34ppm) and curvature (68ppm).

The instrument
The instrument came complete with its original box, tripod, prism rods, various prisms, and the field books Alphacord and Betacord (see figure 12). Although it looks like two prisms because of the orange targets in front of it, the prism has a single rectangular body of glass designed to fit the ray-path of the distance meter (see figure 9).

The way the instrument is mounted on the tripod differs hugely from all other period instruments (see figure 6 and figure 10). Kern had devised a new way of forced centring and applied it to all of her instruments. On itself the method was rather smart, but it made it hard to combine Kern equipment with instruments and accessories from other manufacturers.

Despite being bulky the distance meter still allows the instrument to transit. The instrument, together with the DM503, weighs a whopping 10 kilograms (15 kilograms with the box). Compared to this my 1999 Leica TCRA 1101 total station I use for my work is a lightweight at only 6 kilograms (10kg with the box).

Not only the weight is considerable, the price was that as well. In 1984 the electronic theodolite with one tripod and one prism would have cost roughly fl.60,000.-, while the distance meter with the Alphacord data collector would have added another fl.20,000.- (in today's money this would have been €57,500.- for the whole set).

Notes

[1]: Deumlich, F., Staiger, R., Instrumentkunde der Vermessungstechnik, (Heidelberg, 2002), p.184.
[2]: The DM503 is advertised on the rear cover of BulletinKern, no. 35 (June 1983), while edition 34 (January 1983) advertised the improved accuracy of the DM502 without mentioning the DM503.

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

The Kern E1 and the DM503 separated.
Figure 3: The Kern E1 and the DM503 separated.
 
The plate vial can only be seen when the DM503 is not mounted.
Figure 4: The plate vial can only be seen when the DM503 is not mounted.

A small visor can be used for coarse aiming when the DM503 is not in place.
Figure 5: A small visor can be used for coarse aiming when the DM503 is not in place.
 
The self-centring base of the Kern E1.
Figure 6: The self-centring base of the Kern E1.

The Rijkswaterstaat inventory number "Kern 2".
Figure 7: The Rijkswaterstaat inventory number "Kern 2".
 
The adjustment switches, which are normally hidden behind caps.
Figure 8: The adjustment switches, which are normally hidden behind caps.

The prism is a single rectangular body of glass designed to fit the ray-path of the distance meter.
Figure 9: The prism is a single rectangular body of glass designed to fit the ray-path of the distance meter.
 
The forced centring is done by the tripod.
Figure 10: The forced centring is done by the tripod.

The Kern E1 still is in full functional order.
Figure 11: The Kern E1 still is in full functional order.
 
The Kern E1 with Betacord and Alphacord
Figure 12: The Kern E1 with Betacord and Alphacord

The bracket that holds the Alphacord and Betacord.
Figure 13: The bracket that holds the Alphacord and Betacord.
 
The spec sheet of the Kern E2.
Figure 14: The spec sheet of the Kern E2.

Surveyor's crosses Geodetic Sextants Theodolites Total Stations Levels Standards Tools Firms
1980 SAT AGA-Minilir 1980 Wild TC1 1984 Kern E1 1986 Geodimeter System 400 1992 Krupp Atlas PolarTrack 1999 Leica TCRA 1101