Some Modern Theodolites
Modern theodolites have evolved to offer superior precision and functionality for geodetic and astronomical surveys. These advanced instruments are compact, lightweight, and feature etched glass circles with finer graduations for highly accurate angle measurements. They are equipped with improved micrometers, waterproof and dustproof designs, and electrical illumination for nighttime or tunnel work. High-magnification telescopes, automatic centering, and advanced digital features, such as CCD sensors and integrated electro-optical distance measuring devices, allow for quick, precise readings. These technological advancements make modern theodolites invaluable for precise surveying in even the most challenging environments.
Some Types of Modern Theodolites
Modern Theodolites offer improved precision, making them essential for high-accuracy geodetic and astronomical surveys.
Geodetic and astronomical surveys demand a high level of precision to ensure accurate measurements and reliable results. In order to meet this need, high-precision theodolites are manufactured nowadays. The characteristic features of modern theodolites are as follows:
1. They are more compact and light.
2.The graduations are etched onto a glass circle and are finer, allowing for more precise readings.
3. Improved micrometers, which allow the observer to take readings with accuracy to one second, are provided with these instruments.
4. The instrument is made waterproof and dustproof.
5.It is electrically illuminated to make it easier to work at night or in tunnels.
6. Adjustments for the micrometer are not necessary.
7. Magnification is higher by about 40 diameters.
We shall now describe a few high-precision theodolites.
1. Watt’s Micro-optic Theodolite
There are three models of this type. The first and third models can read up to 5″, while the second model can read up to 1″.
The horizontal and vertical circles of this theodolite are made of glass, and micrometers for measuring horizontal and vertical angles are included. The other accessories are similar to those in the transit theodolite, but the design is more compact and well-protected from atmospheric conditions.
This instrument is manufactured by M/s Hilger and Watt Ltd. The procedure for operation is described in detail in the catalog supplied by the manufacturer.
With features like digital readouts and waterproof designs, Modern Theodolites are built for reliable performance in various environments.
2. Wild T-2 Theodolite
The horizontal and vertical circles of this instrument are made of glass, with the horizontal circle having a diameter of 90 mm and the vertical circle having a diameter of 70 mm. These circles are electrically illuminated using an adjustable mirror. The telescope has a length of 148 mm, and the vertical axis is equipped with an axle bush and ball bearings. The instrument is automatically centered by its own weight, and readings are taken through a micrometer using the coincidence system.
The theodolite is manufactured by M/s Wild Heerbrugg Ltd. Details of operation are available in the catalog.
Modern Theodolites are compact and lightweight, making them easy to transport without compromising on precision.
3. Wild T-3 Precision Theodolite
The level and upright circles are made of crystal and are finely marked. The minimum measurement of the horizontal circle is 4′, while that of the vertical circle is 8′. Angles are measured using an optical micrometer, which provides accuracy up to 0.2″. The upright axis is made up of an axle casing and roller bearings. The instrument is self-centered by its own weight. It includes a set of clamps and adjustment screws to control the motion of the vertical axis.
This instrument is manufactured by M/s Wild Heerbrugg Ltd. The procedure for operation is described in the catalogue.
Equipped with advanced micrometers, Modern Theodolites can take angle measurements accurate to one second.
4. Wild T-4 Universal Theodolite
This instrument is widely used for determining geographical positions and taking astronomical observations with the highest precision. It features a level circle with a 250 mm width, graduated to a minimum measurement of 2′. Using the optical gauge, readings can be taken as finely as 0.1″.
The upright and horizontal circles are equipped with a “measuring micrometer” that automatically provides the average of two diametrically opposite readings. This instrument is manufactured by M/s Wild Heerbrugg Ltd.
The innovative design of Modern Theodolites ensures enhanced magnification and clarity, ideal for detailed surveying tasks.
5. The Tavistock Theodolite
The horizontal and vertical circles are made of glass and are finely graduated, allowing readings as low as 1″ to be taken, with estimates as precise as 0.25″. A unified optical micrometer is provided for both scales. Both circles are illuminated by a single reflector. Additionally, the instrument is equipped with an optical plummet for centering over the station.
The Tavistock theodolite is manufactured by M/s Vickers Instrument Ltd., England.
6. Electronic Theodolite
An electronic theodolite features a moveable telescope mounted on two perpendicular axes: the horizontal and vertical axes. When the scope is directed at a desired object, the angle of each axis can be measured with great accuracy in a very short amount of time.
Electronic theodolites operate like any optical theodolite with one major difference that these instruments have only one motion (upper) and hence have only one horizontal clamp and slow motion screw.
In electronic or modern-type theodolites, charged coupled device (CCD) sensors added to the focal plane of the telescope allow auto-targeting and the automated measurement of the residential target offset. All these are possible by embedded software.
Modern Theodolites are designed to provide exceptional accuracy and efficiency, making them a crucial tool for precision surveying in various professional fields.
In recent years, modern theodolite equipped with integrated electro-optical distance measuring device, generally infrared based, allow distance measurement in one go under three-dimensional vectors, popularly known as resection solution.
From automatic centering to integrated electro-optical devices, Modern Theodolites incorporate cutting-edge technology for seamless surveying.
(a) Characteristics of Electronic Theodolite
- Angle for least count can be 1″ with precision ranging from 0.5″ to 20″,
- Digital read-outs eliminate the personal error associated with reading and interpolation of scale and micro-meter settings,
- Display window or unit for horizontal and vertical angles available at either or both ends,
- Some digital theodolites have modular arrangement where they can be upgraded to be a total station or have an EDM attached for distance measurement,
- Large dot-matrix dual-line LCD screen to display both vertical and horizontal angles simultaneously,
- Introducing unique linear focussing mechanism to simplifying focussing, and
- Continuous operation for up to 48 hours with fresh alkaline-manganese batteries.
(b) Specifications for Digital Theodolite
- Magnification: 26X to 30X
- Field of view: 1.5
- Shortage viewing distance: 1.0 m
- Angle read-outs, direct: 5″ to 20″
- Digital angle display is user-switchable from 5″/10″ to 1″/5″
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