The Lens of Precision: Unveiling Image-Assisted Total Stations

Chapter 1: The Dawn of IATS

In the quiet corners of surveyor’s workshops, where the scent of aged paper mingles with the hum of electronic devices, a new chapter unfolds. It’s the story of the Image-Assisted Total Stations (IATS), born at the intersection of tradition and innovation.

Our protagonist, the seasoned surveyor, once wielded a classic theodolite—a sturdy instrument with brass accents and glass eyepieces. Its purpose? To measure angles with unwavering precision. But theodolites, like old sages, had their limitations. They whispered secrets of distant peaks and hidden valleys, yet their gaze remained fixed on the horizon.

Chapter 2: The Marriage of Optics and Pixels

Enter the IATS—a hybrid creature with the heart of a theodolite and the eyes of a camera. Picture it: atop a tripod, its sleek body adorned with sensors and lenses. The surveyor adjusts the eyepiece, not to peer through glass, but to frame reality in pixels. The IATS captures the landscape—an intricate tapestry of contours, buildings, and ancient oaks.

Chapter 3: The Dance of Precision

The IATS dances to a new rhythm. It doesn’t merely measure angles; it sees them. As the surveyor pans across the skyline, the image sensor records every detail—the rusty weathervane atop the church spire, the gnarled roots of an oak tree, and the distant glimmer of a river. Theodolites of old would envy its vision.

Chapter 4: Applications Unveiled

Structural Guardianship:

The IATS patrols bridges and skyscrapers, vigilant in its duty. It detects shifts—subtle tremors or creeping deformations. Engineers pore over its data, ensuring the safety of millions who traverse those steel sinews.

Geo-Monitoring Secrets:

On rocky cliffs and unstable slopes, the IATS stands sentinel. It watches for landslides, rockfalls, and the slow erosion of time. Its images reveal the Earth’s whispers—the gradual retreat of a coastline or the sudden collapse of a sea cave.

Chapter 5: The Surveyor’s Oath

The surveyor, once tethered to the ground, now roams with purpose. Armed with the IATS, they traverse forests, traverse deserts, and traverse the boundaries of possibility. They no longer squint through eyepieces; they interpret pixels, decode landscapes, and safeguard our world.

And so, dear reader, when you glimpse a surveyor on a hilltop, know that they carry more than a tool—they carry a legacy. Theodolites may fade into memory, but the IATS? It gazes into the future, pixel by pixel, angle by angle.

The story of the first all-Ireland mapping survey 200 years ago

By Catherine Porter, UL and Keith Lilley, QUB

Maps help us to connect with our localities and many of us are familiar with maps of our local area. Historic maps in particular provide us with an important window onto our past and reveal how a place has changed over time. This year marks two centuries since the beginnings of the most detailed historic land survey of Ireland. Led by the British military led Ordnance Survey (OS), and popularised in the 1980s through Brian Friel’s play, 'Translations’, the impacts and traces of the survey on Ireland’s landscape are still seen today.

We often will turn to the first edition Ordnance Survey maps to explore the townlands of our ancestors (perhaps where our families still live today), or to figure out the location of a particular building, well or a stream, or simply explore the complex geographies and histories of the island. The historic outputs of the Ordnance Survey challenge us too in how to reconcile the complex cultural heritage and legacies of the survey with what was the most detailed country-wide large-scale mapping and survey in the world at the time.

The cultural complexities of the OS in Ireland are recorded in a variety of source materials, not just maps. In various archives, museums and repositories across Ireland and Great Britain lie correspondence, statistical accounts, drawings and sketches, and comprehensive lists of place names, providing a pre-famine record of Ireland and its population.

How and why the survey began

In early nineteenth century Ireland, land taxation based on the county cess, and earlier surveys such as the Strafford and Down surveys of the seventeenth century, were deemed an inaccurate reflection of land value. In March 1824, a Select Committee on the Survey and Valuation of Ireland was set up to explore a detailed revaluation of the land. A recommendation by Thomas Colby of the British Ordnance Survey, and later placed in charge of the Irish survey, was to incorporate townlands, and that to do so would require ‘a scale of six inches to one English mile’ (Item 1, Colby’s ‘Instructions for the Interior Survey of Ireland’, 1825).

The geographic extent of the survey also required bespoke instruments to deal with the inclement weather and to construct an accurate framework of invisible triangles from the tallest mountain tops to the smallest hills, based on a minutely accurate base line near Lough Foyle (remember your trigonometry from school!), which lies between Derry and Donegal. These same techniques and equipment were later applied to other colonial mapping exercises elsewhere in the world.

Placing boundaries

Determining the shape and size of the smallest administrative boundaries in Ireland, the townland, was far from simple. The engineer and civilian, Richard Griffith, led the ‘boundary team’ in setting out the limits and margins for every townland on the island.

As with modern property boundaries, informants often disagreed, and disputes were common. Step by step and with the assistance of local civilians, Griffith and his staff not only marked and defined known townland boundaries, but they also removed reference to the historic land divisions such as the ploughland, tate and ballibo, and created new townlands through a process of addition, amalgamation and splitting of land to form the townlands we are familiar with today.

Placing names

Core to any map are place names, but determining how these would be printed on the final cartography was a complex process. The Topographical Department led by John O’Donovan (Seán Ó Donnabháin) referred to a multitude of written authorities and travelled Ireland collecting and compiling lists of the historical forms to determine the final map presentation of place.

The details recorded by the OS field ‘name books’ are a core source material for today’s linguists and historians in charting the changes to place names and the Irish language across time and geography. Similar to townland boundaries, those authorities consulted differed in opinion and O’Donovan often sought out what he termed ‘the last of the aborigines’ (Irish speakers) to assist him in determining the place names and their histories.

Placing people

The memoir scheme, originally devised as a supplement to the maps, had military and civilian teams collect and collate details on the landscape, nature, geology, history, infrastructure, people and culture, and make ‘suggestions for improvement’. This important record of pre-famine Ireland unfortunately covers only the north of the island – the scheme was cancelled in 1840 - and shows, in particular, connections between the people and their ancient roots.

It also reveals the bias of some OS staff, especially evident in their ethnographic study of people and culture. Irish homes were frequently described as less clean and the habits of the people less virtuous, inferior, and generally ‘uncivilised’ when compared to the Scottish and English settlers who were remarked on as being industrious, neat and the cause of what was deemed as ‘improvement’ in a parish.

The complex cultural histories and legacies of the OS in Ireland cannot be denied, but nor can the achievement of the venture overall in setting down the bounds and place names for a whole country two centuries ago.

From late June 2024, there will be the opportunity to explore four of the key OS source materials through a free online resource developed by researchers based at the University of Limerick and Queen’s University Belfast through the project, ‘OS200: Digitally Remapping Ireland’s Ordnance Survey Heritage’. More about the project, team and partners can be found at the project website or on social media.

About theodolite

Types of Theodolites

There are two different kinds of theodolites: digital and non digital. Non digital theodolites are rarely used anymore. Digital theodolites consist of a telescope that is mounted on a base, as well as an electronic readout screen that is used to display horizontal and vertical angles. Digital theodolites are convenient because the digital readouts take the place of traditional graduated circles and this creates more accurate readings.

Parts of a Theodolite

Like other leveling instruments, a theodolite consists of a telescope mounted on a base. The telescope has a sight on the top of it that is used to align the target. The instrument has a focusing knob that is used to make the object clear. The telescope contains an eyepiece that the user looks through to find the target being sighted. An objective lens is also located on the telescope, but is on the opposite end as the eyepiece. The objective lens is used to sight the object, and with the help of the mirrors inside the telescope, allows the object to be magnified. The theodolite's base is threaded for easy mounting on a tripod.

How Does a Theodolite Work?

A theodolite works by combining optical plummets (or plumb bobs), a spirit (bubble level), and graduated circles to find vertical and horizontal angles in surveying. An optical plummet ensures the theodolite is placed as close to exactly vertical above the survey point. The internal spirit level makes sure the device is level to to the horizon. The graduated circles, one vertical and one horizontal, allow the user to actually survey for angles.

How to Use a Theodolite

1. Mark the point at which the theodolite will be set up with a surveyor’s nail or a stake. This point is the basis for measuring angles and distances.
2. Set up the tripod. Make sure the height of the tripod allows the instrument (the theodolite) to be eye-level. The centered hole of the mounting plate should be over the nail or stake.
3. Drive the tripod legs into the ground using the brackets on the sides of each leg.
4. Mount the theodolite by placing it atop the tripod, and screw it in place with the mounting knob.
5. Measure the height between the ground and the instrument. This will be used a reference to other stations.
6. Level the theodolite by adjusting the tripod legs and using the bulls-eye level. You can make slight tunings with the leveling knobs to get it just right.
7. Adjust the small sight (the vertical plummet) found on the bottom of the theodolite.  The vertical plummet allows you to do ensure the instrument remains over the nail or stake. Adjust the plummet using the knobs on the bottom.
8. Aim the crosshairs in the main scope at the point to be measured. Use the locking knobs on the side of the theodolite to keep it aimed on the point. Record the horizontal and vertical angles using the viewing scope found on the theodolite’s side. 

Theodolite vs Transit Level

A theodolite is a precision instrument used for measuring angles both horizontally and vertically. Theodolites can rotate along their horizontal axis as well as their vertical axis. Theodolites have a lot in common with transits.  

A transit is a surveying instrument that also takes accurate angular measurements.  Along with the transit, theodolites have mounted telescopes that can be rotated in different directions. Both theodolites and transits can be used for similar projects, but there are slight differences between the two instruments. Transits use vernier scales and external graduated metal circles for angular readings. Theodolites use enclosed graduated circles and angular readings are taken using an internal magnifying optical system. Theodolites tend to have a more precise reading and provide greater accuracy in measuring angles than transits do.

Theodolites are mainly used for surveying, but they are also useful in these applications:

• Navigating
• Meteorology
• Laying out building corners and lines
• Measuring and laying out angles and straight lines
• Aligning wood frame walls
• Forming panels
• Plumbing a column or building corner

Advantages of Using a Theodolite

Theodolites have many advantages when compared to other leveling instruments: 

• Greater accuracy.
• Internal magnifying optical system.
• Electronic readings.
• Horizontal circles can be instantly zeroed or set to any other value.
• Horizontal circle readings can be taken either to the left or right of zero.
• Repeat readings are unnecessary.

Theodolites have an internal optical device that makes reading circles much more accurate than other instruments. Also, because the theodolite allows you to take fewer repeat readings, these measurements can be made much more quickly. Theodolites with optical instruments have advantages over other layout tools. They have more precise measurements, they are unaffected by wind or other weather factors, and they can be used on both flat ground and sloped ground.  

Caring For a Digital Theodolite and Helpful Hints

Like other instruments, theodolites require proper care and maintenance to ensure the best results and reduce wear and tear on the instrument.

• Do not submerge instrument in water or any other chemical.
• Do not drop instrument.
• Make sure theodolite is locked in its case while transporting.
• When raining, use cover over instrument.
• Do not look directly into the sunlight through the telescope on the instrument.
• Using a wooden tripod can protect the instrument from vibrations better than an aluminum tripod would.
• Using the sunshade attachment is important; any sudden temperature changes can cause incorrect readings.
• Never hold the instrument by the telescope.
• Always have a substantial level of battery power on your instrument.
• Always clean the instrument after using.
  • Dust in the case or on the instrument can cause damage.

• If the theodolite is damp or wet, allow it time to dry out before storing it in its case.
• When storing, make sure that the telescope on the instrument is in the vertical position.
• When the theodolite is being re-leveled, the position over the ground point must be checked and rechecked to ensure the same position.
• When the theodolite is being repositioned over a ground point, the level must be checked and rechecked to ensure its accuracy.

Laser Level v Theodolite

Both laser levels and theodolites are key instruments in the construction and survey industry and since their introduction in the last 50 years they have become the cornerstone for set-out and site levelling in the industry. 

Having an understanding of the differences between a laser level and a theodolite is fundamental to all leveling and set-out tasks and construction contractors need to be aware that they designed for different tasks and have quite different capabilities.  

In simplistic terms, laser levels are simpler to use, while theodolite is more versatile and used on a wider range of tasks.  

Laser Levels

A laser level projects a laser beam onto a surface directly or via a receiver which picks up the beam to create a perfectly level line or plane.  

It is generally used for creating a level or straight line over a relatively short distance and is the instrument of choice for builders, concreters and interior fit-out trades where accuracy and a perfectly level line is required either in a horizontal or vertical plane. 

Many advanced laser levels have a slope mode capability that can deviate from a true 0° or  90° line but again this is for the objective of creating a straight line. 

From a layman’s point of view think of a laser level as the way to ensure the structure is level and plumb.  These are easy to use and quick to set up and are commonly used now by all trades and increasingly by DIYers.  

Theodolites 

On the other hand, a theodolite is typically used for more complex tasks that require measuring angles and distances in both vertical and horizontal planes and often over longer distances.  

It has a telescopic sight that can be angled and rotated to measure angles of a distant object or reference point. 

Theodolites are usually used by surveyors, civil contractors, earthmoving contractors, and builders for setting out infrastructure such as roads, earthworks and set out of building foundations and the other structural components that fit around a more complex structure. 

Often a theodolite is used in conjunction with GPS receivers or more comprehensive total stations to provide even more precise measurements and data and due to their versatility and the complexity of information and measurements that they can provide they are usually operated by specialists in their respective field.  

As always when providing a professional construction service, it is best practice to use high quality reputable brands of instruments and these include iMEX and Topcon for laser levels and Topcon for theodolites.