Cohen & Associates Land and Aerial Surveyors

Cohen & Associates Land and Aerial Surveyors Land and Aerial surveyors based in Launceston, Tasmania operating statewide including Flinders Island and King Island.

Cohen & Associates Pty Ltd has operated throughout Tasmania in all aspects of surveying since being established by well respected surveyor John Cohen in 1946. Cohen & Associates Pty Ltd is owned and directed by Adrian Fairfield, a Registered Land Surveyor and RPAS Pilot. We maintain a permanent office in Launceston and provide a full range of land and aerial surveying and planning consultancy services throughout the State. We make regular visits to Flinders Island and can assist with any surveying and subdivision matters on the Island.

Knockup is a high point on the Sideling near Scottsdale. J.R. Scott and D. Stronach surveyed a line for the road to the ...
25/09/2026

Knockup is a high point on the Sideling near Scottsdale. J.R. Scott and D. Stronach surveyed a line for the road to the Ringarooma River March 1859. The plan also includes an early reference to Mt Scott and Mt Stronach.

Frank Pitt identified its potential for a trig station during his 1903 survey, and the reserve was surveyed later that year by G. Eddie—though it remains unclear if an official station was ever installed. Instead, a fire lookout tower was constructed, which is clearly visible in this 1969 aerial photo!

The local geology adds another twist: the basalt here (olivine nephelinite with mantle xenoliths) is strongly magnetic and known to send compass needles into a spin. That wasn't the only trap early surveyors had to worry about!

Can you identify Sprent’s trig station?Article printed in the Launceston Examiner on Saturday, 21 February 1863—a classi...
20/09/2026

Can you identify Sprent’s trig station?

Article printed in the Launceston Examiner on Saturday, 21 February 1863—a classic example of the geographic confusion that existed before the establishment of the Nomenclature Board!

Does anyone know the modern name or exact spot?

I'll add other photos later but can't make it too easy!🕵️‍♀️

Pennyroyal Creek now Isis River but this article is referring to the other Pennyroyal Creek now known Liffey River.

From a wild hailstorm trying to blow us off the map to blue skies the next day—Flinders Island truly never disappoints. ...
16/09/2026

From a wild hailstorm trying to blow us off the map to blue skies the next day—Flinders Island truly never disappoints. 🌬️☀️

We ticked off Pillinger Peak and logged its exact coordinates for future reference. Because of its distinctive profile, local surveyors have relied on this peak as a key landmark for decades!

Does a compass needle actually point straight to the Magnetic Pole? 🧭Surprisingly, no! A compass simply aligns with the ...
09/09/2026

Does a compass needle actually point straight to the Magnetic Pole? 🧭

Surprisingly, no! A compass simply aligns with the local magnetic field where you’re standing, not a single point on the globe.

The difference between True North and Magnetic North is called magnetic declination (or magnetic variation)—and it’s constantly shifting over time and location. In fact, we could be creeping closer to the Earth's next magnetic pole flip! The last full reversal happened about 780,000 years ago (and roughly 171 times in the last 71 million years).

The Compass was often used to survey boundary lines of the land grants leading to many bends in the bush boundaries of the otherwise straight lines shown on the plans. It wasn't until the 1884 survey Regulations that it was banned for this purpose.

In 1918, Donald Fraser prepared an isogonic map of Tasmania showing lines of equal magnetic declination based on field observations from 1916–1918. 🗺️

Today, calculating magnetic declination is a lot easier and methods available.You can explore historical modelled values back to 1590 using NOAA’s interactive map tool (thanks to Richard Sands for pointing this site out):
🔗 https://www.ncei.noaa.gov/maps/historical-declination/

Stacks Bluff (previously known as the "Butts") stands at the southern end of Ben Lomond. Trigonometrical surveyor James ...
01/09/2026

Stacks Bluff (previously known as the "Butts") stands at the southern end of Ben Lomond. Trigonometrical surveyor James Sprent recorded observations here in December 1851.
Originally, the site featured stacked logs built inside stone walls to shield instruments from the fierce alpine winds. When the Automobile Club visited in 1913, the remains of the "stockade" were still standing (as seen in the photo). Today, no timber remains—it's long since been used to warm up the visitors.
For decades, Sprent’s trig site was assumed to be the highest point on Ben Lomond, despite growing suspicions that the plateau's northern end was higher. Interestingly, the attached viewshed plots show that key trig sites visible from Stacks Bluff are completely hidden from Legges Tor due to its setback from the plateau's edge.
Between 1905 and 1909, Colonel William Vincent Legge directed 'rough' surveys of the uncharted area. However, it wasn't until Christmas 1912 that Authorised Surveyor Herman Robert Hutchison conducted careful observations to officially confirm Legges Tor as the true summit.
Hutchison’s 1912 survey relied on a baseline measured between Sprent’s trig station and a flag installed 1,553 feet away—perched right at the cliff's edge to maximize the distance. While the flag is long gone, the legacy of that survey remains!

A most interesting rock—proof that you're never far away from history.This granite boulder, like many in the area, is th...
28/08/2026

A most interesting rock—proof that you're never far away from history.

This granite boulder, like many in the area, is the exact one noted on a 1908 survey by Henry Frank Miles. Miles and Percy Henry Winter Sams completed several surveys around here. As if the dense vegetation and brutal terrain weren't enough, they couldn't find a single original survey mark from James Scott’s 1844 work.

Why the discrepancy? It might have something to do with Scott allegedly surveying "800 acres" in a single day. When Sams and Miles resurveyed the entire area, they also discovered it actually contained 955 acres!

When James Sprent visited Cape Raoul in 1850, he noted a 4 foot 9 inch high stone cairn with a pole. That original pile ...
21/08/2026

When James Sprent visited Cape Raoul in 1850, he noted a 4 foot 9 inch high stone cairn with a pole. That original pile was broken down into smaller piles by a survey party in 1979—remains visible here in the 1981 photo.

While the area today features a network of well-maintained tracks, it was a very different story in the 1830s.

On November 19, 1834, Captain Charles O'Hara Booth set off: "Started to visit Starkeys Gang at Cape Raoul, a very heavy road..."

By day two, his party ran out of food. By day three, they "toiled the whole of the day without a Morsel over most desperate ground and could make out nothing - all exhausted... no grub - to add to our misfortune could not get the tinder to ignite more cold and miserable than words can utter."

Finally, at noon on day four, with hope almost gone, they arrived at the head of Opossum Bay (now Carnarvon Bay), utterly spent.

Booth was the Military Commandant of Port Arthur, famous for establishing a semaphore signaling network across the Tasman Peninsula connecting to Hobart. Conveniently, these prominent structures were included in his trigonometric surveys!

📖 Sources: John Thompson, "Probation in Paradise" 2007 & Dora Heard (ed.), "The Journals of Charles O'Hara Booth", THRA Hobart, 1981.

What do you see in this great photo that has lost it's name over the years? (hint 1 - named by the Cradle Mountain Reser...
15/08/2026

What do you see in this great photo that has lost it's name over the years? (hint 1 - named by the Cradle Mountain Reserve Board 1937). Extra hints may be supplied but lets see how people go.

hint 2. Not a trig or peak.
hint 3. Involves a Lord and Lady and textile business.
hint 4. Does relate to a swim.

ANSWER: Elinor's Tarn being the largest of the Twisted Lakes was named following a visit by John & Elinor Kemp. Elinor swimming in the lake Christmas 1936. John Kemp from Kelsall and Kemp (Tasmania) Ltd a textile business constructed in Launceston in 1920's making use of the cheap hydro power from Duck Reach.

Selection of correspondance from the Board papers held by Tasmanian Archives now attached.

(Photo Source: Tasmania Parks and Wildlife Service Facebook 1st May 2026)

Technology changes, but sound surveying principles endure. 📐It’s amazing using modern high-tech equipment to unravel mys...
09/08/2026

Technology changes, but sound surveying principles endure. 📐
It’s amazing using modern high-tech equipment to unravel mysteries from over 180 years ago. I wonder what James Sprent would think if he saw us today using satellites, robotic total stations, drones and LiDAR to trace his original footsteps!

P.S. Adrian is still on the hunt for historic photos at the St Valentines Peak summit—ideally 100+ years old! If you have any leads on local camera clubs, historic walking groups, or historical societies we'd love your suggestions.

It's not often you find a mountain with multiple historic trigs. The early tree may have served a dual purpose as a sema...
07/08/2026

It's not often you find a mountain with multiple historic trigs. The early tree may have served a dual purpose as a semaphore station. Sprent 's crew rebuilt the 26 feet 6 inch high log pyramid following his observations on 17th Dec 1850. The survey team had been out for 4 months working on the East Coast and Midlands and after missing Christmas at home arrived back in Hobart on New Years Eve. A grant survey in 1858 by Arthur Thompson made use of the trig as the title corner which is quite rare. The survey notes include reference and offsets to the pyramid logs.

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Launceston, TAS
7250

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