Observations

The stone survey marker on the meridian line at Sydney Observatory has an unclear history

The stone pyramid at Sydney Observatory

In this photograph from the early 1900s, the stone survey marker in front of Sydney Observatory is surrounded by what appears to be an uncompleted wooden platform. The white thermometer shed is adjacent to the survey marker while the Observatory’s meteorological instruments can be seen on the lawn behind it. The large structure on the left is the dome for the astrographic telescope that was still standing, although the telescope itself had been moved to Pennant Hills. Photo Powerhouse Museum

The historic stone pyramid that stands in front of the Observatory is a survey marker or trig station. It is marked as the latter in an 1880 plan of the Observatory drawn up by its then director, Henry Chamberlain Russell. In the plan the trig marker is drawn as circular suggesting that the timber platform seen in the image above was a permanent structure.

Observatory 1880 plan detail

A detail from Henry Chamberlain Russell’s 1880 map of Sydney Observatory and its surroundings. The survey marker is denoted as Trig Statn and is drawn as circular. Powerhouse Museum

The marker stands on the Sydney meridian, which is the line passing through the Observatory’s Transit Circle Telescope and running north-south. By observing stars, astronomers using the Transit Circle could establish both its longitude – how many degrees it was located to the east of Greenwich Observatory – and its latitude – how many degrees it was to the south of the equator. Thus the longitude of the survey marker was precisely known and its latitude could be easily calculated from the slight offset in distance from the telescope just inside the building.

This stone marker with its highly accurate position would have been essential for 19th century surveyors to use in any surveys of Sydney. The accurate position of the marker would have ensured that their surveys for property boundaries or sewage lines were also accurate.

The platform with steps leading up to it suggests that surveyors would climb to the top of the marker with their theodolites and measure angles to landmarks that were visible. With these angles they could use triangulation or trigonometry to draw up their maps.

The small triangular marker for Trig Station E

The small triangular marker for Trig Station E that was on top of the tower of Sydney Observatory. Powerhouse Museum

As the area around the Observatory became built up in the late 19th and early 20th centuries, gradually the view of distant church steeples and other landmarks would have been lost. Presumably this explains why a new survey marker was placed on the top of the Time Ball Tower, from where surveyors had excellent views over most of Sydney. It is not known when Trig E was first placed on top of the tower, but the existing marker in the collection of the Powerhouse Museum is inscribed: REFIXED/SUR. RICHMOND/[1927]/TRIG STN./E.

Surveyors were still using Trig E in the late 1970s and early 80s. They would have to haul their theodolites up the steep stairs to the top of the tower. The main concern of the Government Astronomer in charge of the Observatory was that the spikes at the bottom of their theodolite tripods could damage the flat roof of the tower and the surveyors had to promise to ensure that that did not happen.

In the 1980s surveyors stopped using Trig E and the marker was removed during a subsequent refurbishment of the roof of the tower.

Recently, at the request of the Observatory, staff from the NSW Department of Lands replaced the survey marker on top of the tower and re-established its position with the latest GPS techniques. Now known as Observatory E, its coordinates are:

Latitude 33° 50′ 55” S

Longitude 151° 12′ 4” E

Buried deep in the archives of Sydney Observatory and the NSW Department of Lands there is probably much more information on the stone survey marker than outlined here. In the meantime though if there are any surveyors out there who know more of the story, or used Trig E in the past, please make a comment on this post or contact Sydney Observatory. Any information would be much appreciated.

14 responses to “The stone survey marker on the meridian line at Sydney Observatory has an unclear history

  • What is the Lat. & Long. & H.o.E. of Trig Station E at your Sydney Observatory? I wish to know this so I can complete some survey work for a friend at Bowral. I am a retired sea Captain & live at Newcastle, so I cannot use my car device to get your altitude.
    Please send your reply to my email address which I can access whilst not at home.

    Respectfully Yours,
    Alan Chapman, Capt. Ret’d.

  • Excellent article. Can you clarify? the stone marker is the stone pyramid, which was surrounded by the octagonal wooden platform that surveyors climbed. The trig station E marker (of cast iron perhaps) was placed on top of the bell tower in the current location of the UTS and became the benchmark survey point till the 80s. Have I read this correctly?

    • Hello Brian. Thanks for your comment. Yes, the stone marker is the stone pyramid. This was at one time surrounded by an octagonal wooden platform so that the position of trig E could be established. The brass trig E marker was placed on top of the Sydney Observatory time ball tower and surveyors used to climb the tower with their theodolites when they were making surveys in the central area of Sydney.

  • (Please delete the earlier version of this, as it seemingly lost its formatting and Discus would not let me re-edit it!)

    I read this story with much interest, as I have being doing some general work on the subject. (as with the previous Wolf-Rayet story.)May I begin by suggesting that one of the most interesting reads on the earliest problems in astronomy and issues of latitude and longitude appear in a book entitled; Federal Handbook of the British Association for the Advancement of Science. [Download 24.4Mb.] In Chapter VIII “Astronomy and Geodesy in Australia” pg.326 (1904) written by Pietro Baracchi (Then Government Astronomer of Victoria in 1904) discusses the overall science here. On page 366, is an extensive discussion on “e.) Determinations of Australian Longitudes”, which is highly illuminating on this subject!

    It says among other things, that before 1883, the fundamental meridian was Fort Macquarie on South Head; whose corrected position is longitude 10h 04m 52.14s.

    – This remained the established geographical position when dividing up subdivisions of the entire Australian colonies.

    – The first surveying work in Sydney was made in 1839 by C.J. Tyers, who used the adopted Fort Macquarie longitude of 151° 15′ 14″ (The history of this appears pg. 370-374 in the given reference above.)

    About the “Alignment Stones” 

    It seems the first director and Government Astronomer of NSW, Rev. W. Scott made the important detailed position of the Observatory site in April 1857., as so recommended by George Airy (Astronomer Royal) and by William Denison. Rev. Scott first determined Sydney Observatory’s position in 1858 as 10h. 4m 49.0s from twenty-one Moon transits.

    The first positional observations were done using the Jones transit circle from Paramatta Observatory, which produced very unsatisfactory results. During this time, the ground based position stones would have been set.
    (I think, though I might be wrong, that the southern stone was about 8 meters due south of the ‘pyramid’, that was once on the left hand side of pebbled path. (It would appear where the “0” in “1800” in the caption of Figure 2 of the observatory’s grounds. This stone about 40-50 cm. tall and 30cm square. It has a small dimple in its centre, if I can recall.) All star transits (6600 in total) were made between 1859 and 1862 probably used the alignment of the north-south line.

    In 1863, this work was mostly discontinued, due to George Smalley’s doubts of the quality of the systematic work.

    In my reading and listening to various BAA lectures by the late Dr. Harley Wood, I was under the impression that the transit telescope has to be precisely aligned north-south to under 0.1 arcsec or better. To do this, a preliminary survey is done between marked stones — one well north of the instrument, one closer to the instrument in the south. The proportion is determined by forming two triangles, where the northern marker forms a triangle that points towards the SCP with a point above the instrument at zenith. The southern stone also forms a similar triangle which is aligned to the meridian and the aequator (0° declination). If you know the distance between the northern and southern stones, then you can deduce the angles (and sizes) to good precision. (The longer the base line, the more accurate the results.) By making small adjustments, you can make the this north-south line more accurate. These stones would normally remain years after, because the baseline can be checked in case of movement by earthquakes or continental drift over time. (These days we have other methods.)

    When the transit circle instrument was installed at Sydney Observatory in February 1877 (135 years ago), they used a new north-south, which is where Dr Lomb’s interesting story starts here. (Observations between 1877-81 were published by Henry Russell in 1881. I believe this was when the new markers of the meridian line were installed. [A similar procedure was made in April-May 1884 at Melbourne Observatory when setting up their transit telescope.]   

    Again I might be wrong, but one of the uses of an even longer north-south baseline used a marker was located on the opposite side of the harbour in North Sydney.

    Question. I notice that the transit telescope axis has a central square box, where two sides are attached on pivot bearings holding the telescope to the instrument mount. The other two sides each have a circular cover and has a latch, and the covers can be moved aside to allow an aperture aligned north-south. Once outside, covered by a wosden box, there was a small brass telescope aligned horizontally, that passed through the opened circular apertures of the transit telescope, and onto the survey marker. Is this the basis of the meridian line of Sydney?     

    Note: A discusion of the triangular methods of determining survey positions appears on pg.376-378 in the given reference. New South Wales territory is discussed on pg. 379-83 – especially the early role of Smalley positional works. Sydney Observatory geodetic latitude and longitude, the basis of all other datum, was in 1904 — 33° 51′ 41.1″ (S) 151° 12′ 23.1″ (The references wrongly says 141°, BTW.)

    Cheers,

    Andrew James

    (Again apologies for the length)

    • Hello Andrew. I knew you would have something useful to contribute to this topic! Thanks especially for the online link to Pietro Baracchi’s most informative article. Just a few quick comments:

      Fort Macquarie was at Cattle Point, later Benelong Point and now the home of the Sydney Opera House.

      The south marker for the transit telescope was and, still is, inside the thermometer shed. In the top photo above you can see the little window that allowed line of sight from the collimation telescope on the north side. The collimation telescope is currently in storage, but hopefully will be placed back in its original position in the near future.

      The stone you mention as the south marker came from the west side of the transit room, but had little significance and made use of the room impossible. Hence it was moved to the position you mention in the mid 1980s. Recently, it has been moved westwards to the fence to allow better access to the piers of the Jones transit circle.

      Yes, there was a marker in North Sydney that was erected in 1866 on Alexander Berry’s property. Happily, the marker is still in existence on Mount Street Plaza, corner of Pacific Highway and Miller St, North Sydney.

      Thanks again for your contribution. Nick

      • Thanks for the prompt return comments. Also thanks for quite rightly correcting me on Fort Macquarie. Ihave been sometimes confused with the basic positional work made at and near the lighthouse placed on South Head during the 1790s.   

        As for; “The stone you mention as the south marker came from the west side of the transit room, but had little significance and made use of the room impossible. Hence it was moved to the position you mention in the mid 1980s. Recently, it has been moved westwards to the fence to allow better access to the piers of the Jones transit circle.
        As for the stone marker, I’m a little bit confused over which stone you are referring too here. 

        The small stone I refer to was a rectangular partly-moss covered masoned stone was still outside in the leaf-strewn garden during 1972, and was aligned north-south with the transit room and was further south of the current marker. (I have a slide image of it from c.1974, but I’ll have to look for it.). The stone was about 15-20 metres due south from the transit room slit, and only about two or three metres from the old green fence in 1972. It looked like it had been there for a long time.

        I feel sure, there were once two main stone markers not just the current one.

          • OK. I’ll have to look for this slide and sent it to you.

            In the meantime, I would suggest you have a look a close look  “Plan of Flagstaff Reserve, Fort Phillip.” This shows the grounds of the Observatory from about 1860. (I think it was actually from 1864.) This drawing was from the Lands Department, S 319.858, which has in it key, the “Azimuth Pillars” 1&2, of which Pillar 2 is the one I am referring too. [This appears in James Kerr’s “Sydney Observatory” top pg,26.] Compare this to Russell’s whole image of 1880 [pg.28] in Kerr’s book, and illustrate potion of the second image beginning this very story. 

            Size of the placement is not to scale, but the current marker does not really correspond to the Pillar 2!

            I do think you might find that Pillar 2 might be this ‘missing’ stone.

            Note: If it were in the Lands Department, you might find either Pillars 1 or 2 are the original survey markers (supposition of course.) for Sydney!

            Kindest Regards,
            Andrew

          • Interesting observation Andrew. Allowing for the 30% difference in scale between the 1860 plans on page 26 of Kerr’s Sydney Observatory 2002 ed. and the 1880 plans on page 28, Smalley’s azimuth marker was in the middle of the thermometer shed or shade house where it still is today. Note that the stone pyramid or survey marker is related but separate from the azimuth marker for the transit circle telescope. Also note that the shade house was rebuilt in the mid 1980s so that part of the Observatory grounds looked somewhat different in the 1970s.

      • Your response on the Northern Sydney (northern marker) jolted my thoughts. This was commented by Harley Wood on the “Sydney Observatory : 1858 to 1958”, where he says under the part on “George Roberts Smalley”; 

        Smalley decided, that he could go on with the magnetic work and tidal observations and urged that the trigonometrical survey be started, but, having in mind the experience of Scott, he decided to restrict the programme on the meridian instrument which, he said in his first report to the Observatory Board, should be replaced by a first class instrument. However he made an arrangement to provide an azimuth mark on the northern side of the Harbour at a distance of 1.79 miles. [2.88 kms.]
        Note: If true, then this should indicate roughly the original positions of any one of the pair of markers along the original baseline using simple trigonometry. (as long as you know the distance of at least one marker.) 

        Another comment, not mention, is the height of the transit circle / telescope above mean sea level. (needed for calculations of latitude and longitude. This explains Smalley’s research into the tides in Sydney Harbour — which he requested to be the “Eastern extremity of Goat Island.” They selected Fort Denison instead.

        As a final comment, you might like to read something like; “Field and Astronomy for Surveyors” by Bennett & Freislich (1979) Published by NSW University Press. (It was once in the Library at Sydney Observatory.) It was used as a general text to train surveyors at university level.   

        This gives a good perspective on the methods used on with surveying equipment from more equatorial latitudes. It gives a brief but useful summary too of the complexity of the establishment of Fundamental Stations for transit instruments and astronomical observations that were needed to be made. [This book originally cost at Dymocks $122.50 in 1976, which I bought new a few years later for only $5!]      

  • I read this story with much interest, as I have being doing some general work on the subject. (as with the previous Wolf-Rayet story.)
    May I begin by suggesting that one of the most interesting reads on the earliest problems in astronomy and issues of latitude and longitude appear in a book entitled; Federal Handbook of the British Association for the Advancement of Science. [Download 24.4Mb.] In Chapter VIII “Astronomy and Geodesy in Australia” pg.326 (1904) written by Pietro Baracchi (Then Government Astronomer of Victoria in 1904) discusses the overall science here. On page 366, is an extensive discussion on “e.) Determinations of Australian Longitudes”, which is highly illuminating on this subject!It says among other things, that before 1883, the fundamental meridian was Fort Macquarie on South Head; whose corrected position is longitude 10h 04m 52.14s.- This remained the established geographical position when dividing up subdivisions of the entire Australian colonies.- The first surveying work in Sydney was made in 1839 by C.J. Tyers, who used the adopted Fort Macquarie longitude of 151° 15′ 14″ (The history of this appears pg. 370-374 in the given reference above.)About the “Alignment Stones” It seems the first director and Government Astronomer of NSW, Rev. W. Scott made the important detailed position of the Observatory site in April 1857., as so recommended by George Airy (Astronomer Royal) and by William Denison. Rev. Scott first determined Sydney Observatory’s position in 1858 as 10h. 4m 49.0s from twenty-one Moon transits.The first positional observations were done using the Jones transit circle from Paramatta Observatory, which produced very unsatisfactory results. During this time, the ground based position stones would have been set.(I think, though I might be wrong, that the southern stone was about 8 meters due south of the ‘pyramid’, that was once on the left hand side of pebbled path. (It would appear where the “0” in “1800” in the caption of Figure 2 of the observatory’s grounds. This stone about 40-50 cm. tall and 30cm square. It has a small dimple in its centre, if I can recall.) All star transits (6600 in total) were made between 1859 and 1862 probably used the alignment of the north-south line.In 1863, this work was mostly discontinued, due to George Smalley’s doubts of the quality of the systematic work.In my reading and listening to various BAA lectures by the late Dr. Harley Wood, I was under the impression that the transit telescope has to be precisely aligned north-south to under 0.1 arcsec or better. To do this, a preliminary survey is done between marked stones — one well north of the instrument, one closer to the instrument in the south. The proportion is determined by forming two triangles, where the northern marker forms a triangle that points towards the SCP with a point above the instrument at zenith. The southern stone also forms a similar triangle which is aligned to the meridian and the aequator (0° declination). If you know the distance between the northern and southern stones, then you can deduce the angles (and sizes) to good precision. (The longer the base line, the more accurate the results.) By making small adjustments, you can make the this north-south line more accurate. These stones would normally remain years after, because the baseline can be checked in case of movement by earthquakes or continental drift over time. (These days we have other methods.)When the transit circle instrument was installed at Sydney Observatory in February 1877 (135 years ago), they used a new north-south, which is where Dr Lomb’s interesting story starts here. (Observations between 1877-81 were published by Henry Russell in 1881. I believe this was when the new markers of the meridian line were installed. [A similar procedure was made in April-May 1884 at Melbourne Observatory when setting up their transit telescope.]   Again I might be wrong, but one of the uses of an even longer north-south baseline used a marker was located on the opposite side of the harbour in North Sydney.Question. I notice that the transit telescope axis has a central square box, where two sides are attached on pivot bearings holding the telescope to the instrument mount. The other two sides each have a circular cover and has a latch, and the covers can be moved aside to allow an aperture aligned north-south. Once outside, covered by a wosden box, there was a small brass telescope aligned horizontally, that passed through the opened circular apertures of the transit telescope, and onto the survey marker. Is this the basis of the meridian line of Sydney?     Note: A discusion of the triangular methods of determining survey positions appears on pg.376-378 in the given reference. New South Wales territory is discussed on pg. 379-83 – especially the early role of Smalley positional works. Sydney Observatory geodetic latitude and longitude, the basis of all other datum, was in 1904 — 33° 51′ 41.1″ (S) 151° 12′ 23.1″ (The references wrongly says 141°, BTW.)  

    Cheers,
    Andrew James

    (Again apologies for the length)

  • Dear Nick, thanks for this blog. You will be pleased to note that the latitude and longitude coordinates will feature on the new sign soon to be installed.

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