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Suggestion: New Benchmark Hunt

Captain Morgan
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I read today new "Tähdet ja avaruus" (Stars and space) magazine of Ursa astronomical association. There was very interesting article about astronomer Wilhelm Struve. One paragraph of the article told about Struve triangulation chain, which starts from the delta of Danube and goes along the Dorpat meridian through Belarus, Poland, Baltic countries, Finland, Sweden and Norway to the coast of the Arctic sea. (This chain is also called Struve Arc.) What makes this chain interesting to us geocachers is that Struve and his colleagues marked all the points in this chain on the solid rock by drilling a hole. The hole was filled with lead and on the top of the lead was a plate of brass. In the course of time the plates have disappeared first. Most of them were found missing in 1890's already. Later the lead has been digged out, maybe to be made shots for hunters. However, nobody has been able to take along the holes in his pockets.


When i read the above facts, i realised that this could be a new kind of international benchmark hunt! To search benchmarks of Struve Arc. I guess the coordinates of those points are available somewhere, so what do you think, should we try to obtain those coordinates from somewhere and suggest to Jeremy Irish and other admins about this new benchmark hunt?


See also:

Struve Arc by Seppo Härmälä




Google results of the subject...




[This message was edited by Captain_Morgan&Family on August 14, 2003 at 12:18 PM.]


[This message was edited by Captain_Morgan&Family on August 14, 2003 at 11:19 PM.]

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Hey !


Check this:


Struve Arc 150


It says that they are goint to continue investigation into connection between Struve Arc and the Arc of the 30th Meridian in East Africa. It would be the the longest World Heritage Monument, stretching from near the North Cape of Norway at latitude N70°40'11" to S33°59'32" in South Africa !




[This message was edited by Captain_Morgan&Family on August 14, 2003 at 11:20 PM.]

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good morning captain,


this project really seems to be really great!!

I followed all your links, but I did not found a map where I can see which countries ly on this triangulation chain .


of course I know they are all gone but it would be great to see a sample of the plate of brass.

do you have a picture?


did you already found a rock wih a hole?


regards from cologne - germany




go eat

go sleep

go geocaching

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Interesting, very intersting indeed!

The modern triangulation points in Finland would be too easy as a local Benchmark hunt, they are well documented in Finnish topo maps and there are too many of them to make it a real challenge (just my opinion).

The Struve Arc has a good potential for a benchmark-type caching in the old continent.

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Picked up the thread from our country discussion - Thanks!


The prospects of establishing a benchmark hunt across countries and continents sounds very interesting to me - in South Africa. After having read a couple of the PDF's and discussing it with a friend in the game, some questions comes to mind:


1. How do we establish benchmark accreditations for finding a site? Photo by digital camera and GPS?


2. How/Where do we find documentation on where the Triangulation points are to be found or can be established/calculated.


3. How do we establish WHICH points in each country are to be nominated, and how many?


I am very interested in hearing comments...


Cashing regards


icon_confused.gif Global_Viking

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Originally posted by Global_Viking:

1. How do we establish benchmark accreditations for finding a site? Photo by digital camera and GPS?


I guess that's the only way to do it.


2. How/Where do we find documentation on where the Triangulation points are to be found or can be established/calculated.


I'm trying to get them from the people involved with the World Heritage project.


3. How do we establish WHICH points in each country are to be nominated, and how many?


Naturally all the points that are part of the arcs.



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From one of the PDF's I picked up the name of Jim Smith and his Email. I wrote to him to enquire. Below follows the correspondance.


I will try to gain more insight into how we can get coordinates on these Arc's and we can take it from there.


icon_smile.gif Global_Viking


Copy of latest email sent to Jim:


Dear Jim,


Thanks for your response. There is an interest amongst Geochachers (see www.geocaching.com) to look at each of the points on the Struve Arc possibly from a 'virtual cache' and 'benchmark caching' point of view. I saw on some of the documentation that some thoughts and/or work has been done on the 'Arc of the 30th Meridian', which has been done from South Africa, and I would be interested in making contact with those involved with that. I noticed a name of a Mr Brian Warner(?) somewhere along the lines, and if he has been involved with this then I would be interested in making local contact to him. If you have details on the people involved here (or Brian) then I would kindly ask for their contact details from you.


I could imagine the Geocaching community would be interested in the location of each of the points (both Struve and 30th Meridian) and to be able to locate these with their GPS. Is there a list available on where and which coordinates these points are located?


On the FIG site (www.fig.net) I noticed a beautiful picture of one of the marks which, if found by the Geocachers, would be impressive as the physical evidence that a Cache was found.


Yours sincerely,


Eyvind Jonsson


P.O. Box 782059



South Africa


Tel: +2711 706 3352 (H)

Tel: +2772 251 9418 ©

Email: viking@global.co.za



-----Original Message-----

From: JamesR.Smith [mailto:101765.332@compuserve.com]

Sent: 21 August 2003 18:00

To: Equator - Eyvind Jonsson

Subject: Struve Arc


Dear Eyvind,

Thank you for your e-mail re Struve. I hope you have not got confused along the way

but the actual Struve Arc is from North Cape in Norway to the Black Sea.

The arc in Africa

is roughly down the 30 th. degree of longitude and is called the "Arc of the 30th Meridian". This runs from near Port Elizabeth to Cairo.

It was said in the late 1800s that there was an extension from the Black Sea to Greece and then in the 1950s there was a connection from Crete to North Africa.

However as of now

there is still some of this connection between the two that has not been found in any Archive.


If the connection materialises then it would mean that there is a continuous triangulation

Arc from North Cape to Port Elizabeth.


It is the Struve Arc - ie North Cape to Black Sea - that we are hoping to submit to UNESCO

in Jan. 2004 as a possible World Heritage Monument. If that is successful, then we would try to get it extended all the way to S Africa.


If you could be more explicit in what you would particularly like to know about all this I will

try to fill you in.




Jim Smith

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Originally posted by Captain_Morgan&Family:


Could you please give the exact URL of that picture, as i couldn't find from that site.


The URL is:

Pictures of Stuve Arc Conference


I have posted a Word document, with all search results on the Query 'Stuve Arc', which you can down load by following the below link. Here you can read more about the various aspects of the work, that is being done. The link is:

Stuve Arc Search Results on FIG.Net

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In my communication with Jim Smith we have established 3 points so far. To me it looks like a bit of a task (time) to establish the points for this possible benchmark hunt.


Nevertheless, I still think it is a good idea. We just need to pool some resources in order to establish where the points are.


Next I have an opportunity I will contact our local university to find out if there is a way of establishing these points.


Please be careful with the coordinates provided in the response as I think there is a mixup between North and East. Copy of response from Jim smith:


Dear Jim,


Thanks for this information at least. I think for the part of the South African Arc we probably need to go via our local Wits University or via some Surveyors, who have local knowledge of this in order to establish the points here. I will post your answer on the board so long, as we at least have 3 initial points.


Thanks very much for the information you have provided us with.


Best regards




-----Original Message-----

From: JamesR.Smith

Subject: RE: Struve Arc


Dear Eyvind,

Thank you for your note.

As far as I am aware there are only a few points on the Struve Arc that have

substantial monuments. They are:-

Near Fuglenaes in Northern Norway. Lat. 70d 40m 11s Long. 23d 39m 48s.

Near Kittis in Finland. Lat. 66d 48m 34s

Long. 24d 00m 34s

Near Staro-Nekrassowka in Ukraine Lat. 45d 19m 54s Long. 28d 55m 48s


All I fear, a rather long way for you to go.

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Originally posted by Captain_Morgan&Family:

Eyvind, do you have any idea of the map datum of those three coordinates? Is it WGS-84 or some old system?


I guess it's WGS-84. I checked the first coordinates that should point to Fuglenäs, and in Genimap it points little bit north from Hammerfest, where Fuglenäs (Fuglenaes) is. The second point, which is near "Kittis" (Kittilä i guess), points in Genimap near Pello, about 97 km SSW from Kittilä.



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Originally posted by Captain_Morgan&Family:

Eyvind, do you have any idea of the map datum of those three coordinates? Is it WGS-84 or some old system?


Jim advised me that:


1) Coordinates must be NORTHERN Latitudes and EASTERN Longitudes. I guess most of us could work that out from the description, but in

anycase there we are.


2) The Datum is not known, but as they are very prominent monuments they should be easily found. The coordinates are only approximates.


I think this is very exciting as the Geocacher community can potentially "ad some value" by determining the exact coordinates for the "general public" according to the WGS-84 standard.


I have located a person in our National Library, who may have further knowledge on publications on the 30th Meridian. I will see where that leads me.



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icon_smile.gif I have good reason to believe that we should be able to contribute from South Africa to this exciting venture. I have now located a couple of people in our Directorate Survey and Mapping in Cape Town, who have worked a lot on this.


If you read the extract of my communication with Richard Wonnacut below, you will find that during the next week or two we should be able to get some 20 to 25 points to start off with.


I will probably load them initially as Virtual Caches, and if we can expand more we can then upgrade them to benchmarks, if we can get Geocaching in on the idea. Indeed very interesting...




Dear Richard,


Thanks for your encouraging response. I look very much forward to receive the about 25 points in South Africa. There seems to be a move towards establishing a so-called Benchmark hunt for points on the 30th Meridian and Struve Arc and as such connecting the Northern and Southern hemisphere. All this is quite ambitious and will probably take some time to achieve given the challenges on the rest of the continent.


Based on the 25 SA points I can suggest that we in preparation for the Benchmark hunt construct the points as a set of Virtual Caches along the lines of the rules for this. That means that we for our SA Caches can implement a rule for accreditation of these caches that a picture of the caches together with the actual coords of the GPS must be supplied (to me / us) in order to obtain accreditation. I have seen other caches where a picture must be taken of the GPS with its coords visible on the site, so that visible identification can be ensured.


In a roundabout way I think this can even possibly assist you guys too with your maintenance efforts albeit the GPS we operate with typically only have an accuracy of 2-4M. By having hundreds of people out there regarding this as a sport creates a lot more feet on the ground! If you are interested we can set it up in such a way that Chief Directorate : Surveys and Mapping will take part in the accreditation process, perhaps utilising a particular employee/student for this (if you are interested, of course), and in that way ensure data is coming your way. If we have success on the 25 points we can perhaps consider expanding by including such points that may be a challenge for you to maintain. Let me know what you think is feasible from your side.


On the issue of the rest of Africa, it would be very interesting for us to get an idea of how to establish the coords regardless of how crude they may be. This because the sport could be to locate the actual beacons and seek accreditation along the lines of above and thereby connecting through. I realise that this is a massive and challenging task, but nevertheless very interesting. It would basically be possible to ask the Geocachers (nearly) anything, because you can create the rules in such a way that accreditation can only be obtained following the rules. As long as the rules are not onerous it will become an interesting facet of the game and as such create a high number of followers interested in logging their caches.


I wonder if we could try a couple of the 'crude' transformations out, say in ZIM, to see if it is feasible. Is there such a thing as a publication from which one can do the transformation? Can lay-people do this (perhaps with guidance from either your people or a surveyor) on our own? In a way it could be an interesting thought to establish coords in the WGS-84 format in a de-facto manner in this way. I should think that an African unification of datums have a very slim chance of being carried out during the next many years, and perhaps the scores of some 60 000 Geocachers world-wide will give their contribution back using the WGS-84 standard of unification?


A great point to start with would be our local 25 points, and I really look forward to getting them from Tom, when convenient. I would be happy to procure some return favours to you guys as a part of this. You must just let me know how we can best contribute.


Thanks for your efforts in this regard.


Yours sincerely,


Eyvind Jonsson


-----Original Message-----

From: Richard Wonnacott

Sent: 03 September 2003 12:35

Subject: RE: Arc of 30th Meridian


Dear Eyvind,


I have been out of town for a while and have not had the opportunity to respond to your emails between Prof Liebenberg, Tom Zakiewicz and Jim Smith.


Tom and I had a look at the section of the arc as it is represented in South Africa. There are more than 150 points involved in this section of the arc stretching from Port Elizabeth to Beit Bridge on the RSA/Zim border. If you are happy we would like to suggest that we pass on the co-ordinates of only the stations that were used for the main astronomical observations. This would reduce the number of points to about 25. We converted our coord system to WGS84 at the begining of 1999 and will be able to supply these coords in that system (ie compatible with the GPS coord system) in latitude, longitude and ellipsoidal height. I have asked Tom to arrange for this to be done for you.


Unfortunatley, we are not in a position to assist you with coords of points in neighbouring countries. There could be an alternative route which we can take to get some of these coords. I will try to follow up on this for you.


While discussing the coords of arc points in other countries, I should point out that the coords systems in most of those countries are not based on WGS84 hence the coords supplied by the local Surveyor General will be on a non-WGS84/ GPS friendly coord system. One could be a few 100m out of position. This problem is the reason for a project ot unify the geodetic datums of Africa and which will not be completed for many years to come. As a result of this some rather crude co-ordinate tranformations may be necessary.


As part of the Geocaching exercise of these points would it be possible to ask that participants in the sport send us a photograph of the beacon. We do this as part of our normal maintenance programme but it takes up to 10 years and more in very remote areas to return to point. We would need the date and time at which the photo was taken plus a position.


Tom should be able to send you the coords of the 20-25 astro points by the end of next week.






R T Wonnacott

Director : Survey Services

Chief Directorate : Surveys and Mapping

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Just to let you know that I have received 26 points on the original Arc of the 30th Meridian, which was initiated in South Africa and goes up through the African continent.


I have started loading these, initially as virtual caches, to see what the result is.


I have been given an extensive document on the background of the Arc of the 30th Meridian, which you can read on the below URL.


Arc of 30th Meridian


I am not sure how well the figures turn out.


With a bit more research, we can possibly establish the (theoretical) points on the entire arc, but there are some issues associated with this, as beacons in the rest of Africa may not be fully maintained or on the exact position according to WGS84 datum.


I shall post the link to an example, once it has been approved by Geocaching.com


Happy hunting


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Hello !


I received today e-mail from Mr. Pekka Tätilä from National Land Survey of Finland. He writes that the points Mr. Smith has mentioned are (almost) the only points where is some memorial etc. He told also that "Kittis" is point that is located in Kittisvaara, near Pello and there is a memorial near it. (So it's not Kittilä, as i guessed.)


About the coordinates Pekka Tätilä says that they are more or less approximations and they have been given in different datum systems: the point in Norway is about in WGS84 and the other two points, which are from the end of 1800 - beginning of 1900, are in system called Bessels's ellipsoid and their values differ few seconds from GRS80-values.


Tätilä says also that things will get more clearer when project goes on.



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Originally posted by Captain_Morgan&Family:


He told also that "Kittis" is point that is located in Kittisvaara, near Pello and there is a memorial near it.


I tried to find information about this memorial and noticed that there really is a memorial in Kittisvaara, but it's not for Struve arc but for Pierre Louis Moreau de Maupertuis who did grade measurements in the area in 1736 - 1737. But did Struve use the same point 150 years later that Maupertuis, i don't know...?



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I have been given the scientific writeup on the topic of the Arc of the 30th Meridian and how it links up with the Stuve Arc. You can read all about it on the below link.


Arc of the 30th Meridian


The initial idea of logging the points as virtual caches can not be done because of the current rules, which by and large means that somebody has to visit the site or a place nearby in order to log a cache.


In order to set up the benchmark hunt we first need to identify the physical location of the points and then to discuss how we put it together.


I have been given 26 of the historical orginal astrological measured points in South Africa, and are still trying to get them logged as caches (difficult because of rules). I shall post a cache once I have one approved.


Best regards


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I bumped into this when reading some older postings.


I tried to find information about this memorial and noticed that there really is a memorial in Kittisvaara, but it's not for Struve arc but for Pierre Louis Moreau de Maupertuis who did grade measurements in the area in 1736 - 1737. But did Struve use the same point 150 years later that Maupertuis, i don't know...?


CM's first message in this thread includes a link to pdf that says: "In Sweden the responsibility for the work was given to the astronomer N. H. Selander. There the chain followed first the old Maupertuis Arc, western points at the Swedish side and the eastern ones at the Finnish side of the boundary." Well, it does not say whether exactly the same points were used or not.


What actually got me slightly interested in this is that I happen to have two books that also mention Maupertuis. I have borrowed them from the library already before reading this thread.


The first one is Osmo Niemelä's Suomen karttojen tarina 1633-1997 (Story of the Finnish maps, probably not available in English). Pages 16-17 tell shortly about Maupertuis' expedition. There is also a map of triangulation points he used. Kittisvaara is the northernmost point and Tornio church is the southernmost. Aavasaksa is also one of the points, for example. Finnish names in the map are funnily spelled, but recognizable. Memorial in Kittisvaara can be seen in another (new) map.


The second book is Réginald Outhier's Matka Pohjan perille, Otava 1975 (original in French: Journal d'un Voyage au Nord, 1744. Probably available also in English and Swedish). Outhier was a member of Maupertuis' expedition. Previously mentioned map is also in this book (page 92).


I haven't read the whole book yet. So I don't know if Maupertuis placed any permanent marks to those points.


Probably Captain Morgan already knew the things I said here... Or?


Edit: typos

Edited by MapMax
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