HOw ARBITRARY LOCATIONS TURN INTO PLACES OF INTEREST

. This article describes points that have almost become pilgrimage sites for people with geographic ent-husiasm. Details are given of three different types of special points where the coordinate values have been the key drivers for the site location. The first type is the well discussed Geographical Centre of Europe, the second type are points chosen by the Russian scientist Friedrich Georg Wilhelm von Struve to measure his legendary geodetic arc. The third kind of points is devoted to the so-called “degree confluences” that are integer valued intersections of WGS84 latitude and longitude lines. A global web-based project to collect and publish information about the points is presented including visitor statistics. Besides the provision of global statistics, special attention is given to those points located in Lithuania.


Introduction
Usually special attractions such as famous buildings, beautiful landscapes or extraordinary natural wonders decide weather a place is worthwhile a visit. This article however, is devoted to a different approach. It's about those places that have become meaningful simply through their coordinate values: The Geographical Centre of Europe and Confluences of Integer Degree Lines. As a third category -although not driven by coordinate only -the Struve Arc points are introduced. Figure 1 gives an overview of these special points in Lithuania.

Fig. 1. Location of Various Special Points in Lithuania
One point of each type has been visited as part of the social programme during the "2nd Swiss Geodetic Science Week" held in Lithuania in September 2007. This seminar was carried out as part of the cooperation between the Institute of Geodesy and Photogrammetry at ETH Zurich and the Institute of Geodesy at Vilnius Gediminas Technical University (VGTU).

The Geographical Centre of Europe
In 1989 Jean-George Affholder, a scientist at the Institut Géographique National (French National Geographic Institute) determined that the Geographic Centre of Europe is located at 54°54'N and 25°19'E. The method he used for calculating this point was that of the centre of gravity of the geo metrical figure of Europe. This point turned out to be lo cated in Lithuania, specifically 26 kilometres north of its capital city, Vilnius, near the village of Purnuškės. A monument (Figure 2), composed by the sculptor Gediminas Jokūbonis and consisting of a column of white granite surmounted by a crown of stars, was erected at the location in 2004.
According to the French scientists, the boundary of the continent runs along the Kara River, the highest crest of the Urals, along the Ural River and the Caspian Sea, along to the Apsheron Peninsula, over the highest crests of the Caucasus mountains, through the Black Sea and the channels of the Dardanelle and the Bosphorus, along the eastern shore of the Aegean -the border between Greece and Turkey -and through the Mediterranean Sea and the Gibraltar channel. The scientists did not take into account the location of Malta in the middle of the Mediterranean; in either case, this would change the location of the geographical centre of Europe by only 100 metres.

Fig. 2. Monument of the Centre of Europe in Lithuania
Lithuania's claim for the Centre of Europe is not unique. There are different opinions on the definition of the boundaries. One disagreement is in the answer to the question whether islands should be included or not? Should the extreme points count or the centre of gravity? Interestingly, many national surveying institutes managed to determine the Centre of Europe to be located in their own country's territory. As a result, about 10 locations far apart from each other are claimed as "The European Centre" -see Figure 3. Counties with their 'own' Centre of Europe are Germany, Poland, Slovakia, Ukraine, Estonia and Norway. Most of these centres have their own monument that can be visited.

Survey Triangulation Station Points of the Struve Geodetic Arc
The Struve Arc is a chain of survey triangulations, stretching from Hammerfest in Norway to the Black Sea, through 10 countries and over 2820 km. These are points of a survey, carried out between 1816 and 1855, by the astronomer Friedrich Georg Wilhelm Struve. The survey represents the first accurate measurement of a long segment of a meridian and was essential for determining the shape and size of the earth. The accuracy of the Arc measurement was 1/232390 (4 ppm). The original arc consisted of 258 main triangles with 18 station points located in Lithuania. Doubtlessly, the site selection was driven by topographic conditions, but eventually the coordinates follow geometric constraints along the 26th Meridian in form of triangles sides with ca. 25 km in length. The UNESCO World Heritage "Struve Geodetic Arc" nomination includes 34 out of 258 original station points. Three of these stations are located in Lithuania, see Table 1 and Figure 4. The location of the 18 triangulation points in Lithuania are shown in Figure 1. Most of the stations were originally marked with natural stones or wooden logs and remonumented with concrete blocks by Polish surveyors in the 1930s. More details on the Arc can be found in the thesis of Peterhans (2008) that includes an international online forum for the Arc at the website http://struvearc.wikidot. com/. This site gives opportunity for the 10 participating countries to keep records on the Struve points up to date and the world to watch progress in the research.

Intersections of Integer Degree Lines
How would the world look like if you were standing on an arbitrary point on earth? In order to get an unbiased view of the world the following attempt is being made: each of the latitude and longitude integer degree intersections in the world are visited, pictures are taken at each location, stories about the visits are collected and posted at a website. Altogether there are 64'442 intersections -let us call them "degree confluences" since these are the meeting places of geographical latitude and longitude degree lines, see Figure 5. 21'543 confluences -almost exactly one third (33.4%) are on land. Ignoring those confluences without view of land and after thinning out the poles region which has an impropriate density of degree intersections, still 16'194 confluences are considered as worthwhile visitingin the following denoted as "primary confluences". Standing on any point on Earth, there is always one confluence within 79 km radius. Typically, confluences are about 100 km apart. Using the WGS84 system that includes the mathematical GRS80 ellipsoidal model of the Earth we find that the distance between degrees of latitude varies from 110.57 km at the equator to 111.69 km near the poles. The distances between longitude lines continuously decrease from 111.32 km at the equator towards the poles. However, the locations are reasonably well equidistributed for representing the earth, but also creating a huge task for reaching them. This is in particular the case, because the confluence locations go against all human infrastructures.

The Degree Confluence Project
76'681 pictures and 10'461 stories about confluence visits in 179 countries have been collected at the project website with the URL www.confluence.org. One of the project's principles is to keep the confluence points as they are. Any changes made by visitors -e.g. leaving souvenirs, or even placing markers, sign posts, cairns is considered as pollution and visitors are encouraged to follow the policy "take nothing but pictures, leave nothing but footprints". It all began in February 1996 when the US-American citizen Alex Jarrett used his new hand-held GPS receiver in order to reach the nondescript location 43°00'00"N 72°00'00"W. After bicycling 16 km and a bit of a hike he was able to exactly locate and document the spot. An then he posted his pictures of the confluence to a website that showed some snow covered trees of New Hampshire's winter. From there snowballing began. Alex visited another confluence in May of the same year, in the following year the number of visits doubled to 4. Other people joint the project quadrupling the number of visits each year, so that in 2001 the tremendous number of 1513 postings had been reached. Since then, progress continued at a constant rate between 1000 and 2000 postings each year. Figure 6 shows that the total number of confluence visits each month has been approximately at a constant level over the last 6 years. Clearly, there is an obvious yearly cycle with a summer-peak and a winter low.
Even though the total number of visits hasn't changed, progress towards the project goal has in fact slowed down. After taking revisits out of the statistic in Fig. 6, we find that the actual rate of first conquers has halved within the last 5 years. The project progress differs largely in from country to country. As can be seen from Figure 7 and 8, initially all of the world's first visits had been occurred in the USA. The passion for confluencing reached Europe in 2001 and Russia in summer 2004. From Figure 8 it can be witnessed how quickly Lithuania and Germany (as comparatively small countries) were captured almost totally within one single year. The USA still remains 25% incomplete due to remote Alaska. Densely populated countries such as China find more and more enthusiasts -now being finalised by 40% China has overtaken the world average in terms of reaching completeness. However, huge remote unpopu lated areas such as the Himalaya region in China or the Siberian tundra in Russia will prevent completion for quite a while. Apparently, key factors such as Gross National Product (GNP) and population density seem to be the main drivers for both, light emission and confluence visiting. Figure 10 presents the distribution of confluences by latitude. Antarctica causes all intersections at latitude 78°S or further to the South Pole to fall on land. But almost none of these Antarctic confluences have been visited. At the equator as well as close to the poles, finding integer degree intersections seems to be rather difficult due to remote jungles, swampy tundra and ice. The two peaks in black in Figure 10 indicate that temperate zones are preferable regions for 'confluencing' .

APŽVALGINIS STRAIPSNIS
The reported accuracies of locating confluences are driven by two key factors: the minimal distance at the nearest point and the GPS accuracy. Initial positional accuracies had been around 10-30 m, but after removal of selective availability in May 2000 accuracies improved to 5-10m. Nowadays with the help of augmentation systems accuracies of 1-5 m are typical. In the year 2012, assuming availability of 35 Beidou Navigation Satellites ( ) ), 18 GLONASS satellites, 30 Galileo satellites and an improved GPS, positional accuracies of less than a meter can be expected. With 107 satellites in the sky, positional service will cover deep canyons and forests. Even today a fix position solution is oftentimes possible for confluences that are located in forests or valleys but accuracies are low due to shading of satellites. Figure 11 shows how close confluence visitors were able to reach their target. The maximum at 5m correlates How clos e did visitors approach the con uences? Fig. 11

2. Confluence Points in Lithuania
10 confluence points are on Lithuanian land; their details are given Table 2. Most of them are located on fields and can be easily accessed by car. However, three points are located in water such as 55°N 24°E, see Figure 12.

when will the confluence project get finished?
At the time of writing 10'886 unvisited primary confluences out of 16'194 that belong to the project goal are waiting to be reached. Currently, the rate of first visits to primary confluences is 1-2 a day, or 500 a year. Assuming a linear trend, the last confluence should be visited in 22 years, i.e. in the year 2030. However, when it comes to finish the last 1%, I predict a clear slowdown: as can be seen an asymptotic completion for individual countries from Figure 8 this may well be valid for the whole world. Imagine that the very last unvisited intersections may need special permission due to restricted areas or they are just extremely unattractive for a visit. This fact could postpone project completion beyond the year 2050.

Conclusions
This article has shown that originally insignificant locations that had neither a meaning nor a specific feature have become meaningful just from their determined coordinate position. Three very different types of such points have given proof that arbitrary locations can turn into well visited attractions not only for geographic enthusiasts but also for tourists and the general public.