Eclipsed Tower Mystery Cache
Hidden : 11/13/2011
Difficulty:
3 out of 5
Terrain:
1.5 out of 5

Size: Size: small (small)

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Geocache Description:


The cache is not at the listed coordinates. This puzzle involves lining up two towers located in West Hobart and then obtaining numerical information that is used to determine the coordinates of the cache.

An Australian Government AUSSAT Earth Station was built in a disused quarry in Knocklofty Terrace, West Hobart in the 1980s. The 13m receiving dish was later removed and Optus now controls the site. The main visual feature is a communications tower. Also visible is a second smaller, now decommissioned, tower approximately to the south of the main tower. We will call the small tower Tower A and the large tower Tower B.

The first part of this puzzle involves finding objects bearing numbers that lie along the line (Line L) originating at the centre of Tower A, that then passes through the centre of Tower B and proceeds approximately north through West Hobart and Mount Stuart (and onwards). When standing near most of the objects, the two towers can be seen with Tower B in front of and eclipsing Tower A. However at some of the objects one or both of the towers are not visible and you will need to work out how to solve this dilemma.

The Objects

The required number-bearing objects are either houses or Aurora power poles. Numbers to be identified are represented in the following table by the letters A—H, I and J where each is a digit in the range 0—9.

Street name Object Number
Elphinstone Road Pole 1726AB
Lower Jordan Hill Road House CD
Mellifont Street House EF
Mount Stuart Road House GH
Summerhill Road Pole 1781JK

House numbers: In each specified street find the house with an odd number that is on a block of land that Line L passes through. If the line is on a boundary choose the house with the higher street number.

Power poles: In each specified street find the main power distribution pole, made of wood, closest to Line L. The pole will be numbered with a 6 digit number preceded by the word "Aurora".

The Two towers

Both towers are on private property that is surrounded by a security fence. It is therefore not possible to directly measure the towers' coordinates. The Register of Radiocommunications Licences (web site) that is maintained by the Australian Communications and Media Authority reports the location of the main tower (Tower B) as S 42° 52' 53" E 147° 18' 11". The precision is said to be within 10 metres and the Australian Geodetic Datum 1966 [AGD66] was used. (Note: this is not the WGS84 Datum.) Tower A is within about 20 metres of the security fence and it is possible to make a crude direct measurement of its coordinates.

The Cache

The cache is hidden at:
  • S 42° 52.uvw E 147° 18.xyz
Where u—z is each a digit in the range 0—9.

To evaluate u—z some simple numerical manipulation has to be performed.
  • u = A - K
  • v = B - C
  • w = J
  • x = G - F
  • y = E
  • z = H - D - E
The cache is in a small plastic jar in a black bag. It consists of a log book, pen and a few small swaps. Please help preserve the anonymity of this cache location when writing logs and presenting photos.

You can check your answers for this puzzle on GeoChecker.com.

Additional Hints (Decrypt)

Ebpx-obggbz Nyybpnfhnevan

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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