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What is geocaching?

Australia's first geocacher

Head shot of Paul EdwardsPaul Edwards (kerravon) hid Australia's first geocache on 18 May 2000. To mark the 10 year anniversary, Paul tells how he become Australia's first geocacher.

At the recent 10 Years! event, I kept getting asked "how did you find out about geocaching?"

For me this is a strange question. It's a bit like asking someone "how did you know you were in a car crash?"

It's not that I "found out", it's more that it was "just there". I happened to be part of a community in which someone announced what use he had personally made of the switching off of Selective Availability (SA).

First some even older history ...

In the 1980s, the US and USSR were establishing GPS and GLONASS respectively. GPS had SA on, making it deliberately inaccurate - GLONASS didn't.

By 1991, both systems were mostly operational. But when the first Gulf War started, counter-intuitively, the US switched off SA because many soldiers were using civilian gear. With SA switched off, GPS was better than GLONASS (as they both stood at that time).

In 1995, GLONASS was fully operational. Due to the lack of SA, I believe it was theoretically the best system available to civilians in world history, a record it would hold until May 2000. But soon after 1995, the system began to degrade due to lack of maintenance, making GPS the only practical solution. And GPS was the only practical solution due to availability of relatively cheap receivers anyway.

I bought my first GPS (a Garmin GPS 12) in 1999 and joined the sci.geo.satellite-nav newgroup.

By February of that year I started asking questions about SA, such as who we needed to convince to get it switched off, or failing that, what techniques could be used to defeat it. I pointed out to some Americans (much to their chagrin) that while ever SA was on, they couldn't claim it as being the best navigation system ever.

Read more about selective availability here.

There was a solution to SA already known called DGPS. But it required extra, expensive, inconvenient hardware, plus the availablity of a transmitter, at a properly surveyed site.

Solutions that were eventually offered were:

  1. Normal DGPS
  2. Average the data over a long period, noting the correlation period of 3-4 minutes where measurements were effectively independent
  3. Get DGPS information via internet via mobile phone and feed that into the Garmin live
  4. Switch Garmin receiver into "raw" mode where it gives low-level info about the satellites, save that info onto a computer, and post-process it using DGPS information from the internet, to calculate manually
  5. Hacker's DGPS - note which satellites are in use at the time the waypoint is taken, then use that information to determine what error would have been in place, and make a correction to the waypoint.

The last option would have been the most convenient. It was proposed by a guy called ingen, and it was being debated in March 1999 and April 1999.

Some experts in this news group thought this was all nonsense, but I believed ingen to be correct. Unfortunately it was never resolved.

On the "averaging" option, there was a truly massive debate (more than 1000 messages) about that, that started in July 1999.

The argument was that two points taken one minute apart were not statistically independent, thus short averages were useless. But I said that even though they weren't statistically independent, I'd still rather have the average of two points than just one or the other. And thus it was better to average, even for short periods.

For example, if the first is 80 metres out and the second 60 metres, I don't know whether the 80 or the 60 is correct. But if I average them and get 70, I know I've reduced the maximum error.

The debate actually continued right up until May 2000, when SA was finally switched off. David Wilson actually produced data to prove that averaging was always the right option to take.

1 May 2000, SA was switched off.

Despite the fact that SA took a matter of hours to switch off worldwide, there continued to be a stream of 'reports' of SA being off in various countries. On the principle that "if you can't beat 'em, join 'em", on May 4-5, I reported that my street (Lamont St) in Sydney was now free of SA.

Two days after SA was switched off, Dave Ulmer planted the first geocache, which at the time he called a 'gps stash'.

It didn't take long for the debate over the name to start, with the first mention of geocaching occuring a few week's later.

Australia's first geocacher Paul Edwards by Geocaching NSW

On 19 May 2000, I reported the location of Australia's first geocache.

For digging up a National Park? Surely that's not against the law? Is that a potential fine for littering or what? Maybe I should dig it up and move it, as I left my email address in there. Oh, location is:

LCNPSH S33 47.2527 E151 08.7752 Sun Dec 31 00:00:00 1989 Lane Cove Stash

The 'stash' appeared on the first two listing websites; Alan Hennessy's website and Mike Teague's GPS Stash Hunt Homepage -

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

From: "Alan Hennessy"

To: "Paul Edwards"

Sent: Friday, May 19, 2000 7:05 PM

Subject: Re: Lane Cove GPS stash

Fantastic Paul....... Congratulations !!! - you're the first one in Oz !!!

I'll put the photos on the page as soon a spossible...but.......... what is the lat/long ?????

I need it in the same format as on the master site (

Hope to hear back from you soon so I can publish the site

Again...well done, mate !!!

All the best


It took several months before the next geocache appeared in Australia. I got so desperate that I had already obtained some more buckets, and was going to plant some more, when finally the second one came online.

Australia's slow uptake of geocaching is completely masked by the date of the first one. Fortunately no-one ever thinks to do stats based on time between first and second!

Looking back at how I exited the activity, and now the people pulling in the biggest numbers are in fact retirees, it is interesting that this is the only hobby where a younger generation made way for the older generation, instead of the reverse. Obviously the first geocachers were relatively young people who were willing to pay for a relatively primitive GPS so that they could play around with it, and were enthusiastic enough about the technology to participate in a newsgroup on the topic.

With SA now switched off, the technical challenge (of defeating the US military encryption) was gone, and I found other technical challenges to occupy my life with. Unless one day I tire of those, I don't expect to be actively involved in geocaching. I'm about as likely to do that as you are to participate in the sort of newsgroup I am actively involved in (which in 2010 was something even more obscure than Selective Availability was in 2000)!

I hope that the Lane Cove National Park will also be chosen as the venue for the 20 year anniversary, and that the many friendly and enthusiastic people that I met at the 10 year anniversary will return - even if they are no longer actively geocaching - and that no-one thinks "not here AGAIN – I'm sick of turning up to the same place every 10 years"!