Ale Trail June 11th 2022

As “post-pandemic normality” creeps back into everyday life the first local Ale Trail since 2020 has been announced. With an all new route including nine of our favorite pubs to visit. If you have never been on the Ale Trail, in the past there has been a wide variety of beers, including our local microbreweries Purple Moose, Cwrw Llyn, Bragdy Lleu and Cwrw Cader, all served in some of the very best, off the beaten track and hidden pubs that the area has to offer. I hope to see you there.
Tickets are £20 in advance, £22 on the day available from all participating pubs from May and online. Full details here

This summer’s route

Answers to the Big 2021 Quiz

Here are the log awaited answers to the Big 2021 Quiz. How did you do?

  1. Who was the winner of the Grand National? Horse & Jockey

    Minella Times ridden by Rachael Blackmore who became the first woman to win the race

  2. Which country won the Eurovision Song Contest?

    Italy won with the song “Zitti e buoni” by Måneskin

  3. Pete & Ann were away on holiday for nearly all September, Where were they?

    Azores, Portugal

  4. Which county was this years UK Mega held in?


  5. In which month did Prince Philip die?

    April 9th

  6. What vehicle did Prince Philip choose to carry his coffin at his funeral?

    Land Rover Defender TD5 130

  7. A new £50 note entered circulation in June this year. Which scientist is celebrated on the new note?

    Alan Turing

  8. A ship blocked the Suez Canal for days causing worldwide delays: What was the name of the vessel?

    Ever Given

  9. A legal dispute hit the headlines in April when Colin launched legal proceedings against Cuthbert: Who are Colin and Cuthbert?

    Caterpillar cakes, from Marks & Spencer and Aldi respectively

  10. Bitcoin became the official currency in which Central American country?

    El Salvador

  11. The Zoom meeting of a UK council went viral this year, with one guest memorably exclaiming “You do not have the authority, Jackie Weaver!” What council was it?

    Handforth Parish Council

  12. The cast of which long-running American sitcom reunited for the first time since the show’s finale in 2004 this year?


  13. Who was the female tennis star from South London who won the US Open this year?

    Emma Raducanu

  14. Which American singer terminated a 13-year legal conservatorship giving their father and others control over their finances and personal life?

    Britney Spears

  15. This year ITV announced they had axed The X Factor – what year was the show first aired?


  16. What is Adele’s long awaited album called?


  17. Matt Hancock resigned as Health Secretary in June, after being caught doing something in his office – what was it?

    Cameras caught him snogging his aide Gina Coladangelo

  18. In January 2021, online retailer Boohoo acquired which brand and website for £55 million?


  19. Which news channel was launched on 13 June?

    GB News

  20. Who was the former owner of a Ford Escort sold at auction for more than £52,000?

    Princess Diana was the owner of the 1981 Ford Escort Mk 3 Ghia

  21. Police are called as hundreds flock to Diddly Squat Farm Shop – who is its famous owner?

    Jeremy Clarkson

  22. What is the name of the new James Bond film?

    No Time To Die

  23. September saw the eruption of a volcano on which Canary Island?

    La Palma

  24. The 2021 Labour Party conference took place in which seaside resort?


  25. The contactless payment limit is increased from £45 to how much?


  26. Alec Baldwin was filming on the set of which upcoming film when a terrible and fatal accident occurred?


  27. Hollywood stars Ryan Reynolds and Rob McElhenne visited which British non-league football club’s stadium for the first time since buying it earlier in the year?

    Wrexham AFC

  28. Voyage is a studio album released on 5 November 2021 by which group?


  29. Which supermarket chain spoofed the John Lewis Christmas advert?


  30. At the end of November, which country became the world’s newest republic?


  31. The northern part of which English county saw a massive swing from the Conservatives to the Liberal Democrats in a by-election?


  32. Where was “I’m a Celebrity 2021” held?

    Gwrych Castle

  33. Who was the winner on “I’m a Celebrity 2021?

    Danny Miller

  34. What is the is the current Geocaching Souvenir Challenge called?

    Reach the Peak

  35. In February, Captain Sir Tom Moore passed away, aged 100. He raised more than £30m for NHS charities by initially walking how many laps of his garden?

    100 laps of his 25 metre garden in Marston Moretaine in Bedfordshire

  36. In July, Unesco removed its world heritage status from which UK site?

    Liverpool, because new buildings undermined the attractiveness of its Victorian docks

  37. On which planet did Nasa fly a small helicopter called Ingenuity, bearing a fragment of the Wright brothers’ first aeroplane?


  38. Name the drummer of the Rolling Stones, who died aged 80?

    Charlie Watts

  39. Who controversially won the Formula 1 Championship in Abu Dhabi?

    Max Verstappen

  40. Which sports personality was awarded an MBE for their campaigning to help vulnerable children?

    Marcus Rashford

  41. In June which MP defected from Conservative to Labour, calling his former party “reactionary, populist, nationalistic and sometimes even xenophobic”?

    John Bercow former Speaker of the House of Commons

  42. Which landscape in Northwest Wales is given UNESCO World Heritage status?

    The Slate Landscape of Northwest Wales

  43. AUKUS, a trilateral security pact with was formed between the UK, Australia and the United States to provide what to Australia?

    Nuclear Submarines

  44. Who was the first civilian aboard his own winged rocket ship to reach space, attaining an altitude of 53 miles above ground—three miles beyond the threshold of space?

    Richard Branson

  45. Who filed a lawsuit against Disney — the parent company of Marvel Studios — over their decision to stream Black Widow on Disney+ simultaneously with the theatrical release?

    Scarlett Johansson sued Disney, accusing Disney of breaching her contract

  46. We all have heard of PCR Covid tests, what does PCR stand for?

    Polymerase chain reaction

  47. Which famous BBC DJ passed away on Christmas Day?

    Janice Long

  48. Who was the above’s famous brother?

    Keith Chegwin

  49. Which European country’s flag change went largely unnoticed?

    France, the blue is now a darker shade

  50. Slovenia laid claim to having the largest pile of which substance in Europe?


Geminids meteor shower.

As we approach the shortest day in mid December in the UK, on a clear night we see the Geminids meteor shower. This is one of the most active and reliable meteor showers in the astronomical calendar. Although this peaks on the early morning around 14th, it starts on the 4th and extends to the 16th of December. The best time to see this phenomenon is around 02:00 to 03:00 in the morning. The name Geminids comes from the “apparent” source of the shower the Gemini constellation which is currently to the east. That said, meteors from this shower can appear from just about anywhere in the sky, although they will appear predominantly from the direction of the Gemini constellation. Meteors are small stony or metallic natural objects from space usually the remains of a comet or collision between asteroids. When a meteoroid enters the Earth’s atmosphere, it is traveling faster than a speeding bullet, estimated to be greater than 11 km per second (25,000 miles per hour). Friction produced by the collision with the atmosphere, causes them to vaporise, and heat the air around it giving the characteristic trail, any colour is given by the material that is burning usually white for iron-nickel but can be blue, green or red . If the meteor reaches the ground it’s known as a meteorite.
The Geminids are intensifying every year and recent showers have seen 120–160 meteors per hour!

Geminids photo by Jeff Sullivan

Here’s hoping for a clear sky tonight.

Saturday’s Litter Pick

GC9HE10 CITO Season 2 by 9 Usual Suspects

19 geocachers gathered for Cache in Trash Out (CITO) season 2 at Morfa Common Park / Parc Y Dre on the banks of Arfon Seiont, returning for the 5th time since 2018. As we stood in the drizzle for the safety briefing it was an unpromising damp start, both in the weather and the amount of litter that had accumulated since our last pick at this location. We split up into groups and got on with the task in hand keeping a steady flow of bags back to the collection point, for kerbside sorting of the recyclables into their respective categories. As the litter pick progressed, the weather improved with some autumnal blue sky putting in an appearance and Morfa Common Park looking much tidier than when we had started. We would like to say a very big thank you to everyone for all your hard work.

Thanks Andy (YnysMonBirders) for the photos.

We would like to make everyone aware that a syringe complete with needle was found in one of the arches. Please be vigilant when out and about geocaching, you never know what you may come across.

Our GPS history and why we still use them along with our phones

We have been using a GPS since we started Geocaching way back in 2010. Our first GPS was the eTrex 10 with no maps, we just ‘followed the arrow’, it did however support downloading Geocaching GPX files via USB which made it ideal for Geocaching. A testament to the eTrex’s toughness and simple design is that this model, although revised is still available today. It was bomb proof had no touch screen just a thumb-operated joystick, monochrome display and a pointer to where the destination was, and how far away it was. The eTrex has exceptional battery life but was slow to get a signal and its accuracy was truly hit or miss under tree canopies. This little unit spawned many adventures for us.

Garmin eTrex 10 Patche99z, CC BY-SA 3.0, via Wikimedia Commons

After a few years of finding ourselves on the wrong side of a river or having to make a long hike due to a dual carriageway or some other obstacle blocking our progress we decided on the Oregon 450T which had Ordnance Survey maps 1:50 k. This was a revelation and for the first time allowed us to see a map which allowed us to plot a route unhindered by obstructions. The Oregon 450t had a touch screen, a SD card slot for maps and extra data, an electronic compass, a barometric altimeter and could store thousands of Geocaches. We got about 6 years of use and abuse out of these units. Maintenance, mainly due to rough handling, resulted in screens being replaced, buttons fixed and other sundry parts replaced until they both were beyond repair. I recycled parts from both and with some bits off a Russian GPS breaker on eBay, a ‘Frankenstein’ Oregon 550 GPS was created, this had all the same features as the 450T it now sported a 3.2 megapixel geotagging camera. Although this unit has now slightly out of date OS maps it is still fully functional and in constant use to this day.

By Garmin -, CC BY-SA 3.0,
Garmin 450T By Garmin –, CC BY-SA 3.0,

I personally own a Garmin GPSMAP 64s now, I never liked the touchscreen which with my big hands didn’t work so well for me, I love the buttons and simple menu system. The unit has a good sized display that can be read in bright sunlight which was always a problem with the older models and mobile phones. The reception is great even under trees, and the unit is quick to get a GPS lock. The 64s uses GPS + GLONASS + WAAS although not Galileo. I also 3D printed a simple mod that allows rechargeable batteries to be used and charged in the unit whilst connected to USB. Bluetooth is available and in reality only useful for transferring Geocaches to another compatible unit, it’s a battery killing extra I don’t need and is designed for external sensors like heart rate, therefore remains switched off.

Garmin GSMAP 64S By Virgilinojuca – Own work, CC BY-SA 4.0

So why do we still use this old tech? We get at least a couple of days battery life out of both the 550 and 64s which is a lot more than our mobile phones. If the battery runs out we just pop in another couple of AA batteries and off we go. They survive rough treatment much better than mobile phones. Detailed maps can be downloaded from sites like Open Street Maps and preloaded on SD Cards, these are always available even when there is no phone signal, this is also great for caching abroad where maps can be preloaded. They accurately track our route which can be examined in Garmin’s Basecamp software when we get home. I’m not saying GPS units are more useful than mobiles, but a phone with apps like Geocaching, C:geo, Looking 4 Cache is a perfect compliment to a GPS.

International Geocaching Day 2021

On Saturday 21st August, the 9 Usual Suspects celebrated 10th International Geocaching Day. The event was hosted by Bess’s Friends at Rocklands in Caergeiliog and despite the Met offices gloomy forecasts the rain held off. There was a great turnout with lots of the Usual Suspects along with some new faces. With the Geochat and food, of course, there were games this time organised by Bess’s Friends. The two teams were picked at random from a ‘hat’ with Bob and Steve being the first people out of the hat and therefore were nominated as team leaders. A treasure hunt was the first event and a great success for ‘Team Steve’, there was also a new throwing game donated by Team Marzipan which was successfully trialled, Elaine, Jude and Dawn were the only players to get a point, I think this says more about our collective dexterity than the game itself. ‘Team Bob’ fought back in subsequent games to win the competition by a narrow margin. Ray manned the BBQ and cooked the contributions bought by all, keeping up a regular supply of hot food for the afternoon. There also was a selection of home made cakes & puddings including a trifle from Sion, which complemented the great spread put on by Ray and Julie. The annual raffle was drawn, this one spanning 2 years due to covid with all the prizes being collected or posted to the winners. As part of the celebrations the 2021 TB Race was also started and the TBs embarked on their travels. The race can be tracked here as it unfolds over the coming year.

A huge thank you from all of us to Ray and Julie for their hard work in putting this event together.

CITO 14th August 2021

This CITO (Cache in Trash Out) was our first post-covid lockdown official geocaching event since 14 March 2020 and a chance to restore some normality. The weather forecast was iffy so kudos to all who defied the Met Office forecasts and turned out, as on the day, we had only the occasional light shower to contend with. This location was selected because: we have picked here before and know the location, it is fairly child friendly, and above all there was some litter to be picked. It was great to catch up with friends some of whom came from as far as Macklesfield and Oldham. It was also great to see some new faces and junior cachers who made a great contribution. In all 23 assisted with the litter pick including Diapason16 who happened to be in the area looking for a cache, he rolled up his sleeves and mucked in, unlike his daughter, who like a stereotypical teenager rolled her eyes and sat on the wall with her mobile phone :-). We cleared from Penygroes to Groeslon and collected about 12 bags of rubbish from the cycle path. The litter was sorted and taken to Rhwngddwyryd, Garndolbenmaen Recycling Center for disposal.

Many thanks to Inigo Jones Slate Works for letting us use their car park as a base for the CITO

Geocaching – 5 things you need to know

Geocaching HQ, Seattle

Geocaching is both a game and a business
 Groundspeak who manage Geocaching are a business. Groundspeak shows adverts on their website if you are not a premium member but this is minimal and restricted to a couple of small ones in your sidebar. They don’t get into big contracts to promote other people’s wares, so the money has to come from somewhere! Premium membership is their primary source for funds and about 7p a day, it isn’t a bad deal for Website in 26 languages, iPhone and Android Geocaching App, Adventure labs & Wherigo. Hours of fun for a few pence a day!

The orginal design of a Geocache

Play Fair
Don’t be a Geocaching tyrant, it’s a game played by many people most of whom you will never meet or know anything about. When Caching, it’s helpful to remember that the cache belongs to the owner, and if they say no photos of logs, signatures required, they are perfectly within their rights to delete your log if it doesn’t live up to the requirements set out in the geocaching page. If you don’t like this, then avoid that users caches, there are millions more out there. While there are rules, people’s interpretation of them may differ from your own. Rules like leaving a throw down when the cache is obviously there goes without saying, but deleting someone’s log for not signing because it’s too wet isn’t fair play IMHO.If you are a cache owner, please try to be understanding. People from all walks of life and all abilities cache, not everyone is as perfect as you might like. When submitting a new cache remember that reviewers are people, volunteers, and fit Geocaching in around their lives. Reviewers try to be objective and ensure everyone follows the same rules, but they are Cachers, like you and I, work with them to get your caches published. Check what is required before you submit a cache and make sure all the required information is on your submission, missing information is the largest cause of rejected caches. It’s not the reviewers job to do the leg work for you when you submit your new entry, if a reviewer rejects a cache and you don’t understand why, ask them.

Damp conditions at Cwmorthin

Go equipped
Having the right equipment makes for a great day of geocaching running out of battery or getting soaked is not. The primary item of course is a pen or pencil, and maybe a spare or two, there must be thousands of ‘lost’ writing implements left by Caches each week. Spare batteries or a power bank is essential for a day’s intensive caching, constantly using the GPS on your device is a heavy drain on batteries, and there’s nothing more infuriating than coming towards the end of lengthy series, only to have your phone die on you.
If you are heading up to the moors or into the mountains, appropriate footwear and waterproofs are the absolute minimum, snacks, water and a whistle should be carried as well. There are many articles on what to carry in your day bag online that can help you better than I can. Check the weather before you set out, because in the UK, it’s not unusual to have 3 seasons in one day. If venturing up a mountain or moors, it is worth noting as you gain altitude, the temperature drops surprisingly fast, around 1°C for every 100m, cold, wet and miserable isn’t a great day and possibly the quickest way to put someone off caching. If you are going into the wild and off the paths for a day hike, tell someone where you are going and when you expect to be back, it might just save your life, and don’t forget to let them know you are back at the end of the day.
Carry extra logbooks and pencils. We all know that it’s the Cache Owners’ responsibility to keep caches maintained, but sometimes life gets in the way, if you discover a cache with a full or wet log, please be kind and drop a new log in for them, don’t forget to message the cache owner and let them know what you have done. Please don’t slap a “Needs Archiving” on straight away, a simple message to the cache owner or a “Needs Maintenance” log is sufficient.

Ready for any weather

Get Social and meet other Cachers
Geocaching can be a lonely game, it is usually played in secret, and that’s half the fun. There are lots of events where Cachers gather and share stories of their adventures and great finds. There’s all sorts of social events from Cache In Trash Out which could be a litter pick or working with an environmental group to remove an invasive species from an area to a get together for a chat. It’s a great way to make new friends and catch up with old ones.

People who cache with kids love SWAG (Stuff we all get), it makes the day more exciting searching for treasure and primes the next generation of Cachers. The golden rule about SWAG: if you take something, leave something of equal or higher value. Kids and some adults love to find treasure, and it’s so much better if they can take a new toy away and leave something behind for others. If we want to keep the sport alive and growing, it’s our responsibility to pass our enthusiasm to the next generation.
Ideas for what to put in: Small toys, Key Rings, souvenirs like woodies or path tags, Trading cards (in a waterproof seal easy bag), foreign coins, rain ponchos
Do not put in: Perishables, e.g. sweets that go horrible quickly and mess up a cache, non family friendly items, fireworks, lighters, drugs, alcohol and any illegal materials should also not be placed in a cache, although if someone is considering placing any of the above items they really need to have a word with themselves.

A well stocked Cache

Lastly it’s a game have fun and help each other, it’s not that difficult 🙂

Numbers Stations, secrets hiding in plain sight

In the mid-late 20th century, before digital technologies, the radio was the easiest way to communicate over very long distances. The shortwave frequencies were crammed with pop stations, political propaganda and ham radio users. Jammed in between these transmissions, there were occasional unexplained broadcasts, some obvious analog data transmission and other unexplainable stations. Some of these broadcasts consisted of just a series of figures being read out in a mechanical voice, these often started with a short jingle beforehand to identify the station. Officially, no one knew what they were for, governments vehemently denied their existence, however, just about everybody knew these were spy communications. These mysterious transmissions were nicknamed numbers stations because of their transmissions consisting of apparently nothing else but sequences of numbers, and for want of a better name it stuck. I can vividly remember as a boy discovering these stations and being both puzzled and excited as I tried to decode them.

Antenna “G1” at Hörby Shortwave Station, near Hörby in the south of Sweden

Numbers stations were mysterious and suggested top secret agents, clandestine meetings, this was at the height of the cold war where the eastern bloc was the enemy from an unknown land and nuclear war was an ever present threat. They had names like the Linconshire Poacher, Cherry Ripe & The Russian man. It’s now certain these were transmitting codes using what’s called a One Way Voice Link (OWL) that required no response from the listener, apart from being tuned into a radio frequency at a given time along with their code book to decrypt the incoming message. The code was decrypted using One Time Pad (OTP), which at the time was considered completely unbreakable without the corresponding code book. The OTP was so called because the decoding sheet usually tiny was used just once then disposed of, each sheet had a random set of numbers which was used to decode the incoming message. There are 5 factors in using a OTP

The key must be as random as possible.
The key must be at least as long as the plaintext so it never repeats.
The key must never be reused even reusing part of the code would compromise the message.
The key must be a secret between the sender and receiver.
The key must be destroyed after use.

Using a one time pad

Every letter of the alphabet has its own number equivalent.


Convert letters to numbers

Replace letters with numbers from the table.

Replace letters with numbers

Now add the Numbers from the pad to our replacement numbers, if more than 100 use the last two digits only, then divide into groups of 5 and transmit


Encode using sender OTP

Our message becomes
79577 72928 96245 62806 09104 81713 76737 32342

To decode the message, the recipient uses the same page from his own one-time pad. Numbers are broken into pairs once again and subtracted, we will have to add 100 I the product of the 2 numbers is less than 0



Decoded message at numbers stage
Reconvert into the alphabet

Some OTP used X for spaces and punctuation and added an XX at the end of the code with padding letters after to make the code up to the required 5 letter blocks.

Copyright Mark Pitcher
Russian Shortwave Volna-K radio set

OTP is still in use today as a medium to send encoded messages that require little equipment to decrypt once received. Even using brute force methods on super computers isn’t thought to be able to crack the code and is as secure as when it was devised in 1882 by Frank Miller, although Quantum Computing will change this when they become large enough.

Times have changed, with the opening up of the eastern bloc, greater knowledge of these places due to travel most of the mystery has gone. Now the internet is currently used for most of our day to day communications these transmissions are laborious and largely redundant, although a few number stations still exist because of their simplicity to operate in remote parts of the world.

GPS Systems

GPS is now a part of everyday life, the ability to know exactly where you are on the planet was the dream of every navigator for millennia, now this is available at the press of a button. GPS is widely used in a variety of technologies such as mobile phones apps, cars navigation for both mapping and incident reporting, wildlife tracking which has yielded some interesting results for migratory birds and mammals and preventing crime by tracking desirable objects. This tech has only been available to the public since the year 2000 and has since become the most popular method of accurately establishing a location within metres. 


A short history of GPS Systems

The first publicly available Global Navigation Satellite Systems (GNSS) was the USA’s Navstar GPS satellite constellation. This was a satellite-based radio navigation system owned by the United States government established in 1978 for the USA military and made public in the year 2000 by the Clinton administration. America’s newest GPS system is now just one of many that provide geolocation and time information to a GPS receiver anywhere on Earth where there is an unobstructed line of sight to four or more GPS satellites. Other GPS systems include Russia’s GLONASS, the European Union’s Galileo, and China’s Beidou Navigation Satellite System which offer varying degrees of accuracy, the Galileo system being the most accurate at less than 1 metre for public use and up to 20 cm accuracy for paying customers in 2021.

NAVSTAR Global Positioning System satellite
Artist’s concept of a NAVSTAR Global Positioning System satellite, a space-based radio navigation network.

How does a GPS work?

GPS systems use sets of dedicated satellites, called constellations, these are not stationary but are circling the earth so ‘rise and set’ twice a day, the satellites constantly send out signals, the GPS receiver listens for these signals they don’t transmit anything back to satellites. To determine the location of the GPS satellites two types of data are required by the GPS receiver: the almanac and the ephemeris. The almanac contains information about the status of the satellites and approximate orbital information allowing the receiver to see which satellites should be visible. After establishing what satellites should be available for you to get a fix, your GPS receiver requires additional data transmitted by each satellite, called the ephemeris, this data gives very precise information about the orbit and location of each individual satellite. The GPS receiver uses the ephemeris data to calculate the location of a satellite within a couple of metres and then by using the information that was transmitted to the GPS, your position can be calculated by triangulation using the delta in time signal transmitted and when it was received plus the location of the satellites. The ephemeris is updated every 2 hours and is usually valid for 4 hours, so If your GPS receiver has been off for a while, it may take up to several minutes to receive the ephemeris data from each satellite, before it can get a fix, this is known as a cold start. Obstacles such as mountains and buildings block the relatively weak GPS signals, this will ‘lengthen’ and therefore distort the time to receive the data or even give a false location. On a Mobile phone, there is an additional A-GPS mode which uses the cell towers to calculate the initial position of the user very quickly but with less accuracy, unlike pure GPS this may send information back to a server where that might be helpful to process position. Once the receiver calculates its distance from four or more GPS satellites, it can figure out where you are to approximately a 7.8-metre accuracy and depending on the system in use the accuracy might increase. Using GPS for locating a point of the earth is a key component for Geocachers in their quest to find caches, hence the saying follow the arrow.

Photo: ©GSA, ©European GNSS Agency
One of the Galileo Satellite Constellation

Tips and tricks
1 Having obstructions between the GPS and satellites causes issues where 3 – 4 satellites cannot be seen simultaneously, this is most often seen in cities and forests where accuracy quickly degrades.

2 Multi-path or Signal reflection occurs when the GPS signal is reflected off buildings or other objects, this can delay the time-clock signal sent out by satellite and cause a miscalculation again resulting in degradation of accuracy.

3 In the Northern Hemisphere Face the internal Antenna toward open Southern, SW, SE, in the Southern Hemisphere revers this, most of the satellites are clustered around the equator, this will make getting a fix and maintaining on easier.

4 Low batteries invariably cause issues with GPS systems, make sure that your batteries aren’t on their last legs.

5 When you switch on GPS after moving more than 25 miles or replacing batteries keep it in one position in the open air to allow the ephemeris data to update, it will get a fix far quicker than moving with it.

6 Keep firmware up to date, if there are any bugs in your GPS program an update will fix the issues. If there are more up-to-date base maps in GPS standalone system, an update will repair that, too. 

7 GPS systems are not infallible so use common sense and your Mk 1 eyeball to check what you are being told by the system matches reality, learn to read a map and research where you are going. Most Geocachers will have stories of reaching a river or cliff face and being just meters from a cache that could not be reached without retracing their steps and trying another path.