Welcome to Boss James Reserve.
This cache is intended primarily for Geocachers who have yet to hide their first cache, although of course, all cachers are welcome to complete it to obtain a smiley. It is intended to fill in some potential gaps in the basic concepts which you need to understand in order to be a proficient Geocache Owner.
Multi or Mystery?
This cache is a multi. You might ask why is it a multi and not a mystery, as you need to complete a task akin to a puzzle. If you look at the differences between a multi and a mystery here, you'll see that with this cache it is necessary to visit all the waypoints. On the other hand, a mystery can usually be solved without visiting the Posted coordinates, often from your desk at home. (Who solves puzzles in an armchair anyway?)
How do Coordinates work to identify a location?
We live on the earth, which is a sphere, or more correctly, an oblate spheroid as it is a bit squashed and fatter around the equator and not a perfect sphere. Therefore to create a map, we need to come up with a way to represent the curvy earth on a flat map. The methods of doing this are called "Projections".
There are different ways of doing this, depending on what your objective is.
- To represent an area on a map that is directly proportional to an area on the earth's surface we could use the Lambert Projection.
- To produce a map where a straight line on the map is the shortest distance between two places on the earth we could use the Mercator projection.
There are very many different projections and we don't need to worry too much about this, as long as the system of coordinates we use works correctly with the map we use.
In Geocaching, we generally use the projection used by Google Maps and Open Street Mapping, which is the Web Mercator Projection. The important thing for us is the Datum which ties it all together and ensures that a set of Latitude and Longitude Coordinates on the map, usually expressed as South and East for us in Australia, correctly ties a location on the map to a location on the earth. The Datum that does this for us is called WGS 84. Your GPS unit (usually a Garmin or Magellan) needs to have this set correctly or your coordinates will not be accurate. Usually, Smartphones have this hardcoded and it will not be an issue you need to worry about.
Coordinate Formats
There are three main formats.
DD MM SS (Degree Minute Seconds or DMS) eg. S 37 56' 30'' E 145 1' 17''
This is the traditional format which is probably the first one you came across. It has been in use from the earliest times of navigation and is still in use today. The iPhone Compass app still uses this system I believe. It has a serious problem for Geocaching, however. The precision of the system is based on the distance between adjacent measurements, that is, the distance you move to travel 1 second. In Melbourne, this is about 30 metres. Fine for navigating a ship, but not much good for Geocaching. Converting it to another format doesn't increase the accuracy of your coordinates because the precision is not there to begin with. Sometimes decimals of seconds are added, but that makes it very complex.
DD.dddddddddd (Decimal degrees or DDG) eg. -37.94185 145.021433
This is the format commonly used in computing and things like Google Maps. It's fine as far as precision is concerned as long as you use at least 5 decimal places. This should give you a system capable of resolving down to about 1 metre which is a bit more than your device can measure usually. The problem with this format is that the string of numbers can be awkward to use without making mistakes, such as transcription errors. And then there's the +- NESW convention to remember.
DD MM.mmm (Degrees and Decimal Minutes or DDM) eg. S 37 56.511 E 145 01.286
This is the format we use for Geocaching and is the format you should use to measure your coordinates. The precision of the last digit is about 2 metres which is a good match between what our devices can measure, the resolution we need for Geocaching, and our human ability to manage numbers without making too many errors.
You should set your GPS or Smartphone app to use this format, and get used to using it consistently in all your Geocaching activities.
How the Global Positioning System works.
There are about 24 GPS satellites in orbit around the earth, at 20,180km above sea level. Each one completes an orbit once every 11 hours and 58 minutes. Signals from these satellites are picked up by your GPS or Smartphone. At any location at least 4 satellites should be able to be received, but usually quite a few more. Each satellite continuously transmits the time and its position and your device uses this information from a minimum of 4 satellites to calculate your location.
The important thing here is that atmospheric conditions, angle of the satellite above the horizon, objects in your vicinity or other factors can slightly affect the time of each signal to arrive, so the GPS unit uses as many satellite signals as possible to determine the most accurate result it can, and eliminate outlier results.
This is one of the reasons why when measuring coordinates, you need to let your device settle at the location, and give it time to detect as many satellites as possible and calculate a large number of results in order to come up with the best set of coordinates for your location.
Measurement Techniques
Don't try and get coordinates from Google Maps. This can be a good way to do a reasonableness check on your measured coordinates, but sometimes the results can be 10 to 20 metres out, and not great for Geocaching. Also, in many locations, it's very difficult to pinpoint your location on the map anyway due to lack of, or too many, landmarks such as trees. And you'll need to convert the DD.dddddd format to get to DD MM.mmm, an error-prone process.
So, we need to be at our location, with our GPS unit or Smartphone.
The best way to get accurate coordinates is to take a number of readings and average the results. Don't just front up, turn on your device and take a reading. You might get something in the next suburb as your result.
You should let your device settle, and take about three readings, 2 minutes apart and average them. This is easy to do as you really only need to look at the last three digits, probably only the last one will vary in good conditions.
Most good quality GPS units will have a function to measure a waypoint using averaged readings. These will continuously take readings and average them until after a large number of readings over several minutes, the average doesn't change.
There are also some smartphone apps that do this. On iPhone use GPS Averaging, and on Android use GPS Point. There are others, but these are both very good. These apps make it very easy to get an accurate reading, and then copy and paste, or export the reading by email or whatever, to make it easy to use later. Note that apps like Cachly and C: Geo don't average readings, not yet anyway, so they are not a good choice for this function.
Always Test your Coordinates on-site
To ensure your coordinates are accurate, put them into your device as a new waypoint. Walk away about 40 metres and then use your device to navigate back to the location. Do this from several different directions to ensure your coordinates get you to where you need to be. If not, start again. This really the only way to justify having full confidence that your coordinates are accurate.
THE CACHE
Thanks for staying with me. If you're an experienced Geocacher you probably jumped to here pretty quickly, but if you read to here, I hope we might have cleared a few things up.
Waypoint 2
At the Posted coordinates, look around you. Not too far away, you'll see some cricket nets and a shed beside them.
You need to go to the shed.
Once you arrive at Waypoint 2, you need to find a sprinhler controller cover. Use your device to measure the coordinates. Hold it directly over the cover, but don't place it on the ground, as the metal cover and rebar in the concrete may cause issues.
This is what you seek.
Once you have what you believe is a good set of coordinates, put them into the following checker. If you have measured your coordinates accurately, the checker will give you the final location of the cache, which is a short drive or ride, or a 15-minute walk away.
If you have trouble, try measuring again or vary the least significant digits a little. I'm looking for coordinates within 3 metres, which means the least significant digit in the decimal fraction can be one-off on either side of my measurement.
I hope you enjoyed this cache, and if taking accurate coordinates has been causing you some grief, perhaps this will in some way have helped to pave the way for you to master this skill.