A Reverse cache is a type of geocache where a finder is guided to a specified location or target location. i.e. The box will help you to arrive at a specific location. At the location, either a log book is revealed to be signed (for example, a box can be opened) or a logging requirement (such as a description of the location or code) is made known to the finder.
In the few examples that are listed at Geocaching Australia the GPS-enabled box presents users with a deceivingly simple button and a small display. You press the button and the display reads a distance. Players only have a limited number of chances to move the box to the correct location before the box locks forever. At location 1 you might be given a distance of 2000m. You know know that the box will unlock on a circle with a radius of 2km from your current location, but where? Way too many possibilities. You move to a new location and press the button again. You are given a different distance, say 2100m. You now have two circles. The first based on your original location and the second at your current location.There are two places at where those circles intersect. The box will open at one of the those two locations. But which one? Move for a 3rd time and try again. The three circles will intersect at only one location. Find that and the box will open. In general the cache owner will provide instructions on their specific reverse geocache when you pick it up from them.
A Reverse cache is normally an electronic hardware device, utilising its own GPS location to determine how far it is from the target location. However, it could also be a software application or web page, which then utilises the GPS functionality in smart phones.
If you are going to publish a reverse cache, consider how people will contact you to organise picking up a hardware device. Please also consider how people will know when the device is being used by another cacher and therefore not able to "find" the reverse cache at that time.
From April 2021, Geocaching Australia developed the capability to use your smart phone and the Geocaching Australia website to track down a reverse geocache that is not a specialised hardware Reverse Geocache. When listing your Reverse Geocache follow the simple suggestions to make the geocache fun for everyone.
- The geocache container should be a lockable geocache which requires a code to unlock to keep this in the same vein as a specialised hardware Reverse Geocache.
- Set the co-ordinates of the geocache as either the location of the physical geocache or use it as a general area where the Reverse Geocache may take you (see the Codeword Response bullet point below for other uses).
- Use the "Final Co-ordinates" in the GeoChecker" on the geocache listing page to:
- Tell the Geocaching Australia website and the seeker "how far" the Reverse Geocache is from their current location.
- Set the location (within 10m) at which the Geocaching Australia website will provide the codeword.
- Use the "Codeword" on the geocache listing page to list the key to unlock your physical geocache container when the seeker finds it.
- Use the "Codeword Response" on the geocache listing page to provide additional information about the geocache if desired.
- If you choose, you may use the co-ordinates on the geocache listing page as the general area and then use the Codeword Response area to provide additional co-ordinates to find the locked geocache container, adding in an additional level of challenge.
For a listing which is not a specialised hardware Reverse Geocache then using your smart device with GPS enabled do the following:
- Click or tap on the link "Reverse Geocache Tracker" in the Actions area of the geocache listing page.
- Give permissions for the Geocaching Australia website to access your GPS.
- Note: Geocaching Australia does not use your co-ordinates for any purpose other than calculating the distance to the Reverse Geocache.
- Take a note of the distance that the geocache is from your current location.
- Move in any direction by half the distance shown and "Refresh the page" to see the new distance.
- Note: You may only take a reading every two minutes, so be wise with your choice of distance and direction and remember that your GPS will never be 100% accurate so small changes in the distance may be evident.
- Continue to plot distance from each point taken until you can determine the direction to hone in on the geocache codeword location.
- Once you are at the location the codeword will be provided for you to unlock the geocache and additional information may be provided as to where the physical geocache is located.
Hints, Tips and Tricks
Making a physical hardware Reverse cache will be expensive to buy the necessary parts and some electronics and programming knowledge will be required to construct one. Also the device should be robust enough to survive being used by other cachers.