How to get good coordinates (when hiding)
Many cachers complain when they find a cache and the coordinates are 75 feet away. To help prevent this from happening to your caches, use one of the following methods:
- Approach your cache and hold the GPSr as close to it as possible, with as clear a view of the sky (GPS satellites) as possible. You can suspend the unit over the cache from a branch or walking stick.
- Wait for 3-6 minutes without moving your GPSr, then mark a waypoint.
- Repeat the previous steps multiple times, walking away and returning from a different direction each time.
- For even better accuracy, repeat the previous steps on another day when the weather is different.
- Return to your cache, wait several minutes, and check which waypoint is the closest to your current location.
- Repeat the previous step until it becomes obvious which waypoint is actually the closest to the cache.
This method works very well for units that auto-average like Magellan's SporTrak series.
- Approach your cache and hold the GPSr as close to it as possible. You can suspend the unit over the cache from a branch or walking stick.
- Ensure you have good satellite geometry and signal at the point you are marking.
- Let the unit average for about 3 to 5 minutes.
- Move the unit just enough to break auto-averaging and immediately replace in the same spot.
- Let the unit now average for at least 10 minutes if you have good signal and coverage, longer when signal and coverage is poorer.
- Mark the waypoint.
Make note of the Datum that your GPS unit set to use. The common datum used on Geocaching.com is WGS84, although they no longer print that fact next to the coordinates of a geocache. If you wish to publish your geocache on geocaching.com, and you are using a different datum, few, if any people will find your geocache, unless the hint very explicitly describes the location.
Magellan SporTraks are notorious for their "sling shot effect" so obtaining accurate readings are completely different from many other units, but the above method will yield very accurate results
Some tips for getting good readings
- If the cache is in an area with very bad reception, go into a nearby area with good reception, get a good number of satellites, then walk in a straight line toward your cache before taking a mark.
- Always wait at least 2 minutes before taking a mark, even with lots of satellites. This way, the GPS has time to average the signal from the satellites and get more accurate coordinates.
- Read the users manual. It should tell you how to hold your GPS to get better reception. For Magellans, at least, you should hold the GPS vertically, so that the top is pointing up.
- Pretend to place a cache in your backyard or nearby common area. Use one of the above methods to mark the "cache." Return on a different day and repeat the procedures to gain confidence your method is working for you.