Geocaching
Navigating the Final 20m
You'd think that after having got to within 20m or so of your desired location with a GPS, the final few meters would be a walk in the park (minor pun intended!). After all, GPS manufacturers boast superb accuracy nowadays so in theory you should be able to walk right up to geocache and reach right under that log or in that bush and retrieve your prize. In fact, all things being equal, the final 20m or so can be the most difficult. Before we look at ways that you can make the final leg easier, let's take a quick look at why this end bit is harder than any other part.
- Your GPS isn't 100% accurate! It doesn't know where you are, it estimates where you are. There is a big difference.
- Playing the averages - As you travel , GPS in hand, the device is averaging your position all the way. The further you are away from the cache the less all these averaging errors matter because when you are say 1000m away from the cache (or 100m for that matter) the direction of travel arrow on your GPS is still going to point in the general direction you have to go.
- As you get closer to the cache there is natural tendency to slow down ... after all, the slower you go, the more accurate everything will be, yes? Well, in fact, no. Most GPS receivers (GPSr) relay on the GPS being in motion to work out the right direction to go in (it uses the GPS signal as a compass - although some GPSr do have a in-built compass). Slowing down as you get nearer to the cache is not normally going to help you!
- Cachers usually don't hide caches in plain sight or on open ground. Look for things that stand out - a lone tree of a rocky outcrop. Usually there is substantial trees involved which can interfere with the signal to your GPSr.
- Remember too that the cache itself has been hidden - the geocacher that placed the cache doesn't want to make your find too easy!
OK, this is what you are up against. So, what are the best strategies to help make finding the caches that you are seeking easier? Here are a few of the best:
- Don't aim for the cache - aim beyond it
- Look for signs of disturbance
- Look for a break in the tree cover
- Search patterns
- Stop and average
- Come at it from a different direction
- Look for the unnatural
Let's take a look at each of these in a bit of detail.
1 - Don't aim for the cache - aim beyond it.
This sounds like the normal thing to do. Walk and walk and walk until the distance reading reads 0m and then you must be there. You've been conditioned by the GPSr to count down the distance over however many hundreds of thousands of meters you've been walking so it's natural to think that this is what you can expect.
A far better trick is to aim beyond the cache - the GPSr is unlikely to take you much closer than say 5 - 10m so use this to your advantage. So, make a note of when your GPSr is telling you that you are 10m away from the cache and then keep going. The direction of travel arrow will then probably begin to waver and spin erratically. Keep walking in the direction you were going and eventually the arrow will settle and point behind you. Keep going until you are about 10m away. Now stop. Look behind you to where you made a mental note of being 10m away from the cache and halve the distance between where you are and that point. That gives you a very good starting point for your search.
Resist the temptation to slow down and stop when doing this 20m bit - this will only add to your errors! Rather than slowing down, stop and let your GPSr get a good lock instead.
2 - Look for signs of disturbance
Chances are, you're not the first person that's looked for and visited the cache - and even if you are, the person who placed the cache has been to where it is already! As you are approaching the cache keep a good look out for signs that others have been there before you. Many of the popular caches are dead easy to find because the previous cachers have left a trail like a motorway leading right up to the cache. To add to this ground disturbance, many cachers, after finding the cache, have a sit down to open the cache and fill in the log book near to the cache hiding place.
The things to look for are:
- Footprints
- Flattened grass
- Broken twigs
- Litter(!)
- Objects out of place
- Other disturbances, such as overturned logs or rocks
These signs can quickly give away the position of a cache from many meters away. In fact, get good at this and you won't look at the GPS when you are within 50m of the cache!
3 - Look for a break in the tree cover
If the cache you are seeking is under tree cover, things are going to be harder. Leaves absorb the signal from the GPS satellites and thins means that accuracy will suffer. Your best option here is to look for a break in the tree cover and then sit there for a few minutes until your GPSr gets a good signal lock before resuming the hunt. Once you regain signal lock, start moving again make a mental note of the direction your receiver is telling you to go and go that way. If you lose signal lock again try to find a different spot that has break in the tree canopy and wait there for a few minutes again to get a good lock. Once you begin to move again you should get a direction to the cache - if you are lucky, the direction that you are being told to go in will intersect with the previous direction you were being told to go in ... this will give you a good clue as to where the cache is.
4 - Search patterns
Sometimes, getting to the cache can seem harder than others. No matter how hard you try, getting the distance to go down to something manageable (like 10m) seems impossible. It is under these circumstances that carrying out a search following a search pattern is the easiest way to do it.
The purpose of a search pattern is to cover the ground in a methodical way. As you move, watch how the distance and direction to the cache changes. Do this carefully enough (you might need to do a search pattern more than once) and you'll soon home in on the cache!
Here are two search patterns that are quite effective and easy to do:
5 - Stop and average
Some caches are just plain elusive - maybe they're well hidden or hidden under a log or rock - in a massive filed of logs of rocks. This can make things mega tricky. It is at this point when it might be a good idea to just take a break and let your GPSr get a good lock (a few minutes) and give you a good, high precision estimate of the distance to the cache. The move a bit and let the GPSr get another lock. Keep doing this until you have narrowed down the position of the cache.
This is a slow process but it does get results.
6 - Come at it from a different direction
A simple but effective trick. Just overshoot the cache location an come at it from the opposite direction. Many caches are only well hidden from the direction that the cacher thinks you are going to approach from!
7 - Look for the unnatural
This is a common cache giveaway that most geocachers (both cache placers and finders) don't spot. When they hide a cache they disturb the area around the cache, but this isn't all. Geocachers will use materials they find to cover the cache - rocks or tree bark are common - but the thing to notice is using bark from a different tree (this is most noticeable when they use the wrong bark to cover a cache hidden at the base of a tree) or a rock that's different to the other rocks in the area.
Learn to spot things that are "out of place" and recognize signs to disturbance.
Summary
Here we've looked at a few tricks and techniques to help you make the last few meters of geocaching easier - try them out next time you are out caching!
Kathie Kingsley-Hughes
Last updated: May 4th 2004
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