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Why Sub Meter Accuracy Is Useless

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Why Sub Meter Accuracy Is Useless

Postby postholer » Wed Apr 30, 2014 6:30 pm

Since most people who read this are metrically challenged, let's get rid of this 'meter' stuff. A meter is about 39 inches or a bit more than a yard or about 3 feet.

So when we talk of sub-meter accuracy, we are saying that our GPS device records our location with an error of less than 3 feet. Pretty impressive stuff. Equipment that can achieve this is rather pricey and/or tends to be heavier than an average hiker would consider packing.

Let's look closer at a trail trace collected with sub meter accuracy.

That recreational grade GPS you're carrying on your hike, given perfect conditions, will have an error of about 6 feet at absolute best. In terrain, tree cover, etc, you may be looking at average errors like 20, 30, 100 feet or more.

So you're asking yourself, "What's the point of sub meter accuracy if my GPS is giving me an error of 30 feet?" Good question. In the real world you'll never get close to the 'exact' location on average.

Let's take a different look.

Go grab your favorite printed topo map. Got it? OK, good. Now look at the colored trail trace on your map. If your map has a 1 inch = 1/2 mile size and you painted the trail trace on the ground, it would be 90 to 120 feet wide!!!

At this point it should be glaringly obvious of how unimportant sub meter trail alignment is. For those of you fixated on your sub meter trail trace you collected, try this. Using a 1:30,000 map scale, lay down your sub meter quality trace and then lay down your recreational grade trace on top of it.

There is no noticeable difference, none. The sub meter and other trail trace lay down right on top of each other.

So what's the point? Another good question.

Collecting a hyper-accurate trail trace is just chest pounding and has no practical application for the hiker or hiking maps. It's a waste of valuable resources. We realize this. We devote our energy to improving the topo base maps, that is where hikers will benefit most. We also realize that hikers will benefit by having detailed trail information, that is why we dedicated so much energy to collecting that data last year.

There are a number of ways to get the best returns on your map making efforts. Throwing away resources on sub meter accuracy is not one of them.

-postholer
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