Do I need a Gps (*1) as part of hiking essential gear?
This is a common question I get from new hikers, and my answer is always emphatically no.
What have I against GPS?
Actually I have nothing against Gps in the outdoors.
In the hands of an experienced hiker who understands that a Gps is only another information source, along with the normal navigation tools, it is a very useful tool.
The problem however lays with those who are have not learned to navigate without a Gps and are unaware of what it can not do;
- A Gps doesn’t actually know where it is on the landscape, only where it in relation to the orbiting satellites.
- When navigating to a fixed point with a Gps, it will direct you with a straight line, but it is totally unaware if a human can actually follow its line and survive. ( yes there are people who do actually believe the Gps knows best!)
- All electronic devices depend on a power source, and software – both of which can happily fail for no particular reason. (*2)
In the hands of someone who believes the Gps word is law… and has not learn any other means of navigating, the clock is ticking to disaster.
How do GPS work
The Term Global Positioning System was originally the name of the US developed satellite based precise positioning system, but has now become the generic term for all systems.
Orbiting the earth many satellites (including the US (GPS) and Russian, (GLONASS) each satellite constantly transmits a signal containing its reference information and a time. The computer in your Gps uses this information to figure out how far it is from the satellite.
For your Gps to figure out its 3 Dimensional place on the earth’s surface (North – South and altitude) it requires a good signal from a minimum of four different satellites.
For it to define an accuracy that is useful hiking, it requires closer to 8 -10 at least.
In the outdoors there are many more things to interrupt Gps signal strength including;
- The Gps receiver you are using.(*3)
- Type of Gps Antenna.
- Signal strength
- Organic and Inorganic obstructions to the signals: Hills, Mountains, Narrow valleys, Rock, Dense bush cover, Concrete, Steel.(buildings)
- How many Satellites are “visible” to your receiver in that chunk of sky.
- Minute errors in the signal from the satellites or your receiver magnified by distance
- The Ionosphere(up in space) blocking the timing signals
- Your movement
The two diagrams below are actually Gps track logs(*4) recorded on a hike to a local 900m summit, and return. The hiking track we were following was;
- Narrow, requiring us to walk single file with barely enough room for our packs.
- Covered by thick native bush
- Below the main ridge climbing a spur.
The first picture (above) shows what the Gps got up to while we were sitting still eating our lunch for 30 minutes in the red circled area. Despite being stationary the track log indicates our position changed constantly up to 6 meters in all directions.
In the second picture (below) there are two parallel tracks from the same hike;
- One is climbing the spur (arrows pointing to top of page)
- The second is returning via the same track around 3 hours later.
Even though we were following the same narrow walking track in both directions, the recorded track doesn’t show that, in fact in several places their was up to 40 meters difference.
While 40m might not seem like a lot on and open paddock, in heavy bush its extremely easy to never see a track that is running only 2-4 meters parallel to the direction you are walking.
Not all GPS are Equal
As technology advances we are seeing an increase in smart devices that also include GPS chips, demonstrating very good accuracy in Urban areas, but not always so good under bush and hiking conditions.
The picture above shows 2 track logs recorded simultaneously, while walking under medium bush cover, on a steep ridge line.
- Track (a) was record by a Smart phone navigation app using the phones Gps only, recording at the most often interval.
- Track (b) Is a Garmin hand-held Gps receiver, 30 cm from the smart phone, recording track at 10m intervals and displaying a device accuracy of 7m.
(The red dotted line is the walking track we were following, on the NZMS Topo 50 electronic map.)
The closest the phone track came to the Gps track was 7m, the average being 20-40m away.
Before you get a GPS
The most important step is to fully develop and practice your foundation navigation skills until they become second nature;
- Learn to read a Topographical map and relate it to the ground around you.
- Develop your own awareness of where you are in the terrain (positional awareness) and “common sense.”
- Learn how to navigate with a magnetic compass and a Topographical Map.
When you have mastered these basic skills, if you then decide to get a Gps you will be far more inclined to view it as just another tool that you use along with your other skills all the time.. then to make the error or depending completely on the Gps
Learning GPS Lore
If you have go ahead and buy a GPS , then another useful learning tool is playing a GPS game like Geocaching, which will aid you in seeing the strength and weakness of the device before you need to depend on it.
- The use of GPS devices and smart phones as navigation aids
- How does GPS work
- Why back country GPS units are overrated
- How Gps works
(*1) While the name GPS (Global Positioning System) is now used to describe the device, it has also generally come to represent the USA technology(originally called NAVSTAR) while Russian system is known as GLONASS. Most modern hand-held GPS and Smart phones have both systems included.
(*2) Like other electronic devices, GPS’s do crash, freeze and run out of batteries and or loose the way points or tracks I had specially loaded… (best to carry any important Gps data on your phone and get and OTC cable in case you have to reload.)
(*3)While public GPS Receivers are not accurate to more than 3-5 meters, those used by Surveying, Construction and Military GPS can accurate to cm’s.
(*4) When a GPS is set to record where you have been, this is called a “track.”