How accurate is GPS?
Under ideal conditions, a modern consumer GPS receiver can achieve a typical horizontal accuracy between 3 and 5 meters.
Vertical accuracy is generally worse than horizontal accuracy and may show errors greater than 10 meters.
Smartphones and smartwatches may also introduce additional errors due to smaller antennas and power-saving modes.
Satellite geometry and HDOP
The position of satellites in the sky directly affects GPS accuracy. When satellites are well distributed, positioning becomes more stable.
This parameter is expressed through DOP values (Dilution Of Precision), including:
- HDOP: horizontal accuracy
- VDOP: vertical accuracy
- PDOP: overall three-dimensional accuracy
Low DOP values indicate better conditions for GPS positioning.
Multipath effect
Multipath occurs when the GPS signal is reflected by buildings, rock walls, water or metallic surfaces.
The receiver may therefore receive both the direct and reflected signals, introducing errors in the calculated position.
This problem is particularly evident:
- in urban canyons
- in dense forests
- near rock walls
- in narrow valleys
Why do GPX tracks appear noisy?
GPS errors can produce continuous position oscillations, even when the user is standing still.
This effect generates:
- artificial zig-zags
- overestimated distances
- unstable elevation data
- unrealistic tracks
Recordings made in difficult environments may therefore require corrections or data filtering.
How to improve GPS accuracy
- Wait a few seconds before starting recording
- Keep the receiver with a clear view of the sky
- Avoid reflective walls and metallic obstacles
- Use multi-constellation GNSS devices
- Disable aggressive power-saving modes
Analyzing GPS errors with OkMap
OkMap allows you to display, correct and analyze GPX tracks using raster maps, DEMs and advanced editing tools.
With OkMap you can:
- display GPX tracks on topographic maps
- correct elevations using DEM data
- edit incorrect points
- analyze elevation profiles
- compare multiple GPS tracks