Cost-efficient localisation system for agricultural
use cases
Gábor Paller, Sébastien Aubin, Gábor Élő and
Olivier Camp
SENSORNETS 2017
2017 February 20

Localisation in agriculture
● For high-value machinery
High-end GPS receiver price: up to 10000 USD (also, usually purchase is restricted)

What about the lower-value stock?
We need about 1m precision with low-cost receivers!

Participating projects
● Széchenyi University, Győr: AgroDat project
(AGRODAT VKSZ_12-1-2013-0024),
localization of agricultural robots, financed by
the government of Hungary
● ESEO, Angers: Vagabond project, localization
and health of livestock (cows), financed by
“Pays de la Loire” region

Low-cost GPS receiver study
● With differential (SBAS) support
● With a high-precision geodetic GPS as
reference

Typical measurement
• Origo: location with known, precise coordinates (geodetic reference point) where
all the devices were placed.
• Color code:
• Red: geodesic GPS receiver (Ashtech Z-Xtreme)
• Blue, green, cyan: MT3339 (three receivers, same location, locked to SBAS)
• Magenta: Samsung Galaxy S4 mini smartphone
• Conclusion: standalone low-cost receivers will not satisfy the precision requirements!

Low-cost differential GPS
Herrera, A. M., Suhandri, H. F., Realini, E., Reguzzoni, M., and Lacy, M.
C. (2016). goGPS: Open-source MAT-LAB software. GPS Solut.,
20(3):595–603.
NMEA data (not used)
Corrected positions
Raw data (pseudorange, carrier phase)
NMEA data
(not used)
Raw data (pseudorange, carrier phase, ephemeris)
or
Fixed station
Rover station
Raw data (e.g. RINEX)
Low-cost GPS
receiver (raw data)
Professional
reference station
Low-cost GPS
receiver (fixed)
goGPS
software

Low-cost GPS receiver
U-blox LEA-6T, directly supported by goGPS

Position noise
Precision after low-pass
filtering of goGPS corrected
positions with different GPS
receiver sampling frequency

Need for short-range localization
● GoGPS is not suitable for localizing moving
objects due to long filtering period
● However, it is quite precise when localizing
objects that are stationary for >10 minutes
● For robots, these stationary objects can be
positioning poles
● For cows, these stationary objects can be other
cows if they stay in the same place long enough

Are cows stationary?

Time-of-arrival (TOA) localization
• Radio trilateration (Time-of-arrival, UWB)
r1
r2
r3
Fix points with known position
Point with unknown position

Effect of reference point positioning
error
● 1000 iterations
● Color “rectangles”: 10 fix points plus added errors
● Color “patch” around -50,60: calculated positions

Distance error vs. fix point error
● Simulation to find out whether measured distance error vs. fix point
localization error has more effect
– 10 fixed points
– 1000 iterations
● Error added to distance measurements:
– maximum x,y error: 9.7, 9.9 meters respectively
– mean of the error: 2.9 meters
● Error added to fixed point measurements
– maximum x,y error: 9.4, 10 meters respectively
– Mean of the error: 0.2 meters
● It is better to have error on the fixed point positions than on the distance
measurements

Angle-of-arrival (AOA) localization
Point with known
position
Point with unknown
position
α1
α2
α3
Directional antenna

Effect of angle measurement error

Conclusions
● Standalone receivers have problems satisfying the less than 1m precision
requirement (even expensive ones)
● With differential setup, low-cost GPS receivers can produce the required
precision for stationary targets
● GoGPS is able to locate targets with 1m precision using low-cost receivers if the
target stays in place for at least 10 minutes
● At least some cows move infrequently enough so that they can act as quasi-
stationary reference points
● For moving targets, short-range positioning methods are proposed
– Distance-measurement (UWB) works well if there are enough many reference points
(>4) and the reference points are separated well. Also, if the same error is introduced
into the fixed points positions vs. the distance measurement, error in fixed point
positions gives better results.
– Angle-measurement works well if the target to locate is not far away (<50m).

● Paper available:
https://www.researchgate.net/publication/31389
1088_Cost-efficient_localisation_system_for_ag
ricultural_use_cases