Using GNSS around Vegetation and Urban Canyons-

Best Practice Guide

PresenterWarren Eade – GeoSystems NZ Ltd

Using GNSS around Vegetation and Urban Canyons

Using GNSS around Vegetation and Urban Canyons

What’s the Issues?If GNSS Positions are based on Time, then• Anything that blocks

signal• Anything that

interferes with signal propagationIs unwanted and

causes errors

Using GNSS around Vegetation and Urban Canyons

How so?• So anything that

interferes with the direct path causes a timing delay

• Signal the bounces off other objects also have a time shift causing error

Example- Juno SB

BackwardForwardCombined

Juno Needs 1 min to warm up filter

Pause both ends

Canopy Example – GeoXH 2008/ Zephyr

Result pre and post canopy better.

Note 4 position missing Backward

ForwardCombined

Using GNSS around Vegetation and Urban Canyons

Post processed accuracy

While all these units are manufactured by Trimble they are all quite different!

3-5m 1cm

Increase satellite availability

Stabilise acquisition and tracking

Improve accuracy and limit position outages

Multi-constellationpositioning

Advanced trackingalgorithms and filters

Altitude-constrained positioning

Trimble FloodlightSatellite Shadow Reduction Technology

* Standard on GeoXH, available as an optional upgrade on GeoXT

Trimble FloodlightSatellite Shadow Reduction Technology

Trimble FloodlightSatellite Shadow Reduction Technology

Using GNSS around Vegetation and Urban Canyons

• Use planning tools• Understand your

environment• Know how your system

works• Follow best practise

guidelines

Using GNSS around Vegetation and Urban Canyons

Best Practice• Turn GNSS receiver on 3min before work• Avoid blocking antenna• Never point receiver towards the ground• Log 30sec of data for point features

(There are exceptions, see below)• Mount receiver to a pole if accuracy is required• Consider offsets and vertex

Exception• Around multipath areas, 5sec point feature