1 / 19

# Understanding GPS-GNSS - PowerPoint PPT Presentation

Understanding GPS-GNSS. Michael Buschermohle Precision Agriculture Specialist UT Extension. Global Navigation Satellite System (GNSS). Satellite Systems. GNSS = GPS + GLONASS + future additional satellite systems. Global Positioning System (GPS): 24 Satellites ( USA)

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about ' Understanding GPS-GNSS' - aisha

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

• Michael Buschermohle

• Precision Agriculture Specialist

• UT Extension

Satellite Systems

GNSS = GPS + GLONASS + future additional satellite systems

Global Positioning System (GPS): 24 Satellites (USA)

GLONASS : 18 Satellites (Russia)

Galileo: 2 Satellites (European Union)

Compass: China

QZSS: Japan

IRNSS: India

• Increased accuracy and reliability due to tracking more satellites

GNSS

GPS

Need 5 satellites to maintain RTK-fix

Satellites broadcast several pieces of information

• Emphemeris (Orbital) data

• Timing data

• Clock Errors

• Atmospheric Interference

• Ephemeris (Orbital) Variation

• Satellite Configuration

• Signal Multipath

Clock Errors

Let’s put some numbers on it

Altitude = 12,500mi.

Speed of light = 186,000 mi/sec

Transmission Time = 0.067 sec

What happens if we are off a little?

0.001 sec * 186,000 mi/sec = 186 mi

Atmospheric Interference

Ephemeris (Orbital) Variation

Precision Agriculture

University of Tennessee Extension

Satellite Configuration

Good (low) DOP

Poor (high) DOP

Signal Multipath

• Land-Based Differential Correction

• Satellite-Based Differential Correction

• Real-Time Kinematic Correction

Satellite-Based Differential GPS Correction

WAAS

OmniStar

JD StarFire

)

)

)

)

)

)

Differential GPS Corrections

Real-Time Kinematic (RTK) GPS Correction

Base Station

Virtual Reference Station

Continuous Operating Reference Station (CORS)

• Pass-to-Pass Accuracy

• Represents the short-term (<15 min.) relative accuracy of a GPS/GNSS receiver. You can think of this as the accuracy between adjacent, parallel passes made within 15 minutes of one another.

• GPS/GNSS Drift - Year-To-Year Accuracy

• Drift can be defined as GPS/GNSS receiver (guidance system) accuracy over time. Causes of drift are changes in satellite configuration, operating near trees or other obstacles, and satellite data errors.

Courtesy of Fulton, Auburn University