Understanding the Global Navigation Satellite System or GNSS

Introduction

GPS Satellite

GNSS stands for Global Navigation Satellite System. This is a satellite system that is capable of pinpointing geographic locations of receivers all over the world. There are three GNSS types in existence right now; GPS or Global Positioning System, GLONASS or Global Orbiting Navigation Satellite System, and Galileo. GPS is operated by the United States, GLONASS is operated by the Russian Federation, and Galileo is operated by Europe. These satellite systems involve constellations of satellites and ground networks that communicate with each other to achieve navigation and geographic location determination. The GNSS satellite surveying system is a particular form of GNSS that is used in the field of surveying.

How It Works

GNSS used by the surveying field utilizes transmitted signals at precise intervals to determine a particular location and its features. This gives surveyors a clear view of the landscape they are working with in terms of location and elevation. The signals transmitted come from various satellites within the network so precise information can be acquired. Usually, it involves at least four satellites to get a coordinating current signal that receivers can effectively use.

Precision

Precision between different GNSS systems vary depending on the technologies employed. GPS accuracy is limited to 15 meters of precision while Galieo is limited to 1 meter. Intentional degradation via available technologies can be done to limit precision in satellite systems, which is exactly what happened initially with GPS. The United States Department of Defense intentionally used available technologies to limit precision to 100 meters. This ceased to be the case after the Presidential Order in May of 2000 that stipulated that the 100-meter limit is lifted.

Surveyors rely on the precision of GNSS systems for them to do their best work because wrong calculations and information will not just ruin a project, it can even endanger lives due to faulty design and construction. This is why even with GNSS systems and receivers becoming more available, surveyors still use traditional surveying tools to make sure that their surveys are accurate and precise.

Receivers

Receivers can be designed to receive signals from different GNSS satellite systems. While most of these receivers only support one type of signal, more and more of them are being built to accommodate several signals, giving users more accurate, precise, and reliable navigation applications. Surveyors use receivers that are most beneficial for them, and those are the ones that receive signals from the GNSS system that covers the area being surveyed more prominently.

Applications

In the field of surveying, a GNSS satellite surveying system is used for a variety of purposes. These purposes include land development, engineering surveying, topographic surveying, cadastral surveying, urban design, urban planning, hydrographic surveying, land administration, geodesy, mining surveying, and construction surveying. These applications used to be conducted using mechanical tools like the theodolite, but as GNSS satellite systems are becoming more prominent and as receivers are becoming more available, using GNSS satellite surveying systems in surveying is becoming more popular in surveying circles all around the world.

References:

Tech Target, https://searchnetworking.techtarget.com/definition/GNSS

Geoscience Australia, https://www.ga.gov.au/earth-monitoring/geodesy/geodetic-techniques/global-positioning-systems-gps/survey-global-positioning-system-gps.html

Photo Courtesy of Wikimedia Commons / Supplied by NOAA