Difference between revisions of "Global navigation satellite system (GNSS)"

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Note: I (Bendik) have copy-pasted this as it was from the report. I don't think it is very good or that it necessarily belongs here. Review/revise.
 
 
=Quick summary=
 
=Quick summary=
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[[file:basement_1d_2d.png|thumb|250px|Figure 1: Combination of 1D and 2D models in BASEMENT (source: VAW).]]
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[[file:gps_boat_remote.png|thumb|250px|Figure 1: Differential GPS mounted on a remote-controlled boat for bathymetry and discharge measurements (Sweco).]]
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[[file:basement_gui.png|thumb|250px|Figure 2: Graphical user interface of BASEMENT (source: VAW) (click to enlarge).]]
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[[file:gps_single_point.png|thumb|250px|Figure 2: RTK-GPS for single point measurements at very high accuracy (< 1 cm) (Sweco).]]
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[[file:basemet_qgis.png|thumb|250px|Figure 3: Visualization of BASEMENT results with QGIS plugin Crayfish (source: VAW) (click to enlarge).]]
 
  
 
Developed by: USA, EU, China, Russia
 
Developed by: USA, EU, China, Russia
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Date:  
 
Date:  
  
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Type: [[:Category:Methods|Method]]
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Type: [[:Category:Methods|Methods]]
  
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Suitable for the following [[::Category:Measures|measures]]:
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Suitable for the following [[:Category:Devices|Devices]]: [[Lidar]], [[Particle image velocimetry (PIV)]], [[Acoustic Doppler current profiler (ADCP)]],
  
 
=Introduction=
 
=Introduction=
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GPS is often used as a synonym for all of the different systems
+
Global navigation satellite system (GNSS) is a general term describing any satellite constellation that provides positioning, navigation, and timing (PNT) services on a global or regional basis.
 +
While GPS is the most prevalent GNSS, other nations have provided their own systems to provide complementary, independent PNT capability. GPS is often used as a synonym for all of the different systems (Table 1).
  
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<table style="height: 177px;" border="1" width="810">
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<table style="height: 177px;" border="1" width="770">
 +
<caption>Table 1: Different systems called as GPS.</caption>
 
<tr>
 
<tr>
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<td style="text-align: center; width: 122.4px;">
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<td style="text-align: center; width: 120px;">
 
<p>System</p>
 
<p>System</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 250.4px;">
+
<td style="text-align: center; width: 250px;">
 
<p><strong>BeiDou</strong></p>
 
<p><strong>BeiDou</strong></p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p><strong>Galileo</strong></p>
 
<p><strong>Galileo</strong></p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p><strong>GLONASS</strong></p>
 
<p><strong>GLONASS</strong></p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 160.8px;">
+
<td style="text-align: center; width: 160px;">
 
<p><strong>GPS</strong></p>
 
<p><strong>GPS</strong></p>
 
</td>
 
</td>
 
</tr>
 
</tr>
 
<tr>
 
<tr>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>Owner</p>
 
<p>Owner</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 250.4px;">
+
<td style="text-align: center; width: 250px;">
 
<p><strong>China</strong></p>
 
<p><strong>China</strong></p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p><strong>European Union</strong></p>
 
<p><strong>European Union</strong></p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p><strong>Russia</strong></p>
 
<p><strong>Russia</strong></p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 160.8px;">
+
<td style="text-align: center; width: 160px;">
 
<p><strong>United States</strong></p>
 
<p><strong>United States</strong></p>
 
</td>
 
</td>
 
</tr>
 
</tr>
 
<tr>
 
<tr>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>Coverage</p>
 
<p>Coverage</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 250.4px;">
+
<td style="text-align: center; width: 250px;">
 
<p>Regional, global by 2020</p>
 
<p>Regional, global by 2020</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>Global by 2020</p>
 
<p>Global by 2020</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>Global</p>
 
<p>Global</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 160.8px;">
+
<td style="text-align: center; width: 160px;">
 
<p>Global</p>
 
<p>Global</p>
 
</td>
 
</td>
 
</tr>
 
</tr>
 
<tr>
 
<tr>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>Status</p>
 
<p>Status</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 250.4px;">
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<td style="text-align: center; width: 250px;">
 
<p>Basic service by 2018, to be complete by H1 2020</p>
 
<p>Basic service by 2018, to be complete by H1 2020</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>Operating since 2016, 2020 completion</p>
 
<p>Operating since 2016, 2020 completion</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>Operational</p>
 
<p>Operational</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 160.8px;">
+
<td style="text-align: center; width: 160px;">
 
<p>Operational</p>
 
<p>Operational</p>
 
</td>
 
</td>
 
</tr>
 
</tr>
 
<tr>
 
<tr>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>Precision</p>
 
<p>Precision</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 250.4px;">
+
<td style="text-align: center; width: 250px;">
 
<p>10 (public) 0.1m (encrypted)</p>
 
<p>10 (public) 0.1m (encrypted)</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>1m (public) 0.01m (encrypted)</p>
 
<p>1m (public) 0.01m (encrypted)</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 122.4px;">
+
<td style="text-align: center; width: 120px;">
 
<p>4.5m - 7.4m</p>
 
<p>4.5m - 7.4m</p>
 
</td>
 
</td>
−
<td style="text-align: center; width: 160.8px;">
+
<td style="text-align: center; width: 160px;">
 
<p>15m (no DGPS or WAAS)</p>
 
<p>15m (no DGPS or WAAS)</p>
 
</td>
 
</td>
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=Application=
 
=Application=
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The 1D model of BASEMENT is based on river cross sections and its main application are river reaches where the level of detail is less important. The 2D model uses a triangular computational grid to reproduce the topography and can be applied to more detailed and complex problems than the 1D model, e.g. the inundation or river bar formation. BASEMENT supports Windows as well as Linux platforms and includes a graphical user interface (GUI) which supports the user during the model setup and simulation process (Figure 2). For grid generation, the QGIS plugin BASEmesh is provided by the developers and for visualization of the results, among others, the QGIS plugin Crayfish (QGIS 2.8) from Lutra Consulting (https://www.lutraconsulting.co.uk) can be used (Figure 3).
+
GNSS systems are used to georeferenced measurements. It is coupled with other systems, such as ADCP, Drones, devices for monitoring fish migration, and other devices where the exact location is nessary.
 +
 
 +
It is important to be aware of the accuracy of the GNSS data and if it fits the measurement requirements. For bathymetry measurements in small rivers and for analyses of low discharges it is recommended to have high accuracy, while a lower accuracy could be sufficient for bathymetry of large water bodies or measurements of high discharges. 
 +
 
 +
There are mainly three different types of GNSS accuracy:
 +
#Standard, such as in cell phones and car navigation. The accuracy is within 3-5 m horizontally and 5-20 m vertically. These systems don’t receive any correction signal.
 +
#Advanced receivers, usually referred to as “differential GPS”. These are used in most scientific instruments. The accuracy is below 1 m horizontally and 2 m vertically.
 +
#RTK-GPS need an internet connection or a local base station to receive a correction signal. This usually is a real time signal (RTK = Real Time Kinematic), but it is also possible to get the correction for post processing. Typical accuracy for the obtained position is in the range of 1 to 3 cm.
  
 
=Other information=
 
=Other information=
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In addition to the use on regular Windows and Linux workstations, the upcoming version 3.0 of BASEMENT (March 2019) is designed to run on graphical processing units (GPUs) and distributed memory computer clusters allowing engineers to tackle problems with very large computational domains or long simulation time.
+
General accuracy is depending on
 +
*Number of satellites / selective availability
 +
*Angle between the satellites = Dilution of Precision (DOP)
 +
*Reflection from buildings/obstacles = multipath error
 +
*Atmospheric conditions
 +
Only the last point, the atmospheric conditions, can be corrected with the differential and RTK GPS.
  
 
=Relevant literature=
 
=Relevant literature=
−
*Vetsch D., Siviglia A., Caponi F., Ehrbar D., Gerke E., Kammerer S., Koch A., Peter S., Vanzo D., Vonwiller L., Facchini M., Gerber M., Volz C., Farshi D., Mueller R., Rousselot P., Veprek R., Faeh R. 2018. System Manuals of BASEMENT, Version 2.8. Laboratory of Hydraulics, Glaciology and Hydrology (VAW). ETH Zurich. Available from http://www.basement.ethz.ch.
+
*https://en.wikipedia.org/wiki/Satellite_navigation
 +
*https://eos-gnss.com/elevation-for-beginners
 +
*https://www.e-education.psu.edu/geog862/node/1828
 +
*https://gisgeography.com/gps-accuracy-hdop-pdop-gdop-multipath/
  
 
=Contact information=
 
=Contact information=
−
Website (download, tutorials, etc.): http://www.basement.ethz.ch
 
−
 
−
Email: basement@ethz.ch
 
−
 
−
 
−
[[Category:Methods]]
 

Latest revision as of 13:11, 30 September 2020

Quick summary

Figure 1: Differential GPS mounted on a remote-controlled boat for bathymetry and discharge measurements (Sweco).
Figure 2: RTK-GPS for single point measurements at very high accuracy (< 1 cm) (Sweco).

Developed by: USA, EU, China, Russia

Date:

Type: Methods

Suitable for the following Devices: Lidar, Particle image velocimetry (PIV), Acoustic Doppler current profiler (ADCP),

Introduction

Global navigation satellite system (GNSS) is a general term describing any satellite constellation that provides positioning, navigation, and timing (PNT) services on a global or regional basis. While GPS is the most prevalent GNSS, other nations have provided their own systems to provide complementary, independent PNT capability. GPS is often used as a synonym for all of the different systems (Table 1).

Table 1: Different systems called as GPS.

System

BeiDou

Galileo

GLONASS

GPS

Owner

China

European Union

Russia

United States

Coverage

Regional, global by 2020

Global by 2020

Global

Global

Status

Basic service by 2018, to be complete by H1 2020

Operating since 2016, 2020 completion

Operational

Operational

Precision

10 (public) 0.1m (encrypted)

1m (public) 0.01m (encrypted)

4.5m - 7.4m

15m (no DGPS or WAAS)

Application

GNSS systems are used to georeferenced measurements. It is coupled with other systems, such as ADCP, Drones, devices for monitoring fish migration, and other devices where the exact location is nessary.

It is important to be aware of the accuracy of the GNSS data and if it fits the measurement requirements. For bathymetry measurements in small rivers and for analyses of low discharges it is recommended to have high accuracy, while a lower accuracy could be sufficient for bathymetry of large water bodies or measurements of high discharges.

There are mainly three different types of GNSS accuracy:

  1. Standard, such as in cell phones and car navigation. The accuracy is within 3-5 m horizontally and 5-20 m vertically. These systems don’t receive any correction signal.
  2. Advanced receivers, usually referred to as “differential GPS”. These are used in most scientific instruments. The accuracy is below 1 m horizontally and 2 m vertically.
  3. RTK-GPS need an internet connection or a local base station to receive a correction signal. This usually is a real time signal (RTK = Real Time Kinematic), but it is also possible to get the correction for post processing. Typical accuracy for the obtained position is in the range of 1 to 3 cm.

Other information

General accuracy is depending on

  • Number of satellites / selective availability
  • Angle between the satellites = Dilution of Precision (DOP)
  • Reflection from buildings/obstacles = multipath error
  • Atmospheric conditions

Only the last point, the atmospheric conditions, can be corrected with the differential and RTK GPS.

Relevant literature

Contact information

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