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Prof. Ludovico Biagi Satellite Navigation and Monitoring Navigation: trajectories control positions estimations in real time, at high frequency popular applications: low accuracy (10 m) required specific applications require better accuracy Monitoring: positions monitoring in time positions estimations for campaigns and time series analysis typically high accuracy required (10 cm -> 1 mm) GNSS provides navigation and monitoring From geodetic theory to geomatics methods
Γεωδαισια: Earth parcelling, Greek agricultural needs The science of measuring and mapping the Earth surface (Helmert (1800) definition): 1. determination of Earth gravity field and its linear functions, 2. determination of (precise) global, regional and local three dimensional positions, 2.a. measurement and modelling of geodynamical phenomena, 2.b. kinematic positioning and navigation.
The beginning of Geodesy Eratosthenes (276-194 BC)
First measure of the Earth radius (ε ≈ 1%) Angles by Sun observations directions and distance on Earth surface by camel travel time!
Physical geodesy Geoid: an assigned equipotential surface of the Earth gravity potential Geoid undulation (N): the height of the geoid wrt an assigned 'simple' surface (ellipsoid)
Geoid undulation knowledge allows the conversion from ellipsoidal (h) to orthometric (H) heights
Geoid undulation is known with accuracy of few cm at the global scale
Positioning (our main interest) In the past (traditional): observations to the stars, terrestrial angles and distances measurements (topographic surveys) At the present: terrestrial surveys + GNSS observations
GNSS (Global Navigation Satellites Systems) Several constellations of artificial satellites around the Earth A receiver observes signal travel times from all the in-view satellites The satellites positions are known from ephemerides The travel times are converted to distances (d=cT) The observations are used to estimate the receiver position
Estimation principle 1 distance from 1 satellite
2 distances from 2 satellites
3 distances from 3 satellites
Measurement problems and errors Synchronization of satellites and receiver clocks Atmospheric delays Observation (electronic) noises Integer fixing è Different classes (cost) of receivers and data processing algorithms è Different classes of positioning accuracy
The spatial scale Global A constellation allows positioning everywhere at every time on the Earth
Regional A constellation allows positioning in limited regions of the Earth
The constellations GPS, USA, www.gps.gov first project in '60, development started '70 fully operating from 1995 GLONASS, Russia, www.glonass-iac.ru/en/ first project and development in '70 (USSR) economical crisis and partial dismission from '90 to 2000 fully operating from 2011
The constellations BEIDOU/Compass, Cina, en.beidou.gov.cn first project in the '80, regional (Asia) coverage from 2011 a second project for a global coverage forseen for 2020 GALILEO, European Community, www.gsa.europa.eu first project in the '90, slowered from 2000 to 2010 4 experimental satellites in orbit
Real time GNSS autonomous navigation ≈ 5-10 m accurate
Instrumental cost: ≅ 50-500 €
Applications people, cars, boats, trains, planes,...: guidance and control Applications Industrial: route optimization, real time overview,.. Public security: critical transports, car/trucks theft,... Assistive technologies Recreational: hiking, sailing,...
Relative kinematic and fast static positioning A reference and a rover GPS stations observe range differences: the rover position can be estimated with accuracies in the range 2-5 cm – 1-2 m.
Instrumental cost: ≅ 500 - 10000 € (for the rover)
Accurate navigation applications Instrumental cost: ≅ 500-2000 € Accuracies better than 1 m Applications cars, boats, trains, planes guidance and control in critical areas (construction sites, railways stations, airports, ...) assistive technologies others: sport performance monitoring, ...
Real Time kinematic: cadastral and cartographic surveying Instrumental cost: ≅ 5000 - 10000 € Required accuracies: 2-3 cm
Post-processed static surveys: geodetic monitoring Instrumental cost: ≅ 10000 € for each receiver required accuracies better than few centimeters Local networks for structures / landslides / ... control Regional permanent networks for local geodynamics Global permanent networks for global geodynamics
SLOMOVE (www.slomove.eu) experiment for landslide monitoring
Permanent Networks A network of GPS stations continuously operating and observing range differences: accuracies up to some mm.
Instrumental cost: ≅ 15000 - 20000 € for each station
Post-processed time series: movements ...
A four year time series for a station...
Global network for the determination of the Earth shape and its movements in time
Estimated velocities of ITRF permanent stations
Survey type Absolute kinematic in real time Absolute static in real time
Notes According to the receiver types and new signals availability
Accuracy
Still a research topic
10 cm
From 10 m to 1 m
According to the receiver type Relative kinematic in From 1 m to and the distance between real time or post 2-5 cm reference and rover processing Static relative and post processing
By very long surveys
Better than 1 cm
Needed tools Reference systems and frames Statistics for navigation and monitoring GNSS Satellites systems Signal propagation Observations equations Point positioning Relative positioning Geodetic post-processing Networks adjustment Real Time Kinematic
Course structure Lectures: 38 Hours All the above topics! Exercises: 12 Hours Laboratory: 12 Hours
Exercises Reference frames transformations Coordinates transformations Kalman filtering Leveling network adjustment Integer (cycle slip / ambiguities) fixing Geodetic network simulation and adjustment Analysis of coordinates time series
Laboratories (3 slots of 4 hours) Static and RTK Survey Data post processing Network adjustment
Slides and teaching material http://geomatica.como.polimi.it (course webpage under the courses link)
Time schedule and practical details See monthly timetable (course webpage)
Exam written reports on exercises/laboratory + oral examination Professor: Ludovico Biagi,
[email protected], office V2.9, 031/3327562. Consulting hours: Tuesday, after the lecture
