Χρήση συστημάτων πληροφορικής στην οδική υποδομή

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1 ΕΘΝΙΚΟ ΜΕΤΣΟΒΙΟ ΠΟΛΥΤΕΧΝΕΙΟ ΕΜΠ Εργαστήριο Συγκοινωνιακής Τεχνικής Χρήση συστημάτων πληροφορικής στην οδική υποδομή Συστήματα συλλογής δεδομένων Βύρωνας Νάκος Καθηγήτης ΕΜΠ

2 Άδεια χρήσης Το παρόν εκπαιδευτικό υλικό υπόκειται σε άδειες χρήσης Creative Commons. Για εκπαιδευτικό υλικό, όπως εικόνες, που υπόκειται σε άδεια χρήσης άλλου τύπου, αυτή πρέπει να αναφέρεται ρητώς. 2

3 Συστήματα Γεωγραφικών Πληροφοριών & Μεταφορές Συστήματα συλλογής δεδομένων Βύρωνας Νάκος, Καθηγητής Ε.Μ.Π.

4 Contents Photogrammetry Aerial photogrammetry Close-range photogrammetry A cost-effective road surveying method for the assessment of road alignments Remote-sensing Advantages of satellite observation Sensors Global Positioning System Static Differential Mobile Real-time kinematic

5 What is photogrammetry? Is the science of making measurements from photographs The art, science, and technology of obtaining reliable information about physical objects and the environment through processes of recording, measuring and interpreting photographic images and patterns of recorded radiant electromagnetic energy and other phenomena (American Society for Photogrammetry & Remote Sensing)

6 Aerial photogrammetry The camera is mounted in an aircraft and is usually pointed vertically towards the ground Multiple overlapping photos of the ground are taken as the aircraft flies along a flight path These photos are processed in a stereo-plotter (an instrument that lets an operator see two photos at once in a stereo view) These photos are also used in automated processing for Digital Elevation Model (DEM) creation

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11 Close-range photogrammetry The camera is close to the subject and is typically hand-held or on a tripod (but can be on a vehicle too) Usually this type of photogrammetry is non-topographic - that is, the output is not topographic products like terrain models or topographic maps, but instead drawings, 3D models, measurements and point clouds Everyday cameras are used to model and measure buildings, engineering structures, forensic and accident scenes, mines, earthworks, stock-piles, archaeological artifacts, film sets, etc This type of photogrammetry is also sometimes called Image-Based Modeling

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13 A cost-effective road surveying method for the assessment of road alignments

14 A cost-effective road surveying method for the assessment of road alignments

15 A cost-effective road surveying method for the assessment of road alignments

16 A cost-effective road surveying method for the assessment of road alignments Measurements on the digital image ΔX Δx y y F Y 0

17 What is remote-sensing? Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object The term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth (both on the surface, and in the atmosphere and oceans) by means of propagated signals (e.g. electromagnetic radiation emitted from aircraft or satellites)

18 Advantages of satellite observation Enables to observe a broad area at a time Enables to observe the area for a long period Repeat pass observation (time series data, change detection) Enables to know the condition without visiting the area Enables to know invisible information Sensors for various electromagnetic spectrum (infrared, microwave)

19 Sensors Optical Visible Near Infrared Thermal Infrared Microwave Passive (Scatterometer) Active (SAR, Altimeter) Laser Active Reflectance Reflectance Thermal Radiation Microwave Radiation Backscatter Intensity, Time

20 Components of Remote Sensing A. Energy source or illumination B. Radiation & atmosphere C. Interaction with the target D. Recording of the energy by the sensor E. Transmission, reception & processing F. Interpretation & analysis G. Application

21 Sputnik The first artificial satellite (decade 1950)

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24 What is GPS? The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit GPS was originally intended for military applications, but in the 1980s, the U.S. government made the system available for civilian use GPS works in any weather conditions, anywhere in the world, 24 hours a day There are no subscription fees or setup charges to use GPS

25 How GPS works? The collection of geographic positions is accomplished with a GPS receiver that determines the position of a GPS antenna using trilateration and solves for four unknowns: the x, y, and z coordinates and the difference between the satellites clocks and the GPS receiver s internal clock To determine a location on the Earth s surface, a sphere for each satellite GPS receiver communication link is identified To eliminate clock drift, a minimum of four satellites (four spheres) are required to determine x, y, and z positions. If only x and y positions are required and a constant z (elevation) value can be assumed then three satellites will suffice

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27 Static GPS When a GPS unit is placed at a single location for a period of time it collects numerous data points. This is called static data collection. The points can be used to calculate an average position The static data collection method has an accuracy of 5 10 m This is the type of data collection commonly used by mappers, GIS analysts, and transportation planners

28 Differential GPS Differential correction can be accomplished in real time or data can be post-processed later on a computer Real-time differential correction is accomplished by using a GPS receiver placed at an established surveyed position, Point A In real-time differential correction, the corrections are calculated at the receiver (Point B) The receiver at B will use the broadcast signal from A in real time to correct the position at B and generate a more accurate set of coordinates The static differential GPS method has an accuracy of 0,20 1 m

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30 Differential GPS (post processed) Post-processed differential correction can also be accomplished by taking GPS data from the receiver at Point B and processing the data on a computer at a later time using corrected data in files from a GPS base station In this case, the corrected data are placed into a computer file rather than being broadcast over a radio or satellite frequency in real time

31 Mobile GPS GPS data can also be collected while a vehicle is in motion Collecting GPS points without differential correction can provide adequate positioning for some applications An example is to track a vehicle s general position using a dashboardmounted antenna and reporting the results on a lap top computer Mobile GPS data collection means gathering differentially corrected points while the GPS unit is located in a moving vehicle The obvious disadvantage to in-motion data collection is that only one point will be collected for a given position The static mobile GPS method has an accuracy of 10m

32 Real-Time Kinematic GPS Real-time kinematic GPS can significantly improve the accuracy of GPS positions for limited mobile surveying applications Real-time kinematic GPS also uses two receivers - a base station and a remote station in motion As with DGPS, the C/A code correction information from the base station is transmitted to the remote station The carrier phase measurements from the base station to the remote station are also transmitted in real time This allows the remote station to perform survey quality computations in static and limited mobile modes of operation

33 References Burrough P.A. & McDonnell R., 1998, Principles of Geographical Information Systems, Oxford: Oxford University Press. Jones C., 1997, Geographical Information Systems and Computer Cartography, Essex: Addison Wesley Longman Ltd. Psarianos B., Paradisis D., Nakos B. & Karras G., 2001, A Cost-Effective Road Surveying Method for the Assessment of Road Alignments. In Proceedings of the 4th International Symposium Turkish-German Joint Geodetic Days, Berlin. David F.W. & Simonett D.S., 1991, GIS and Remote Sensing. In Geographic Information Systems. Principles & Applications, (Longley P.A., Goodchild M.F., Maguire D.J. & Rhind D.W. eds.), Vol. 1, New York: John Willey & Sons, pp Robinson A.H., Morrison J.L., Muehrcke Ph.C., Kimerling A.J. & Guptill S.C., 1995, Elements of Cartography (6 th ed.), New York: John Wiley & Sons. Transportation Research Board, 2002, Collecting, Processing, and Integrating GPS data into GIS, NCHRP SYNTHESIS 301, Washington D.C.: National Academy Press.

34 Χρηματοδότηση Το παρόν υλικό έχει αναπτυχθεί στα πλαίσια του εκπαιδευτικού έργου του διδάσκοντα. Το έργο υλοποιείται στο πλαίσιο του Επιχειρησιακού Προγράμματος «Εκπαίδευση και Δια Βίου Μάθηση» και συγχρηματοδοτείται από την Ευρωπαϊκή Ένωση (Ευρωπαϊκό Κοινωνικό Ταμείο) και από εθνικούς πόρους. 1