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 αναφοράς θέσης 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 αναφοράς θέσης Βύρωνας Νάκος, Καθηγητής Ε.Μ.Π.

4 Contents Locational Reference Systems Datum geographic co-ordinates Linear location referencing methods Route Milepost Route Refernce Post Link-Node Route-Street Reference Developing a Linear Location Reference System

5 Locational reference systems - Georeferencing Georeferencing is defined as positioning objects in either two- or three-dimesional space Continuous Continuous georeferencing system implies continuous measurement of the position of geographic phenomena in relation to a refernce point with no abrupt changes or breaks Discrete In discrete georeferencing systems the positions of geographic phenomena are referenced relative to fixed, limited units of the surface of the Earth

6 Locational reference systems - Georeferencing Continuous systems include direct & relative georeferencing: Direct georeferencing Datum Coordinate systems Map projections Relative georeferencing Offset distance Measurement along (road) networks

7 Datum To determine a position on the Earth s surface we have to know the shape & the size of the Earth The shape of the Earth is expressed by the shape of the ellipsoid Datum is a model & gives the relationship of a co-ordinate system to the Earth Datum is defined by: 1. Size & shape (semi-major axis a & semi-minor axis b) of the ellipsoid 2. Positioning of the ellipsoid in relation to the physical surface of the Earth by an anchor point

8 Geodetic Reference System 1980 GRS-80 a b a Major-semi axis: a Minor-semi axis: b Flattening: f = (a-b)/a a = 6,378,137 m b = 6,356,752 m 1/f =

9 Prime meridian (Greenwich) Geographic co-ordinates Earth s rotation axis meridians parallels Equator

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11 Geographic co-ordinates Parallel Earth s rotation axis Equator Geographic longitude (λ) Prime meridian Meridian Geographic latitude (φ)

12 Map projection co-ordinates Map projection co-ordinate systems give the positions of points relative to two mutually perpendicular axes in a plane (Cartesian co-ordinates) The axis are called Northings and Eastings and are writen as y & x resp. Many countries have national, and even local, georeference systems of rectangular co-ordinates The best known map projection co-ordinate system is the UTM. UTM covers the surface of the Earth from 84 North to 80 South with the help of 60 zones of 6 width

13 Physical Earth surface Geoid The long trip of spatial data P P E P G Ellipsoid Plane (map) p

14 Linear location referencing systems/methods When conducting a data collection survey on transportation networks, it is important that the data is properly referenced and that location can be assigned repeatedly over time with a level of confidence The key components of linear referencing are: Linear location referencing methods Linear location referencing systems

15 Linear location referencing systems/methods Linear Location Referencing System is the total set of procedures for determining and retaining a record of specific points along a transportation network. The system includes the location referencing method(s), together with the procedures for storing, maintaining, and retrieving location information about points and segments on the transportation networks Linear Location Referencing Method is the technique used to identify a specific point (location) or segment of transportation network, either in the field or in the office

16 Linear location referencing methods Route-Milepost (RMP) Route-Reference Post (RRP) Link-Node (LN) Route-Street Reference (RSR) Geographic Coordinates

17 Route Milepost Method (RMP) In the RMP method, distance is measured from a given or known point, such as the route beginning or a jurisdictional boundary (e.g., a county line), to the referenced location The point of interest (i.e., crash or roadway feature) is always offset in a positive direction from the zero milepoint, and is not referenced to other intermediate points along the route

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19 Route-Reference Post Method (RRP) The Route-Reference Post (RRP) is a method that uses signs posted in the field to indicate known locations These signs, known as reference posts, may or may not reflect mileposts All data collected in the field are referenced to these markers in terms of distance and direction The advantage of this system over an RMP system is the elimination of the problems caused by changes in route length that may be the result of realignment

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21 Link-Node Method (LN) In a Link-Node (LN) method, specific physical features, such as intersections, are identified as nodes Each node is considered unique and is assigned a unique identifier or node number Links are the logical connection between nodes and may vary in length. Links also have unique identifiers that are often derived from the associated pair of Node identification (ID) numbers All data are measured as an offset distance from the nearest or lowest node number along a link

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23 Route-Street Reference Method (RSR) In the Route-Street Reference method an event is typically recorded as occurring on one street at a specified distance and direction from another street that is used as a reference A variation of this method is the use of two reference streets and no distance measurement (for example, a crash may be coded as occurring on Street A between Streets 22 and 23) The last option results in a loss of detail with regard to precise location, but still provides enough information to determine sections of roadway that may have a high number of events

24 Geographic Co-ordinate Method Cartesian co-ordinates use x and y to measure distance along perpendicular axes of a co-ordinate plane Geographic co-ordinates use latitude and longitude to measure distance in degrees along the axes of the sphere of the Earth. Events (and beginnings and endings of route segments) can also be located using GPS technology to reference, by latitude and longitude, a location on the Earth s surface Local transportation authorities may use map projection coordinates to measure the distance east and west or north and south along an origin or datum

25 Developing a Linear Location Reference System The collection of roadway event data (i.e., number of lanes, shoulder type pavement surface) is accomplished in the field by driving along the roadway As the inventory item is located, its attributes are recorded, along with the road name (or Route ID) and the mileage driven (or milepost) Point features (signpost or a culvert) Are recorded as a single mileage attribute Linear features (number of lanes, shoulder type, or pavement surface) Are recorded by a beginning mileage and ending mileage

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27 Developing a Linear Location Reference System Public or private organizations collect and maintain attribute data on roadway characteristics as a single table containing records representing homogeneous sections of highways

28 Developing a Linear Location Reference System The information may also be entered into a relational database management system (RDBMS). Each record in the database would be entered for each observed and recorded occurrence The attributes for roadway inventory would include Route ID, Mileage, and Inventory Type Each data type could be entered into database tables, such as a Pavement File, Shoulder File, and Intersection File

29 Developing a Linear Location Reference System Partial illustration of a route system roadway inventory data model

30 References Bernhardsen T., 2002, Geographic Information Systems. An Introduction (3rd ed.), New York: John Wiley & Sons. Boston S., 2011, Harmonisation of Location Referencing for Related Data Collection, Sydney: Austroads Publication No. AP T Miller H.J. & Shaw S.-L., 2001, Geographic Information Systems for Transportation: Principles and Applications, Oxford: Oxford University Press. Sutton J., 1998, Data attribution and network representation issues in GIS and transportation, Transportation Planning and Technology, 21(1-2): Trentacoste, M.F. (ed.), 2001, Implementation of GIS-Based Highway Safety Analyses: Bridging the Gap, Report No. FHWA-RD , McLean: U.S. Department of Transportation, Federal Highway Administration.

31 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