Road Cadastre

INTRODUCTION:

         According to the Italian rule of the road, boards who own roads are bound to set up and to keep up to-date the cartography and the cadaster of roads and related fixtures. According to Ministerial Decree 1/6/2001, which enforces it formally, the road cadaster is a data system, representing the inventory of every road having public assignment, whose primary goal is to fix the size of the national roads network. The enforcing rule sets the survey and representation standards according to the pattern provided by the GDF (Geographic Data Files) v. 3.0 standard (CEN 1995), as emitted by Technical Committee 278 of the European Normalization Committee. MMS vehicle GIGIOne, owned by the Excellence Centre for Tele geometrics Research of Trieste University, is able to provide surveys of geometrical and descriptive characteristics in order to set up the data base of the road cadaster as requested by the Ministerial Decree. This paper describes a sample  processing and representing of data output from this specific MMS, collected during a survey carried out from km 287 350 to km 299 800 of ss1 Aurelia, from the crossing north of Vada to the center of Campolecciano, near Livorno.

GDF and road’s cadastre:

The GDF standard is by its own definition application independent, whereas MD 1/6/2001 explicitly requires a GIS  application allowing for the representation of the land's  cartography and the road graph, as well as the selection of the single elements and the visualization of the values of the related  attributes. As regards the physical data model, the GDF standard requires a sequential ASCII structure, while the road cadaster requires a generic relational, client-server compatible data base, leaving ample freedom for its implementation.  Suggested solutions range from SQL-compatible formats,  managed via RDBMS, to XML-like formats, up to hybrid  formats for graph and attributes representation (such as XML  and shape file), much similar to the current GIS application  model. No one of these formats can be chosen beforehand, since the effective implementation of road cadaster data will require integration with the local information systems of the proprietary boards. It is on the contrary suitable to require the different local systems to output reports containing road cadaster data in a single interchange format, which could be reasonably based, as for the current state-of-the-art, on XML standards (Palermo 2004).  The present example deals with a XML structure of raw data, deriving from manual analysis of the photograms, which will then be adequately processed to provide, via Autodesk Map scripts, graphical layers containing the different characteristics surveyed for the road cadaster.

MMS SURVEY AND RAW DATA: The survey, as it has been carried out, is based on the precision vehicle positioning and the analysis of the photograms shot along the path and synchronized with position data.  Vehicle positioning is defined with sub-decametric precision and is covered by a couple of satellite receivers fitted on the vehicle itself and working in phase differential mode. This mode requires another GPS geodetic receiver to be used, during the survey, over a fixed point, of known coordinates, located at less than 20km from the MMS collecting every second its raw observation data.  In this case, since no suitable permanent GPS or regional virtual reference stations were available in the surveyed area at the time, a new master point has been set up to the purpose, in the parking lot between vl. S. Allende and Market Place  (Rosignano), where a Leica 530SR GPS receiver has been  recording non-stop for the entire duration of the survey, thus  providing data for the post processing of the paths, which  ensure to obtain the requested precision in road axis point  positioning.

The position of the local master in the GPS WGS84 global system has been checked towards the permanent GPS station of the Civil Engineering Department of the Pisa University.

ROAD’S CADASTRE GIS: Auto desk MAP scripts, which create layers referring to the different cadastral codes, have been automatically generatedfrom the table of the segmented data. First of all, the polyline  representing the borders of the roadway has been created,  starting from its width data (figure 4), on the basis of the  coordinates of the axis point and the azimuth value output by  the INS, referring to the same distance from start point.   This way, a visual analysis of the consistency of the cartographic support on which cadastral data are input is possible.  Hence, in case of differences, it is possible to update the cartographicsupport at the scales used in regional technical maps (1:2000).

CONCLUSIONS: The overview of GIS applications based on data collected for the road cadaster is quite varied: there are different software platforms, as well as different ways of file management. Public agencies managing the road network have pointed out some common requirements, the first of which is the need for user friendly data management applications, capable of being queried in order to extract just the data subsets required by ongoing researches. Besides, these applications should allow for a GUI-based data management, i.e. by clicking on the elements which make up the different layers direct access to the data base should be granted, as well as the ability to perform any required edit/maintenance session via data input masks.