GML BASED MANIPULATION OF GEODETIC AND MECHANICAL DATA

: Ever since the Rulebook on cadaster of infrastructure has been published there has been constantly growing need for efficient data manipulation. However, data manipulation has been an issue for a very long period of time. This paper will provide solution in manipulation of geodetic and mechanical data for City of Zagreb gas plant. All the solutions are given in Geography markup language, GML.


INTRODUCTION
Since the computation power became sufficient to process geospatial data, many geo-data systems have been developed. Some of the early geo-data systems were BUDS [1], GADS [2,3], NISP [4] or FIRS [5], all designed to retrieve and display facilities using their own query language and internal data structures [6]. [6] proposed approach on manipulation and display of geographic data where all geographic data is treated as relations. [7] proposed model for storage and manipulation of geographic data called GISER whose main advantage was use of procedure-valued attributes. However, all of the authors were developing their own query languages and data structures. Since this was major issue in interoperability, experts needed to find structured data in order to resolve issues in geo-spatial data organization, interoperability, query and processing. First sign of resolving this issue was with the emergence of Geography Markup Language (GML) in year 2000 [8].
[9] created a GML-based interoperable geographical database for conservation of the lunan stone forest landscape to easily manipulate and query different types of data and after the testing the database concluded that it is interoperable with different spatial functions. [10] proposed a framework for feature-level geospatial data sharing, for transportation network data. [10] concluded that proposed framework has a great potential for sharing, accessing, extracting, transporting and displaying distributed geospatial data at the feature level, all in a web browser. [11] proposed a framework for GML storage, processing and interface for users or applications that need geo-spatial data manipulation service. All of the authors' general conclusions were that the GML is useful tool for providing framework to manipulate geospatial data. This paper will present framework to manipulate geodetic and mechanical data, similar to work done in [10] but with upgraded GML schemas and queries.

CASE STUDY
Over the years, geodetic experts have been collecting data for different infrastructure data, such as gas pipelines, water pipelines, communication cables, etc. Faculty of Geodesy in Zagreb has been collecting gas pipeline data for the City of Zagreb gas plant in period from 2005 to 2007. Such data will be used in this paper to show how to accelerate manipulation on such data. In order to develop a solution, what type of data geodetic expert should provide to fulfil the task first needs to be defined. According to the City of Zagreb gas plant, geodetic expert should provide them with four different files. Cartographically well-structured file is file which has all the necessary elements to be used in cadaster and to be manipulated in the GML schema. Fig 1. represents cartographically well-structured CAD file with chartered path of gas line and with mechanical data.   Having in mind that such structure depends on memory capabilities and PC processing power, next chapters will describe Geography markup language as a better solution to format data and structure. Chapter 4 will provide short overview of new rulebook on cadastre of infrastructure and in Chapter 5 will present proposed GML schema for data management.

GEOGRAPHY MARKUP LANGUAGE
The OGC (Open Geospatial Consortium) is an international not-for-profit organization committed to making quality open standards for the global geospatial community. These standards are made through a consensus process and are freely available for anyone to use to improve sharing of the world's geospatial data [12]. OGC standards are used in a wide variety of domains including Environment, Defense, Health, Agriculture, Meteorology, Sustainable Development and many more [13]. Among all the other standards for this paper most interesting standard is one on Geography Markup Language, or shorter GML. The Geography Markup Language (GML) is an XML grammar for expressing geographical features. GML serves as a modelling language for geographic systems as well as an open interchange format for geographic transactions on the Internet. As with most XML based grammars, there are two parts to the grammar -the schema that describes the document and the instance document that contains the actual data. A GML document is described using a GML Schema. This allows users and developers to describe generic geographic data sets that contain points, lines and polygons. However, the developers of GML envision communities working to define community-specific application schemas [14] that are specialized extensions of GML. Using application schemas, users can refer to roads, highways, and bridges instead of points, lines and polygons. If everyone in a community agrees to use the same schema they can exchange data easily and be sure that a road is still a road when they view it [15], or as shown in this paper, gas pipelines.
GML represents expanded XML schema, which can define geospatial object classes, features. GML defines content and it does not shuffle content and its presentation [16].

RULEBOOK ON CADASTER OF INFRASTRUCTURE
On 23 rd March 2017 the principal of Croatian state geodetic administration brought out Rulebook on cadaster of infrastructure. In the rulebook, how and which data should be collected for cadaster of infrastructure is pointed out. Since in this paper enhanced manipulation of gas pipeline data is shown, further chapter will only present parts of rulebook regarding gas pipeline. For gas pipeline network it is necessary to obtain data about production, transport, distribution network and connection to such network [17]. Data about basic technical characteristic refers to the type of pressure, material and pipe diameter in millimetres. For every type of infrastructure the data should be collected in Croatian Terrestrial Reference System 1995.55 (HTRS96/TM) and in Croatian Height Reference System 1971.5 (HVRS71). Data about owners, or about administrator of infrastructure that should be collected are name, address, id number and other data necessary for communication such as official mail address, phone number, etc. [17] Figure 7 GML Geometry Classes [16] Cadaster of infrastructure consist of written and numerical part. Written part is: • list of infrastructure, • list of owners and infrastructure administrators.
Numerical part is: • map of infrastructure, • collection of geodetic elaborate of infrastructure [17] List of infrastructure contains: • number of entries within one year and label of confirmed geodetic elaborate of infrastructure of cadaster, • type of infrastructure and its current use (in usage, abandoned or removed), • id number of infrastructure and its objects, • data about owner, or administrator of infrastructure • names of cadastral municipalities in which infrastructure is settled, • names of municipalities, settlement and streets in which infrastructure is built, • house number if the infrastructure is built as home connection, • length of built infrastructure [17].
List of owners and administrators contains of: • number of entries of owners or infrastructure administrators, • data about owners or infrastructure administrators, • type of infrastructure [17].
Map of infrastructure is graphical plan of infrastructure and related objects of infrastructure. Graphic basic of infrastructural plan is digital orthophoto map in measure 1:2000 or 1:5000 with overlapped digital cadaster map [17].
According to the Rulebook on cadaster of infrastructure geodetic survey contains: • survey of points of infrastructure in horizontal manner, • survey of points of infrastructure in vertical manner (for drainage at the bottom of pipe, for other infrastructure at the top of pipes), • survey of intersections of new infrastructure with existing infrastructure, • survey of existing infrastructure objects, • obtaining data about infrastructure owners or infrastructure administrators [17].
Taking the aforementioned into consideration, similar gathering of infrastructural data has been done from 2005 to 2007. Main difference is in geodetic projection since in 2004 was new state horizontal projection datum defined. Since there was a transitional period, the data could be still obtained in old Gauss-Krueger projection.
In the next chapter there is a proposed solution for standardizing process of manipulation of obtained geodetic data for cadaster infrastructure. Main difference in proposed solution is in geodetic projection, but other data is standardized and synced, even in 2005, with new Rulebook of cadaster infrastructure.
<xs:element name="Point" type="gpz:PointType" substitutionGroup="gml:_Feature"/> After the whole GML file is completed and data input standardized, the GML should be evaluated. Due to GML basically being XML, it can be evaluated in special software, like XML editor Oxygen 10 or XML Spy. GML document should be well formed and validated. A well-formed document is document that follows the syntax rules specified by the XML 1.0 specification [18]. Valid GML document must be well formed, and it must conform to a document type definition [19]. There are two different document type definition that can be used with GML:

RESULTS
After definition of GML file and filing out GML file with data there are preliminary results. In municipality Mikulići there is 11.5 km of main pipeline and GML data takes about 500 kB of memory space on hard disc. In whole cadaster municipality around 5000 home connections were built. Data for each home connection contains ten points and mechanical data for each connection. Total data for municipality Mikulići is around 25 mB. In the City of Zagreb there are forty cadaster municipalities under the jurisdiction of city gas plant. Using simple math there is at least 10 gB of data. This presents a challenge in data manipulation, data safety, speed of searching, modifying and storing such data. Since the GML files are well structured and well defined, above mentioned issues are easily solved with use of transaction technology which is basic in every relation database, object -relation database, or object-oriented database.

CONCLUSION
New Rulebook on Cadaster of infrastructure standardize the way data should be gathered. Having in mind that standardizing the process of gathering data results in standardizing the processes of data manipulation. This paper gives an overview of Geography Markup Language, new Rulebook on Cadaster of infrastructure. Proposed GML schema is a direction in which all data manipulation should strive. Main advantage in the data stored using GML is in standardized process of data manipulation, higher data safety and greater speed of searching, modifying and storing such data. Schema and framework proposed in this paper have a better response time and take less memory compared to frameworks proposed in Introduction.