Data Flows, Standards and Incremental Cadastral Update

Transcription

1 Data Flows, Standards and Incremental Cadastral Update Wolfgang W. Effenberg Ian P. Williamson University of Melbourne, Australia Presented at the 8th Colloquium of the Spatial Information Research Centre, University of Otago, New Zealand, July Abstract The initial map captured digital cadastral database (DCDB) is undergoing a continual update and upgrade cycle as new cadastral data is added and old data is revised. The role of the DCDB as a spatial reference for Geographic Information Systems (GIS) in local government and the utility companies has firmly established them as customers (Wan and Williamson, 1995). The custodians of the DCDB must now tackle the problem of acquiring and distributing these incremental updates and upgrades. This paper examines the incremental data flow both into and out of the DCDB for the two Australian states of New South Wales and Victoria. This transfer of cadastral data is modelled from the surveyor as the supplier of the data through to the customers of the DCDB. One of the many considerations in the propagation of the incremental update is specifying the format and standards for the data and of the data transfer. The paper looks at the planning of these two states in regard to transfer standardisation and the possible use of transfer standards such as the Spatial Data Transfer Standard (SDTS). 1 Introduction The initial capture of the Digital Cadastral Database (DCDB) for both Victoria and New South Wales was completed in the last few years. Whilst there may be some areas in each state that lack completeness each state can rightly claim to have state wide coverage. The DCDB has now entered a maintenance phase that involves both updates and upgrades. Updates refer to the incorporation, into the DCDB, of all new cadastral activity generally represented by the deposited plans registered at the Land Titles Office (LTO). Upgrades include corrections, alterations and adjustments to improve the accuracy of the DCDB. In both states the major land development activities are in the metropolitan areas, particularly in the outlying suburban areas, where the majority of new housing development occurs. To maintain the currency of the DCDB this continual subdivision activity must be captured by the custodians of the DCDB. The original capture of the DCDB was largely from the available paper map base. In rural areas the source maps, if they existed, were generally at the 1:25000 scale while the metropolitan areas were sourced from paper map scales ranging from 1:5000 down to 1:200. The outlying suburban areas and to some extent the rural areas represent the major requirement to upgrade the accuracy of the DCDB where the original capture was from 1:25000 maps with errors of up to ± 25 metres. 2 Data Flow Models for the Incremental Update of DCDB The increasing use by utilities and local councils of the DCDB as the spatial reference for the mapping of their assets and services means that the updates and upgrades to the DCDB must be acquired and delivered in a timely, incremental and convenient manner. Whilst it is important to distinguish between updates and upgrades in the maintenance of the DCDB the distinction is not a priority for data flow models. In this paper the term update is used to describe both the upgrade and update processes. Before consideration of the transfer formats or standards that facilitate the incremental transfer of spatial data Proceedings of the Spatial Information Research Centre s 8th Colloquium 53

2 for the maintenance of the DCDB it is important to comprehend the total data flow for the maintenance of the DCDB. The incremental cadastral data flow starts with the surveyor whose deposited plans must ultimately be incorporated into the DCDB and eventually these changes need to be distributed to the customers of the DCDB. The maintenance of the DCDB is therefore an incremental transfer of data both into and out of the DCDB via a number of other entities. The incremental data flow model models for Victoria and New South Wales (NSW) concentrate on the subdivision planning data originating from the surveyor through to the DCDB and eventually to the customers of the DCDB. These models attempt to represent and capture all the incremental data flows that impact on the DCDB in order to investigate the possible use of transfer standards. tributes. Both Victoria and NSW have government and commercial activities that are not necessarily transacted through the LTO. Such activities include gazetting of information and some titling of land in freeway development. The strength of this LTO centred model is that it will capture all registered deposited plans. Victoria claims the rural map base is current to within 10 days of the plan being registered (OGDC, 1995). 2.2 Metropolitan Victoria The data flow model in Figure 2 represents the significant influence of Melbourne Water, the utility authority responsible for metropolitan water and sewerage. While Melbourne Water has been split into a number of commercial entities, for the incremental data flow purposes, it can currently still be regarded as one entity. These incremental data flow diagrams are the current best estimate and do not necessarily account for all data transfers such as in the development approval process where there is no perceived impact on the DCDB. These simplified models do not attempt to fully depict data flows associated with the changing of subdivision plans inherent in the development approval process. 2.1 Rural Victoria Figure 1 depicts what is essentially the insertion of a digital cadastral database into what was and currently is a paper based transfer of cadastral plans to and from the Land Titles Office. Figure 1 Flow of data for Victorian rural and urban DCDB This model relies on the fact LTO will capture all activity which will impact on the cadastral fabric and its at- Figure 2 Flow of data for Victorian metropolitan DCDB The metropolitan cadastral map base was both captured and managed by Melbourne Water until June As of the first of July 1995 the metropolitan map base is now outsourced to the private sector (currently Dataflow) to manage, maintain and distribute. The metropolitan map base comprises nearly 70% of Victorian land parcels and includes most of the state s subdivisional activity (OGDC, 1995). Melbourne Water and its commercial entities still remains the most significant customers of the Victorian metropolitan DCDB. The presence of the water authority in the incremental data flow and its role in the creation of the DCDB gives the model two significant advantages. Firstly, data is easily distributed to the water authority because they and the custodian of the DCDB essentially maintain the same GIS software platform. 54 Proceedings of the Spatial Information Research Centre s 8th Colloquium

3 Secondly, in addition to the local authority the water authority must ultimately approve the plans. The simultaneous interaction of the surveyor with both the water authority and the council confirms the status of the water authority. This enables the OGDC to maintain a proposed plan of subdivision stage as well as a Land Titles Office approved or registered stage. The early recording of the proposed changes are available to users usually three months before the Land Titles Office registers the plans (OGDC, 1995). The paper transfer of all the registered deposited plans from the LTO to DCDB is used to verify the plans already entered into the proposed layer, to change the status of plan from proposed to approved and to capture cadastral activity not transacted through the water authority. 2.3 New South Wales The Land Information Centre (LIC) has moved from a role of DCDB capture to a role of DCDB maintenance. The incremental data flow model in Figure 3 is a LTO based model. The plans deposited at the LTO are forwarded directly to LIC following registration and incorporated into the DCDB. Two initiatives by the LIC to enhance the DCDB are worth noting. Figure 3 Flow of data for cadastral data in NSW Firstly LIC has been piloting a proposed layer in response to the demonstrated need for cadastral information at the planning and development stage. The intent here is to access the development application, if possible in digital form, at the local council approval stage (Council Clerk Certificate - CCC). The LIC is attempting to have the affected cadastral data available for dissemination to approved organisations via a public distribution mechanism within 24 to 48 hours (Ranshaw, 1995). Secondly the Cadastral Spatial Referencing System (CSRS), a survey database, is an initiative to retain the survey accurate data supplied by the surveyor (Mortensen and Baitch, 1996). In the current update procedure for the DCDB in both states the accuracy of this data might be compromised to maintain the cartographic fabric of the existing DCDB. Also no formal structure exists to distinguish the survey accurate data from the data originally captured from paper maps at a far lower level of accuracy. 3 Key Data Transfers The maintenance and distribution of the DCDB in both states depends on a number of entities supplying data to the custodian of the DCDB and the arrangement of distribution of this data to customers. Separately reviewing individual data flows into and out of the DCDBs will help to focus on the specific mechanism and format of each data flow. 3.1 Data transfers to DCDB The Surveyor The surveyor is increasingly able to offer both greater accuracy for his plans and to offer them in digital format. In NSW approximately 70% of new parcel surveys are connected to survey control (LIC 1996). In the Victorian metropolitan DCDB the water authority requires that subdivisions of greater than 10 parcels must be submitted in digital form to Melbourne Water. It is this plan in whatever format it is required to be submitted that eventually is used to update the DCDB Local Councils and Utilities The Custodians of the DCDB in both states have maintained or are moving to capture a proposed plan of subdivision content in the DCDB. This is a clear recognition of the fact that once the subdivision plans have been registered at the LTO all the planing authorities such as the councils and the utilities have already finished with the data. In both Victoria and NSW some utilities and local councils may already have included this data in their own version of the DCDB well before it reaches the end of the LTO approval and registration process. Proceedings of the Spatial Information Research Centre s 8th Colloquium 55

4 3.1.3 Land Titles Office The unit of transfer is the deposited plan which must be incorporated into the DCDB. Under the present structures this will always essentially be a non digital transfer whether on paper, micro fiche or an image on optical disk Other Data Sources To ensure the integrity and completeness of the DCDB other data sources such as government gazettes, parish plans, etc, are consulted to capture all boundary data. While the cadastral activity that is not required to pass through the LTO is generally easily identified it is often difficult to capture the related survey data. The construction of freeways represents such an instance where the road authority has no real need to establish title to many of the parcels associated with the freeway, once the freeway is built. As a specific example, in NSW more than one third of the DCDB update transactions are currently from non deposited plan sources (LIC, 1996) 3.2 Data Transfers from DCDB The custodians of the DCDB have been able to offer customers a complete copy of the DCDB in a number of digital, vendor specific and AS2482 formats for some years. The DCDB is held in a tile based format and the distribution in this block format is also currently possible. The frequency of the update delivery is also flexible but in the absence of a proposed layer, customers must take account of the time required the for deposited plan to complete the LTO approval registration process. In NSW the supply cycle for the updated DCDB to existing customers is an annual one Utilities The distribution to the utilities is very much on an individual arrangement basis. At one end of the spectrum a national utility is requesting multi state coverage which requires a third party to join the data sets from a number of states. In contrast for the Victorian Metropolitan DCDB, OGDC is able to deliver Melbourne Water, on a weekly basis, a bulk replacement of any of the 2,800 predefined tiles that have changed (Hesse and Jacoby, 1995) Local Government For the larger councils the situation is very much an individual arrangement as for the utilities. The council s position in the data flow means that they have access to the deposited plans at a very early stage. In the absence of a proposed layer NSW and Victorian councils incorporate this information in their own copies of cadastral data base (in their own way) and only utilise the annually distributed copy of the DCDB as a check Other Customers In both Victoria and NSW a wide range of customers have taken advantage of the availability of the portions of a state s DCDB in their preferred format. Customer requests for non tile based regions are more costly to supply and it is often these infrequent and irregular requests that are the most time consuming to fulfil. As these GIS applications mature these customers will be eager to explore incremental updates of their specific areas. 4 Future Cadastral Update Data Flow Models Future data models must attempt to reduce the time for the surveyor s deposited plan and the proposed plans of subdivision to reach the customer of the DCDB. Figure 5 shows a possible data flow model that is both flatter and integrated. Figure 5 Flow of data for DCDB update The implication of this flatter data model is that the cadastral plan data needs to reach the planning authorities at the same time. This would ensure a parallel rather than a serial process of approval or data acquisition takes place before the plan is forwarded to the next entity in the data flow. t 56 Proceedings of the Spatial Information Research Centre s 8th Colloquium

5 From a data flow point of view the integration of the entities in the dotted frames attempts to depict a situation where the data is simultaneously available to enclosed entities, changes made by either entity are accessible by the other entity. Since the surveyor s cadastral plan data is eventually forwarded on, this model suggests that the real physical institutional barriers exist only between the surveyor and either of the integrated entities and between the customers of the cadastral data and its supplier. If there is to be a consideration of introducing standards to facilitate more efficient data transfer, maximum consideration should be at the interfaces where real physical barriers exist. 5 Spatial Data Transfer Standards Spatial data transfer standards are preferred rather than using the de facto standard of any particular GIS vendor. These standards must be able to hold all the types of information from each of the individual GIS formats to ensure that no data is lost in the transfer of spatial data between incompatible GIS systems. Each country appears to have its own data transfer standard (Moellering, 1991). In Britain the National Transfer Format (British Standard BS 7567) has become the accepted standard format for the transfer of digital map data. The National Transfer Format (NTF) is an exchange format that permits the transfer of vector data with five different levels of complexity. The Republic of Ireland and also Hungary have adopted or are using a variant of NTF. While there are moves to make NTF a European standard, Australia has taken an approach to adapt an American standard that would be more likely to be supported by the major GIS vendors and to be used in the immediate international neighbourhood. The Spatial Data Transfer Standard (SDTS) or the Federal Information Processing Standard (FIPS Publication 173) is a United States Federal standard designed to support the transfer of different types of geographic and cartographic spatial data. This standard was fully approved in July 1992 after about 9 years of work by American government, industry, and academia (Fegeas et al, 1992). SDTS was approved as a joint Australian and New Zealand Standard in 1994 (AS/NZS 4270:1995). SDTS is a standard that has been recommended for use in NSW as the method for both input and output of spatial data to the DCDB (Calm, 1995). SDTS specifies a structure and content for spatially referenced data in order to facilitate data transfer between dissimilar spatial database system. SDTS is a standard that is able to handle the full range of spatial data and all aspects of the digital representation of this spatial data (ie vector data, raster data and attribute data of many different models and structures). An implementation of SDTS does not require the full range of spatial data from simple line geometry to digital imagery. To overcome broadness complexity of the standard an actual implementation of SDTS is accomplished by the use of profiles. A profile is a clearly defined subset of SDTS, designed for use by a specific type of spatial data. The topological vector profile (TVP) has been defined to appropriately handle vector data and approved in the United Sates as an amendment to the FIPS 173. The US Geological survey which is one of the instrumental parties in the development of SDTS has also been heavily involved in the development of the TVP profile and has started to develop the raster profile. 6 Transfer Standards in the Incremental Cadastral Update There is no doubt that problems exist in the transfer of incremental updates to and from the custodians of the cadastral data. Any mechanism that increases the quality and integrity of the spatial data, reduces the loss of data in an exchange process and generally makes distribution of spatial data more robust must be welcomed. In addition any mechanism that can be introduced to reduce the time for the data to reach the DCDB update process must also be considered. 6.1 Incremental Data Transfers to DCDB In discussion with both NSW and Victoria it is noted that about 50% of the update activity is associated with updates to one or two parcels. There is some indication that this level of update is more efficiently handled with a paper input rather than utilising digital formats. The requirements to standardise the technical format of surveyors plans in term of coordinate types (eg AMG), and whether it is necessary to include survey control Proceedings of the Spatial Information Research Centre s 8th Colloquium 57

6 represent some major considerations to improve the incremental cadastral update. The LIC report on the collection and processing of cadastral plans (Calm, 1995) recommends the use SDTS as the standard for electronic lodgement. Clearly the pressure for standards is one that is consistent with the concept of survey accurate cadastral database. The incremental data flow models examined suggest that other considerations need to be addressed to insure a faster and more efficient incremental update process of the DCDB especially at the proposed cadastral plan level. 6.2 Incremental Data Transfers from DCDB In the past the customers requirements were generally for the entire DCDB or any of the maintained subsets of the DCDB. These subsets are the predefined blocks or tiles of the DCDB or in the case of Victoria the subsets of metropolitan and rural areas. Clients of the DCDB are therefore faced with updating their own versions of the DCDB or accepting a complete new version of all or parts of the DCDB that have changed. The customers of all DCDBs in Australia report difficulties in the transfer of this data (Wan and Williamson, 1995). This is a strong argument for the adoption of transfer standards that are able to adequately handle all types of cadastral spatial data. The cost recovery principle has meant that custodians of the DCDB invested resources to create marketable, vendor specific formats. Vendors of the DCDB therefore see the conversion process as a value adding process capable of generating funds. Some work has been done on how incremental changes might be transferred (Hesse and Jacoby, 1995). Customers certainly are eager to investigate methods of incremental data transfer, but discussion of standards may be premature given that the processes for incremental data transfer have not been solved. 7 Conclusion The utilities and the local councils will continue to be the major customers of the DCDB. The priority for these customers is for the DCDB update process to incorporate and distribute the proposed changes to the DCDB as early as practical in the development process. In order to achieve this custodians of the DCDB must have access to the planning data as soon as practical to facilitate this proposed layer. In addition the incremental data transfer cycle period for the customers must be reduced to achieve the greatest currency of the DCDB product. Where data transfers occur in the update data flow models, serious consideration must be given to reducing the number of data flows. The necessity for a translation, transfer and translation process might be circumvented by examining data integration and cooperation between entities such as the LTO and custodians of the DCDB. In NSW the investigation of the use of the DCDB as an title index system and similarity of the DCDB update and the title examination process represent real integration possibilities (LTO, 1996). There is no doubt that there is a need for standards to facilitate the transfer of spatial data. SDTS is already a standard that in computing time scales has been around for some time and has not been implemented by anywhere sufficient GIS vendors despite their public commitment. The TVP profile is not suitable for cadastral spatial data. The real current alternatives are the defacto standards such as DXF (data exchange format), etc, or the vendor specific formats acceptable to the custodians of the DCDB. These formats are not GIS compatible and although used cannot be recommended. Future incremental cadastral data transfer to current customers of the DCDB will have a process as well as a data component An incremental update process based on unique feature identification (Hesse and Jacoby, 1995) will specify spatial data that has to be deleted as well as spatial data addition. It is therefore necessary for the spatial data transfer standard to be able to incorporate the process component as well as the spatial data. The process component is not a feature of a data standards such as SDTS. 8 References Altheide, P. (1992) An Implementation Strategy for SDTS Encoding Cartography and Geographic Information Systems, American Congress on Survey and Mapping 1992, 19(5) Australian Surveyor (1995) Digital Cadastral Databases in Australia Technical Report. The Australian Surveyor. 1995, 40(3) 58 Proceedings of the Spatial Information Research Centre s 8th Colloquium

7 Benwell, G.L. (1991) Casting Petri Nets into the Systems Development Life Cycle in the Context of Spatial Information Systems. PhD Thesis. University of Melbourne. Calm (1995) Collection and processing of Plan Information in Electronic Form. Internal Document edited by Price Waterhouse Urwick. Department of Conservation and Land Management. April Fegeas, R.G., Cascio, J.L. & Lazar, R.A. (1992) An Overview of FIPS 173, The Spatial Data Transfer Standard. Cartography and geographic Information Systems, American Congress on Survey and Mapping. 1992, 19(5) Hesse, W. & Jacoby, S. (1995) Incremental Updates, Unique Feature Identification and Version Management in Modern GIS. Conference Proceedings, Australasian Urban and Regional Information Systems Association. November 1995, Melbourne, Australia Hesse, W.J. & Williamson, I.P (1990) A Review of Digital Cadastral Databases in Australia and New Zealand. The Australian Surveyor. 1990, 5(4) LIC (1996) Discussions with personnel at the Land Information Centre, Bathurst NSW. LTO (1996) Computerised Cadastral Index. Internal Report. Land Titles Office NSW. Moellering, H., Editor (1991) Spatial Data Transfer Standards: Current International Status Elsevier Science Publishers. London and New York Mortensen, J. & Baitch, G. (1996) Cadastral Digital Data Transfer or Cadastral Spatial Referencing System from Start to Finish. Presented at the 72nd Annual Conference of Staff Surveyors of NSW Inc. Neff, K. (1992). The Spatial Data Transfer Standard (FIPS 173): A management Perspective. Cartography and geographic Information Systems, American Congress on Survey and Mapping 1992, 19(5) OGDC (1995). Report on the State Digital Map Base Office of Geographic Data Co-ordination, Department of Treasury, Victoria. December Ranshaw, G. (1995) Geographic Information Systems in Local Government. Internal document. Land Information Centre, Department of Conservation and Land Management. NSW. Wan, W.Y. & Williamson, I.P (1995) The Users View of Digital Cadastral DataBases In Australia. The Australian Surveyor. 1995, 40(1) Wan, W.Y. & Williamson, I.P (1995) A Review of Digital Cadastral Databases in Australia and New Zealand. The Australian Surveyor. 1995, 40(1) Proceedings of the Spatial Information Research Centre s 8th Colloquium 59

8 Minerva Access is the Institutional Repository of The University of Melbourne Author/s: Effenberg, Wolfgang W.; Williamson, Ian P. Title: Data flows, standards and incremental cadastral update Date: 1996 Citation: Effenberg, W. W. & Williamson, I. P. (1996). Data flows, standards and incremental cadastral update. In Proceedings of the Spatial Information Research Centre s 8th Colloquium, University of Otago, New Zealand. Publication Status: Published Persistent Link: File Description: Data flows, standards and incremental cadastral update Terms and Conditions: Terms and Conditions: Copyright in works deposited in Minerva Access is retained by the copyright owner. The work may not be altered without permission from the copyright owner. Readers may only download, print and save electronic copies of whole works for their own personal non-commercial use. Any use that exceeds these limits requires permission from the copyright owner. Attribution is essential when quoting or paraphrasing from these works.