COMPARISON OF DIGITAL CADASTRAL MAP AREAS IN GAUSS- KRUGER AND UTM PROJECTION

Transcription

1 INTERNATIONAL SCIENTIFIC CONFERENCE AND XXIV MEETING OF SERBIAN SURVEYORS PROFESSIONAL PRACTICE AND EDUCATION IN GEODESY AND RELATED FIELDS 24-26, June 2011, Kladovo -,,Djerdap upon Danube, Serbia. COMPARISON OF DIGITAL CADASTRAL MAP AREAS IN GAUSS- KRUGER AND UTM PROJECTION Milivoje Avramović 1 Željko Cvijetinović 2, Dragan Mihajlović 2 1 Republic Geodetic Authority, Belgrade, SERBIA, mavramovic@rgz.gov.rs 2 Faculty of Civil Engineering, University of Belgrade, Department for Geodesy and Geoinformatics, Belgrade, SERBIA, zeljkoc@grf.bg.ac.rs, draganm@grf.bg.ac.rs Summary: The new law on state survey and cadastre stipulates Universal Transversal Mercator projection (UTM) of GRS 80 ellipsoid as a national projection of Serbia. Currently, all cadastral map data are given in Gauss-Kruger projection that has been adopted as national projection of Serbia. This paper presents experimental comparison of areas for the same features from digital cadastral map (DCM) database, calculated from coordinates given in Gauss-Kruger and UTM projection. Experiments have been carried out using data for several cadastral municipalities (CM). Comparison of areas has been performed for CM, parcels, buildings, and the results have been presented. Keywords: Real estate cadastre, digital cadastral map, digital orthophoto, parcel 1. INTRODUCTION The new Law on state survey and cadastre from 2009 prescribes Universal Transversal Mercator projection (UTM) of GRS 80 ellipsoid as a national projection of Serbia [4]. The same law prescribes that transition to the new coordinate system shall start no later than January Meanwhile, very few things have been done to solve the problems of transition from old to new reference system. Transition to new reference system cannot be implemented without production of digital cadastral map (DCM) [2]. DCM production in new reference system entails DCM production in the existing reference coordinate system, determining and adopting transformation parameters from the existing to the new spatial reference system of Serbia, and transformation of DCM data to new spatial reference system of Serbia. In this paper experimental comparison of areas for the polygon features of DCM (CM s, parcels and buildings) is given. For each DCM feature two areas are calculated using coordinates given in Gauss-Kruger and UTM projection and the difference is obtained. Experiment was done using data for several cadastral municipalities. The objective is to determine the level of differences in areas for DCM polygon features. It is to assume that the level of these differences might influence the methodology of DCM database production database in UTM projection, having in mind legal issues related to the establishment of official areas of parcels and buildings within cadastral database. 2. DCM PRODUCTION IN GAUSS-KRUGER PROJECTION Transformation of analog maps into digital form, i.e. DCM production, started in Serbia in 1990 s. DCM production is being performed: by entering original (numeric) field survey data; by scanning, georeferencing and vectorization of analog cadastral map; or combination of the above. The first legislation covering this field was adopted in 1995 the Rulebook on establishing, acquisition, production and distribution of DCM database [6]. Rulebook on cadastral and other maps was adopted in 2000, and Decree on DGM in 2003 [5]. Professional instruction for DCM production was adopted in April 2006, and 281

2 the Instruction for data organization in DCM establishing process in MapSoft 2000 environment was adopted in November 2006 [7]. In 2007, Republic Geodetic Authority (RGA) intensified works on DCM production. By December 29 th, 2010, DCM has been produced and published for the official use for 1023 CM s in Serbia. Figure 1 shows realization of works on DCM production per Regional Cadastral Offices (RCO). Beograd - 61 Number of cadastral municipalities Број катастарских општина Beograd 0 Zaječar 51 Kragujevac 229 Kruševac 435 Niš 38 Novi Sad 15 Pančevo 141 Užice Šabac 53 Zaječar - 0 Kragujevac - 51 Kruševac Niš Novi Sad - 38 Pančevo -15 Užice Šabac - 53 Figure 1: DCM production per RCO s by December 29 th, 2010 By December 29 th, 2010, DCM has been produced for the area of ha. The most of DCM databases has been produced for the territory of RCO Nis (435 CM s), while none has been produced for the territory of RCO Zajecar. For DCM produced by December 29 th, 2010, the status is the following: Of total number of 5826 CM s, DCM has been produced and published for the official use for 1023 CM s; Of total number of 1023 CM s produced and published for the official use, 1008 CM s are in Gauss- Kruger projection, 14 CM s are in Zoldner s projection (municipality: Ub 7 CM s, Lajkovac 3 CM s and Smederevo 4 CM s) and one CM is in stereographic projection (CM Krnjesevci, municipality Stara Pazova); DCM was produced using the original data for 330 CM s with total area of ha and parcels; by digitalization for 689 CM s with total area of ha and parcels; and using combined method for 4 CM s with total area of 4507 ha and parcels; DCM areas were admitted in REC records for approximately 850 CM s; DCM was produced and published for the official use using MapSoft 2000 software for 1023 CM s, while 27 CM s were produced using various software applications and delivered to the RGA in ESRI Shapefile format, which is being maintained using ArcGIS software (for these 27 CM s, DCM is not yet published for the official use); During DCM production, analysis of geodetic network that was used for the official cadastral survey was done for only few cadastral municipalities. Numerous DCM s has been produced in Serbia during the survey renewal or land consolidation procedure, and accepted by the supervision, i.e. by the RGA (CM s Sabac, Uzice, Pozarevac, Novi Pazar, etc), but these were not published for the official use, since REC had not been established for those CM s. For some CM s, DCM had been produced within survey renewal procedure and accepted by the RGA (Gornji Milanovac), but REC was established using the existing analog cadastral maps [1]. DCM has been produced for a significant number of CM s on the territory of Serbia. Due to errors of the original cadastral survey or maintenance thereof, detected during DCM production procedure and performing administrative procedure to remedy those errors (as performed by competent LCO s), DCM has not been published for the official use. 282

3 3. COORDINATE TRANSFORMATION PARAMETERS FROM GAUSS-KRUGER TO UTM PROJECTION The results of the research suggested that the optimal model for horizontal transformation for the territory of the Republic of Serbia, should be seven-parameter Helmert s transformation with residual grid [3]. Parameters of global Helmert s transformations has been given, covering the entire territory of Serbia, i.e. seven parameters has been determined, being 3 translation parameters, 3 rotation parameters and 1 exchange parameter (Table 1). Table 1 : Estimations of global Helmert s transformation parameters Parameter tx ty tz Value m m m ex " ey " ez " dm ppm Residual grid has been formed to cover the entire territory of Serbia, with resolution of 1 km. Residual values per coordinate axes in grid nodes has been calculated using inverse distance weighted method (Figure 2), based on residual in reference points, in relative proximity of the grid node. For each reference point, weight is calculated as inverse distance from the node. Table 2 contains presentation of data on other proposed parameters for the establishment of residual grid for the territory of the Republic of Serbia. Table 2 : General parameters of residual grid remained after global Helmert s transformation for the territory of Serbia Parameter tx ty tz Value m m m ex " ey " ez " dm ppm Grid node Reference point Figure 2: Principle of residual grid formation after global Helmert s transformation Considering that horizontal differences are vectors, separate residual grids were calculated for both coordinate axes y (direction East-West) and x (direction North-South). Both grids consist of 328 column and 437 rows. 283

4 4. DCM PRODUCTION IN UTM PROJECTION After production of DCM in Gauss-Kruger projection, DCM data are being transformed to UTM projection. Transformation is being performed using transformation parameters from the existing Gauss-Kruger to UTM projection, which are calculated and officially accepted by the RGA. This chapter presents transformation of DCM data from the existing Gauss-Kruger projection to UTM projection using software applications MapSoft 2000 and GRIDER. DCM data produced by the MapSoft 2000 software is transformed from Gauss-Kruger to UTM projection in the following manner: Software application MapSoft 2000 is used for conversion of all active entities (points, lines, polygons and labels) to ASCII files (*. tac, *.lin, *. pov and *.naz); ASCII files *.lin i *.pov are projection independent, i.e. they are the same for Gauss-Kruger and UTM projection (only topology and thematic attributes are stored for these entities, no geometry); Application GRIDER is used for transformation of point coordinates from Gauss-Kruger to UTM projection (ASCII file *.tac shall be changed only in the part where point coordinates are stored, and the result is a new file *-utm.tac); Application GRIDER performs transformation of reference point of name coordinates from Gauss- Kruger to UTM projection (ASCII file *.naz shall be changed only in the part where point coordinates for label text box corner are stored, and the result is a new file *-utm.naz); Using coordinates of all points of the DCM, a new map sheet division in UTM projection is produced for each CM or scale territory (part of CM where the same map scale is used); New Mapsoft project in UTM projection is created using MapSoft 2000 and ASCII files *-utm.tac, *.lin, *.pov and *-utm.naz are imported into the project database; Calculation and rounding of polygon areas in UTM projection is being performed using MapSoft 2000; DCM is published for the official use in new spatial reference system. Procedure given above is quite straightforward and it does not require any other specialized software. The work could be done by using some GIS or other software capable of performing transformation of coordinates for points and other spatial features from one to another cartographic projection. Some minor software modification might be necessary depending on the software used. For a large number of CM s, DCM has been produced without analysis of geodetic network that was used for the geodetic survey. Transformation of DCM data from the existing projection to UTM projection should not be performed without analysis of geodetic network. This should be followed, if necessary, with recalculation of coordinates for geodetic network points and with recalculation of coordinates for all DCM points. 5. COMPARISON OF DCM AREAS IN GAUS-KRUGER AND UTM PROJECTION Calculation of differences for areas could be done simply by using mathematical approach, i.e. formulas for the coordinate transformation and formula for calculation of polygon areas from coordinates. Obviously differences depend on geographic location, size and shape of polygon in question. However, authors of this paper opted for experimental comparison of areas. Motivation for experimental comparison was to obtain more realistic results by using real DCM data for several Serbian CM s (with specific geographic location, size and shape of polygon features) and also to demonstrate transformation of data from one to another cartographic projection with real data and software tools already at disposal. After DCM production in Gauss-Kruger and UTM projection (for the same CM), analysis of the following areas has been performed: CM s, parcels and buildings. Analysis has been performed as follows: Recapitulation report of rounded areas was produced using DCM database in Gauss-Kruger projection; covering area of CM, parcels and buildings are included in report; Recapitulation report of rounded areas was produced using DCM database in UTM projection; covering area of CM, parcels and buildings are included in report; Both recapitulation reports has been loaded in Excel and differences has been calculated; by data filtering and defining specific queries on areas, differences per entity layers and values are easily obtained. 284

5 Selection of test area has been performed to cover various map scales and different parts of Serbia. Analysis has been performed for the following CM s: Gornji Milanovac 500, Raca 500, Vlasotince part , Ljubovija 1000, Hajducica 1000, Mali Beograd 1000, Opovo 1000, Zavidince 2500, Lipovica 2500, Simicevo 2500, Hajducica 2500, Klajic 5000 and Strizevac 5000 (Table 3). Numbers 500, 1000, 2500 and 5000 designates surveyin scales. Table 3 : Analysis of DCM polygon areas in UTM and Gauss-Kruger projection CADASTRAL MUNICIPALITY TOTAL NUMBER OF PARCELS TOTAL NUMBER OF BUILDINGS CM AREA IN UTM PROJECTION [m 2 ] CM AREA IN GAUSS-KRUGER PROJECTION [m 2 ] DIFFERENCE OF CM AREAS UTM-GK [m 2 ] NUMBER OF PARCELS FOR WHICH ROUNDED AREAS IN UTM AND GK ARE DIFFERENT PERCENTAGE OF PARCELS FOR WHICH UTM AND GK AREAS ARE DIFFERENT NUMBER OF BUILDINGS FOR WHICH ROUNDED AREAS IN UTM AND GK ARE DIFFERENT PERCENTAGE OF BUILDINGS FOR WHICH UTM AND GK AREAS ARE DIFFERENT DIFFERENCE UTM-GK=1m 2 DIFFERENCE 1m 2 <UTM-GK<5m 2 DIFFERENCE 6 m 2 <UTM-GK<10m 2 DIFFERENCE 10m 2 <UTM-GK<50m 2 DIFFERENCE 50m 2 <UTM-GK<100m 2 DIFFERENCE UTM-GK>100m 2 GORNJI MILANOVAC SCALE 1: RACA VLASOTINCE PART 1 SCALE 1: LJUBOVIJA HAJDUCICA MALI BEOGRAD OPOVO SCALE 1:2500 ZAVIDINCE LIPOVICA SIMICEVO HAJDUCICA SCALE 1:5000 KLAJIC STRIZEVAC Analysis of obtained data, presented in Table 3 indicates as follows: Areas of CM or scale in Gauss-Kruger projection are greater than areas in UTM projection; differences range from 502m 2 (CM Raca 500 whose area is 81ha) to 27973m 2 (CM Zavidince 2500 whose area is 4703ha). Logically, differences of CM (scale) areas, parcel and building areas are directly dependant on area, i.e. larger area involves larger differences of areas in Gauss-Kruger and UTM projection; Differences of CM (scale) areas in Gauss-Kruger and UTM projection range from 5.51m 2 /ha (CM Zavidince 2500) to 7.14m 2 /ha (CM Vlasotince part ). Parcel areas in Gauss-Kruger projection are greater or equal to areas in UTM projection; differences of parcel areas are lowest for CM Vlasotince part (22.8%) and highest for CM Simicevo 2500 (95.5%). Building areas in Gauss-Kruger projection are greater or equal to areas in UTM projection; differences of building areas are lowest for CM Lipovica 2500 (0.9 %) and highest for CM Hajducica 2500 (27.5%). The majority of parcel and building areas in Gauss-Kruger and UTM projection have difference of 1m

6 Authors of this paper are convinced that areas of CM s, scales, parcels and parcel parts should not be admitted to REC registers by calculation of these areas from DCM databases produced in Gauss-Kruger, Stereographic or Zoldner s projection. Instead of that, DCM database in UTM projection should be produced firstly, and areas from this database should be calculated and used for official REC registers. 6. CONCLUSIONS The new Law on state survey and cadastre from 2009 prescribes Universal Transversal Mercator projection (UTM) of GRS 80 ellipsoid as a national projection of Serbia, and transition to the new coordinate system shall start no later than January 1 st, Transition to new reference system cannot be implemented without DCM production. The following needs to be done within DCM production procedure in UTM projection: For CM s where DCM was produced in Gauss-Kruger projection without analysis of geodetic network used for the cadastral survey, this analysis should be done and, if needed, recalculation of geodetic network points coordinates; corrected geodetic network points should be used to recalculate correct coordinates for all points belonging to entities within DCM database (it is assumed that these points are calculated using geodetic network points and field survey data); Within the procedure of new DCM production, analysis of geodetic network that is used for cadastral survey must be previously performed; Although the proposed model of horizontal transformation on the territory of Serbia (seven-parameter Helmert s transformation + residual grid) is already being used, it is necessary to formally accept it in by-laws; Division of state coordinate system of Serbia into trigonometric sections and map sheets for scales S=1:2500, S=1:1000 and S=1:500 must be prescribed by the appropriate by-laws; Within the DCM production procedure, upon transition to the new spatial reference system of Serbia, REC records areas should be admitted to DCM as the official areas; in this case, no information letters are to be legislated; resolution needs to be legislated ex officio, only for the parcels and buildings where there is an obvious blunder in area calculation; ex officio correction of errors may also be performed within the DCM maintenance procedure; Changes of areas in REC records should be performed after DCM is being produced in new spatial reference system of Serbia. REFERENCES [1] Aleksić, I.; Gospavić, Z.; Avramović, M. : Digital Cadastral Maps prouction in the Republic of Serbia, INTERGEO EAST Conference for Landmanagement, Geoinformation, Building Industry, Environment, Belgrade, [2] Avramović, M.; Božinov V.: Establishment of new Reference System in Serbia and implications in cadastral survey, in Serbian, Establishment of new Reference System (coference), Belgrade, [3] Blagojević, D.: Research on optimal model of horizontal transformation for the territory of Republic of Serbia, Final report, in Serbian, Republic Geodetic Authority, Belgrade, [4] Law on state survey and cadastre, in Serbian, Official Gazette of Republic of Serbia, No. 72/09 and 18/2010, 2009 and [5] Decree on Digital Geodetic Map, in Serbian, Official Gazette of Republic of Serbia, No. 15/2003 and 18/2003, [6] Rulebook on production, maintenance, distribution and archiving of Digital Geodetic Map database, in Serbian, Official Gazette of Republic of Serbia, No. 37/95, [7] Practical guide for the production of Digital Cadastral Map Ver. 01, in Serbian, Republic Geodetic Authority, No /06,