IMPROVEMENT OF QUALITY CONTROL SYSTEM IN CROATIA
S. Lemajić *, N. Rožić, M. Rapaić
Croatian Geodetic Institute, Savska 41/XVI, 10144 Zagreb p.p.19, Croatia - hgi@hgi.hinet.hr
KEY WORDS: Geoinformation project, Data upgrade, Quality control, Quality Plan, Croatian Geodetic Institute, ISO
ABSTRACT:
Croatian Geodetic Institute (CGI) was founded in February 2001 and started with professional work at December of 2001. CGI is an
independent institution but working closely with State Geodetic Administration (SGA). According to Law on State Survey and Real
Estate Cadastre (Croatian Parliament, 1999) CGI is responsible for scientific geodetic and surveying works and for quality control of
geodetic products produced by geodetic companies. At the beginning of professional work CGI started with performing of digital
orthophoto control and analogue topographic maps control. At that time the CGI quality system was not in accordance with ISO
standards. The Book of Ordinance (State Geodetic Administration, 2001) was the key document for ensuring quality control. Lack
of software systems and hardware infrastructure, supporting data necessary for quality control, procedures and formal QC
documentation were the main reason to start establishment and development of new CGI Quality System for quality control of
geodetic products. Croatian-Norwegian Geoinformation Project (CRONO GIP) started in June 2002. Implementation of component
c) of the Norwegian assisted Project in Croatia for enhancing the capabilities of the Croatian Government to build a National Spatial
Data Infrastructure has according to Terms of reference (Statens Kartverk, 2001) three objectives: CGI shall be able to control the
quality of topographic data produced by geodetic companies for SGA, CGI shall be able to perform satisfactory controlling of the
quality of topographic maps and orthophotos produced by geodetic companies and CGI shall be able to prepare draft regulations and
standards in line with international standards, to be applied by geodetic companies for assuring and documenting quality in the
production of geographic data. Before Implementation of CRONO GIP results, CGI performed the Test Quality Control. The
Dataset, which was the subject of Control, CGI have controlled according to Specification which are made for Data Upgrade. The
Results with Reports of Test Control are delivered to Producers for corrections. After Corrections the Structure of Dataset was
acceptable for further methods of control.
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1. INTRODUCTION
At the end of 2001 CGI started with professional work in the
field of control of orthophoto in the scale 1:5000 and control of
topographic map in the scale 1:25000. The control of these
products was not based on ISO rules. Lack of experience,
equipment and specifications which were needed for control,
demanded to make full control of these products. Also, before
establishment of CGI there was no institutional system for
making quality control but CGI started with improvement of the
quality of products.
CRONO GIP which started in June 2002 had a main goal to
improve quality control system in CGI. Consultant Team made
Inception study report (Program Management and Mapping PMM, 2002) for producing detailed project plan, for reviewing
all activities defined in Terms of Reference, for verifying the
project objectives and local awareness for the Project, setting
guidelines and procedures for execution and building the team.
The base activity of CRONO GIP which is connected with
Croatian Geodetic Institute is to establish capacity in CGI to
control the quality of geodetic data produced by geodetic
companies for State Geodetic Administration. From the
beginning, the planned activities if the Project are:
Specification and verification of controlling
procedures and methods for CGI according to ISO
Verification of existing documentation with
comparing to ISO standards
Drafting new regulations and standards
* Slavko Lemajić, dipl.ing.geod.
slavko.lemajic@hgi.hinet.hr
Croatian
Geodetic
Specification and procurement of equipment
(hardware and software)
Education in the use of new equipment (training)
Practical execution of controls on products and
making the reports.
The realization of the Project is based on a set of
documentations:
Products and product specifications
Quality plan
Procedures and checklists
Reporting.
1.1 Products
Product is a set of work results, which can be used for several
purposes. The Product is defined by Product Specifications. For
each Product, requirements are set to the Process leading up to
the final product. These processes are subject to Process
Specifications. The process specification will mainly be
required to process documentation. The Process Specifications
are subject to more frequent changes due to development of
technology and methodology, compared to the product
specifications that are of a more permanent character.
Product Specifications and Process Specifications are related to
Quality Elements and Quality Sub elements ISO/DIS 19113 and
ISO/DIN
19114
(International
Organization
for
Standardization, 2001 and 2002). Each of these elements is
described with:
Definition of the quality element/sub element
Institute, Savska
41/XVI,
10144
Zagreb
p.p.19,
Croatia
–
Specification
Producers documentation requirements.
The control of these elements is described with respect to:
Sampling strategy
Accept/reject rules
Quality control method.
Following products are defined:
Aerial Photography and Ground Control Points
Scanned Photo
Aerial Triangulation
Topographic Data
Digital Terrain Model (DTM)
Topographic map in scale 1:25000 (TK25)
Digital orthophoto in scale 1:5000 (DOF).
1.2 Quality Plan
Quality Plan defines the organization, policies and procedures
applied by CGI when undertaking quality control of product
deliverables. Developing and inspection plan and execution
describes how individual inspections are planned and
undertaken. Inspection of a product may consist of many
individual inspections.
Developing of inspection plan describes the steps to follow
when developing an Inspection Plan. The result of this
examination shall be written in the Inspection Plan for the
Project. The same Inspection Plan template can be used over
again for new projects of similar nature.
Execution shows the steps to follow when undertaking the
Inspection Work. The inspection itself must be new for each
project however the procedure can be the same for similar
projects.
a) The development of a control plan follows the next six
steps:
Identification of dataset
When identifying the dataset, the relevance of the data should
be emphasized.
Identification of data quality elements
The control might involve one or more quality elements. The
control plan will identify all data quality elements and data
quality sub elements relevant for the product or service.
Identification of data quality measure
The data quality measure has to be defined.
Identification of tolerances
Requirements for geographic information specified as tolerance
are standard parts of the specifications for the data set.
Identification of data quality scope
The geographic area for the control and groups of objects has to
be identified. A choice has to be done between full inspection
and sampling. If sampling is chosen, the size of the scope and
geographic location has to be identified.
Identification of control method
The control method has to be defined.
b) Execution of inspection contains the following:
Undertake control measurements and calculate Values
for data quality measures
True values must be obtained, usually by control measurements.
Corresponding values are selected from the dataset. The
difference between the value of the dataset and the true value is
the discrepancy. Based on all differences, the value for the
current quality measure can be evaluated.
Compare calculated values for quality measures with
tolerances.
Values from the control measurements shall be compared with
the tolerance of the data quality measure. It has to be decided
whether the quality corresponds with the product specifications
or not. The result must be significantly worse than the tolerance
before the dataset is rejected.
Approval and handling of gross errors/discrepancies
When the control is finished, it has to be decided whether the
dataset shall be approved, rejected or if the control shall be
expanded.
Reporting
Reporting can be done in two ways:
Prepare a special inspection report
Report as metadata.
It is recommended to report by means of inspection reports.
1.3 Procedures and Checklists
A Checklist is a Formal description of a task mainly built up of
boxes to be filled in, ticked or signed.
All Procedures and Checklists are controlled by a system of
sponsor and custodian where both signatures are required
before the documents are released for use. Custodians are
responsible for the distribution and revision control of all
documents assigned to them. Sponsors authorize the content of
the document for use. As a general rule, sponsors are
departmental managers.
Data quality methods are divided into two main classes, direct
and indirect. Direct methods determine data quality through the
comparison of the data with internal and/or external reference
information. Indirect methods infer or estimate data quality
using information on the data such as lineage. The direct
evaluation methods are further sub classified by the source of
the information needed to perform the evaluation.
a) Direct Evaluation Methods
Types of Direct Evaluation Methods: internal and
external.
Means of Accomplishing Direct Evaluation: for both
external and internal evaluation methods, there are
two considerations, automated or non-automated and
full inspection or sampling.
Full inspection
Sampling
b) Indirect Evaluation Method
The indirect evaluation method is a method of evaluating the
quality of a dataset based on external knowledge. This external
knowledge may include, but is not limited to, data quality
overview elements and other quality reports on the dataset or
data used to produce the dataset.
1.4. Reporting
Reporting of Data Quality Evaluation Information is possible
as:
Reporting in Metadata
Reporting in a Quality Evaluation Report
Reporting Aggregated Data Quality Result.
It is recommended to report by means of Inspection Reports.
2. TEST QUALITY CONTROL OF TOPOGRAPHIC
DATA
Before the end of Project CGI has preformed test quality
control of topographic data. Preliminary tasks that are done can
be described as:
Verification of existing data according to CROTIS
(State Geodetic Administration, 2002)
Data upgrade specification (PMM, 2003)
Quality control of upgraded data.
2.1 Verification of existing data
2.3 Data upgrade quality control
For verification of existing data six Croatian private companies
delivered a part of data from dataset that were the object for
comparison with Croatian Topographic Information System
(CROTIS) data model. Another objective was how to bring the
existing data up to new Specification. The task was to
determinate differences between datasets and existing
specification. It resulted in the the report about the existing data
based on examples of six companies. Findings were divided on:
Global remarks to existing specification (or
incomplete specification)
Global remarks to all companies
Specific remarks for a single company.
2.2 Data upgrade specification
Data upgrade specification describes:
Content of specification
Terminology used in specification
Deliverables
Specification for geometry and topology
Specification for topographic data
DTM specification.
According to this Specification companies have upgraded the
Data. The main activity in pre qualification process was
changing attributes and topological cleaning the data. Such
prepared data will be ready for input into database.
The integral parts of specifications are:
Object selection criteria
Mapping catalogue
Library of symbols
Quality elements.
In the specification, there is also the terminology described that
is partly based on Simple Feature Specification by Open GIS
Consortium.
According to specification, the contractors should deliver final
production report and the dataset. Final production report
contains Production metadata and other information,
Descriptions of topology processing procedures and
Descriptions of quality control procedures for important
processes. Dataset to be delivered is Topographic vector data
in 2D and Digital terrain model (DTM) vector data in 3D. All
data should be delivered in „dgn” format (Microstation).
Coordinate system of dataset, file names ad media are described
too. Specification for geometry and topology describes that
delivered data should contain only line string and point
geometries. Data topology describes that polygons are not
allowed but polygons should be automatically generated from
the data. The same rule with requirements for topology is
described. Specification of topographic data describes groups
of feature classes and representation in „dgn” files.
Representation of feature classes is described in „Mapping
catalogue” and selection criteria in „Selection criteria” for data
capture. Distribution of feature classes is divided by groups,
levels and files. The specification also describes which feature
classes and in what way they should be represented. There are
following feature classes: Toponyms, Buildings, Utility,
Transportation and elevated features, Vegetation, Hydrographic
and digitized feature. DTM Data Specification contains Digital
Terrain model and DTM data processing procedures. DTM
features are spot heights, mass points, break lines, form lines
and areas of unreliable DTM. In DTM data processing
procedures are data preparation, data vectorization, data editing,
data specification, quality control and delivery formats.
State Geodetic Administration (SGA) contracted data upgrade
for six map sheets of Topographic map in scale of 1:25000
(TK25) with six geodetic companies. They upgraded existing
dataset according to Data Upgrade Specification and Mapping
Catalogue. Before starting the job consultant team of CRONO
GIP made training for geodetic companies. Companies
delivered upgraded data with technical reports.
CGI, in coordination with CRONO GIP Team, made a strategy
for quality control. The Strategy contained:
Quality Plan
Quality methods with realization
Results of control
Reports.
2.3.1 Quality Plan
Quality Plan defines requirements for quality control of
upgraded data and Quality Management System. Quality
system in this Quality Plan covered Product of Topographic
Data. Quality Plan covered following steps:
Control of deliverables
Control according sources
Control of structure of data
Control of topology
Control of DTM dataset.
Geodetic companies delivered mainly the following files:
- YYYY-MM-DD-<ContractorID>-<MapNumber>-BUILDINGS.dgn
- YYYY-MM-DD-<ContractorID>-<MapNumber>-UTILITY.dgn
- YYYY-MM-DD-<ContractorID>-<MapNumber>LANDCOVER.dgn
- YYYY-MM-DD-<ContractorID>-<MapNumber>-DIGITISED.dgn
- YYYY-MM-DD-<ContractorID>-<MapNumber>-TOPONYMS
- YYYY-MM-DD-<ContractorID>-DTM.dgn
- YYYY-MM-DD-<ContractorID>-DEM-GRID.dgn
- YYYY-MM-DD-<ContractorID>-REPORT.pdf,
where YYYY-MM-DD is date of deliverry, ContractorID
represent name of company, MapNumber represent map
number and at the end content of files with file format.
Examples of topographic data and DTM data are shown on
Figure 1 and Figure 2:
Figure 1: Example of topographic data
Figure 4: Unprecise creating of road centerlines
Visual control of DTM was done with the help of derived shade
(tiff format) and DEM (dgn format) as shown on Figure 5.
Some questionable parts on raster file are checked.
Figure 2: Example of DTM data
Sources which are used for control were Data inventory report,
Data upgrade specification and Mapping catalogue. For the
control of toponyms there were aslo the old maps of TK25
used. Data structure control included was done acoording to
mapping catalogue which describes level, color, line style and
weight for linear objects, cell name for point elements and
representation point (text) for areal objects.
Control of topology included checking closing areas, duplicate
lines and boundaries, open boundaries, number of
representation points in areas, missing representation points in
areas, detecting unused boundaries, etc.
Control of DTM included also checking of structure elements in
files and deriving DEM from delivered elements and detecting
of possible errors.
2.3.2 Quality methods
There are two methods for quality control:
Visual control with Microstation and SCOP
Automatic control of data structure and topology
(using FME).
Microstation was used for visual control of data. There was a
system to control elements, which were wrongly represented
before data upgrade process. Mostly, bridges were wrongly
represented, roads were without center lines, waters were not
represented under bridges (Figure 3) and culverts, creating
centerlines were also not enough precise (Figure 4).
Figure 5: Visual control of DTM
Automated quality control was done with FME (Feature
Manipulation Engine) software. Partly based on FME training
and partly with help of CRONO GIP consultants in CGI the
FME factory files were used for checking the structure of
datasets and for checking topology. The inputs for control of
dataset structure were all legal levels, colors, line styles and
weights for linear elements, for point elements input there was
a list of symbol (crotis.cel file) and for area elements a list of
codes (representation points). FME detected all open
boundaries, unused boundaries (which are not necessary for
creating area topology), missing classifications points (text
codes), duplicate classifications points, overlapping lines and
boundaries, self intersected lines and boundaries.
2.3.3 Results of control
Figure 3: Water line not represented under bridges
After the control, the results were divided to:
Comments connected to undefined specification
Comments connected to misinterpretation of
specification
Comments to topological processing.
In the process of quality control CGI detected some cases which
are not enough described or are not described in Specification.
Typical example of that case is joining of road center lines.
There was no rule for joining narrow paths with road center
lines which are very important for creating road network
topology (Figure 6).
2.3.4 Reports
For each company CGI wrote report, which includes:
Introduction
Authority for control
List of Sources
Content of control
Findings
General and single comments
Comments
connected
to
topologic
processing
Conclusion.
2. CONCLUSION
Figure 6: Narrow path not connected to road centerline
Some producers interpreted object in their own way. Typical
example is representing of culverts (Figure 7)
Croatian Geodetic Institute has done Data upgrade Quality
Control of structure and topology processing of topographic
data in short period of time. Control of accuracy and
correctness of representation and classification have not been
included in this process. Complete quality system should be
implemented at the end of the project.
Even though complete quality system was not implemented,
CGI has done quality control in part and results of control were
very useful. Before completing the specification, some elements
will be changed and enhanced and the difference between
producers reduced to accepted level. There is also a team in
CGI for all tasks and challenges. This test quality control
confirmed that contention.
REFERENCES
Croatian Parliament, 1999, Law of state survey and real estate
cadastre, Narodne novine br. 128/99, Zagreb.
Figure 7: Different ways of representing culverts
Most comments connected to topology processing were in using
wrong attributes for linear elements (wrong color or weight for
lines and boundaries). Distribution for errors and companies is
shown in Table 1.
Error type
Invalid element type
Invalid line attribute
Invalid boundary
attribute
Unused boundaries
Missing classification
point (textual code)
Unknown
classification point
Excess classification
points
Self intersecting lines
Self intersecting
boundaries
Invalid cells
Company
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Statens Kartverk, 2001. Terms of reference for the
implementation of component b) and c) of the Norwegian
assisted Project in Croatia for enhancing the capabilities of the
Croatian Government to build a National Spatial Data
Infrastructure. Appendix A to the Contract, Oslo, Norway.
Program Management and Mapping, 2002. CRONO GIP
Croatian Norwegian GeoInformation Project - Inception study
report, Zagreb, Croatia.
Program Management and Mapping, 2002. CRONO GIP
Croatian Norwegian GeoInformation Project – Data Inventory
report, Zagreb, Croatia.
Program Management and Mapping (PMM), 2003. CRONO
GIP Croatian Norwegian GeoInformation Project – Data
upgrade specification, Zagreb, Croatia.
International Organization for Standardization, 2001, ISO/DIS
19113 Geographic information – Quality principles.
International Organization for Standardization, 2002, ISO/DIS
19114 Geographic information – Quality evaluation procedures.
State Geodetic Administration, 2001, Book of Ordinances,
Zagreb, Narodne novine br. 55/2001, Zagreb.
Table 1: Distribution error types for each company
State Geodetic Administration, 2002, Croatian Topographic
Information System CROTIS, Zagreb.