The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
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for metadata (Figure 3). In continuation is given an overview of 
Quality Control on Orthophoto example. 
Figure 3. Geoportal in relation with NSDI and Inspire 
4. ORTHOPHOTO PRODUCTION 
Production of orthophoto is based on Product Specification 
(SGA, 2003) which describes all important issues. Some 
predecessors are also important to product orthophoto (Scanned 
Photos if applicable or digital aerial images, DTM and Aerial 
Triangulation) i.e. for correct orthophoto the condition is that 
previous products passed on Quality Control. The Figure 4 
shows the hole system of products and previous products which 
are documented through CRONO GIP. 
Figure 4. Products and products' predecessors 
The initiate Orthophoto production was based on gray scale 
aerial photography and first Product specification described 
gray scale orthophoto. The final orthophotos shall have a 
radiometric resolution of 8 bits; 256 grey levels. The 
distribution of the histogram shall be approximately between 5 
(black) to 250 (white). Changes in the product specification are 
based on user needs and on new technology methods and 
processes. The latest Product specification describe color 
product (24 bit colour raster). The delivery consists of delivery 
list, production report and data (raster data, vector frame and 
toponyms data and orthophoto print). Specification for 
Orthophoto Production (SGA, 2003 a) consist od description of 
Images used for Orthophoto production, way of Image 
rectification, mosaicing, retouch. Also there is described the 
way how to collect and represent vector data (toponyms) and 
draw map frames. Main parts of Product Specification are also 
appendices: Delivery List Requirements, Maps Sheet 
Nomenclature, Cartographic Key for Toponyms and Official 
gazetteers for public roads and settlements. 
The accuracy of final Orthophoto should have standard 
deviation of 1 meter (for well defined objects). 
5. QUALITY CONTROL SYSTEM 
Quality control system is based to fulfill 95% confidence level 
for delivered data. The whole QC system includes 
documentation (general documents, guidelines for QC and 
check list), human recourses and equipment (software, 
hardware and professional devices). . General principles are 
described in Quality Control Principles of Geographic 
Information (CGI, 2004b). General principle of methos are 
shown on Figure 5. All the data needed to perform an internal 
direct data quality evaluation method is internal to the dataset 
being evaluated, e.g. controls by means of software. External 
direct quality evaluation requires reference data external to the 
dataset being tested, e.g. check against other data. 
Figure 5. Quality evaluation methods 
QC Process includes determination of quality plan and quality 
methods, executing and reporting. Concrete quality plan means 
defining dataset, identification quality elements and 
subelements and tolerances, control methods, acceptable level 
of quality and way of reporting. 
The Quality Plan is developed according to definitions of ISO 
quality elements, subelements, descriptors, evaluation methods 
and selected tolerances (ISO, 2001). 
Execution of the Quality Plan on Spatial data results with the 
Quality Evaluation Reports with information about dataset, 
used quality elements, executed measurements i. e. controls, 
tolerances according to specification, used methods - full 
control or sampling (CGI 2004c), used equipment or software, 
processing of measurements, comparing results with tolerances 
and finaly quality evaluation of product delivery (product is 
acceptable or not). 
Quality elements and subelements used for spatial data quality 
control are used according to Product Specification (State 
Geodetic Administration) and described in separated document. 
The process of quality control procedures can be divided in four 
classes depending of the control type used: manual full (MF), 
automatic full (AF), manual sample (MS) and automatic sample 
(AS). 
In praxis the quality control process includes: control of 
delivery, execution of control (manual, sampling or automated) 
and reporting.