REQUIREMENTS FOR PHOTOGRAMMETRIC DATA COLLECTED IN NATIONAL GEODETIC AND CARTOGRAPHIC RESOURCE

The Registers of the national geodetic and cartographic resources deliver reference information for other resources of Spatial Data Infrastructure (SDI). It is essential that the good quality information from public resources has a direct impact on the correctness of the conducted processes and analysis of public and private sectors. Besides knowledge about quality of data is crucial for users to compare datasets to determine which best fulfils for their needs. Therefore requirements for data are a vital to the process of selecting a data set in that the value of data are directly related to its quality. This paper presents concept of Polish Registers for photogrammetric data: technical standards for aerial imagery, elevation data, ortophotomaps, among others completeness, accuracy and spatial characteristics. In addition, article presents current state of the photogrammetric data in the Polish Geodetic and Cartographic Resource.


INTRODUCTION TO PHOTOGRAMMETRIC REGISTERS
The basic requirements for photogrammetric data are defined in The Geodetic and Cartographic Law (Polish Parliament, 1989), Regulation regarding databases on aerial and satellite imagery, orthophotomap and a digital terrain model (Ministry of Interior and Administration, 2010) and Regulation regarding the National Spatial Reference System (Councils of Ministers, 2011). More detailed requirements are described in technical standards for the tender.
The national geodetic and cartographic resource in Poland is divided into three groups of geodetic and cartographic documentation: the central resource, voivodeship resources and district resources. The central resource is provided by Head Surveyor of the Country and contain data sets and databases of spatial data infrastructure including photogrammetric data: aerial and satellite images, orthophotomaps and digital terrain models. All registers include metadata describing them and the services they perform in accordance with the Act on Spatial Information Infrastructure (Polish Parliament, 2010). The data stored in national geodetic and cartographic resource in Poland are published in the national broker: www.geoportal.gov.pl. The web application lets browse and search spatial data sets and services which belong to the National Spatial Data Infrastructure. Besides, Head Office of Geodesy and Cartography provides web services, such as view services (WMS, WMTS), discovery services (CSW) and download services (WFS, ATOM, WCS). These allow web clients to query and receive spatial data in the form of image, vector or coverage data.
The following photogrammetric information is verified and collected in the national geodetic and cartographic resource: -in the register of aerial and satellite images: The Head Office of Geodesy and Cartography use this law regulations and specifications to acquire photogrammetric data and to create consistency across all data and partner-funded photogrammetric collections from public fund. Local conditions and application in any given project, or the preferences of partners may mandate more stringent requirements. In these cases, the Head Office of Geodesy and Cartography support or encourage to the collection of more detailed, accurate, or valueadded data. Local conditions may also prevent a given collection from meeting these specifications (for example writing format).

Quality of photogrammetric data in other countries
Information about quality of spatial data allows a data producer to evaluate how well a data set meets the criteria set forth in its product specification and assist data users in evaluating a product's ability to satisfy the requirements for their particular application (ISO19157:2013). Therefore it was very important to prepare quality control model for aerial imagery, orthophotomaps and elevation data, including requirements stemming from legal regulations and technical standards, such as correctness, consistency and accuracy. It is essential that data into national geodetic and cartographic resource has defined standard.
In comparison to other countries the basic difference in photogrammetric data is current horizontal and vertical coordinate systems and spatial characteristic (comparing to current technical specification for Great Britain, Texas-Statement of Work for the Acquisition and Production of High Resolution Orthoimagery in Texas,2019, Virginia-Digital Orthoimagery Base Specification V1.0, 2014). Photogrammetric data in polish resource are defined in plane rectangular coordinates PL-1992 (for topographic scale) and PL-2000 (for large scale), that use Gauss-Krüger projection to implement a one-zone system with a 19° meridian axial (PL-1992) and the realization of a four-zone system (with a width of 3° each) with 15°, 18°, 21° and 24° meridians axial (PL-2000). In the case of vertical reference frames, vertical reference frames are marked by symbols PL-KRON86-NH and PL-EVRF2007-NH, which are the mathematical and physical implementation of the European Vertical Reference System (EVRS). The vertical reference frame PL-KRON86-NH is associated with the tide-gauge in Kronstadt, PL-EVRF2007-NH is associated with the tide-gauge in Amsterdam.
In case of technical parameters, Poland is in the top of European countries in the field of LIDAR data. Density 12 points/ m 2 for cities, 4 points/m 2 for other areas and accuracy (xy:15 cm-20 cm, z: 20cm) of LIDAR data is one of the best in Europe: Sweden -2 points/m 2 , Westfalia > 4 points/m 2 , Netherlands > 8 points/m 2 (Vosselman, 2018). Aerial photography and orthophotomaps are very similar to other European countries (RGB/CIR, pixel size 3-10cm for cities and 10-25 cm for other areas).
What is very important data specifications mostly do not define the methodology and technology of processing, they define only final products.

Basic requirements for aerial imagery
Quality criteria of aerial imagery for polish resource are similar to another countries in Europe. The difference are mainly connected with writing format. Aerial imagery in polish resource must be written with following parameters: 1. Overlap shall be sufficient to provide full stereoscopic coverage of the areas to be photographed. Endlap shall average not less than sixty percent (60%). Sidelap shall average not less twenty-five-thirty percent (25-30%), 2. Aerial photography shall not be undertaken when the sun angle is less than twenty (20-30) degrees above the horizon. 3. Each camera shall have been calibrated, tested, and certified. In practice, current legal regulation allow only large format cameras. 4. The axis of the camera should be in a vertical position.
The tilt (departure from the vertical) should not exceed four degrees (3˚) or the relative tilt between images or strips exceed six degree (5 ˚) 5. Aerial photography shall not be taken when the ground is obscured by haze, snow, foliage, flooding conditions or when clouds or cloud shadows. 6. Photography shall be executed so as to minimize image movement at the moment of exposure. 7. It's necessary to use GCP.
GSD depends on area of aerial photography and on application. Nowadays, normally for cities/counties the standard is 3-10 cm, for other areas 10-25cm.
The most common reason for aerial imagery rejection is fuzzy imagery caused by image movement at the moment of exposure. Sometimes imagery are not correct geometrically (values of ω, φ, κ are exceed allowed values 3,3,15 degree).

Basic requirements for orthophotomaps
Orthophotomaps in national geodetic and cartographic resource must meet the following criteria: Pixel size of orthophotomaps depends on area and on application. Normally for cities/counties the standard is 3-10 cm, for other areas 10-25cm. Nowadays cover of Poland of 25 cm orthophotomaps takes place in 3-years cycle, 10 cm and better (cities/counties) in 5-years cycle.

Basic requirements for LIDAR DATA
LIDAR data for national geodetic and cartographic resource must meet the following criteria:  Table 3. LIDAR data-parameters of writing Besides: 1. Scan angles> ± 25 are not allowed 2. Registration of a minimum four "echoes" is required. 3. It is required to register the intensity of the reflected signals 4. The average distance of the LIDAR points in the flight direction and in the transverse direction ranged from 1: 1.5 to 1.5: 1. 5. LIDAR data should be classified: 0 -Created, never classed, 2-Ground, 3-Low vegetation, 4-Medium Vegetation, 5-High vegetation, 6-Building, 7-Low points (noise), 9-Water, Overlap points. 6. 99% LIDAR points must be correctly classified to ground class 7. 95% LIDAR points must be correctly classified to class used to generation digital surface model. 8. The most common reason for LIDAR rejection are errors caused by wrong classification and incorrect header of LAS files.
Density of Lidar points depends on area and on application. Normally for cities/counties the standard is 12 p/m2, for other areas 4p/m2. Cover of Poland of LIDAR data is planned in 6years cycle.
The figure 5 below presents actual state LIDAR data in national resource, figure 6 presents planned state on the finish of 2019 year: Figure 5 Actual state LIDAR data in national resource Figure 6 Actual state LIDAR data in national resource

PHOTOGRAMMETRIC DATA AS A PART OF NATIONAL SPATIAL DATA INFRASTRUCTURE
The term of Spatial Data Infrastructure SDI was introduced by U.S. Vice President Al Gore and propagated by international organisations such as FIG or ISPRS (Konecny, 2005). SDI fundamentally means facilitation and coordination of the exchange and sharing of spatial data between stakeholders from different jurisdictional levels in the spatial data community (Williamson, Rajabifard, 2003). Therefore, in the national context, develop and success of a SDI depends mainly on the availability of data. The key components of SDI are geoportal (most visible part of SDI), metadata and search functions (Hu, Li, 2017). According to art. 13 section 2 of the Law of 4 March 2010.
Spatial data infrastructure '"Surveyor General for Poland establishes and maintains publicly available register of spatial datasets and services covered by the spatial data infrastructure and gives them uniform identifiers.'' and Regulation of the Minister of Investment and Development of 28 November 2018 amending the regulation on the registration of spatial data sets and services covered by the spatial information infrastructure. "The register are kept in the IT system whose database is integrated with the geoportal of the spatial information infrastructure, referred to in article 13 section 1 of the Act of 4 March 2010 on Spatial Data Infrastructure" the register of spatial data sets was made available. Head Office of Geodesy and Cartography in Poland provided services of photogrammetric data sets: WMS, WMTS, CSW, WFS, ATOM, WCS. It can be integrated into any mapping application for web application allowing for an easy-to-use way to exploit the data. The  Table 4. Web services for photogrammetric data provided by Head Office of Geodesy and Cartography Furthermore, national photogrammetric data sets are published in the national broker: www.geoportal.gov.pl. The web application lets browse and search spatial data sets and services for aerial imagery, orthophotomaps and elevation data.
The figure below shows user interface of national geoportal with loaded orthophotmaps and indexes: What is very important, photogrammetric data and services are important part of national Spatial Data Infrastructure and deliver reference information for other resources. For example, LIDAR data was reference data for 3d building models-CityGML LOD1 (almost 9 million buildings) and LOD2 (above 10 million buildings) created by Head Office of Geodesy and Cartography. The model buildings, published by ATOM service, are very popular among users. The present number of downloads city model buildings is about 22016, what is success of national SDI. Figure 8 presents 3d model buildings-LOD1 for Poland: Figure 8. Screenshot of 3d model building-LOD1.

CONCLUSIONS
Requirements for aerial imagery, orthophotomaps and elevation data are necessary to ensure consistency of national photogrammetric resource. Polish requirements for photogrammetric data are very similar to European standards.
Photogrammetric data and services are important part of national Spatial Data Infrastructure and deliver reference information for other resources. Furthermore develop and success of national SDI depends mainly on the availability of data.