Comparative study on the determination of surfaces from the digital orthophotomaps and field measurements with precision GPS receptors

Abstract

In the period between 2003-2007, digital and analog ortophotomaps at a scale 1:10 000 were designed for a series of territorial administrative units in Romania, based on aerial photography methods. The use of the digital support of the ortophotomaps facilitates the retrieval in real time of the position, configuration and size of the agricultural and nonagricultural physical blocks surfaces, which represent the primary technical database for the general cadastre. In the case study of Bilca territorial unit from Suceava County, 315 physical blocks were identified, out of which: 189 agricultural physical blocks in the area outside the township, with a surface of 1853.81 ha and 126 nonagricultural physical blocks, within the built-up area, with a surface of 146.62 ha. For the testing of the retrieval method of surfaces on digital support and from field measurements with GPS receptors, six agricultural physical blocks from the unincorporated area have been considered, with the numbers: 225, 243, 254, 275, 231 and 255, with areas comprised between 10.38 ha (block 275) and 23.23 ha (block 225). The field measurements were carried out with the help of a GPS receptor (Global Position System), of a GNSS South S82T type, which ensured advanced technologies of satellite GNSS (Global Navigation Satellite System – GPS and GLONASS) measuring. Field observations were conducted with the kinematic positioning method in real time, which is also known as the RTK method ((Real-Time Kinematic). In the case of the carried out measurements the ROMPOS – RTK (Romanian Position Determination System) was used, which is based on the national network of GNSS Stations. By using the ROMPOS – RTK service for precise kinematic applications in real time, a horizontally positioning precision of up to ± 2 cm was acquired. With the help of SurvCE field software were determined the plane rectangular coordinates of the points from the outline of the physical blocks, directly into the national projection system STEREO70. The absolute positioning precision of the considered points allowed for a thorough calculation of the physical blocks’ surfaces.