ALGORITHM FOR THE TRANSFORMATION OF THE COORDINATES NEEDED TO SET OBJECTIVES EXTENDING OVER LARGE AREAS

• Published in: International Multidisciplinary Scientific GeoConference SGEM Vol. 2024; no. 2.1; pp. 173 - 180
• Main Authors: Vasilca, Eng Doina, Biscoveanu, Oana-Mihaela
• Format: Conference Proceeding
• Language: English
• Published: Sofia Surveying Geology & Mining Ecology Management (SGEM) 01.01.2024
• Subjects: Algorithms; Map projections; Romania
• ISSN: 1314-2704
• DOI: 10.5593/sgem2024/2.1/s09.21

Constructions extending over large areas or distances raise problems regarding their setting out, because these elements are determined in the official projection of Romania, namely the 1970 Stereographic map projection. For the territory of our country, this produces distortions from -25 cm/km to approximately +64 cm/km in terms of distances and between -5 sq. m/ha and +12.76 sq. m/ha in terms of areas, depending on the distance from the projection pole and, implicitly, from the circle of zero distortions. For them to be applied on the ground, the coordinates should be calculated in a local projection plane where such distortions are minimal. In the present work, double map projections were studied in which the surface of the reference ellipsoid was first represented on the surface of a sphere, after which the sphere was represented on the plane using conic, cylindrical, and azimuthal conformal oblique projections. The tangent/secant almucantar was chosen to pass through the centre of the area of interest. Through comparing the distortion values in the studied projections, we determined that the lowest values were obtained in the oblique conformal conic projection. Furthermore, we proposed an algorithm for converting the coordinates of the points calculated in the official projection of Romania, according to the regulations in force, to the coordinates obtained from a local projection plane, which can then be transposed directly onto the ground.