Trigonometric method used to correct local coordinates topographic surveys, applied for archaeology

The necessity of Stereo 70 topographical surveys for archaeological sites raises the issue of access to coordinates needed to create a proper measurement aligned to the Romanian national system. In most situations involving our team, Stereo 70 coordinates of sites that had to be measured were unknown or the site itself was still unknown, being unidentified yet, and thereby we were forced to use local coordinates for those particular surveys. Local coordinates involve an orientation issue, orientation mainly achieved with the help of a compass to indicate the magnetic North, thus implying another issue : the difference between true (geographic) North and magnetic North. In our experience the difference between our survey and the reality was between 7 and 12 trigonometric degrees. The software methods used rotations based on the shapefiles thus leaving the source coordinates unaltered, but these created inconveniences because both shapefiles and source coordinates, among other digital data, must be handed over to the Ministry of Culture and Cults in order to obtain the excavation authorization. Also, the archaeologists who requested the surveys need geographically correct data. This trigonometric method involves trigonometric correction of the raw data acquired by the total station and its conversion to Stereo 70, thus offering precise data and surveys to researchers and institutions.Cîntar Adrian. Trigonometric method used to correct local coordinates topographic surveys, applied for archaeology. In: Annales d'Université "Valahia" Târgovişte. Section d'Archéologie et d'Histoire, Tome 15, Numéro 1, 2013. pp. 155-159