vathra.xyz — Crowdsourced Monitoring of Greece's Geodetic Heritage: Architecture, Empirical Results, and Legal Framework

Greece's national trigonometric network comprises 25,258 geodetic survey points established by the Hellenic Military Geographical Service (HMGS/GYS). This paper presents vathra.xyz, an open-source web platform for crowdsourced condition monitoring of these points using Volunteered Geographic Information (VGI) methods. We describe the system architecture (React, PostGIS, Leaflet, browser-based AR compass), report operational results from six months of deployment (52 registered users, 140 condition reports covering 99 unique points across 38 active days), and examine the EU and Greek legal framework governing the re-use of publicly published geodetic data. Among the 99 crowdsourced points, contributors identified 18 DESTROYED or MISSING markers — previously undocumented condition information. To the authors' knowledge, this represents the first systematic, publicly accessible condition assessment of this network.