<![CDATA[Urban wetlands require frequent high-resolution monitoring, yet costs and logistics hamper traditional approaches. This study designs and validates a low-cost photogrammetric protocol using remotely piloted aircraft systems (RPAS) to quantify short-term water-surface dynamics in an urban wetland. Ten fortnightly campaigns were conducted at Santa María del Lago (Bogotá) between 1 May and 4 September 2025 using nadir imagery with 80/75% overlap and a GSD of 2.8–3.2 cm/px. Without ground control points, internal geometric precision was assessed through sub-pixel reprojection error (~0.82 px) and relative scale consistency. Water extent was delineated using HSV thresholding and vectorization with a conservative positional threshold. Over 126 days, water-surface area decreased from 5.60 to 5.20 ha (−0.40 ha; −7.1%), with a median shoreline retreat of 1.1 m and a significant monotonic trend (Mann–Kendall τ = −1.00, p < 0.001). Each campaign required 35–45 min of fieldwork and 2.0–3.5 h of processing, with direct costs of USD 25–40 per flight. The protocol produced reproducible multitemporal datasets with decimetric planimetric sensitivity while reducing time and direct costs relative to conventional monitoring. The protocol proved feasible for high-Andean urban wetlands and potentially transferable to similar environments following local adaptation and validation.]]>
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