Facial asymmetry presents a significant challenge for health practitioners, including physicians, dentists, and physical therapists. Manual measurements often lack the precision needed for accurate assessments, highlighting the appeal of imaging technologies like structured light scanners and photogrammetric systems. However, high-end commercial systems remain cost prohibitive, especially for public health services in developing countries. This study aims to evaluate cell-phone-based photogrammetric methods for generating 3D facial models to detect facial asymmetries. For this purpose, 15 patients had their faces scanned with the ACADEMIA 50 3D scanner, as well as with cell phone images and videos using photogrammetry and videogrammetry, resulting in 3D facial models. Each 3D model (coming from a 3D scanner, photogrammetry, and videogrammetry) was half-mirrored to analyze dissimilarities between the two ideally symmetric face sides using Hausdorff distances between the two half-meshes. These distances were statistically analyzed through various measures and hypothesis tests. The results indicate that, in most cases, both photogrammetric and videogrammetric approaches are as reliable as 3D scanning for detecting facial asymmetries. The benefits and limitations of using images, videos, and 3D scanning are also presented.

Purpose: This study evaluates the reliability of three-dimensional (3D) facial measurements obtained from different acquisition technologies. Specifically, it investigates whether low-cost smartphone-based photogrammetry and videogrammetry can produce measurements comparable to those derived from structured light scanning, and identifies sources of variability associated with each modality. Methods: Fifteen participants were imaged using three techniques: structured light scanning, smartphone photogrammetry, and smartphone videogrammetry. Inter-landmark distances were computed for each resulting 3D model, including both stable anatomical landmarks and those prone to placement difficulty. A statistical workflow was applied, incorporating non-parametric hypothesis testing, iterative outlier detection, and normality assessments to evaluate measurement variability attributable to acquisition modality, subject movement, and landmark uncertainty. Results: The three acquisition modalities produced broadly comparable inter-landmark measurements, indicating no substantial loss of accuracy when using smartphone-based methods. However, increased variability was observed in anatomically complex regions, particularly the perioral area, as well as in landmarks known to be difficult to localize. These discrepancies persisted across all modalities, including structured light scanning. Conclusions: Smartphone-based photogrammetry and videogrammetry represent viable, low-cost alternatives to structured light scanning for 3D facial measurement. Nonetheless, landmark-specific uncertainty remains a critical factor, particularly in challenging anatomical regions. The findings highlight the importance of considering both acquisition modality and landmark reliability in the design and reporting of facial anthropometric studies.

In Brazil, approximately 16.4 million people (8.1% of the population) live in informal settlements (favelas), with Rio de Janeiro among the most heavily affected. This situation results from rapid rural–urban migration and unplanned urbanization, leading to persistent land tenure conflicts, exemplified by the decades-long struggle in the Santa Luzia favela. This study demonstrates how participatory geospatial methodologies can support land regularization while preventing displacement. Unlike conventional participatory mapping studies that often prioritize community empowerment over technical precision or, conversely, state-led cadastres that prioritize accuracy over local participation, this study integrates two complementary frameworks: counter-cartographies (to redress power asymmetries) and fit-for-purpose land administration (to ensure minimal technical standards for tenure security). Through a university–community collaboration, a low-cost cadastral survey of Santa Luzia was conducted using remotely piloted aircraft photogrammetry to generate high-resolution orthoimagery (2 cm ground sample distance), GIS vectorization integrated with resident interviews and local knowledge, and spatial analysis compliant with local technical standards. The findings demonstrate three specific innovations: (1) methodological: volunteer students and community residents co-produced cartography achieving 2 cm precision, meeting legal requirements for land regularization without expensive professional surveys; (2) participatory: unlike purely community-led mapping that may lack legal enforceability or top-down systems that exclude local knowledge, this model embeds participatory data collection within Brazil’s Social Interest Regularization (REURB-S) framework, ensuring both grassroots legitimacy and state recognition; and (3) policy-making: the project operationalizes counter-cartographies not as symbolic resistance but as a legally compliant pathway to tenure security, offering a transferable model for democratizing land administration in informal settlements while challenging exclusionary urban planning.