The Influence of Digital Surface Model Choice on Visibility‐based Mobile Geospatial Applications

Abstract

In this work we investigate the effectiveness of different types of visibility models for use within location‐based services. This article outlines the methodology and results for our experiments, which were designed to understand the accuracy and effects of model choices for mobile visibility querying. Harnessing a novel mobile media consumption and authoring application called Zapp, the levels of accuracy of various digital surface representations used by a line of sight visibility algorithm are extensively examined by statistically assessing randomly sampled viewing sites across the 1 km2 study area, in relation to points of interest (POI) across the University of Nottingham campus. Testing was carried out on three different surface models derived from 0.5 m LiDAR data by visiting physical sites on each surface model with 14 random point of interest masks being viewed from between 10 and 16 different locations, totalling 190 data points. Each site was ground‐truthed by determining whether a given POI could be seen by the user and could also be identified by the mobile device. Our experiments in a semi‐urban area show that choice of surface model has important implications for mobile applications that utilize visibility in geospatial query operations.

Earth Observation for Citizen Science Validation, or Citizen Science for Earth Observation Validation? The Role of Quality Assurance of Volunteered Observations

“…No estimation is returned when either the line of sight does not reach the DEM within a 1000 m distance, or the tilt angle is inadequate, or when the DEM has an issue (no data value encountered, due to holes, etc.) [39]. Out of the 38 points, 26 obtained a topological consistency below 0.6, i.e., the citizen was identified as being too far from the observation.…”

“…In the QA described in Figure 2, the first QC, Pillar 1 Relative Position Line Of Sight QC (RelativePositionLineOfSight), uses the LoS but aims to investigate the quality of the topological consistency. The process uses a Digital Elevation Model (DEM), and the device's bearing, tilt and position information to compute the LoS [39]. For this case study, the Natural Resources Wales LiDAR 2 m resolution Digital Surface Model was used for the DEM input.…”