{ "id": "tower-bridge", "name": "Around Tower Bridge", "center": [ -112.1447304, 37.6321 ], "width_m": 512, "priority": 1, "source_ids": [ "nps-tower", "nps-pois", "osm-locators" ], "question": "How can we show the landscape without inventing the arch underneath?", "theme": "Landscape around an unseen opening", "view_yaw": 1.2, "view_pitch": 0.75, "locator": { "source_id": "osm-locators", "node_id": 391696698, "longitude": -112.1447304, "latitude": 37.6316064, "role": "named rock locator; distinct from NPS viewpoint and trailhead", "accuracy": "Not surveyed; checked against official regional mapping. NPS viewpoint is a different feature." }, "exclusions": [ { "id": "tower-bridge-unknown", "center": [ -112.1449, 37.63177 ], "radii_m": [ 70, 60 ], "reason": "Unresolved Tower Bridge arch, pillars and underside. Conservative context mask includes locator disagreement; no opening geometry is invented.", "local_center": [ -15.412056414526887, 36.4311685920693 ], "nodes_omitted": 13203 } ], "schema": 1, "kind": "landscape-study", "checked_at": "2026-10-02", "surface_method": "upper-envelope", "geometry_status": "Derived from measured airborne returns; upper-envelope terrain study, not a closed rock scan", "coordinate_system": { "native_horizontal": "NAD83(2011) / UTM 12N (EPSG:6341)", "ept_horizontal": "WGS84 Pseudo-Mercator (EPSG:3857)", "export_horizontal": "WGS84 / UTM 12N (EPSG:32612)", "vertical": "NAVD88, Geoid12B; source heights retained", "units": "metres", "axes": "x east, y up from base_m, z south", "base_m": 2160, "center_utm": [ 398993.98793796386, 4165613.1693918244 ], "bounds_utm": [ 398737.98793796386, 4165357.1693918244, 399249.98793796386, 4165869.1693918244 ], "bounds_wgs84": [ -112.1476666727532, 37.62976483400713, -112.14179430652037, 37.63443509841972 ], "vertical_exaggeration": 1, "transform_note": "EPT projection transformed with pyproj; no claim of survey-grade datum alignment. Centimetre export quantization is not source accuracy." }, "statistics": { "returns_in_crop": 7940567, "density_returns_per_m2": 30.291, "ground_returns": 2599672, "retained_returns": 6129421, "vegetation_candidate_returns": 1811146, "excluded_noise_or_other": 4846, "directly_observed_node_fraction": 0.9975985013432433, "interpolated_node_fraction": 0.002401498656756685, "unsupported_node_fraction": 0.0, "isolated_high_cells_repaired": 57, "maximum_nearest_fill_m": 3.0, "cell_m": 1.0, "source_heights_m": [ 2177.409912109375, 2295.06005859375 ], "surface_heights_m": [ 2177.52001953125, 2294.35009765625 ], "intensity_display_percentiles": [ 4160.0, 12512.0 ], "vertical_surfaces": "An upper envelope can join returns across a steep face; it cannot recover undercuts, windows, or unseen interiors.", "surface_method": "upper-envelope", "editorial_exclusion_node_fraction": 0.050169282856263465, "unsupported_or_excluded_node_fraction": 0.050169282856263465 }, "levels": [ { "file": "small.glb.gz", "bytes": 421414, "uncompressed_bytes": 1105932, "sha256": "14acde8c605136dab9117a27cc806bf1ab67a3f6fce5e6cee8963bb3abba646d", "id": "small", "vertices": 16641, "triangles": 30988, "grid_nodes": 129, "spacing_m": 4.0, "degenerate_triangles": 0, "downward_triangles": 0 }, { "file": "balanced.glb.gz", "bytes": 1608840, "uncompressed_bytes": 4398512, "sha256": "74cb58bc84f22d41f6c0649f3032b39a8461c6328eef2e63ee7883b2da71d7a8", "id": "balanced", "vertices": 66049, "triangles": 124206, "grid_nodes": 257, "spacing_m": 2.0, "degenerate_triangles": 0, "downward_triangles": 0 }, { "file": "detailed.glb.gz", "bytes": 6276291, "uncompressed_bytes": 17549652, "sha256": "cdffbea85e88568ac511d0af74b6b1d825b815303a79ba7c41e8d31f3309999e", "id": "detailed", "vertices": 263169, "triangles": 497360, "grid_nodes": 513, "spacing_m": 1.0, "degenerate_triangles": 0, "downward_triangles": 0 } ], "returns": { "file": "returns.glb.gz", "bytes": 1225641, "uncompressed_bytes": 2881236, "sha256": "c0d28cd014542cf80a5eff24b16f60dd3da261e582b55ce821a0acfa0682843b", "count": 120000, "sampling": "fixed seed 20261002, uniform without replacement from valid crop returns" }, "profiles": "profiles.json.gz", "camera": { "yaw": 1.2, "pitch": 0.75, "distance_m": 995.8822583909587, "target": [ 0, 78.139892578125, 0 ], "minimum_distance_ratio": 0.85, "useful_range_note": "Landscape inspection only; camera is not permitted to approach a ground-walk distance.", "reference_viewport": [ 1400, 1050 ], "vertical_fov_degrees": 38, "fit_method": "Runtime projects actual active vertices to fit the viewport with a 14 percent frame margin; distance_m records the poster reference view.", "closest_reviewed_distance_ratio": 0.85 }, "bounds_local": [ [ -256.0, 17.52001953125, -256.0 ], [ 256.0, 134.35009765625, 256.0 ] ], "source_dataset": { "id": "USGS_LPC_UT_Southern_QL1_2018_LAS_2019", "acquired": "2018-04-27 / 2018-07-29 project interval", "published": "2019-06-03", "url": "https://registry.opendata.aws/usgs-lidar/", "license": "US Government Public Domain", "credit": "Map services and data available from U.S. Geological Survey, National Geospatial Program." }, "processing": { "mesh": "Vegetation heuristic applied to an upper envelope. Highest retained return per nearest grid node; nearest interpolation up to 3 m; isolated spikes exceeding all 8 neighbors by 6 m lowered to neighbor maximum. No morphological closing.", "vegetation": "Source classes 3/4/5 plus low-intensity multiple echoes and low-intensity raised returns over nearby gentle classified ground are excluded. This is an imperfect heuristic, not a species/rock classifier.", "lighting": "Normals and static 12-direction terrain occlusion are derived; material color, studio lighting and display category colors are illustrative.", "detail": "Three nested node grids; no-data cells omitted at every LOD; low LOD can omit extra edge triangles to preserve holes.", "exclusions": "Elliptical uncertainty masks remove the entire plan footprint around unresolved arch/alcove geometry; all LODs conservatively preserve these holes. They are not measured opening outlines." }, "limitations": [ "Hidden rock surfaces, undercuts and windows are not reconstructed.", "A vertical face is an interpolated connection between top-surface samples, not a wall scan.", "Vegetation filtering can leave crowns or remove dark rock; inspect the return view.", "NAIP is overhead imagery from a different year; it cannot supply photographic detail on vertical faces.", "The cut boundary is an editorial crop; there is no modeled geology beneath it.", "No route, current condition, erosion rate or collapse forecast is inferred." ], "posters": { "large": "poster.webp", "small": "poster-small.webp" }, "quality_status": "accepted_local_educational_landscape", "source_acquisition": { "path": "acquisition.json", "points_sha256": "6e89f898524d68e3fa80ea5a502fdf8411a78dc77714c74ee88f2a96416a9223", "source_object_count": 262 }, "editorial": { "lede": "The surrounding ridges are visible from above. The arch’s underside needs a different survey.", "body": "Tower Bridge is a named hoodoo reached from the southern part of Fairyland Loop. This exhibit studies its surrounding terrain. A deliberate gap removes the arch area from the surface so an overhead grid cannot quietly turn the opening into solid rock.", "lesson": "Use the return view to inspect what the aircraft actually recorded, then switch back to coverage. The gap is an uncertainty mask, not the shape of the real opening. A ground scan would need converging views of the pillars, openings and underside.", "limit": "Tower Bridge itself is not reconstructed. The conservative exclusion includes disagreement between published locator roles. NPS’s viewpoint and trailhead are separate from the named rock and are not substituted for it.", "caption": "Landscape around Tower Bridge. The deliberate opening in this model marks excluded, unresolved arch geometry; it is not a model of the natural opening.", "evidence_title": "An honest gap in the surface", "evidence_note": "The return sample preserves measured positions inside the omitted area. Scattered overhead returns do not establish a complete underside.", "annotation_title": "Arch area deliberately omitted", "annotation_text": "This conservative mask covers the named Tower Bridge rock and locator uncertainty. The missing surface is an editorial coverage boundary, not measured empty space." }, "imagery": { "publisher": "USDA Farm Service Agency / FPAC", "dataset": "National Agriculture Imagery Program (NAIP), Utah 2024", "retrieved_at": "2026-10-02T09:29:53.239997+00:00", "source_pixels_m": 0.6, "export_pixels": 854, "export_pixel_m": 0.5995316159250585, "crs": "EPSG:32612", "requested_bounds": [ 398737.98793796386, 4165357.1693918244, 399249.98793796386, 4165869.1693918244 ], "export_extent": { "xmin": 398737.98793796386, "ymin": 4165357.1693918244, "xmax": 399249.98793796386, "ymax": 4165869.1693918244, "spatialReference": { "wkid": 32612, "latestWkid": 32612 } }, "flight_dates": [ "2024-07-23" ], "images": [ { "OBJECTID": 195984, "Name": "m_3711223_se_12_060_20240723", "Category": 1, "year_ts": 2024, "ST": "UT", "QQNAME": "3711223SE060", "QQDATE": 1721692800000, "iDate_ts": 1749744257170 } ], "catalog_url": "https://apps.geo.fpac.usda.gov/geo-imagery/rest/services/naip/conus_naip/ImageServer/query?f=json&geometry=%7B%22xmin%22%3A398737.98793796386%2C%22ymin%22%3A4165357.1693918244%2C%22xmax%22%3A399249.98793796386%2C%22ymax%22%3A4165869.1693918244%2C%22spatialReference%22%3A%7B%22wkid%22%3A32612%7D%7D&geometryType=esriGeometryEnvelope&inSR=32612&spatialRel=esriSpatialRelIntersects&outFields=%2A&returnGeometry=false&where=Category%3D1+AND+year_ts%3D2024", "export_url": "https://apps.geo.fpac.usda.gov/geo-imagery/rest/services/naip/conus_naip/ImageServer/exportImage?f=json&bbox=398737.98793796386%2C4165357.1693918244%2C399249.98793796386%2C4165869.1693918244&bboxSR=32612&imageSR=32612&size=854%2C854&format=png&pixelType=U8&interpolation=RSP_BilinearInterpolation&adjustAspectRatio=false&bandIds=0%2C1%2C2&mosaicRule=%7B%22mosaicMethod%22%3A%22esriMosaicLockRaster%22%2C%22lockRasterIds%22%3A%5B195984%5D%2C%22mosaicOperation%22%3A%22MT_FIRST%22%7D", "direct_image_url": "https://apps.geo.fpac.usda.gov/geo-imagery/rest/services/naip/conus_naip/ImageServer/exportImage?f=image&bbox=398737.98793796386%2C4165357.1693918244%2C399249.98793796386%2C4165869.1693918244&bboxSR=32612&imageSR=32612&size=854%2C854&format=png&pixelType=U8&interpolation=RSP_BilinearInterpolation&adjustAspectRatio=false&bandIds=0%2C1%2C2&mosaicRule=%7B%22mosaicMethod%22%3A%22esriMosaicLockRaster%22%2C%22lockRasterIds%22%3A%5B195984%5D%2C%22mosaicOperation%22%3A%22MT_FIRST%22%7D", "original_sha256": "f19c4107e273952a2d001e1db34bcaaca74353855b604a56cb0e51dc1db0ef08", "license": "US Government Public Domain", "license_url": "https://catalog.data.gov/dataset/national-agriculture-imagery-program-naip-imagery", "processing": "Locked 2024 primary rasters, RGB bands 0/1/2, orthographic drape; bilinear export, WebP encoding. No invented detail.", "limitations": "Leaf-on aerial imagery from a different year than the 2018 topography; acquisition shadows, tree crowns and metre-scale registration error remain. Displayed only in the overhead evidence view, never as a wall photograph." }, "sources": [ { "id": "nps-tower", "title": "Tower Bridge", "publisher": "National Park Service", "url": "https://www.nps.gov/thingstodo/tower-bridge.htm", "date": "2024-10-10", "rights": "Paraphrased government text; no photograph copied", "supports": "Official identity and relation to southern Fairyland Loop; not a ground-scan record.", "evidence": "nps-tower.html" }, { "id": "nps-pois", "title": "NPS public points of interest", "publisher": "NPS National Geospatial Program", "url": "https://mapservices.nps.gov/arcgis/rest/services/NationalDatasets/NPS_Public_POIs/FeatureServer/0", "date": null, "rights": "Unrestricted public government mapping; source methods retained; no claim to original US Government works", "supports": "Distinct waterfall, cave, viewpoint and trailhead roles. Waterfall 1994 and cave 5289 agree closely with independently mapped OSM positions. Tower viewpoint 4362 is distinct from the rock locator.", "evidence": "nps-public-locators.json" }, { "id": "osm-locators", "title": "Tower Bridge and Mossy Cave named locators", "publisher": "OpenStreetMap contributors", "url": "https://www.openstreetmap.org/copyright", "date": "2026-10-02", "rights": "ODbL 1.0; copyright OpenStreetMap contributors", "supports": "Tower Bridge node 391696698; comparison points for Mossy Cave and Tropic Ditch Falls. These do not replace NPS arrival points.", "evidence": "osm-target-locators.json" } ], "annotations": [ { "title": "Arch area deliberately omitted", "text": "This conservative mask covers the named Tower Bridge rock and locator uncertainty. The missing surface is an editorial coverage boundary, not measured empty space.", "position": [ -15.412056414526887, 54.080078125, 36.4311685920693 ], "anchor_surface_elevation_navd88_m": 2209.080078125, "display_lift_m": 5, "coordinate_source": { "source_id": "osm-locators", "node_id": 391696698, "longitude": -112.1447304, "latitude": 37.6316064, "role": "named rock locator; distinct from NPS viewpoint and trailhead", "accuracy": "Not surveyed; checked against official regional mapping. NPS viewpoint is a different feature." }, "height_method": "Nearest fine-grid sample at published locator; display lift is illustrative; no surveyed feature elevation asserted" } ], "static_profile": { "row": 64, "direction": "west to east", "north_offset_m": 0, "minimum_m": 2182.63, "maximum_m": 2271.31, "vertical_exaggeration": 1, "source": "profiles.json.gz" }, "source_coordinate_check": "source-coordinate-check.json", "textures": [ { "file": "aerial.webp", "bytes": 214484, "sha256": "3fb3acbfa690d6dad04c833570cf044c9666b1171e7db1aa83005262f322dbf7", "role": "separate overhead evidence image, never wall texture" }, { "file": "aerial-small.webp", "bytes": 82198, "sha256": "c07bb7b6f4434f9ce010fcfd0656acec777812a38c09cebf1af43600051f5a4a", "role": "separate overhead evidence image, never wall texture" } ], "quality_record": "quality.json" }