Real provenance for chicago (USGS 3DEP IL_4County_Cook_2017) - #144
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Replaces the TODO scaffold with metadata taken from USGS's own authoritative sources rather than the original clip script: WESM.csv for the work unit/project ids, collection dates, quality level, specification, acquisition method and CRS; the vendor FGDC XML for producer, accuracy and processing history. Substantive facts now recorded: collected 16 Apr - 7 May 2017 by Geiger-mode lidar (WESM p_method) under USGS contract G16PD00498, processed to classified LAS 1.4 by Dewberry, QL1 at 0.35 m nominal pulse spacing against Lidar Base Specification 1.2, EPSG:6455/EPSG:6360 with GEOID12B, NVA 19.6 cm at 95% confidence from 114 checkpoints, published 2019-08-19. Two traps documented in the manifest because both would be easy to repeat: 1. The vendor FGDC XML in THIS work unit's own metadata directory states its extent as "Lake county, Illinois". It is a project-level document copied per work unit without localising that text, so it is not evidence about Cook County. The county comes from the work unit name and WESM instead. 2. That directory holds ClassifiedPointCloud_Dewberry_8ppsm.xml and ..._20ppsm.xml, which are byte-for-byte identical. The density distinction exists only in the filenames, so neither supports a ppsm claim; both state 0.35 m NPS, which is what the manifest says. Also confirmed there is no USGS EPT for this work unit (ept.json 404s), so unlike the datasets under manifests/usgs-3dep/ the COPC clip in our own storage is the only form served. Kept the id as "chicago" rather than renaming to "chicago-downtown": the id is the published URL and the R2 key prefix, so renaming would break both for a cosmetic gain. Dropped a "citations" key I had guessed at -- it is not in the schema; the accuracy note lives in sci:citation instead.
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Author
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chicago
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www.usgs.gov returns HTTP 403 to non-browser clients. The weekly reachability sweep checks rel=about, so the link I had just added would have reported this dataset as unreachable every week forever -- for a URL that works fine in a browser. Caught by running the sweep locally against the new manifest before merging, which is worth doing for any manifest that adds external links. The programme page is still recorded as the USGS provider url, which nothing probes.
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chicago: ✅ Ingest complete -- 1 asset(s) processed.
DescriptionClassified airborne lidar point cloud of downtown Chicago, clipped to the Loop and the surrounding riverfront and lakefront from the USGS 3DEP work unit IL_4County_Cook_2017 (Cook County, Illinois). Collected 16 April to 7 May 2017 by Geiger-mode lidar for the "WI Kenosha-Racine Counties and IL 4 County QL1 Lidar" project under USGS contract G16PD00498, and processed to classified LAS 1.4 by Dewberry. Acquired to Quality Level 1 at a nominal pulse spacing of 0.35 m, meeting the USGS Lidar Base Specification 1.2 -- the densest specification tier 3DEP publishes, which is what makes the vertical structure of the downtown high-rises legible in the viewer. Hero imageFootprint{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"id": "chicago-downtown",
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
-87.5561757473377,
41.8178400309726
],
[
-87.5248164590843,
41.9391656173198
],
[
-87.6188952221596,
41.9795565090575
],
[
-87.7443341718035,
41.8987497948434
],
[
-87.5561757473377,
41.8178400309726
]
]
]
},
"properties": {
"id": "chicago-downtown",
"pc:count": 358197
}
}
]
}
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Replaces the TODO scaffold with metadata from USGS's authoritative sources —
WESM.csvfor identifiers/dates/QL/spec/method/CRS, and the vendor FGDC XML for producer, accuracy and processing history.Now recorded: collected 16 Apr – 7 May 2017 by Geiger-mode lidar, USGS contract G16PD00498, processed to classified LAS 1.4 by Dewberry, QL1 at 0.35 m NPS against Lidar Base Spec 1.2, EPSG:6455/6360 + GEOID12B, NVA 19.6 cm @95% from 114 checkpoints, published 2019-08-19.
Two traps documented in the file, since both would be easy to repeat:
..._8ppsm.xmland..._20ppsm.xmlare byte-for-byte identical, so the density distinction is filename-only and supports no ppsm claim.Also confirmed there's no USGS EPT for this work unit (
ept.json404s), so our COPC clip is the only served form. Kept the id aschicago— it's the published URL and R2 key prefix, so renaming tochicago-downtownwould break both for cosmetic gain.