47 lines
2 KiB
Markdown
47 lines
2 KiB
Markdown
# Geo Processing Tools — Cortex
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## Overview
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DEM processing, vector tile generation, and PMTiles manipulation tools installed on cortex for compute-tier geospatial batch jobs. Cortex is compute-only — no persistent operational data lives here. Data flows: pi-nas (archive) → cortex (compute) → pi-nas + VM 1130 (outputs).
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## Installed Tools
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| Tool | Version | Package | Purpose |
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|------|---------|---------|---------|
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| gdal_contour | GDAL 3.8.4 | gdal-bin (apt) | Generate contour lines from DEM rasters |
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| gdalinfo | GDAL 3.8.4 | gdal-bin (apt) | Raster metadata inspection |
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| gdal_translate | GDAL 3.8.4 | gdal-bin (apt) | Raster format conversion |
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| gdalbuildvrt | GDAL 3.8.4 | gdal-bin (apt) | Virtual raster mosaics |
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| ogr2ogr | GDAL 3.8.4 | gdal-bin (apt) | Vector format conversion |
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| tippecanoe | v2.49.0 | tippecanoe (apt) | GeoJSON → vector tiles (MBTiles/PMTiles) |
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| pmtiles | v1.30.2 | go-pmtiles (binary) | PMTiles inspection, conversion, tile extraction |
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Installed: 2026-04-22
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## Ephemeral Scratch Convention
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All temporary/staging data goes in `/home/zvx/scratch/`. This directory is cleaned after batch jobs complete. Never treat scratch as persistent storage.
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Typical layout:
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```
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/home/zvx/scratch/
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└── nav-processing/ # Current: staged DEM for contour generation
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└── hillshade-na.pmtiles # 93 GB terrarium DEM (from pi-nas archive)
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```
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## Terrarium DEM Decode
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The Mapzen Terrarium format encodes elevation in RGB PNG tiles:
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```
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elevation_meters = (R * 256 + G + B/256) - 32768
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```
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To use with GDAL: decode RGB → Float32 elevation array → write as GeoTIFF via VRT with `subClass="VRTRawRasterBand"`.
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## Data Tier Architecture
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| Tier | Host | Role | Example |
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|------|------|------|---------|
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| Archive | pi-nas (192.168.1.245) | Source of truth, recovery | `/export/data/nav/hillshade-na.pmtiles` |
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| Compute | cortex (192.168.1.150) | Batch processing, scratch | `/home/zvx/scratch/nav-processing/` |
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| Operational | VM 1130 (192.168.1.130) | Serving tiles via nginx | `/mnt/nav/tiles/` |
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