usgs-lidar-dem

USGS LiDAR DEM Acquisition & Satellite Colorization

Overview

Download USGS 3DEP 1m LiDAR-derived DEM data for any US location, colorize points with ESRI World Imagery satellite tiles, and produce a CRS-tagged LAS file ready for Metashape import as a laser scan. This extends photogrammetry coverage with bare-earth ground truth beyond the camera footprint.

When to Use

• Photogrammetry project needs terrain beyond the scanned corridor
• Need bare-earth ground truth under vegetation/canopy
• Building game environments (AC tracks, etc.) that need surrounding terrain
• DEM data needed as elevation reference for alignment QA

Prerequisites

Python packages (install via pip):

pip install rasterio laspy numpy requests Pillow

Optional for programmatic DEM download:

pip install py3dep

Pipeline Overview

1. Determine project bounds (from Metashape markers/cameras or manual bbox)
2. Find & download USGS 3DEP DEM GeoTIFF tiles (TNM API or py3dep)
3. Download ESRI World Imagery satellite tiles for the same extent
4. Mosaic DEM tiles, grid to points, sample satellite RGB at each point
5. Write LAS file (format 2 = RGB, classification=2=Ground, CRS VLR)
6. Import into Metashape chunk with is_laser_scan=True
7. Apply vertical datum correction (NAVD88 -> WGS84 ellipsoidal)
8. Verify alignment against photogrammetry

Step 1: Determine Project Bounds

Get the geographic extent from Metashape. Use marker positions or camera bounding box.

# Via Metashape MCP
markers = list_markers()  # returns lon/lat/alt for each marker
cameras = get_alignment_stats()  # returns camera count and bounds

# Or specify manually as (west, south, east, north) in WGS84 geographic
bbox = (-122.58, 37.88, -122.54, 37.93)  # Fisheye Loop example

Determine the UTM zone from longitude:

• Zone = floor((lon + 180) / 6) + 1
• For lon -122.5: Zone 10
• NAD83 UTM EPSG codes: 269xx where xx = zone (e.g., EPSG:26910 for Zone 10N)

Step 2: Download USGS 3DEP DEM Tiles