Skill v1.0.2
currentAutomated scan100/10017 files
version: "1.0.2" name: alterlab-geomaster description: Covers geospatial science across remote sensing, GIS, spatial analysis, and machine learning for earth observation — satellite imagery processing (Sentinel, Landsat, MODIS, SAR, hyperspectral), raster and DEM operations, spectral indices (NDVI/EVI/NDWI), spatial statistics, point cloud processing, network analysis, and cloud-native workflows (STAC, COG, Planetary Computer), with examples across Python, R, Julia, JavaScript, C++, Java, Go, and Rust. Use for remote sensing workflows, satellite/raster image classification, terrain/slope/hillshade analysis, spatial ML on earth-observation data, hydrological modeling, marine spatial analysis, or atmospheric science. For pure tabular vector work with no raster/EO aspect (plain GeoPandas sjoin, buffer, overlay, dissolve, choropleths) prefer the geopandas skill; for celestial-sphere astronomy coordinates (ICRS/galactic, FITS, WCS) prefer the astropy skill. Part of the AlterLab Academic Skills suite. license: MIT allowed-tools: Read Write Edit Bash(uv:) Bash(python:) compatibility: No API key required for local geospatial work. Runs via uv run python; cloud-native STAC/Planetary Computer workflows need network access (and provider credentials where applicable). metadata: skill-author: AlterLab version: "1.1.0" last_updated: "2026-09-23"
GeoMaster
Comprehensive geospatial science skill covering GIS, remote sensing, spatial analysis, and ML for Earth observation across 70+ topics with 500+ code examples in 8 programming languages.
When to Use This Skill
Use this skill when the user wants to:
- Process satellite or aerial imagery (Sentinel, Landsat, MODIS, SAR, hyperspectral) and compute spectral indices
- Work with rasters and DEMs — terrain metrics, mosaics, reprojection, zonal statistics
- Search and load cloud-native data (STAC, COG, Planetary Computer, Earth Engine, Copernicus Data Space)
- Train or apply machine learning to earth-observation data, or run hydrological/marine/atmospheric spatial workflows
Does NOT Trigger
| Scenario | Use Instead | |
|---|---|---|
| Pure vector work — sjoin, buffer, overlay, dissolve, choropleths — with no raster/EO component | alterlab-geopandas | |
| Celestial coordinates, FITS images, sky WCS | alterlab-astropy | |
| Simulating the fluid dynamics itself (Navier-Stokes, shallow-water solvers) | alterlab-fluidsim | |
| Mapping historical sources or georeferencing archival maps for humanities research | alterlab-digital-humanities |
Installation
Pick ONE package manager for the GDAL-backed stack. Modern pip wheels for rasterio/fiona/pyproj/shapely bundle their own GDAL/GEOS/PROJ, so a pure-pip (uv) env covers the core libs without a system GDAL. Do NOT mix conda-GDAL with pip rasterio/fiona in the same env — the two ship different GDAL binaries and the ABI mismatch segfaults. The standalone gdal Python bindings do NOT bundle binaries (they need a matching system/conda libgdal); PDAL and rsgislib likewise have no reliable pip wheels — get those via conda (Option B).
# Option A — uv/pip env (recommended here): wheels bundle GDAL/GEOS/PROJ.# rasterio/fiona cover most GDAL needs; standalone `gdal` -> use Option B.uv pip install rasterio fiona shapely pyproj geopandasuv pip install torchgeo earthengine-apiuv pip install scikit-learn xgboost torch-geometricuv pip install osmnx networkx folium keplergluv pip install cartopy contextily mapclassifyuv pip install xarray rioxarray dask-geopandasuv pip install pystac-client planetary-computer odc-stac rio-cogeouv pip install "laspy[lazrs]" open3d # PDAL: use conda (no pip wheel)# Option B — conda env (best for PDAL / rsgislib / system GDAL tooling)conda install -c conda-forge gdal rasterio fiona shapely pyproj geopandas \rsgislib pdal python-pdal postgis libspatialite
Quick Start
NDVI from Sentinel-2
import rasterioimport numpy as npwith rasterio.open('sentinel2.tif') as src:red = src.read(4).astype(float) # B04nir = src.read(8).astype(float) # B08ndvi = (nir - red) / (nir + red + 1e-8)ndvi = np.nan_to_num(ndvi, nan=0)profile = src.profileprofile.update(count=1, dtype=rasterio.float32)with rasterio.open('ndvi.tif', 'w', **profile) as dst:dst.write(ndvi.astype(rasterio.float32), 1)
Spatial Analysis with GeoPandas
import geopandas as gpd# Load and ensure same CRSzones = gpd.read_file('zones.geojson')points = gpd.read_file('points.geojson')if zones.crs != points.crs:points = points.to_crs(zones.crs)# Spatial join and statisticsjoined = gpd.sjoin(points, zones, how='inner', predicate='within')stats = joined.groupby('zone_id').agg({'value': ['count', 'mean', 'std', 'min', 'max']}).round(2)
Google Earth Engine Time Series
import eeimport pandas as pdee.Initialize(project='your-project')roi = ee.Geometry.Point([-122.4, 37.7]).buffer(10000)s2 = (ee.ImageCollection('COPERNICUS/S2_SR_HARMONIZED').filterBounds(roi).filterDate('2020-01-01', '2023-12-31').filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE', 20)))def add_ndvi(img):return img.addBands(img.normalizedDifference(['B8', 'B4']).rename('NDVI'))s2_ndvi = s2.map(add_ndvi)def extract_series(image):stats = image.reduceRegion(ee.Reducer.mean(), roi.centroid(), scale=10, maxPixels=1e9)return ee.Feature(None, {'date': image.date().format('YYYY-MM-dd'), 'ndvi': stats.get('NDVI')})series = s2_ndvi.map(extract_series).getInfo()df = pd.DataFrame([f['properties'] for f in series['features']])df['date'] = pd.to_datetime(df['date'])
Core Concepts
Data Types
| Type | Examples | Libraries | |
|---|---|---|---|
| Vector | Shapefile, GeoJSON, GeoPackage | GeoPandas, Fiona, GDAL | |
| Raster | GeoTIFF, NetCDF, COG | Rasterio, Xarray, GDAL | |
| Point Cloud | LAS, LAZ | Laspy, PDAL, Open3D |
Coordinate Systems
- EPSG:4326 (WGS 84) - Geographic, lat/lon, use for storage
- EPSG:3857 (Web Mercator) - Web maps only (don't use for area/distance!)
- EPSG:326xx/327xx (UTM) - Metric calculations, <1% distortion per zone
- Use
gdf.estimate_utm_crs()for automatic UTM detection
# Always check CRS before operationsassert gdf1.crs == gdf2.crs, "CRS mismatch!"# For area/distance calculations, use projected CRSgdf_metric = gdf.to_crs(gdf.estimate_utm_crs())area_sqm = gdf_metric.geometry.area
OGC Standards
- WMS: Web Map Service - raster maps
- WFS: Web Feature Service - vector data
- WCS: Web Coverage Service - raster coverage
- STAC: Spatiotemporal Asset Catalog - modern metadata
Common Operations
Spectral Indices
def calculate_indices(image_path, bands=(2, 3, 4, 8, 11)):"""NDVI, EVI, SAVI, NDWI from Sentinel-2.`bands` maps (B02, B03, B04, B08, B11) to the 1-based band indices inyour file. EVI's constants (6, 7.5, +1) assume surface reflectance in[0, 1]; raw L2A DN are scaled by 10000, so divide first or EVI is wrong."""with rasterio.open(image_path) as src:B02, B03, B04, B08, B11 = (src.read(b).astype(float) for b in bands)ndvi = (B08 - B04) / (B08 + B04 + 1e-8)evi = 2.5 * (B08 - B04) / (B08 + 6*B04 - 7.5*B02 + 1 + 1e-8)savi = ((B08 - B04) / (B08 + B04 + 0.5)) * 1.5ndwi = (B03 - B08) / (B03 + B08 + 1e-8)return {'NDVI': ndvi, 'EVI': evi, 'SAVI': savi, 'NDWI': ndwi}
Vector Operations
# Buffer (use projected CRS! 1000 = metres in UTM).# Keep the result in the projected frame; don't bolt projected geometry# back onto a geographic gdf or you silently mix CRS in one column.gdf_proj = gdf.to_crs(gdf.estimate_utm_crs())gdf_proj['buffer_1km'] = gdf_proj.geometry.buffer(1000)# Spatial relationshipsintersects = gdf[gdf.geometry.intersects(other_geometry)]contains = gdf[gdf.geometry.contains(point_geometry)]# Geometric operationsgdf['centroid'] = gdf.geometry.centroidgdf['simplified'] = gdf.geometry.simplify(tolerance=0.001)# Overlay operationsintersection = gpd.overlay(gdf1, gdf2, how='intersection')union = gpd.overlay(gdf1, gdf2, how='union')
Terrain Analysis
def terrain_metrics(dem_path, azimuth=315.0, altitude=45.0):"""Slope (deg), aspect (deg clockwise from north, downslope), hillshade [0, 1].Assumes a projected, north-up DEM whose horizontal units match its elevationunits (reproject geographic DEMs first, or the gradients are meaningless)."""with rasterio.open(dem_path) as src:dem = src.read(1).astype(float)xres, yres = src.res # pixel size — gradients need itdz_drow, dz_dx = np.gradient(dem, yres, xres) # rows run north -> southdz_dy = -dz_drow # northward gradientslope = np.degrees(np.arctan(np.hypot(dz_dx, dz_dy)))aspect = np.degrees(np.arctan2(-dz_dx, -dz_dy)) % 360# Hillshade: cos(zenith)cos(slope) + sin(zenith)sin(slope)cos(azimuth - aspect)zenith, az = np.radians(90.0 - altitude), np.radians(azimuth)s, a = np.radians(slope), np.radians(aspect)hillshade = np.clip(np.cos(zenith) * np.cos(s) +np.sin(zenith) * np.sin(s) * np.cos(az - a), 0, 1)return slope, aspect, hillshade
Network Analysis
import osmnx as oximport networkx as nx# Download and analyze street networkG = ox.graph_from_place('San Francisco, CA', network_type='drive')G = ox.add_edge_travel_times(ox.add_edge_speeds(G)) # both return the graph# Shortest pathorig = ox.distance.nearest_nodes(G, -122.4, 37.7)dest = ox.distance.nearest_nodes(G, -122.3, 37.8)route = nx.shortest_path(G, orig, dest, weight='travel_time')
Image Classification
from sklearn.ensemble import RandomForestClassifierimport rasteriofrom rasterio.features import rasterizedef classify_imagery(raster_path, training_gdf, output_path):"""Train RF and classify imagery."""with rasterio.open(raster_path) as src:image = src.read()profile = src.profiletransform = src.transform# Extract training dataX_train, y_train = [], []for _, row in training_gdf.iterrows():mask = rasterize([(row.geometry, 1)],out_shape=(profile['height'], profile['width']),transform=transform, fill=0, dtype=np.uint8)pixels = image[:, mask > 0].TX_train.extend(pixels)y_train.extend([row['class_id']] * len(pixels))# Train and predictrf = RandomForestClassifier(n_estimators=100, max_depth=20, n_jobs=-1)rf.fit(X_train, y_train)prediction = rf.predict(image.reshape(image.shape[0], -1).T)prediction = prediction.reshape(profile['height'], profile['width'])profile.update(dtype=rasterio.uint8, count=1)with rasterio.open(output_path, 'w', **profile) as dst:dst.write(prediction.astype(rasterio.uint8), 1)return rf
Modern Cloud-Native Workflows
STAC + Planetary Computer
import pystac_clientimport planetary_computerimport odc.stac# Search Sentinel-2 via STACcatalog = pystac_client.Client.open("https://planetarycomputer.microsoft.com/api/stac/v1",modifier=planetary_computer.sign_inplace,)search = catalog.search(collections=["sentinel-2-l2a"],bbox=[-122.5, 37.7, -122.3, 37.9],datetime="2023-01-01/2023-12-31",query={"eo:cloud_cover": {"lt": 20}},)# Load as xarray (cloud-native!)# pystac-client >= 0.7: use search.items() (get_items() is deprecated).items = list(search.items())[:5]data = odc.stac.load(items,bands=["B02", "B03", "B04", "B08"],crs="EPSG:32610",resolution=10,)# Calculate NDVI on xarrayndvi = (data.B08 - data.B04) / (data.B08 + data.B04)
Cloud-Optimized GeoTIFF (COG)
import rasteriofrom rasterio.session import AWSSessionfrom rasterio.windows import Window# Read a window of a cloud-hosted COG (HTTP range requests fetch only that window).# Credentials go on a rasterio.Env, not on rasterio.open; for public buckets use# AWSSession(aws_unsigned=True).with rasterio.Env(AWSSession(aws_access_key_id=..., aws_secret_access_key=...)):with rasterio.open('s3://bucket/path.tif') as src:subset = src.read(1, window=Window(col_off=1000, row_off=1000,width=1000, height=1000))# Write a valid COG (tiled + internal overviews + COG layout) with rio-cogeo;# a plain tiled GeoTIFF without overviews is not a COGfrom rio_cogeo.cogeo import cog_translate, cog_validatefrom rio_cogeo.profiles import cog_profilescog_translate('input.tif', 'output_cog.tif', cog_profiles.get('deflate'))is_valid, errors, warnings = cog_validate('output_cog.tif')
Performance Tips
# 1. Spatial indexing (10-100x faster queries)gdf.sindex # Auto-created by GeoPandas# 2. Chunk large rasterswith rasterio.open('large.tif') as src:for i, window in src.block_windows(1):block = src.read(1, window=window)# 3. Dask for big data (lazy, chunked, dask-backed DataArray)import rioxarrayda_raster = rioxarray.open_rasterio('large.tif', chunks=(1, 1024, 1024))# .data is the underlying dask.array if you need the raw chunked array:# dask_array = da_raster.data# 4. Use Arrow for I/Ogdf.to_file('output.gpkg', use_arrow=True)# 5. GDAL cachingfrom osgeo import gdalgdal.SetCacheMax(2**30) # 1GB cache# 6. Parallel processingrf = RandomForestClassifier(n_jobs=-1) # All cores
Best Practices
- Always check CRS before spatial operations
- Use projected CRS for area/distance calculations
- Validate geometries:
gdf = gdf[gdf.is_valid](repair withgdf.geometry.make_valid()) - Drop missing geometries:
gdf = gdf[gdf.geometry.notna() & ~gdf.geometry.is_empty](fillna(None)does NOT work on a geometry column) - Use efficient formats: GeoPackage > Shapefile, Parquet for large data
- Apply cloud masking to optical imagery
- Preserve lineage for reproducible research
- Use appropriate resolution for your analysis scale
Detailed Documentation
- [Coordinate Systems](references/coordinate-systems.md) - CRS fundamentals, UTM, transformations
- [Core Libraries](references/core-libraries.md) - GDAL, Rasterio, GeoPandas, Shapely
- [Remote Sensing](references/remote-sensing.md) - Satellite missions, spectral indices, SAR
- [Machine Learning](references/machine-learning.md) - Deep learning, CNNs, GNNs for RS
- [GIS Software](references/gis-software.md) - QGIS, ArcGIS, GRASS integration
- [Scientific Domains](references/scientific-domains.md) - Marine, hydrology, agriculture, forestry
- [Advanced GIS](references/advanced-gis.md) - 3D GIS, spatiotemporal, topology
- [Big Data](references/big-data.md) - Distributed processing, GPU acceleration
- [Industry Applications](references/industry-applications.md) - Urban planning, disaster management
- [Programming Languages](references/programming-languages.md) - Python, R, Julia, JS, C++, Java, Go, Rust
- [Data Sources](references/data-sources.md) - Satellite catalogs, APIs
- [Troubleshooting](references/troubleshooting.md) - Common issues, debugging, error reference
- [Code Examples](references/code-examples.md) - 500+ examples
GeoMaster covers everything from basic GIS operations to advanced remote sensing and machine learning.
Part of the AlterLab Academic Skills suite.