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SKILL.md
GIS and Remote Sensing Guide
A comprehensive skill for conducting geospatial analysis and remote sensing research. Covers data acquisition from satellite platforms, spatial analysis with open-source tools, and publication-quality map production.
Satellite Data Sources
Key Earth Observation Platforms
Platform
Provider
Spatial Res.
Revisit
Free?
Use Case
Landsat 8/9
USGS/NASA
30m (MS), 15m (pan)
16 days
Yes
Land cover, NDVI time series
Sentinel-2
ESA/Copernicus
10m
5 days
Yes
Agriculture, urban mapping
MODIS
NASA
250m-1km
1-2 days
Yes
Large-scale vegetation, fire
Sentinel-1
ESA
5-20m
6 days
Yes
SAR, flood mapping, deformation
SRTM/ASTER
NASA
30m
N/A
Yes
Digital elevation models
Data Download with Python
import ee
# Initialize Google Earth Engine
ee.Initialize()
def get_sentinel2_composite(aoi: ee.Geometry, start: str, end: str,
cloud_max: int = 20) -> ee.Image:
"""
Create a cloud-free Sentinel-2 composite.
Args:
aoi: Area of interest as ee.Geometry
start: Start date (YYYY-MM-DD)
end: End date (YYYY-MM-DD)
cloud_max: Maximum cloud cover percentage
"""
collection = (ee.ImageCollection('COPERNICUS/S2_SR_HARMONIZED')
.filterBounds(aoi)
.filterDate(start, end)
.filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE', cloud_max)))
# Cloud masking using SCL band
def mask_clouds(image):
scl = image.select('SCL')
mask = scl.neq(3).And(scl.neq(8)).And(scl.neq(9)).And(scl.neq(10))
return image.updateMask(mask)
return collection.map(mask_clouds).median().clip(aoi)
# Define study area
study_area = ee.Geometry.Rectangle([116.0, 39.5, 117.0, 40.5]) # Beijing region
composite = get_sentinel2_composite(study_area, '2024-06-01', '2024-09-30')
Spatial Analysis with GeoPandas
Vector Data Processing
import geopandas as gpd
from shapely.geometry import Point
def spatial_join_analysis(points_gdf: gpd.GeoDataFrame,
polygons_gdf: gpd.GeoDataFrame,
agg_col: str) -> gpd.GeoDataFrame:
"""
Perform spatial join and aggregate point data within polygons.
"""
joined = gpd.sjoin(points_gdf, polygons_gdf, how='inner', predicate='within')
summary = joined.groupby('index_right').agg(
count=(agg_col, 'count'),
mean_value=(agg_col, 'mean'),
std_value=(agg_col, 'std')
).reset_index()
result = polygons_gdf.merge(summary, left_index=True, right_on='index_right')
return result
# Example: aggregate soil samples within administrative boundaries
soil_samples = gpd.read_file('soil_data.geojson')
admin_bounds = gpd.read_file('admin_boundaries.shp')
result = spatial_join_analysis(soil_samples, admin_bounds, 'pH_value')
Remote Sensing Indices
Vegetation and Water Indices
import rasterio
import numpy as np
def compute_indices(image_path: str) -> dict:
"""Compute common remote sensing spectral indices."""
with rasterio.open(image_path) as src:
red = src.read(3).astype(float) # Band 4 in Sentinel-2
nir = src.read(4).astype(float) # Band 8
green = src.read(2).astype(float) # Band 3
swir = src.read(5).astype(float) # Band 11
# Normalized Difference Vegetation Index
ndvi = (nir - red) / (nir + red + 1e-10)
# Normalized Difference Water Index
ndwi = (green - nir) / (green + nir + 1e-10)
# Normalized Burn Ratio
nbr = (nir - swir) / (nir + swir + 1e-10)
return {'NDVI': ndvi, 'NDWI': ndwi, 'NBR': nbr}
Map Production
For publication-quality maps, always include: scale bar, north arrow, coordinate reference system label, legend, and data source attribution. Use matplotlib with cartopy for projected maps, or folium for interactive web maps. Export at 300 DPI minimum for journal submissions.
Coordinate Reference Systems
Always verify and document the CRS. Use EPSG codes (e.g., EPSG:4326 for WGS84, EPSG:32650 for UTM Zone 50N). Reproject all layers to a common CRS before spatial operations to avoid misalignment errors.
