The GIS & Remote Sensing Encyclopedia
61 in-depth articles across 10 disciplines — GIS fundamentals, remote sensing, LiDAR, photogrammetry, drones, spatial analysis, GeoAI, web GIS, cartography and real-world applications. Written by the people who deliver this work, free for everyone who wants to learn it.
GIS Fundamentals
The core concepts every geospatial professional builds on — data models, projections, topology, databases and standards.
What is GIS? Geographic Information Systems Explained
A clear definition of GIS, how a geographic information system works, its core components, and why organisations worldwide depend on it.
Read the article →Vector Data Model in GIS: Points, Lines and Polygons
How the vector data model represents the world as points, lines and polygons with attributes, and when vector beats raster.
Read the article →Raster Data Model: Grids, Cells and Imagery in GIS
The raster model explained — pixels, resolution, bands and when grid data is the right representation for spatial phenomena.
Read the article →Map Projections and Coordinate Systems Explained
Why the Earth cannot be flattened without distortion, how projections and datums work, and how to avoid the classic coordinate mistakes.
Read the article →Topology in GIS: Rules That Keep Spatial Data Clean
What GIS topology means, common topology rules and errors, and why topology-clean data is the mark of production quality.
Read the article →Geodatabases and Spatial Databases: Storing GIS Data Properly
From file geodatabases to PostGIS: how spatial databases store geometry, index it, and serve multi-user enterprise GIS.
Read the article →Spatial Metadata and Standards: ISO 19115, OGC and INSPIRE
Why metadata makes spatial data findable and trustworthy, and the standards — ISO 19115, OGC, INSPIRE — that govern it.
Read the article →Remote Sensing Fundamentals
How sensors observe the Earth from satellites and aircraft — the physics, the resolutions, the corrections and the core analysis methods.
What is Remote Sensing? Earth Observation Explained
A plain-language definition of remote sensing, how satellites and aircraft measure the Earth, and what the data is used for.
Read the article →The Electromagnetic Spectrum in Remote Sensing
How different wavelengths — visible, infrared, thermal, microwave — reveal different properties of the Earth’s surface.
Read the article →Resolution in Remote Sensing: Spatial, Spectral, Temporal, Radiometric
The four resolutions that define any Earth-observation sensor, their trade-offs, and how to match resolution to application.
Read the article →Passive vs Active Remote Sensing Sensors
The fundamental split in Earth observation: sensors that record natural energy versus sensors that transmit their own signal.
Read the article →Satellite Orbits: Sun-Synchronous, Geostationary and Constellations
How orbit choice shapes what a satellite can observe — polar sun-synchronous mappers, geostationary sentinels and modern smallsat fleets.
Read the article →Satellite Image Preprocessing: Corrections That Make Data Usable
Radiometric, atmospheric and geometric correction explained — the unglamorous steps that turn raw scenes into analysis-ready data.
Read the article →Image Classification in Remote Sensing: Methods That Map Land Cover
Supervised, unsupervised, object-based and deep-learning classification — how pixels become land-cover maps, and how accuracy is proven.
Read the article →Change Detection in Remote Sensing: Methods and Best Practice
How multi-date imagery reveals what changed on the ground — techniques from image differencing to time-series algorithms, and their pitfalls.
Read the article →Sensors & Satellite Programs
The missions and sensor technologies that supply the world’s Earth-observation data — from Landsat and Sentinel to SAR, hyperspectral and thermal systems.
The Landsat Program: Fifty Years of Earth Observation
Why Landsat’s continuous archive since 1972 remains the backbone of land-change science, and what its sensors deliver today.
Read the article →Copernicus Sentinel Missions: Europe’s Free Eyes on Earth
Sentinel-1 radar, Sentinel-2 optical and their siblings — what each mission measures and why Copernicus changed operational monitoring.
Read the article →Commercial High-Resolution Satellites: The Sub-Metre Market
Maxar, Airbus, Planet and the new radar constellations — what commercial imagery offers, what it costs, and how tasking works.
Read the article →Synthetic Aperture Radar (SAR): Imaging Through Cloud and Darkness
How SAR builds images from microwave echoes, what backscatter means, and why InSAR can measure millimetres of ground movement.
Read the article →Hyperspectral Imaging: Reading the Chemistry of the Surface
What hundreds of narrow spectral bands reveal — mineral identification, species mapping, water quality — and what makes hyperspectral hard.
Read the article →Thermal Remote Sensing: Mapping Temperature from Above
How thermal infrared sensors measure surface temperature, and what heat maps reveal — urban heat islands, irrigation, leaks and fires.
Read the article →LiDAR & Photogrammetry
Measuring the world in three dimensions — laser scanning, image-based reconstruction, elevation models and true orthophotos.
What is LiDAR? Laser Scanning Explained
How LiDAR measures millions of precise 3D points with laser pulses, its platforms and returns, and what point clouds enable.
Read the article →Point Clouds and LiDAR Classification
What lives inside a point cloud, how classification assigns every point a class, and why the ASPRS scheme and QC dashboards matter.
Read the article →Photogrammetry Explained: Measurement from Photographs
How overlapping images become precise 3D measurements — aerial triangulation, stereo mapping and modern dense matching.
Read the article →DEM, DTM and DSM: Digital Elevation Models Explained
The difference between surface and terrain models, how elevation data is made, and what hydro-enforcement means.
Read the article →Orthophotos and True Ortho: Maps Made of Imagery
Why raw aerial images cannot be used as maps, how orthorectification fixes them, and what makes an ortho “true”.
Read the article →Structure from Motion (SfM): 3D Reconstruction for Everyone
How SfM turns ordinary overlapping photos into 3D models and orthomosaics, and where it matches — or misses — survey-grade methods.
Read the article →Drones & Surveying
Field data capture — UAV mapping, GNSS positioning, ground control and mobile mapping — where accuracy is made or lost.
Drone Mapping Basics: From Flight Plan to Deliverable
How UAV surveys work end to end — flight design, overlap, GSD, processing — and what separates a survey from a flight.
Read the article →GNSS and GPS Surveying: RTK, PPK and Centimetre Positioning
How satellite positioning really works, why raw GPS is metre-grade, and how RTK/PPK corrections deliver centimetres.
Read the article →Ground Control Points and Survey Accuracy
What GCPs and checkpoints are, how many you need and where, and how accuracy is honestly reported.
Read the article →UAV Regulations and Flight Planning for Commercial Mapping
The regulatory landscape of commercial drone survey — categories, permissions, no-fly zones — and how professional operations plan around it.
Read the article →Mobile Mapping Systems: Surveying at Traffic Speed
Vehicle-mounted LiDAR and cameras that capture corridors in a drive-through — how MMS works and where it beats other methods.
Read the article →Spatial Analysis & Modelling
The analytical core of GIS — overlay, interpolation, networks, terrain, hydrology and spatial statistics that turn data into answers.
Spatial Analysis: An Overview of the GIS Analyst’s Toolkit
The families of spatial analysis — queries, overlay, distance, networks, surfaces, statistics — and how real problems combine them.
Read the article →Buffer and Overlay Analysis: The Workhorses of GIS
How buffering and overlay answer “what is near” and “what coincides” — the two questions behind most practical GIS analysis.
Read the article →Spatial Interpolation: IDW, Kriging and Estimating Between Samples
How continuous surfaces are estimated from point samples — the main methods, their assumptions, and how to validate them.
Read the article →Network Analysis and Routing in GIS
Shortest paths, service areas, fleet routing and location-allocation — how GIS models movement along real networks.
Read the article →Terrain Analysis: Slope, Aspect, Viewshed and Beyond
What elevation models reveal when you differentiate them — slope, aspect, curvature, visibility and terrain-driven siting.
Read the article →Hydrological Analysis in GIS: Watersheds, Flow and Flood
How terrain becomes hydrology — flow direction, accumulation, watershed delineation and the path to flood modelling.
Read the article →Spatial Statistics and Hotspot Analysis
Testing whether spatial patterns are real — autocorrelation, Getis-Ord hotspots, clustering and regression that respects geography.
Read the article →GeoAI & Machine Learning
Where artificial intelligence meets geography — deep learning on imagery, training data, spectral indices and cloud-scale analysis platforms.
GeoAI: Where Machine Learning Meets GIS
What GeoAI covers — from feature extraction to prediction — and what it takes to make machine learning work on spatial problems.
Read the article →Deep Learning on Satellite Imagery
How convolutional networks and segmentation models extract buildings, roads and land cover from imagery at scale.
Read the article →Training Data and Annotation for Geospatial AI
Why labelled data decides model quality, how geospatial annotation is done well, and what quality control looks like.
Read the article →NDVI and Spectral Indices: The Arithmetic of Earth Observation
How simple band ratios like NDVI quantify vegetation, water, soil and burn severity — and how to use them without fooling yourself.
Read the article →Cloud Geospatial Platforms: Google Earth Engine and Beyond
How planetary-scale cloud platforms changed Earth-observation analysis — data next to compute, and what that enables.
Read the article →Web GIS & Technology
Maps as software — web GIS architecture, OGC services, vector tiles, open-source stacks, digital twins and developer tooling.
What is Web GIS? Maps as Living Software
How web GIS turns spatial data into browser applications — architecture, components and what separates portals that thrive from those that die.
Read the article →OGC Web Services: WMS, WFS, WMTS and the New OGC APIs
The interoperability standards that let any client consume any server’s maps and features — and how the API generation modernises them.
Read the article →Vector Tiles and Modern Basemaps
Why modern web maps ship geometry instead of pictures — how vector tiles work, and what they change about styling and performance.
Read the article →Open Source GIS: QGIS, PostGIS, GeoServer and the Modern Stack
The open-source geospatial ecosystem — what each major component does, and how full production stacks are assembled without licence fees.
Read the article →Digital Twins in the Built Environment
What separates a digital twin from a 3D model — live data, simulation and decision loops — and how city and asset twins are actually built.
Read the article →GIS APIs and Developer Tools: Building Location into Software
The developer’s view of geospatial — mapping SDKs, geocoding and routing APIs, spatial SQL and the libraries that glue it together.
Read the article →Cartography & Data
Making maps that communicate — design principles, thematic techniques, scale, and where trustworthy geospatial data comes from.
Cartographic Design Principles: Maps That Communicate
Visual hierarchy, colour, typography and honesty — the design discipline that separates readable maps from decorated data.
Read the article →Thematic Map Types: Choropleth, Heat, Flow and Friends
The main thematic mapping techniques, what data each suits, and the classic ways each one misleads when misused.
Read the article →Map Scale and Generalization: Detail That Fits the Zoom
What scale really means, why maps must generalise, and how multi-scale databases keep every zoom honest and legible.
Read the article →GIS vs GPS vs Remote Sensing: Untangling the Trio
The three most confused acronyms in geospatial — what each does, how they differ, and how they work together.
Read the article →Open Geospatial Data Sources: The Free Foundations
Where trustworthy free spatial data lives — imagery, elevation, OpenStreetMap, boundaries and climate — and how to use it responsibly.
Read the article →GIS Applications by Domain
How geospatial technology delivers in practice — agriculture, cities, disasters, environment, utilities and defence.
GIS and Remote Sensing in Agriculture
From satellite crop monitoring to variable-rate prescriptions — how geospatial technology runs modern and smallholder agriculture alike.
Read the article →GIS in Urban Planning and Smart Cities
The spatial backbone of city-making — base maps, land use, 3D models, growth analytics and the operations layer of smart cities.
Read the article →GIS in Disaster Management: Before, During and After
How geospatial technology runs the disaster cycle — risk mapping, early warning, response coordination and damage assessment.
Read the article →GIS in Environmental Management and Climate
Monitoring ecosystems, assessing impacts and planning adaptation — the geospatial toolkit of environmental science and policy.
Read the article →GIS in Utilities and Telecom: Networks as Data
Why network industries run on GIS — connectivity models, outage response, vegetation compliance and fiber rollout.
Read the article →GIS in Defence and National Security
Terrain analysis, geospatial intelligence and mission planning — how location technology serves defence, lawfully and effectively.
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