Vineesh V, Geography

The history of Geographic Information Systems (GIS) is rooted in early efforts to understand spatial relationships and patterns, long before the advent of digital computers. While modern GIS emerged in the mid-20th century with advances in computing, its conceptual foundations lie in cartography, spatial analysis, and thematic mapping. Early Roots of Spatial Analysis (Pre-1960s) One of the earliest documented applications of spatial analysis dates back to  1832 , when  Charles Picquet , a French geographer and cartographer, produced a cholera mortality map of Paris. In his report  Rapport sur la marche et les effets du choléra dans Paris et le département de la Seine , Picquet used graduated color shading to represent cholera deaths per 1,000 inhabitants across 48 districts. This work is widely regarded as an early example of choropleth mapping and thematic cartography applied to epidemiology. A landmark moment in the history of spatial analysis occurred in  1854 , when  John Snow  inv...

Soil profile 

Topology? Topology can be understood as the "rules of spatial behavior" that govern how geographic features relate to one another in a GIS environment. It defines the logical relationships between points, lines, and polygons, transforming a simple digital drawing into an intelligent and analyzable spatial network . Without topology, GIS data remain visually correct but analytically unreliable. 1️⃣ Adjacency (The "Jigsaw Puzzle" Rule) Concept: Adjacent polygons must fit together seamlessly. Rule: There should be no gaps (slivers) and no overlaps between neighboring polygons. Example: Two adjacent land parcels must share a single, common boundary. A parcel cannot overlap another parcel, nor can empty spaces exist between them—just like pieces of a jigsaw puzzle fitting perfectly. Connectivity (The "Plumbing" Rule) Concept: Line features must connect properly at nodes to form a continuous network. Rule: Lines must connect end-to-end , with no undersh...

Shapefile Components 🔹 .shp — Geometry file What it contains: • The actual geographic shapes (points, lines, polygons) Examples: • City locations (points) • Roads (lines) • Administrative boundaries (polygons) 📌 This is the core file — without it, there is no map. ⸻ 🔹 .shx — Shape index file What it contains: • An index of the geometry file • Allows fast access to shapes 📌 Improves performance when loading and navigating data. ⸻ 🔹 .dbf — Attribute table What it contains: • Attribute data linked to each shape • Stored in dBASE format Examples: • Name, population, area, ID • Road type, length, category 📌 Each row corresponds to one geometry in the .shp file. ⸻ 🔹 .prj — Projection file What it contains: • Coordinate Reference System (CRS) information • Projection, datum, units 📌 Without this file, GIS software does not know where the data is on Earth. ⸻ 🧩 Optional (But Common) Shapefile Files 🔹 ...

Etchplain An etchplain is a low-relief, gently undulating erosion surface formed primarily through deep chemical weathering (etching) of bedrock, followed by the removal of the weathered mantle , exposing a relatively smooth rock surface. Process of Formation In warm and humid climates , chemical weathering acts deeply along joints, fractures, and bedding planes. Less resistant rocks are altered into a thick layer of saprolite (weathered regolith) . Subsequent denudation and erosion remove the saprolite. The underlying fresh or slightly weathered bedrock is exposed as a broad, nearly level surface , occasionally interrupted by residual hills. Characteristics Low relief and gently undulating surface Formed mainly by chemical weathering followed by stripping Presence of residual hills such as inselbergs Common in tropical and subtropical regions Examples Peninsular India African Shield regions Inselberg An inselberg (German: "island mountain" ) is an isolated, steep-sided r...

Disaster management  Disaster Impacts

Geo processing tools in GIS 

History of GIS