# Maps & Cartography

## Latitude, Longitude and Coordinate System Grids

Latitude lines run east-west, are parallel and go from -90 to +90. Longitude lines run north-south, converge at the poles and are from -180 to +180.

## Conic Projection: Lambert, Albers and Polyconic

When you place a cone on the Earth and unwrap it, this results in a conic projection. Examples are Albers Equal Area Conic and the Lambert Conformal Conic.

## The State Plane Coordinate System (SPCS)

The State Plane Coordinate System divides the United States into 124 zones to locate any point with a high level of accuracy (one part in 10,000).

## Map Distortion with Tissot’s Indicatrix

Map distortion is best understood looking at Tissot’s indicatrix. It contains circles and shows how map projections distort shape, size and distances.

## Why Are Rhumb Lines (Loxodromes) a Constant Track Direction?

Rhumb lines (or loxodrome) have constant bearings and cross all meridians at the same angle. They are not the shortest distance between 2 points on a sphere

## How to Create Flow Maps with Directional Lines

Cartographers use lines to show the movement of phenomenon in flow maps. To show the magnitude, they change the width of flow lines.

## Cartogram Maps: Data Visualization with Exaggeration

Cartogram maps distorts reality to convey information. It accomplishes this by resizing and exaggerating any variable using a polygons geometry.

## What is a Voronoi Diagram?

In a Voronoi Diagram, when you take a point in any given Thiessen polygon, it indicates that it’s closer to that generating point than to any other.

## Choropleth Maps – A Guide to Data Classification

Equal intervals, quantile, natural breaks, pretty breaks- data classification methods generate different choropleth maps. We explain the types of maps here.

## Azimuthal Projection: Orthographic, Stereographic and Gnomonic

The azimuthal projection plots the surface of Earth using a flat plane. For example, common azimuthal projections are gnomonic, stereographic & orthographic