Working With Maps

Geographical information system (GIS) is a system designed to capture, store, manipulate, analyze, manage, and present all types of spatial or geographical data.

Typical GIS software include ArcGIS and ArcMap.

At its simplest, geographic elements are

• Points: landmarks
• Lines: roads, coarse representation of a river
• Polygons: geographic areas, lots, etc.

The shapefile format is a popular geospatial vector data format for geographic information system (GIS) software. It is developed and regulated by Esri as a (mostly) open specification for data interoperability among Esri and other GIS software products.

We're going to import shapefiles into R and convert them into SpatialPolygons (sp) objects. At its simplest, an sp object consists of:

• A plotting order
• A bounding box of the the geographic extent in question
• A coordinate system (latitude/longitude, UTM, NAD) to project a 3D globe onto a 2D page.
• A list of polygons
• Any relevant data to each geographic object

The last three are the most relevant to you.