data file formats
@
maptime detroit
by Jimmy McBroom -- March 31, 2015

Esri shapefiles are super common

• only one type of shape
• read them with ArcMap, QGIS
• online tools: CartoDB, ogr2ogr web client
• size limit: 2 GB
• not human-readable

Your "shapefile" needs four files:

• .shp contains shapes
• .shx contains index for shapes
• .dbf contains data for shapes
• .prj contains projection data
• if there are other files: keep them
• want to share? .zip it up!!

Esri geodatabases (.gdb)

are not so common

• it's actually a container for shapefiles
• multiple layers (points, lines, polygons)
• read them with QGIS or ArcMap

GeoJSON

is more and more popular

• JavaScript Object Notation for spatial
• can represent points, lines, polygons in one file
• human readable
• coordinates usually in [-83.213, 42.324] format
• but sometimes in a custom projection

sample GeoJSON file w/ one feature

        {
          "type": "Feature",
          "geometry": {
            "type": "Point",
            "coordinates": [125.6, 10.1]
          },
          "properties": {
            "name": "Dinagat Islands"
          }
        }
      

GeoJSON is good for:

• sharing data with people
• web mapping
• editing and collaboration
• being an open standard

TopoJSON

• cousin to GeoJSON
• encodes features with topology
• splits borders into arcs and specifies which arcs describe a feature
• reduces file size via simplification

KML & KMZ
(Keyhole Markup Language)

• XML-based
• associated with Google Earth
• human-readable
• still exists, but I'd convert to GeoJSON

GPX
(GPS Exchange Format)

• also XML-based
• used for tracks & routes
• not just location
• but elevation and time

CSV & TSV
(comma- and tab- separated values)

• flat text files
• not necessarily spatial
• maybe a lat and lon column: points!
• maybe a WKB or WKT column: lines! polygons!

check out the website:

maptimedet.github.io