the data layer!

technically all layers are data layers

but bear with me here

types of objects in geodata:

lines

points

polygons

geodata formats

non-web:

- GPX (GPS Exchange Format)

- NMEA (National Marine Electronics Association spec)

- ESRI Shapefiles (.zip or .shp)

- EXIF (Exchangeable Image File Format)

web-readable:

- KML (Keyhole Markup Language)

- GeoJSON

- TopoJSON

but also like, a CSV even

also PostGIS

this is where I should tell you more about cartodb

converting non-web to web

online services

- CartoDB (subscription-based)

- Mapshaper (free)

desktop/command line tools

- ogr2ogr (part of GDAL)

- GPSBabel

- togeojson, csvtogeojson...

more here

example:

converting exif data to geojson

this isn't necessarily the best method tbh

this just happens to be a way I've done it

and I wanted to introduce you to some relevant tools

gpsbabel -i exif -f image.jpg -o gpx -F image.gpx

togeojson image.gpx > image.geojson

geojson-merge image-1.geojson image-2.geojson image-3.geojson > images.geojson

but whoa whoa whoa

before you convert data

where do you find it?

here is a pile of data sources to look at

pulling data out of OpenStreetMap

Overpass API

overpass-turbo.eu

wiki.openstreetmap.org/wiki/Map_Features

joining geodata to other data

lifewinning.com/submarine-cable-taps

basically, table joins

okay

we have a base layer

we have some data layers

let's put them on a map!!