Creating your own GIS data is time-consuming, except for converting CSV files, in which commas are used to separate values in plain text. CSV files are commonly used for survey sheets, GPS tracking data, mobile call data, network sensors, machine-generated log files, etc. Digitising is a way to create your own data to digitise on georeferenced-based maps. Georeferencing is the transformation of a raw image or scanned map into a coordinated reference image for digitising or overlaying using other map layers. In this chapter, we explain: • Coordinate systems, which are important to know for digitising and overlaying other map layers. • Converting your CSV files into a GIS map layer, which can be done in two ways: table joining, and direct importing (if the CSV data have coordinate information). • Digitising, which is a way to create your own GIS data by digitising (drawing) on a georeferenced image. This section explains the design of the GIS database and the creation, editing, and updating of point, line, and polygon map layers. • Georeferencing, which is the transformation of a raw image or scanned map into a coordinate-referenced map for digitising and overlaying other map layers. • Resources for free GIS data in the public domain, offered by various organisations.