Heads-Up Digitizing, also known as on-screen digitizing, is a method used in GIS software programs liked ArcGIS to convert geographic data into digital formats. This process involves the user manually tracing geographic features from a digital image or map on a computer screen into a GIS.
Steps involved in digitizing in GIS
- First, you’ll need to have some sort of base map or aerial image to trace from. This could be a scanned paper map, a satellite image, a digital photograph, etc. This base layer is known as the source layer.
- The source layer is then displayed on a computer screen. Using a mouse, or sometimes a digital pen, the user manually traces over the features on the source layer. These could be anything from roads, to building footprints, to river courses, to political boundaries.
- As the user traces these features, they create new digital features in a new layer. These new features are typically vector features, meaning they’re made up of points, lines, or polygons.
- The newly digitized features can then be saved, manipulated, analyzed, and displayed within the GIS.
Heads-Up Digitizing is often used when there’s no existing digital data for a particular area or feature, or when existing digital data is not detailed or accurate enough for a particular application. While this process can be time-consuming and sometimes prone to user error, it can also provide a high level of detail and accuracy, especially when performed by an experienced user.
Review of basic digitizing in ArcGIS
The tutorial below reviews basic digitizing using the editor toolbar in ArcGIS desktop.
The demonstration traces sidewalks and buildings from an aerial image in order to create two separate shapefiles (arc shapefile for the sidewalks and polygon shapefile for the building footprints).
The video is 5:06 minutes in length and is demonstrated using ArcGIS 9.3.