A geographic information system (GIS) stores spatial data representing a city or geographical terrain. But storing the data correctly requires knowing a bit about raster vs vector GIS formats. Each type is fundamentally different and best suited for specific applications.

Digital mapping technologies are more heavily relied on as internet literacy grows. This puts increased demand on large format printing specialists to understand the difference between raster and vector data in GIS files in order to achieve the highest-quality map prints.

Knowing when to use raster vs vector GIS formats is key to selecting the right large format printer or plotter, settings, media, and file formats.

Raster saves spatial data in a matrix of cells or pixels. Each cell represents a discrete or continuous value (e.g., terrain type or elevation level, respectively).

Raster is a straightforward way to convey easily quantified geographical data, but it's better suited for analysis than highly detailed graphical renderings. This makes raster more appropriate for simple maps or as a grid-like foundation for vector graphics.

There are dozens of raster formats, and the following raster files types are just some of the most common:

• ERDAS Imagine (.IMG)
• American Standard Code for Information Interchange ASCII Grid (.ASC)
• GeoTIFF (.TIF · .TIFF · .OVR)
• IDRISI Raster (.RST · .RDC)
• Envi RAW Raster (.BIL · .BIP · .BSQ)
• PCI Geomatics Database File, or PCIDSK (.PIX)
• Esri Grid (saves spatial attribute data in a series of databases rather than a single extension or file)

Compressed raster file types, including PNG, BMP, and various JPEGs, are also available, along with proprietary military and USGS raster formats.

Vector data uses a series of points, lines, and polygons to store geometric forms. This makes vectors more suitable for representing varied, complex forms (like curved roads, rock formations, architectural intricacies, etc.).

Vector data is much more accurate and aesthetically refined than raster. This means large format printers made particularly for GIS printing must be capable of a greater level of detail.

There are also numerous vector formats, including:

• Esri Shapefile (.SHP · .DBF · .SHX)
• Geographic JavaScript Object Notation (.JSON · .GeoJSON )
• Geography Markup Language (.GML)
• Google Keyhole Markup Language (.KML · .KMZ)
• GPS eXchange Format (.GPX)
• IDRISI Vector (.VCT · .VDC)
• MapInfo TAB (.TAB · .DAT · .ID · .MAP · .IND)
• OpenStreetMap OSM XML (.OSM)
• Digital Line Graph (.DLG)
• Geographic Base File-Dual Independent Mask Encoding (GBF-DIME)
• ArcInfo Coverage (more of a set of tables than a file format in its strictest sense)

Raster and vector data in GIS applications work very differently. When choosing between raster vs vector GIS format, which is better?

When comparing raster vs vector GIS formats, raster data more efficiently conveys basic geographical information, such as basic city grids. It's also better at showing general differences between types of terrain.

Vector data represents more intricate forms. It's also more accurate than raster. Vector formats are best for geometrically complex printouts.

The main difference between raster and vector data in GIS printing comes down to discrete vs continuous representation of spatial elements.

This means measurements have a wide range of potential values (such as elevation or slope) based on a fixed reference point.

Discrete measurements have clear, well-defined boundaries representing one value rather than a continuous range.

Raster data is better for covering a range of values subject to change, such as elevation, temperature, and slope.

Vector formats are best when a design element either is or isn't a particular value. For instance, a road's elevation is usually unimportant, but it's necessary to show when the area is a drivable surface.

When possible, files should convey continuous spatial relationships between objects with the proper size and distance between them.

Discrete measurements are usually best when the form of a topological feature is important.

Because raster data consists of a large matrix of continuous data points, raster files tend to be larger.

Users can save vector files with nothing more than a series of points and lines. The files then translate into polygonal shapes.

Raster files are limited by the quantity of the grid stored. More data requires a larger grid, and there's usually only so much storage space.

Vector data can easily scale with little change in file size. As far as data storage goes, it makes little difference whether a line is mere millimetres or several kilometres in length.

The primary consideration for raster vs vector GIS is how the GIS map will be used. Analysis usually requires intricate measurements using vector graphics. But the relative relationship between geographic features, as with raster, makes better sense with more conventional uses (like planning travel routes).

As with vector graphics, architectural and other building projects usually demand greater complexity and detail. Even normal GIS web applications require some exact detail, such as the length of a road or city block. Zoning and permitting maps usually require just enough detail to accurately convey boundaries, but not necessarily the size of the buildings. Unless you need greater accuracy or aesthetics, consider raster until file size becomes an issue.

Large format printing experts must additionally consider how large the GIS map will be. Any combination of the factors previously described could affect print quality, which in turn impacts print materials. For instance, more detailed GIS prints may require a wider colour gamut or number of inks to convey subtle but critical differences in the terrain.

The resources available for a given print shop, including time, will also impact how much effort can be put into each GIS printing project.

With a greater understanding of raster and vector data in GIS files, printing professionals can adjust their equipment quickly and accurately in response to different file formats. This saves enormous amounts of time while reducing errors and material waste.

Topography requires displaying elevation, a type of continuous measurement. It works best with raster file types. But when the terrain is highly complex, vectors could also be used with raster to depict curves and topographical features with more accuracy.

Urban planning typically involves zoning and property boundaries. With their smaller file size and more intricate shapes, vector drawings are the most obvious choice. However, when you need the same map for certain engineering processes, raster may also be an appropriate choice.

This depends on the application. 3D modelling programs and certain types of CAD programs can easily display vector graphics. Other web apps are made for simpler uses, such as OpenStreet or Google Maps. So in these cases, raster files are usually sufficient for directions, city layouts, and even satellite imaging.

Still wondering when raster vs vector GIS formats are necessary? Contact an HP sales expert, and tell us about your GIS printing needs. We can direct you to the most suitable HP professional print services to help you fulfill client orders with maximum print quality and efficiency.