Which Is Better?: Raster vs Vector for GIS Map Printing
What Are GIS Maps?
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.
Why Are GIS Maps Becoming Increasingly Popular?
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.
The Importance of Accurate GIS Map Printing
Understanding Raster Data in GIS: What Is It & How Does It Work?
How Is Geographic Data Represented in Raster Format?
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).
What Are the Advantages and Disadvantages of Using Raster Data for GIS Map Printing?
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.
What Are the Common Raster File Formats Used in GIS Applications?
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.
Understanding Vector Data in GIS: What Is It, & How Does it Work?
How Is Geographic Data Represented in Vector Format?
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.).
What Are the Advantages and Disadvantages of Using Vector Data for GIS Map Printing?
What Are the Common Vector File Formats Used in GIS Applications?
There are also numerous vector formats, including:
- Esri Shapefile (.SHP · .DBF · .SHX)
- 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)
Comparing Raster and Vector Data in GIS: Which Is Better?
Raster and vector data in GIS applications work very differently. When choosing between raster vs vector GIS format, which is better?
Data Representation on Maps
Raster Data Showcases as Grids
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 Showcases as Geometric Elements
Vector data represents more intricate forms. It's also more accurate than raster. Vector formats are best for geometrically complex printouts.
Nature of the Data
The main difference between raster and vector data in GIS printing comes down to discrete vs continuous representation of spatial elements.
Raster Data Is Usually Continuous
This means measurements have a wide range of potential values (such as elevation or slope) based on a fixed reference point.
Vector Data Is Usually Discrete
Discrete measurements have clear, well-defined boundaries representing one value rather than a continuous range.
The Application of Raster and Vector Data
Raster Data Is Best Suited for Continuous Phenomena (Elevation, Temperature, or Satellite Imagery)
Raster data is better for covering a range of values subject to change, such as elevation, temperature, and slope.
Vector Data Is Best Suited for Discrete Features (Roads, Buildings, or Administrative Boundaries)
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.
Using Raster and Vector Data for GIS Analysis
Raster Data Is Best Used to Observe Proximity and Spatial Operations
When possible, files should convey continuous spatial relationships between objects with the proper size and distance between them.
Vector Data Is Best Used for Measurements and Topological Relationships
Discrete measurements are usually best when the form of a topological feature is important.
Data File Size Differences
Raster Data Is Larger
Because raster data consists of a large matrix of continuous data points, raster files tend to be larger.
Vector Data Is Smaller
Users can save vector files with nothing more than a series of points and lines. The files then translate into polygonal shapes.
The Scalability of Raster vs Vector GIS Formats
Raster Data Has Limited Scalability
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 Has Infinite Scalability
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.
How to Determine Which Data Type to Use in GIS Map Printing
1. Establish the Purpose of the Map (Analytical or Illustrative)
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).
2. How Much Geographic Data Complexity and Detail Are Required?
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.
3. Identify the Output Requirements: Print Size, Quality, Medium, etc.
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.
4. Consider the Resources and Time Constraints.
The resources available for a given print shop, including time, will also impact how much effort can be put into each GIS printing project.
User Expertise and Familiarity With File Formats
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.
Using Both Raster and Vector Data in Different GIS Map Printing Scenarios
Scenario 1: Large-Scale Topographic Map Printing
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.
Scenario 2: Creating Thematic Maps for Urban Planning
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.
Scenario 3: Mapping Data for Web-Based Applications
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.
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