Is the Old Adage True? Raster Is Faster, but Vector Is Corrector?


Raster or Vector Format War

Image with question "raster or vector?"There is a team working on a new tool for Digital Coast using ship traffic. I was chatting with a team and I asked the question, “Are you going to show that as a raster or vector file in your application?”

Why ask that question in 2013? Is it still an issue? Years ago, GIS geeks argued about which format was better, faster, or easier. Are GIS geeks still fighting the raster vs. vector war of early GIS? Do we really need both types of data in Digital Coast? I would say emphatically YES!

Vector Is Best for Bar Room Napkin Mapping

Let’s say you are talking to your buddy and want to explain the location of the new store. You might start by drawing a sketch on your napkin. On your napkin you are describing relationships to get your point across. You probably generalized features such as putting a single point for a building, or drawing a line for the road or river. Maybe you drew a box for a church. Without thinking about it, you selected a projection, scale, and a vector feature type (line, point, polygon) in your napkin map. Hah, congrats, you’ve just made a model of the earth and you chose a vector format!

And even though you are the best napkin map cartographer on the planet, you introduced errors! All maps (including napkins) are representations of reality and inherently wrong! But if your buddy understands the napkin “model” and finds the store then you have done your job. Can you imagine trying to draw that napkin map using a raster characterization? You will spend the time to draw thousands of tiny blocks covering the napkin and you would need multiple pens to color and characterize the data.

vector map drawn on a napkin
Napkin vector map
Raster map drawn on a napkin
Napkin raster map

Raster Is Everywhere

Just like you, geospatial data developers must ask themselves: “What’s the best way to represent my data so my “buddy” understands and gets the answer that I’ve intended?” “What format works best for modeling, ingesting into a tool, looks the best, or draws the fastest on the intended output device?” One super important consideration is how the data were created. Today many of our data are collected in raster format and we don’t ever think about it. For example, if you start with a digital camera (hand, aerial, or satellite) you already have raster data. Higher end cameras and better TVs and monitors usually have MORE rasters than their low-end counterparts. Depending on the device, they may be called pixels or dots. If you hear dots per inch (DPI) or megapixel (1 million pixels), you are talking raster! If you zoom or magnify in really close you can even see the individual dots or pixels. Your map, photo, or scanned document is just a collection of pixels arranged in rows and each small pixel has a value. Raster data is everywhere in Digital Coast. Or fax a letter, screen grab your monitor, scan a document, or snap a digital photo and you have other examples of data using raster formats.

Sometimes it is not EITHER raster or vector, but BOTH. Elevation is a good example. Lidar is collected as millions of individual points (vector), but often these data are converted to raster formats for ease of use. It helps the humans and the computer comprehend changes in elevation more quickly. And just when you think you got it, often the raster elevation data is converted back into vector data in the form of contours for maps. Crazy, huh?

example of a point cloud of elevation data
Point cloud

raster rendition of an elevation point cloud
Raster elevation

Contours are shows as the vector rendition of elevation
Elevation contours

Raster and Vector Living Together

  • “Yes raster is faster, but raster is vaster and vector just SEEMs more corrector.”- C. Dana Tomlin

You don’t have to choose a camp anymore and fight the war. Both formats live harmoniously in most software packages. Esri, Google, Apple, and Bing are all giving you both options. SO next time you check-in on your smart phone on Foursquare (point), or you map your running route (line) with your fancy GPS watch, or calculate your parcel’s area (polygon), you’ll think VECTOR. If you turn on the satellite imagery in Google, or snap a photo on your smart phone, or scan a document with your signature, you’ll think RASTER.

Are you still fighting the raster and vector war? Do you have a preference that pushes you to one format or the other or is this second nature to all you geospatial professionals these days?

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