Metadata: Powerful Documentation Tool or Gobbledygook Developed by the GIS World?

· SURVEYOR RANDY says …

Surveyors have been providing maps with metadata to our clients for more than 2,000 years. The only difference is we didn't call it metadata. We called it accurate and complete surveying.

In 1400 B.C., Egyptians used surveying to divide land into plots so it could be properly taxed. Around 120 B.C., the Greeks standardized procedures for conducting surveys. And while I didn't start surveying myself until a couple of centuries after the Greeks, I'm pretty sure those guys kept track of the who, what, where, when, and how of their surveys. I know I did.

I'm definitely not saying that metadata is gobbledygook. What I am saying is that metadata has been around for eons, way before GIS was even a gleam in somebody's eye. For example, the copyright page of a book contains metadata in the form of the copyright date, information about the publisher and the author, and the Library of Congress cataloging data. Metadata is very important, but professionals from many walks of life knew that way before the GIS world embraced it as a GIS concept.

And while metadata isn't gobbledygook, some of the data identified in the metadata could be. The value of a GIS is the wealth of information contained in its multiple layers. A GIS can contain such a wide range of information, with such a wide range of accuracy, that metadata may be the only way to determine if you can truly rely on the information displayed on the screen or printed on a map. The problem is the information you need is not right there in front of you. It's hard to determine the varying degrees of accuracy of all those layers. How do you know which layers have the accuracies required for your particular application? How and where do you easily find the metadata that lets you know that what you're looking at is what you really need? And when the metadata encompasses a half page of run-together alpha numeric verbiage, a word such as gobbledygook might come to mind.

The emergency dispatcher to whom you referred needs to know his GIS and the validity of his data without searching for metadata. He doesn't have time to fish for and decode the vital information that enables him to carry out the responsibilities entrusted to him.

Survey maps provide metadata in the form of a title block and one or two certification paragraphs that give the map reader a complete listing of the date, accuracy, scale, datum, location, source of historical information (such as deeds and previous maps), and the survey and map provider. Not only is this information on a hard copy of the map, it also appears when a digital copy of the map is retrieved from a city or county GIS. The surveyor's metadata is right out front, on the same page—no searching to find it. No additional steps to take or time wasted to understand the reliance you can place on the survey data displayed on the map. It takes time, effort, and expertise to locate metadata and drill down through all the verbiage and decipher the value of the data contained in the various layers of the GIS. And that can result in confusion about the data and/or unknowingly relying on bad data.

Of course surveyors understand the importance of metadata. That's why we've furnished it on the face of our maps for centuries.

· GIS JANET says …

Randy, you don't really mean to say that metadata, data about your data, is truly gobbledygook, do you? To me, gobbledygook is a word that is hard to say and doesn't mean anything, like "supercalifragilisticexpialidocious."

On the contrary, metadata is a term that is easy to pronounce and that means something very important. Simply stated, metadata is your owner's manual to your GIS. It's the who, what, where, when, and how of your geographic information data sets. The ESRI Dictionary of GIS Terminology defines metadata as "Information about a data set. Metadata for geographical data may include the source of the data; its creation date and format; its projection, scale, resolution, and accuracy; and its reliability with regard to some standard."

Why is metadata so important to the GIS profession? Because just like surveyors, we need a place to document the specifics about the data sets and analysis we use to create digital thematic maps. But since GIS people don't deal with hard-copy plan sheets, and because all the data we see are seamlessly integrated into one main visual display, there aren't any title blocks that contain all that important background information. Our title block is the metadata tab associated with each map document.

Most standard GIS software provides easy-to-use, easy-to-find metadata sections that are part of the map document system. In a metadata feature I typically use, it takes only two clicks of the mouse to find complete information about a map document.

The following scenario illustrates just how important metadata is. A huge fire is burning out of control and you're in charge of dispatching emergency personnel. You view the aerial photos of the burning area that are displayed in your GIS. According to your photos, no homes are located within the area of concern. With complete confidence, you direct the emergency workers to move into another burning area.

A few hours later you receive word that on-site emergency crews evacuated two dozen residents from their burning homes. You quickly review the aerial photos again and confirm that there are NO HOMES in that area. But on second thought, how can you be sure? What exactly do you know about the aerial photos you're depending upon? When were they taken? Have homes been built in that area since the aerial photos were acquired? Do the parcel data match the aerial photos? Did you read the metadata before you gave the order to divert the emergency workers from the area? How could this happen? Isn't information in a computer always complete and up-to-date?

I agree that surveyors have provided necessary information on the "face" of their work for years, and that solution works well for the survey community. However, GIS has no literal face, only layers and layers of tabular and graphic data. We need a place to put and display the information in such a way that we can reference it at a moment's notice and that, when we are asked for the who, what, where, when, and how, we have the answer!

Every day, decision-makers have to make difficult decisions at a moment's notice. Our job is to support their efforts by providing them with the most up-to-date and accurate information possible; information that contains completed metadata. Decision-makers NEED to know how the data was collected, processed, and assembled so they can make a good decision. And if they're the least bit computer savvy, they can easily find it with the metadata tab. After all, someone's life may depend on it. And that's not gobbledygook.

While Janet and Randy may not see eye-to-eye on all surveying and GIS issues, they do work together on a daily basis, respect other's perspective and point of view, and attempt to "intersect" their professions whenever possible. Randy and Janet invite you to submit your questions to "Intersect." Contact them via email at intersect@mckimcreed.com or at 919.233.8091.

About the Authors

  • Janet Jackson, GISP
    Janet Jackson, GISP
    Janet is certified as a GIS professional and is president of INTERSECT, a GIS consulting firm.
  • Randy Rambeau, Sr., PLS
    Randy Rambeau, Sr., PLS
    Randy is a geomatics office manager with McKim & Creed, an engineering, surveying, and planning firm.

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