Puzzling Over PDFs

October 15, 2008  - By
Image: GPS World

By Art Kalinski, GISP

GeoPDFs have become a very valuable tool for the GIS community, but it has been a slow evolution. My first exposure to GeoPDFs came about five years ago, when I saw a new GIS map-publishing medium offered by Layton Graphics. The local Atlanta firm started out as a microfilm copy specialist, then slowly moved into digital media. While I was in the GIS shop at the Atlanta Regional Commission (ARC), I would occasionally get a visit from one of their salespeople, but they really didn’t have anything we needed.

As time progressed, Layton Graphics evolved further into digital publishing, and eventually into the Adobe Acrobat format. I continued to get an occasional visit, and I always gave them 10 minutes of my time. As the years progressed, however, I grew in age and my patience shrunk proportionately, so when I received a visit from them again in 2003 I barely gave them three minutes.

But to quote my uncle, “Eventually even a blind pig will find an acorn.” The sales rep showed me a new Layton Graphics product based on Adobe technology — and it fit a real need perfectly. For the first time, my perfunctory meeting grew into two hours as I invited more and more ARC staff members to sit in on this new product demo.

What Layton Graphics — now known as TerraGo Technologies — had created was the GeoPDF format, plus tools that manipulated the files in Adobe Reader. It was a brilliant new geospatial publishing medium. For those of you who are not familiar with TerraGo, let me explain the features that caught my attention.

For years, we published our ARC GIS data on CDs (primarily as Shapefiles) and included a copy of ArcExplorer for those users who didn’t have a GIS. The problem with providing raw GIS data to inexperienced users is that it typically resulted in cartographically poor maps, many of which were truly terrible.

ESRI’s Map Publisher partially solved that problem by permitting the creation of a GIS-based map as an MDF, which retained the original cartography of the publisher. The only problem was that the user had to download Map Reader, the MDF, and all the GIS data layers. Additionally, if there was a problem with Map Reader pointing to any of the data, the map would not print. Some of those problems were solved in later versions, but it is still not as elegant a solution as TerraGo’s: a single file viewable in Adobe Reader.

In ESRI’s ArcGIS, users create maps using the data layers, colors, and symbology of their choice. When the GeoPDF is created using TerraGo Publisher (previously known as Map2PDF), the desired “look” will be maintained, but it won’t be a dumb map; the file is actually a self-contained GIS viewing environment. Users can zoom in and out, pan, and — using the table of contents to the left of the map view — turn layers on and off. There is even a query tool that permits the display of attributes as users click on the geographic features. The map layers can be GIS vector data or background ortho imagery. All these manipulations can be performed using the ubiquitous, free Acrobat Reader from Adobe.

The thing that makes the GeoPDF so remarkable is that the GIS map layout, and all GIS data, travels as one single file: no lost or mis-pointed data! It’s foolproof for the receiver, and is very intuitive even for users not trained in GIS.

But it doesn’t end there if the receiver is willing to download TerraGo Desktop, a free collection of even more sophisticated tools. The solution, which until recently was known as the GeoPDF Toolbar, offers users the ability to publish and collaborate on the same GeoPDF file via the Internet (annotations created on the map are viewable by all linked viewers). They can also measure distance, area, and direction, and view vehicle locations if GPS tracking data is available.

This interactive collaboration capability really got my attention for homeland security and first-responder applications, especially in mutual aid situations. Just imagine creating a compact GIS project of a disaster location, then quickly sending the single GeoPDF to anyone responding, even those who are unfamiliar with the area or with GIS software. The annotations can be saved as Shapefiles, which makes the GeoPDF an ideal data collection environment.

TerraGo designed the GeoPDF format with an extensive capability to store and catalog large and complex datasets. That’s one reason why the Army Corps of Engineers has published its entire collection of world maps as GeoPDF files. The National Geospatial-Intelligence Agency is another federal user taking advantage of the format.

Discerning Differences

There has been a Kabuki dance going on between TerraGo, ESRI, and Adobe as they try not to step on each other’s intellectual-property toes. TerraGo and Adobe worked together to get GeoPDF support in Adobe Reader. Adobe and ESRI partnered to extend the ISO 3200 specifications for PDFs to include geospatial. In the meantime, TerraGo is creating GeoPDFs from ArcMap and ESRI is creating PDFs with the proposed geospatial extension to ISO 32000.

Now that TerraGo isn’t the only option anymore, the question for many of us is, What’s the difference between TerraGo’s GeoPDFs and geospatial PDFs created by ESRI software? For simple map creation, the answer is: not much. The Adobe solution and the TerraGo solution are very similar now that TerraGo has signed an alliance agreement with Adobe.

By opening the door, TerraGo hopes to reach many more users to promote the added functionality of their Desktop tools. Specifically, the added functionality enables users to perform the following tasks:

  • Use drawing tools to mark up maps and collaborate between users in remote locations. The remote users don’t need GIS software or special training.
  • Convert the mark-up graphics to GIS data. This makes a GeoPDF a very simple, low-cost field GIS data collection tool. There’s no need for additional GIS licenses to do simple field data collection. This same capability permits the export of the data as Shapefiles or KML files.
  • Create complex linked collections of maps as map books, or combine many maps into a large mosaic.
  • Retain and enable hyperlinks to other documents, files, and HTML sites.
  • Display AVL (automatic vehicle locator) GPS data to show the movement of vehicles on the GeoPDF map.

In addition, according to users of both types of files, many of the common capabilities seem to be more robust and work better in the TerraGo environment. For example, there are more problems selecting attributes in an Acrobat map than in a TerraGo GeoPDF. TerraGo has had years of experience to refine its solution and create more robust, reliable tools.

The simple conclusion is that both options perform the key job of creating cartographically sound maps in a GIS viewing environment. Both are georeferenced. Both provide attribute query. Both provide the ability to turn layers on and off, pan, zoom, measure distances, and obtain coordinates. The subtle differences only become noticeable as you use both solutions. Whether you require the additional capabilities of a TerraGo GeoPDF — such as the collaboration and Shapefile creation — will ultimately depend on your needs.

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