Dr. David M. Theobald is a Scientist at the Natural Resource Ecology Laboratory at Colorado State University in Fort Collins, Colorado. David has been working with GIS since the middle 1980s in the areas of planning, conservation GIS, and landscape ecology. In addition to his work in these fields, he has also also authored a book on using ArcView GIS, GIS Concepts and ArcView Methods, and has written several publicly available extensions to ArcView, including the ArcView Spatial Modeler and AVPrimed!. This article is a rough transcript of an interview conducted in July, 2000 in which I asked David a few questions about his career, his views on GIS education, some of the tools he has developed, and the role of GIS in conservation.
1) Can you please tell me a little bit about your career? How did you become interested in GIS and how doe it apply to the work you do?
While I was a student at the University of Colorado, Boulder (UCB) I took a few classes with Allan MacEachren, including one about “Computer Cartography”, which really got me interested in computer mapping and GIS. After graduation, in my first job as a planning technician in Larimer County, Colorado, I began to see the potential benefits that GIS could bring to the planning process. I returned to school and received my MA from the University of California, Santa Barbara (UCSB) where I worked with Michael Goodchild on a project comparing the use of digital elevation models (DEM) and triangulated irregular networks (TIN) for delineating hydrologic landscape features. After graduation, I returned to my home state of Colorado and worked on a project developing a decision support system (DSS) to assist the Bureau of Reclamation in managing the Lower Colorado River. After receiving lots of technical training at UCSB, I decided to return to UCB and pursue a Ph.D. with a more applied focus in using GIS for studying land use change and the consequences for wildlife habitat. I am currently working at the Natural Resource Ecology Laboratory at Colorado State University and was recently awarded a David H. Smith Conservation Research Program fellowship by the Nature Conservancy. This fellowship will help support the work I am doing on conservation planning in the southern Rocky Mountains. There are three main questions that I am trying to answer. First, given the changing landscape, what areas offer the best chance of conserving biodiversity in the long run? Second, can we better define habitat patches in an ecologically functional way, rather than simply looking at them as purely polygons in a database? And third, what is fragmentation and how can it be measured? If you want to find out more about this, there are some links on my homepage.
2) This may be sort of a silly and obvious question, but I want to emphasize to our readers, in case they may not be already aware, of the ways in which GIS can be a valuable tool. What has GIS enabled you to bring to your field that would not be possible otherwise?
GIS enables us to rapidly test and examine our assumptions about the way systems work. For example, decision makers will often quote general statistics on the subject of land use change and the demise of agriculture in the western United States. The GIS enables you explore these statistics beyond superficial estimates to find out where the change is happening and at a level of detail that could not be done otherwise. GIS gives you the power to look at data and challenge the assumptions that people are making.
3) Do you have any advice for people who are interested in a career in GIS?
First, I would recommend that people get a good mixture of education and experience. Learning in an abstract form such as a classroom and exercising that learning outside of the classroom is the ideal learning environment. Second, identify and work in the niches between disciplines. An easy way to do this is find ways to work to connect the gaps that exist between managers and technical people in the field you are working in.
4) Based on reading the preface to the book you have written, GIS Concepts and ArcView Methods, you seem to have a distinct philosophy about learning GIS that says education should include both procedure and principle. In other words, learning both the abstract high-level academic concepts as well as hands-on type training is important. Can you describe this philosophy in more detail?
After teaching several GIS short courses and university classes, I was struck by the fact that there is a gulf between the available textbooks and the software user manuals. No one is more motivated than the person who has a problem to solve, so I decided to write my own book to bridge this gulf. The user manual shows you thousands of ways to execute a given task with no mention of the reason why. My book attempts to fill-in the reasons why, as well as how, you would want to do a particular task in ArcView GIS. Once you know the reason why, you can apply your knowledge to other areas. This is especially important for the ArcView GIS user who, in comparison to the GIS power-user, may not have the same background or understanding of the underlying operations of the software.
5) I remember when I was first learning ESRI’s Arc/INFO, and that’s INFO all in caps (the old one), the online documentation was helpful because in addition to describing the usage and so forth for all of the commands, there was a lot of background information on algorithm choices and appropriate use. Beyond the documentation that comes with a particular software package, do you have any favorite resources, such as books or URLs, that an intermediate level user would benefit from.
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As far as textbook-type material goes, I am fond of the book Geographic Information Systems for Geoscientists by Graeme Bonham-Carter as well as GIS and Computer Cartography by Christopher Jones. For online resources the various discussion lists that exist are a good source of information. I recommend the ArcView list moderated by Bill Huber.
6) A few years ago (at ESRI UC 98) I saw you speak about the ArcView Spatial Modeler and was impressed with the tool that you were trying to build. In fact, the ideas that you presented look an awful lot like the ModelBuilder extension that ESRI is currently selling. Can you introduce some of our readers to the benefits of this technology.
[Author’s note: Overlay models are simply composite combinations of spatial datasets. For more information on modeling with formal symbols and icons check out an example of an application with STELLA.
The premise behind the Spatial Modeler was to provide a type of flowchart for the data and operations used in an overlay model to enable people to see it visually. When explaining difficult concepts people often resort to using diagrams and it struck me that this is the same way that we should be representing and visualizing our spatial models. In other words, we should be working with the diagram representing the model in addition to the map produced from the model. The Spatial Modeler is nice for two reasons. One, you can see how many of the parameters that are used to produce the “final” map interact. Two, by enabling users to save the structure of spatial models in a digital form, it will hopefully promote the sharing of different models. For example, if a local government in North Carolina develops a planning model they may share this with other local governments who implement and refine the model for their own needs.
7) Can you explain the AVPrimed! extension and some of your favorite features.
The AVPrimed! extension, winner of the 3rd place award in the ESRI UC 2000 Applications Contest, (download it from the ESRI ArcScripts page) is a free tool for ArcView GIS designed to enhance your productivity with the software. There are some workflow documentation enhancements which automatically record changes made within a project or shapefile to a log file so that you have a record of what has been done to each. I have added copy and paste functionality to the Project Document graphical user interface (GUI) to enable you to easily transport single documents between projects. I also added several features to the View Document to facilitate feature selection. For example, I added a tool to allow you to select features within a certain distance of an arbitrary shape, not just other features. I added a batch shapefile export utility so that you can specify a list of shapefiles to export, whether you want them to be cleaned (Author’s note: In the ArcView sense this means there are no self-intersections or overlapping lines and is not the same as polygon topology provided in ArcInfo.) and the records arranged in sorted order prior to exporting. I also rewrote the Query and Calculate dialog for Table Documents to make them more user-friendly.
8) One of the classic paradigms associated with managing a GIS is the realization that the software is the least expensive part of the equation. In reality, data is by far the most expensive part of operating a GIS. Although there is a lot of publicly available data through the federal government, much of it is at the 1:100,000 and 1:24,000 scale. Based upon your experience working with local government and non-governmental associations how does this impact what a grass-roots local conservation organization can do with GIS?
I think that there are three considerations to make when using publicly available data to build the base layers used in a GIS. First, there are definitional differences to consider between what the United States Geological Survey (USGS) names a feature and how you interpret that feature. For example, many small ephemeral streams in your local watershed may not appear in the hydrography digital data distributed by the USGS and you may have to find other ways to map these features if you are interested in them. Second, the data collected by the federal government is captured at a certain level of spatial detail which may overlook the types of features you are interested in. For example, acquiring cadastral information showing the location of local parks and preserves can be difficult and may require a data acquisition effort independent of what is publicly available. Third, you need to be aware of the temporal considerations that affect the accuracy of the data you have downloaded. This last factor will be especially important in an area experiencing lots of urbanization. The bottom line is to prioritize the data that is most important to you and find out how you can collect it and build upon the data provided by the federal government.
9) Urbanization, fragmentation and landuse change are some of the areas in which you have published academic research articles during your career. Can you provide some online links for our readers to explore these areas in more detail?
Sure some of the links I can recommend include (in no particular order):
- Sprawl Watch Clearinghouse
- Trust For Public Land (TPL)
- American Farmland Trust
- American Planning Association
Thanks very much David for the fabulous interview! We covered a lot of ground and I am sure that our readers will be able to get a lot out of some of the ideas and resources you have mentioned. I wish you continued good luck with the important work you are doing.
Interviewed By Marco Morais