Feature: GIS Basics for Surveyors
Professional Surveyor Magazine - October 2012
by David McKittrick
If recent technological trends have taught us one thing, it is that you should steer clear of the prediction game. Not too long ago it was widely anticipated that the Windows and Mac operating systems would soon be completely interoperable, that print media would become a relic of the past, and that surveyors would embrace GIS technology. If the truth be told, we’re still anticipating these will eventually come to pass, but, in each case, we’re not there yet. So, why are many surveyors reluctant to adopt a technology that, by many definitions, is a perfect complement to the tools they currently use?
There is a perception, sometimes justified, that GIS is an overly complicated discipline requiring a great deal of training and know-how, as well as a considerable financial outlay, to be employed effectively. While it is true that some GIS professionals see the democratization of their turf as a threat to their status and thrive on the notion that their field of expertise is inherently inaccessible to the masses, this situation is changing.
Call it the Google Earth Effect: The general populous is now more spatially aware, or at least aware of the existence of spatial technology and its usefulness, than at any time in the past. Not satisfied with simply viewing maps, many moderately tech-savvy citizens are delving into the art and science of interactive mapping technology and are reaping the benefits both personally and professionally. Accessible GIS software packages such as Global Mapper (recently acquired by Maine-based Blue Marble Geographics) offer an inexpensive and easy-to-use alternative to mainstream GIS offerings and dispel the notion that spatial technology is out of reach for most common folk.
When asked why GIS is not part of their workflow, the surveying community offers these three most-common responses: expense, difficulty of use, and, perhaps surprisingly, relevance or usefulness. It is the latter point that this article addresses, showing that there is room for GIS in the surveyor’s toolkit.
Before outlining and describing some of the specific features and functions of a GIS that are of most value for surveyors, let me first define what exactly GIS is. Granted, there are many who navigate the often-tempestuous waters of higher education in order to answer that question, only to emerge more confused than when they enrolled, but in keeping with the underlying theme of this article a more straightforward definition is appropriate. Simply stated, a geographic information system is a tool for managing data in its locational context. Obviously, the specific purpose and intended use of a GIS will likely help refine this definition, but the underlying premise is the same regardless of industry or application.
For surveyors, GIS software can be a powerful asset in many aspects of the surveying process: from project planning to data management to map creation. As with any technology, however, GIS software will prove to be a wise investment only if it can be put to use effectively and is not simply left to collect dust on the shelf. If the application is overly complicated or requires a highly trained specialist to operate, it will likely be beyond the reach of the average surveying professional and may be more of a liability than an asset. GIS is a great first tool for any technology professional looking to step into the fray based on logical organization, intuitive interfaces, and instructive home screens that guide the users to accomplish their tasks.
The question of cost is also a factor. The decision to invest in GIS technology may come down to the likelihood of seeing a return on that investment, and, after factoring the initial purchase of the software, training, maintenance, and other costs, for many it’s not worth the risk. There are inexpensive GIS products as well as many free sources of existing base data available that may help to allay these concerns, and they offer a means for non-GIS professionals to employ GIS functionality in their business processes.
There are many reasons surveyors might embrace GIS; a fairly significant one can be quite simple: new business opportunities. Small- to medium-sized surveying firms can look to the capabilities of GIS to further develop their expertise and offer a host of new services to existing and potential clients. Simple asset inventories (trees, street signs, etc.) are a good example where customers need the expertise and the reliability of a professional land surveyor but do not necessarily need the high degree of accuracy. The combination of an affordable GIS package and freely available base map information can provide a detailed and informative map for a client without the time and/or cost of delivering high-accuracy data.
Other business applications include document management/georeferencing services or even good, old-fashioned cartographic map making. Using GIS and marketing your services can create new opportunities in lean times, but it can also build a new client base that can feed business to your core practice of surveying.
Now that I’ve introduced the basic principles of GIS and offered some reassurance that GIS is not beyond your reach, it’s time to take a look at some of the applications and benefits of this technology in the domain of the surveyor.
A well-organized and accessible GIS can serve as the central project management tool in the surveyor’s toolkit. From initial project planning to data storage to file processing and delivery, GIS technology enables workflow efficiency throughout the project cycle. GIS applications often include efficient file management functions that allow you to open and view the details of each project quickly and easily, providing an historic record of activity. External files, reports, or jobsite photographs can be linked to features on the map, allowing you to access additional details by clicking on the appropriate feature.
You can employ search functions to select specific points or features based on attribute information or their spatial relationship to other features. For example, a surveyor can quickly isolate collected data points that fall within a specified area and assign a unique attribute to each. Given the relatively low cost of certain GIS applications and increased efficiency that can be garnered through the effective deployment of this technology, surveyors can likely see a rapid return on investment due in large part to GIS software’s file- and project-management capabilities.
A fundamental function of a GIS is to provide a visual context to spatial datasets. Integration or importing of survey-derived data is a straightforward process regardless of the format or native projection system. Once imported, the display characteristics of the data can be modified or customized to help convey the inherent attribution or the spatial relationship between and among elements of the data. Survey data, when overlaid on a reference or base map layer such as recent aerial imagery, inherits a spatial perspective that would not otherwise be possible. The imported survey data can also be layered with other readily available datasets such as parcel or property ownership information, allowing the viewer to validate the accuracy and currency of the data.
Taking data visualization to the next level, many GIS applications offer tools for viewing the data in a 3D environment and for rendering survey data on a customizable terrain model. Using the Z value in this way can provide literally a new dimension to the representation of survey data.
Access to and Integration of Other Datasets
A GIS is commonly referred to as a communication tool. Communication in this context refers to the application’s ability to understand, read, and ultimately share data in a variety of formats that can be used on multiple platforms. Although some people argue in favor of focusing development efforts on proprietary formats, there is an increasing trend towards openness and interoperability.
As an example of this trend, GIS software can work with many different spatial file formats and can offer direct access to countless online sources of data through a web mapping service interface. Using a geographic rectification process, even non-geographic datasets or files can be given geographic intelligence and can be aligned and scaled to fit real-world coordinates. For the surveyor, a GIS can therefore act as a central repository and efficient storage archive for relevant project-specific data from multiple sources.
More than simply a viewing tool, a GIS allows data to be processed or converted in many different ways. This processing can take the form of geometric or attribute editing or manipulation. For instance, an array of points might be used to create a line feature or a polygon; features in a layer could be precisely shifted or offset in a particular bearing by a specified distance; or additional attribute fields could be generated based on a calculation applied to an existing field.
For many GIS users, data processing often entails a predetermined and recurring set of steps. For example, survey points might be imported, be re-projected, have attributes added, and ultimately be exported in a format stipulated by the client. For workflows like this, GIS software could automate the process through the creation of a simple script file that initiates the execution of several consecutive processing steps.
As well as allowing the import of preexisting data, most GIS software packages offer the option of digitizing or drawing features on the map. This process can involve simple heads-up drawing of points, lines, and polygon features or it can use more precise digitizing techniques. For example, COGO, or coordinate geometry input, can be used to precisely delineate a feature based on entering the dimensions of that feature. This allows the surveyor to accurately map boundaries by transposing information from the legal description of the property.
Although data analysis ranks nowhere near the top of the list of reasons why most surveyors use GIS technology, there are numerous easy-to-use analysis tools to derive useful information from geographically referenced data. Many of these analysis capabilities involve the use of elevation or terrain data. For example, by simply altering the display characteristics of a terrain layer, it is possible to discern elevation, slope angle, or slope direction, which can help in deciding the best project or construction site.
More advanced terrain analysis functions include view shed generation, in which the extent of the area visible from a specified point on or above ground level is determined. Surveyors often use this to map the optimal location for a communication tower. Watershed modeling is used to delineate the hydrological aspects of the terrain, and frequently surveyors analyze flood zones with it. Cut and fill calculation provides an accurate measure of the volume of displacement required to flatten the terrain at a specific height. Not long ago, these and other analysis functions would require powerful and expensive modeling tools, but they can now be performed using off-the-shelf software by surveyors with minimal experience or training.
Map Generation and Data Sharing
An essential feature of any GIS is the ability to share data or spatial information in a variety of formats. Often sharing entails simply printing a map or capturing the contents of the display as an image or geospatial PDF, but it can also mean publishing a map in a web-enabled format for distribution to a wider audience. For example, some GIS software can integrate with Google or Bing map tiles, allowing survey information to be overlaid on imagery or a base map in a familiar web interface. This map information could then be accessed through a web browser and be shared with the public or with a more limited audience.
For many surveyors, sharing or delivering data is synonymous with exporting or generating files in a client-specified format. With the wide array of possible software titles into which the exported data will be imported, it is essential that the GIS software offers the flexibility to generate files of a compatible type and provides the necessary options and parameters for customizing the structure of the data.
It is safe to say that GIS technology will probably never replace the tools currently used by the surveying community; however there is conclusive evidence that the two technologies can effectively work in tandem and can complement one another. Because a GIS by its simplest definition is a tool for managing data in its locational context, who better to vouch for the inherent value of accurate locational intelligence than the surveyor? GIS technology is no longer the sole domain of highly trained specialists, but, thanks to some affordable GIS software packages available on the market, it is truly within reach of everyone.
David McKittrick works as a senior application specialist at Blue Marble Geographics in Hallowell, Maine. A graduate of the University of Ulster in Northern Ireland, McKittrick has spent more than 20 years in the field of GIS and mapping, focusing on the application and implementation of spatial technology within a wide variety of industries and vertical markets.
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