Even if you aren’t familiar with the textbook concept of the Time-Cost-Quality triangle, you probably manage these concepts in your professional work each day. Many professional project managers use this concept to intentionally choose project biases and analyze the goals of a project. The concepts included here are useful to geospatial managers.
- Time = time to produce a deliverable is estimated.
- Cost = project cost: resources, labor and influencing factors that create cost variances.
- Quality = overall definition of what the project is supposed to accomplish, and a specific description of what the end result should be or accomplish.
It is important to maintain the three aspects of the triangle and to understand that these three project attributes are always in tension with each other. For example, quality can improve but it will drive cost up and require more time. The project could be done in less time, but cost may increase and quality may be negatively impacted. Properly managing the planning, expectations or risk factors not in your control helps keep these project factors in balance. Read this article and collaborate with your service provider to optimize these factors for your next project.
Other closely related concepts are “precision,” “accuracy,” and “resolution.” Many people continue to use the terms "precision" and "accuracy" interchangeably. This is bad. Precision and accuracy are very different concepts. "Resolution" is too-often confused with precision. We’ll explore these terms and learn how to tell the difference.
Time-Cost-Quality Considerations for Geospatial
A key point when considering your project requirements and cost is to understand your schedule tolerances. Knowing your hard deadlines and where you have some flexibility can add cost and make a project more difficult to complete and meet accuracy specifications.
An obvious example is leaf-on or leaf-off requirements for remote sensing operations which provide very little flexibility in the schedule. A project without these restrictions allows the provider to schedule their resources more effectively. Whatever your schedule restrictions may be, communicate them to your provider early. This way you get what you want and when you want it while providing the service provider a wider window for scheduling resources. In reality everyone knows everything is due “yesterday,” but the key point here is keep the service provider informed as much as possible. The more flexibility you can demonstrate, the more cost-effective options are possible.
Another big concern for most geospatial providers is when they do not have adequate time for project work to be completed. Such conditions often result in incomplete or poorly prepared deliverables. One month to six-weeks for a multi-disciplined project is a reasonable response window and should be an important consideration in any procurement plan.
Add Precision, Accuracy and Resolution Triangle
Geospatial projects include a few more components in addition to the time-cost-quality concept: precision, accuracy and resolution. What are these components and how can they affect the time-cost-quality triangle? Each of these factors will have an effect on cost, schedule, and quality.
Imagine a target with a bulls-eye with three arrows shot into it:
- Accuracy is “correctness,” i.e., how closely the shots are to the bulls-eye
- Precision is “repeatability,” i.e., how close together the shots are
- Resolution is “fitness,” i.e., how well you can see the target
It is important to understand the project specifications for these factors because there is a direct relationship between precision, accuracy and resolution and the associated cost of services. More accuracy, precision or resolution will reliably increase the cost of those services. Stakeholders need to carefully determine what their true “needs” are and not request too much of any of these factors or they will unnecessarily increase the project cost.
Accuracy is the conformity with “truth.” The target with three arrows in bulls-eye is accurate. Additionally, the confidence level of each shot (“measurement”) is high. Your professional services provider can help the stakeholders identify the optimum balance between accuracy, precision and resolution in the most cost-effective manner.
Precision is the repeatability of measurements, or how close together the shots are on the target. Its impact on cost and schedule is not as pronounced as accuracy.
Resolution is the “fitness” or how well something can be read. In aerial photography, it is known as ground sampling distance (GSD). LiDAR measures resolution as “density of points on the ground.” Resolution affects the image (or terrain) integrity and clarity? The same factors which affect accuracy also affect resolution. Resolution specifications (GSD and Point Density) will determine if the speed of remote sensing, the altitude of acquisition, the amount of ground control, file sizes, required computing power, etc.
Many Variables, One End Goal
In the life of a geospatial project there are many important concerns. However, knowing the intended use of the data and understanding these concepts will go a long way in helping you maximize your geospatial data investment and get the desired solutions.
Free Seminar Available for Download
In October, Aerial Services presented a webinar, “Key Points to Maximize Your Geospatial Data Project,” presented by Roy Hill. In it he said, "The consistent advancements in remote-sensing technology, such as LiDAR and orthoimagery, can create a confusing and intimidating discussion with your geospatial consultant. After leaving this session you’ll be equipped to help your geospatial consultant better understand what solutions to develop for your needs." You can download a recorded video of this presentation and a copy of the slides for free by visiting: http://aerialservicesinc.com/2013/10/key-points-to-maximize-your-geospatial-data-project-webinar-october-23-2013-video-slides-available/