Best Practices for a Data Collection Event Using a GPS Unit
I have been a part of three different data collection efforts that collected line geometry and infrastructure of recreational trails. One effort was the development of the Fish and Wildlife Services (FWS) Trails Inventory Program. This effort involved collecting trails data in FWS national wildlife refuges across the United States. The second was an effort to collect trails data on all of the recreational trails at Haleakala National Park in Hawaii. This effort was based upon the FWS trails data collection with a few minor changes to how the data was collected. In the third effort I was responsible for taking the data to its final state and for training field staff employed by the Student Conservation Association.
Based on these experiences, I have come to understand that the keys to a successful data collection effort lie in:
- Flexibility, and
- Very clear goals of what is to be accomplished.
The lines of communication need to be open and clear throughout the entire life cycle of the project from the managers in the planning phase down to the field crew actually collecting the data.
Early on, a series of meetings should be scheduled with all of the stakeholders to lay out what the ultimate goals for the data will be and a game plan for reaching those goals. Normally a lot of data will be generated during these efforts and it should be very clear from the beginning the purpose of the data. Will it be used for map making, or long range planning? Usually this question is driven by a need within an organization and will be known up front. Other possible uses for the data may be found during the planning process. In the efforts I worked, the data was primarily used for planning and budgetary purposes, but it was also used for maintenance scheduling and recreational map making.
The uses of the data will usually drive what kinds of data will be collected. You don’t want to be wasting time and money with unnecessary and irrelevant data. These efforts are very expensive and time consuming. The field crew has enough to worry about without collecting attributes and data that won’t be used after they enter it into their GPS unit. And they will know fairly quickly what will be useful and what will not.
Defining Team Roles
The initial planning phases of the effort are a good time to define and document the roles for each participant. Most likely this will be very clearly spelled out in any contracts that are signed between the stakeholders.
Determining Data Collection Methods
After the initial brainstorming sessions have produced set goals and a purpose for the data, it’s time to determine how the data will be collected. There are a lot of questions to be answered in this phase but in my opinion the most important deal with hardware, software, and data schema. Hardware, specifically the GPS unit, is a good place to start.
There are a variety of GPS units that can do any number of different jobs. You can buy a GPS unit to keep track of the progress of construction projects, or a GPS unit that will help ski resorts keep track of their snow making and grooming operations.
GPS units typically come in 3 different varieties:
- Recreational receivers: the least expensive ($100 – $600) and least accurate GPS units. They are usually accurate to about +/- 25 feet and used by the general public during their outdoor activities.
- Mapping grade receivers: Significantly more expensive $1000 – $6000 and much more accurate. Some of the higher end units can log data that is +/- 3 feet or sub-meter. Usually used by government agencies, researchers, or others that need more accurate geographic data.
- Survey grade receivers: The most expensive ($10,000+) and the most accurate receivers. They can collect data that is of sub-centimeter accuracy. These types of units are most often used by professional surveyors.
Your ultimate goal for the data will determine which unit you choose. There is a fairly wide variety of styles and accuracies of GPS units on the market. It’s really important that you choose the correct piece of hardware for the job. For any kind of data collection effort, I would not recommend using any kind of recreational GPS units. As stated above they are not accurate enough and the interface doesn’t always allow for entering attributes in the field. I have worked exclusively with Trimble GPS units that are of the mapping grade variety.
The software you will use for tasks such as running the unit and post processing are also an important consideration when planning a data collection effort. There are a few software products out on the market that you can use and most are compatible with the majority of the popular GPS units. I have used TerraSync , Pathfinder and ArcPad software with the Trimble GeoXH GPS unit. All of these software packages can provide extensions that allow for post processing the data to improve its accuracy. Each will have pros and cons, but if you plan on using ESRI software to manage the data in the office I would recommend using ArcPad to collect and post process the data.
Once you have chosen your GPS hardware and software, it’s time to create the schema for the data. If the effort includes collecting many types of the same data, say lots of different types of trees, types of roads, or feature points that are captured on a regular basis, I recommend the use of drop down menus if using Pathfinder or domains if using a geodatabase, to aid in the data collection. I recommend using a combination of domains and fields to manually enter the data. This provides a good balance of efficiency in collecting commonly found data and the need for entering unique attributes.
Once the hardware and software have been purchased, installed and all working together, the field crew has been assembled, it’s time to roll up your sleeves and get training. This is a great phase because you can potentially learn new skills and explore new pieces of hardware. In my experience I’ve always had the best luck with training programs that mimic what you will be doing in the field. I also think a great way to become proficient and nimble with this vital tool is to play around with the GPS units until the software crashes and you figure out what you did wrong and how to fix it.
When planning the training sessions it is critical to set a goal of getting the field crew comfortable and confident using the tools in a setting that most effectively replicates the actual field conditions. I like taking a few training trips with the field crew to accomplish this goal. I like to take one or two trips without the GPS unit to get the field crew’s head wrapped around what they will be collecting and help them learn how to make subjective decisions like the condition of the road or trail. Training trips without the GPS unit, greatly benefits crews with little to no experience with a GPS unit.
If you’re collecting data for road and associated infrastructure, get the crew in a car to look at the road as they would in the field. Have them take any measurements on culverts, bridges or any other features that will need to be measured. This is a great time to start the list of other equipment they will need in the field. You will probably have a fairly good handle of obvious things like tape measures, roll-a-wheels pens, paper, flash drives, cables, and antennas. But, if you have to collect in inclement weather, how will you do that? Is there a form you can create for items that you have to write down? These are great questions to find answers for before you head out into the field for real.
After the field crew knows the type of geographic data they will collect and their associated attributes, give them a piece of hardware and new software to learn. As stated above I feel crews with no prior GPS experience benefit from splitting the training into two phases. If the crews are thrown into a training where they have to learn both the qualitative and technological aspects of the field work usually the technology piece will win out and most of their attention will be focused on the learning how to run the GPS unit and not what it is they are actually looking at on the ground.
I realize this is the best case scenario when time and budgets are not in short supply, so if the crew is learning both at the same time, it’s critical that those running the training have a proficient working knowledge of how the GPS unit works and that as many bugs as possible have been resolved so time isn’t wasted trying getting up to speed. Having a smooth process will instill professionalism a sense of competent leadership among the staff.
It’s important to give the staff a chance to make mistakes and find solutions without the pressure of actually being in the field. Sending the staff into the field with confidence will improve the quality of the data collection. This doesn’t mean that the first one or two field collection trips won’t generate new and unforeseen questions and mistakes. But overcoming those will be easier and done with less down time.
One other benefit to training the field crew in a real world type scenario is the data schema can be tested and any changes that need to be made can be so everything is ready for prime time. It is much easier to tweak a data schema, data dictionary, or geodatabase domain before real data comes in and the data has to be altered to fit into the new schema.
The next training suggestion I have, realistically, can only happen during a second or third cycle of a data collection effort. It’s fine to tell a crew to do things a certain way, but in my experience, to have it really sink in you need to show them why it needs to be a certain way. Can you show the crew what happened when shortcuts were taken and the data didn’t get cleaned up to the appropriate standards? What about when the QC process didn’t catch every single mistake? Can you show them a report or generate tables that are populated with bad data? These images are pretty powerful in setting an expectation of high data quality.
Now that the all of the foreseeable kinks have been worked out, and a plan in place it’s now time to head out into the field. Planning for each trip is very important, especially when each trip is to a different geographic location. Weather should be one of the first things to plan for, especially if the field crew will be tromping around outside. Locate a hospital or 24 emergency care facility that’s close to where you’ll be collecting data. Lodging, airfare, and car rental should be planned for within the budget. If there is a need for overnight stay the distance between the areas where the data is being collected and where the crew stays should also be a factor.
For example, if the crew needs to drive an hour each way to the data collection site, that’s time that isn’t being spent collecting data.
Communication between all of the stake holders during the field data collection is also important. Regular check-ins to discuss how the data collection is going is valuable and doesn’t necessarily have to be a formal meeting. Emails and phone calls can save time as long nothing significant is being decided.
GPS unit types http://www.extension.org/pages/40145/what-is-the-difference-between-a-recreational-grade-gps-a-mapping-grade-gps-and-a-survey-grade-gps
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