Field Collection Using High Precision GPS – Introducing the Bad Elf

May 11, 2020 — Skye Perry

I had a recent opportunity to utilize some of the technology we implement every day in a real-life situation. And it went so well that I wanted to write about it! For those of you that do not know me well, I ride horses a lot and live down on some ranching property south of Denver. It’s a unique property because I share around 830 acres with nine other owners, and most of the land is deeded as a conservation easement, never to be developed. It’s a wonderful property teeming with wildlife, amazing riding, and scenic views. While this blog post isn’t specific to utility work, it absolutely does demonstrate how easily high-precision GPS gear can enable ANY GIS collection project!

The western boundary of our land borders a cattle ranch who has historically grazed their cattle on portions of our land. Years ago (many years before I moved here), the cattle ranch built a fence between our two properties but based to some extent on the contour of the land (and for other reasons of which I do NOT understand at all), they built the majority of the fence well within our property boundary. In fact, using GIS, I estimated they cordoned off approximately 86 acres of our property based on the fence line they installed. To be clear, these 86 acres are contiguous with their land and are fenced off from our land. In the below picture, the red line depicts the fence they installed whereas you can clearly see the 86 acres of land on the west that has been sectioned off:

This fence line has always been heavily discussed by our owners but was generally accepted because we were working successfully with the cattle ranch managers. In recent years, the relationship has become stressed and we are no longer allowing the cattle to graze our land. This works just fine for the land on the east side of the fence (red line) but as you might imagine, the cattle still graze all the time on the western side of the fence because it’s connected to the cattle ranch land!

In researching the legal implications of this, we were advised that we needed to consider “adverse possession” which is a legality that could allow the cattle ranch to claim that they legally own those 86 acres because they have continually used them over the years. With that in mind, we decided that we needed to add another fence that was on or much closer to the actual current legal boundary to protect our continued ownership and use of those 86 acres.

Since I work in GIS, I naturally volunteered to help with this issue! The goal was to use the county-maintained parcel data to establish an accurate survey of the land to put in a new fence. To accomplish this, I first went to the Douglas County, CO GIS website and was able to get to the Esri parcel data as either a downloadable file geodatabase or as a web service.

I added the parcel data to a new web map within ArcGIS Online with just a few clicks. The next challenge was that I wanted to accurately locate the parcel boundary on our land via stakes. I first considered using my iPhone GPS, but as most of you know, the accuracy of the iPhone GPS leaves much to be desired (10 meters / 32 feet is the general guideline). It’s great and easy to use for driving directions but not, perhaps, so much for ensuring that our new fence is installed in the right location. If we happened to be 32 ft off, that could certainly become an issue

Now, in the utility GIS world, we often need to collect very accurate GPS-related data in the field (ex. gas valves to support tracking and traceability requirements). And when I am asked for recommendations on how to improve iOS or Android accuracy, I often turn to an Esri-recommended GPS partner, Bad Elf. To be fair, I have never met the Bad Elf folks, but because Esri stands behind them, so have I (and they have a pretty cool and memorable name too). I checked out their GPS devices and settled on the Bad Elf GNSS Surveyor unit because it boasts 1 meter / ~3-foot accuracy as well as easy integration with iOS and Collector for ArcGIS. I was excited to try it out both to solve our fencing problem but also so that I could speak (and write) more intelligently about the Bad Elf solution I had been recommending for years.

As I refined my requirements, they really became two-fold. First, I needed to accurately place stakes in the ground matching the county parcel boundary for our property, and second, I wanted to collect the exact GPS location of each stake that I placed. The Bad Elf was intended to help with both of these tasks. I opted to use a Bad Elf pole mount kit as well (see pictures below) that allowed me to keep the GPS mounted at a fixed distance above the ground while also holding my phone in an easy to view location.

Before I could set off to begin the work, I had to create Esri feature services to capture the GPS stake locations. Bad Elf’s VP of Marketing and Business Development, Larry Fox, was kind enough to send over a PowerPoint presentation walking me through the capabilities of the Bad Elf unit along with steps to create a feature service that could capture all the possible GPS-related fields. I then opted to use ArcGIS Pro to create the feature service templates before publishing them to ArcGIS Online. I began by creating a simple point feature class called “Stake” using the standard WGS 1984 (Web Mercator) spatial reference:

Next,  used a handy out-of-the-box geoprocessing tool to add all the standard GPS-related fields to the new feature class, aptly named “Add GPS Metadata Fields”:

This added the following attributes which encompassed everything I could imagine I would need to capture:

I then created this in a standard file geodatabase and then published it to ArcGIS Online with editing enabled to a new service called WebBoundaryStakes (the name of my Pro project) and then added this feature service to the web map along with the parcel boundaries:

My final pre-operational step was to get the Bad Elf unit configured with my iPhone. I simply paired it with the phone via Bluetooth and then configured Collector to use the external GPS directly within the Collector app including setting the height of the GPS antenna (based on using the pole mount) via the main Settings option. It truly could not have been any easier:

I was finally ready to head into the field to start staking! Ahead of time, my youngest daughter painted the tops of the stakes using orange marking paint to make them more visible. I loaded the stakes onto my ATV along with lunch and few other essentials including my girlfriend, Jessica, who volunteered to open gates along the way and to the hammer the stakes while I operated Collector and the Bad Elf.

It was an overcast Saturday morning and I initially wondered how accurate the Bad Elf would be under the conditions. I was quite pleasantly surprised to see that my accuracy improved from 32.8 ft to 3 ft when initially switching from the iOS integrated receiver to the Bad Elf (as shown in the bottom right of the below screenshots) and the accuracy only went up (or rather down… below 3 ft) from there!

We spent the next 4-5 hours working our way along the western boundary of the property. I would first zoom in on the map and align the location of the pole mount to the parcel boundary. Then I would gather a new Stake feature using the standard Collector functionality and Collector was smart enough to auto-populate all of the above-mentioned attributes! Jessica would then hammer in a stake at the exact location. Of particular note, this process led us to every surveying stake that had been placed at the vertexes of our property line, so I feel very confident in the accuracy of the solution.

We placed 56 stakes across quite a bit of varied terrain. This including climbing through tons of scrub oak, up and down hills, and even a few other fences. Though the going was tough, we placed the stakes more densely where the terrain was more challenging to allow you to find the next stake easily without going too far. Overall, we got the job done and the technology was by far the easiest part of the project.

I then created a quick Esri web application to allow the other owners to see the staking locations. They will take the next steps with the fencing contractor to begin the next phase of the project using the stakes. I added the location functionality to the web app to easily allow anyone to match their location from their mobile device to the staking locations on the map (helpful for the other owners and/or future fencing contractors):

I also downloaded the feature service data into an Excel spreadsheet for easy sharing and access. You can see just how good the horizontal accuracy was of the points we collected (I converted the meters to feet) which improved as I had the GPS unit powered on longer during the day. 2 ft or better in many cases!

And lastly, I created a quick video to promote this blog post which also belongs in the blog post itself. This was a fantastic use of a blend of technology to achieve quick and effective results. I would heavily recommend the use of the Bad Elf GPS systems and of course Esri GIS. They’re a great combo and easy to use together! SSP also recommends Bad Elf products for use with our SSP MIMS field product for exactly the same reason.  Whether for staking out property boundaries or capturing the location of your critical utility assets, this solution won’t let you down.

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One comment

  • Linda A Grosskopf says:

    Marvelous use of great technology to solve real-life problem! PS Not all ranchers are pesky, and Not all ranchers fudge the fence lines.

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