Northern Ireland’s Strangford Lough is the largest, most ecologically diverse inlet in the British Isles. But an invasive grass species called Spartina anglica is threatening the region and potentially impacting feeding habitats for thousands of wildfowl and waders. One survey company precisely mapped Spartina’s reach, enabling authorities to develop a mitigation plan to help preserve the Lough.
Any hope for mitigating Spartina’s spread starts with having a precise picture of its prevalence – something the National Trust and the Northern Ireland Environment Agency, who co-manage the area, didn’t have.
To remedy this, the organizations turned to HeritageNI, a drone and mapping company based in Northern Ireland. Its task was to map the distribution of Spartina along the lough’s more than 150 kilometers of intertidal area.
HeritageNI originally planned to conduct the survey via drone, which had the necessary resolution to capture the spectral signature of Spartina’s specific shade of green. The problem, however, was that the technique struggled to identify Spartina when it decays and becomes brown. This meant that using drone imagery alone, HeritageNI would have missed the very small, single outbreaks happening in the middle of this natural salt marsh.
As a result, it was decided very early on that the trained eye was the best method for identifying all Spartina outbreaks. But that meant heading out on foot. And in a region notorious for short days, cold winters, lots of rain, varying tides, and hundreds of kilometers of challenging terrain – this would be no easy feat.
Needing a versatile surveying solution that was light to transport, easy to use, and capable of providing the precise level of accuracy the project required, HeritageNI opted for Trimble's Catalyst solution.
Trimble Catalyst is a subscription-based GNSS solution offering professional-grade positioning as an on-demand service. Its easy-to-use, lightweight, plug-and-play USB antenna, and smartphone compatibility, made the Catalyst particularly convenient for visually inspecting the shoreline on foot.
HeritageNI founder David Craig registered more than 30,000 GNSS data points along the lough’s 150 km of shoreline—using Catalyst for the clumps along the perimeter identified by eye and by drone for the larger swaths located in salt marsh areas.
After entering the collected GNSS data points into the previously installed Trimble UAV Ground Control app, Craig sent the data by email as a CSV attachment and then imported it as a layer in Quantum GIS (QGIS). Next, the points were hand digitized on a separate overlaid polygon shapefile layer. The polygon points in the CSV file were then removed and the remaining points merged into a global shapefile layer containing just single points.
The resulting dataset contained two shapefiles, one with points representing single plants or small clumps less than 0.5m2 and the other with polygons of the larger clumps. The area of these clumps is automatically calculated and stored in the attribute layer of the shapefile.
The data files were then turned over to the National Trust and the Northern Ireland Environment Agency. “Having a very accurate picture of nearly every occurrence of Spartina in the lough means these organizations can prioritize their mitigation efforts and, hopefully, preserve this important habitat for generations to come,” said Craig.
As Mother Nature can be a formidable foe, this multi-pronged technology approach may have planted an effective way to weed out a natural threat.