The Whole Ground Truth
A Typical Day in the Field
Grab your partner, gear, GPS, maps, notes, camera, and compass. Don’t forget your lunch. Now, hike for miles through forests and across lava fields. Reapply sunscreen. Try to navigate to the very center of a pre-selected 90 square meters circle. Record the plants you see (e.g. 40% of the circle is koa trees, 32% is pūkiawe, 18% is molasses grass, the rest is bare lava). Later, check to see if what you found matches what the professional mappers thought was in that circle. Take more notes, then adjust the vegetation map if needed.
Locate and go to the next circle. Repeat over 2,000 more times.
That’s accuracy assessment (AA) for the vegetation mapping inventory.
What is a Vegetation Map ?
The maps are snap-shots in time of the land cover (e.g. plants, buildings, lava) in a park. Developing a vegetation map is an extensive process which integrates field data, vegetation classification (e.g. area “X” is a koa/pūkiawe woodland), expert park knowledge, spatial analysis, and complex computer models. The layering of all this information leads to a map of the land cover across a park landscape. Vegetation maps are important tools to assist resource managers, and they provide comprehensive data for future research.
Remind Me What Accuracy Assessment is Again ?
The final stages of field work for vegetation mapping requires rapid physical assessments across the parks’ landscapes to test the accuracy of the maps (known as accuracy assessment or AA). You may have heard it referred to as “ground-truthing”.
At each Pacific Island Network (PACN) park, scores or hundreds of sites are visited by field crews. Armed with dichotomous keys and descriptions of the parks’ vegetation communities, field crews hike far and wide to gather real, on-the-ground data to compare against the current vegetation maps. Afterwards, the accuracy assessment data is analyzed by the mappers (Kass Green & Associates) to determine how accurate the map is. This process helps to ensure that the best possible vegetation maps of the parks are born.
Accuracy assessment field work is extensive and requires help from many hands. Field crews are based at several parks. However, due to the substantial number of AA sites and the vast landscapes involved, a broadly collaborative effort is required to meet our goals. For instance, at Hawaiʻi Volcanoes National Park (HAVO), two (of three) field crew leaders are cooperating employees from the Research Corporation of the University of Hawaiʻi (RCUH). The HAVO team receives additional help from NPS Volunteers, NPS field crews from other parks, and HAVO Resource Management staff. Even PACN office employees get an occasional opportunity to get out in the wild and help the field teams. In total, for just the HAVO vegetation map inventory, at least 17 people have been involved in some aspect of the project.
The Assessment Continues
The vegetation mapping crew has completed accuracy assessment field work in several parks, however, final maps are still works-in-progress for most parks. Accuracy assessment is underway at HAVO, and field work will begin in November, 2013 at Haleakalā National Park.
–Meagan Selvig, RCUH
–Kathryn Akamine, RCUH