Wetlands

Data Construction

Wetland mapping is created to the Wetlands Mapping Standard endorsed by the FGDC in 2009 (FGDC-STD-015-2009). As projects are completed, they are incorporated into the Montana Wetlands Framework. Data are also submitted to the U.S. Fish and Wildlife Service for inclusion in the National Wetlands Inventory (NWI). However, due to staff and funding reductions at the NWI, there can be a considerable time lag between when Montana data are delivered to the NWI and when they are incorporated into the NWI.

The dataset is provided in geodatabase versions 10 or 9.3. Data are downloaded at a statewide scale. New wetland and riparian features are added as individual project areas are completed.

Five full-time GIS Specialists/Photo Interpreters with Montana Natural Heritage Program create the dataset; between 80%-100% of their time is devoted to creation of the dataset. GIS Specialists use 1-meter resolution color-infrared aerial ortho-rectified imagery to develop photo signatures and interpret wetlands and riparian areas. Wetland and riparian mapping data are produced through on-screen digitizing performed at a mapping scale of 1:4,500. Ancillary data layers such as multiple imagery years, topographic maps, digital elevation models, and hydrography data are used to improve mapping accuracy.

Mapping is completed for U.S. Geological Survey 1:24,000 quadrangles. Once mapping is complete for an individual quadrangle, several verification checks are run to fix any errors in polygon attribution. Any topology errors are also fixed to eliminate overlapping polygons. Three rounds of internal quality assurance/quality control (QA/QC) procedures are conducted for each mapped quadrangle once the above steps are completed. The image analyst who mapped the quadrangle makes any necessary corrections based on comments made during each round of QA/QC. Once final edits are complete, verification checks are completed a second time. Mapping within the wetland and riparian layer is edge-matched with surrounding areas to produce a seamless layer.