Chapter 3 Thermal Imagery Data
Figure 3.1: Example of airborne thermal infrared imagery showing temperature contrast in a stream. A cold water inflow (purple and blue colors) enters the main channel (yellow color). Figure from NV5 Geospatial consultants report.
3.0.1 Introduction
On July 5, 2020, NV5 Geospatial collected thermal infrared imagery from a helicopter-mounted camera for four steams on the Kenai Peninsula in southern Alaska. These streams included:
Kenai River Tributaries
Beaver Creek
Funny River
Moose River
Kasilof River Tributary
- Crooked Creek
All streams were flown during the afternoon hours in order to maximize the thermal contrast between the river’s water and the banks.
The surveys extend for a total length of 59.1 km of the streams, covering upstream extents from their outlets at the Kenai or Kasilof rivers. The data were collected to aid the team in identifying the spatial variability in surface temperatures as well as thermal influence of point sources, tributaries, and surface springs.
Specific deliverables generated by NV5 Geospatial from the thermal imagery data include:
Rasters (map image files; .tif and .jpg formats)
Shapefiles (longitudinal temperature profiles, stream centerlines, others; .shp format)
Other supplemental items (coordinates of significant thermal features, maps and figures, and others)
The full technical report from NV5 Geospatial describing detailed methods and interpretation can be accessed at the following link:
The image raster files are of a large size (~3 GB) and may be acquired by contacting staff at Cook Inletkeeper, Kenai Watershed Forum, or Kachemak Heritage Land Trust.
3.0.2 Parcel data summary
We generated a table in GIS (ArcMap Pro 10.8.1) of parcels in the Kenai Peninsula Borough that intersect with cold-water inputs (e.g. seeps, springs) within the surveyed areas of Beaver Creek, Crooked Creek, Moose River, and Funny River.
Figure 3.2 summarizes the ownership type of these parcels by general category of owner type.
Figure 3.2: Parcel ownership
3.0.3 Ground truth data
On July 7-8, 2021 we visited a subset of sites containing significant thermal features identified in the NV5 Geospatial Consultants report. We visited 12 of 63 total sites. We recorded water temperatures of identified features as well as the main stem using a using a Hach Sension 5 portable meter. We sketched the layout of the feature, and took site photos.
Field forms, including site sketches, can be accessed at the following link: Thermal Imagery Ground Truthing Field Forms.
Figure 3.3 visualizes water temperature data sourced from the significant features in aerial imagery on July 20, 2020 alongside ground-truthed measurements from July 7-8, 2021.
Figure 3.3: Thermal imagery ground truthing data. ‘GT’ indicates data is sourced from ground truthing; ‘TIR’ indicates data is sourced from aerial thermal imagery
3.0.4 Collaborative Assessment
Researchers with participating organizations used data from several sources to assess conservation strategies within each study watershed, and recorded their notes on a shared platform. These collective notes are being used internally to inform strategy for outreach approaches with local property owners.
Data sources used to assess parcel-specific conservation strategies include:
Custom maps for each significant thermal feature, including information about the parcel or parcels that it occupies
Information about individual thermal features from the NV5 Geospatial Consultants Report, including mean value and contrast with the main stem
Project collaborators may access the Thermal Imagery Database Google Sheet using the link below:
Link: Thermal Imagery Collaborative Assessment
An example map is shown in figure 3.4.
Figure 3.4: Example of airborne thermal infrared imagery map with parcel overlay