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Maps - References

i-Tree Landscape offers users a wide variety of data and map layers.

More information can be found in the Landscape section of the i-Tree Tools Archives.

The references are grouped in separate pages.

Maps Layer Metadata

Boundaries

US Census Block Groups
Administrative boundary data displaying the 2010 block group boundaries. Block groups are clusters of blocks within the same census tract. Block groups generally contain between 600 and 3,000 people.
US Census Places
Administrative boundary data displaying the 2010 place boundaries. Places include both incorporated places and census designated places. Incorporated places are established for the provision of services for a concentration of places, whereas census designated places are not legally incorporated under state laws.
US County Subdivisions
Administrative boundary data displaying the 2010 county subdivision boundaries. County subdivisions are the primary divisions of counties and their equivalent entities for the reporting of census data. They include census county divisions, census subareas, minor civil divisions, and unorganized territories. Different states maintain different types of subdivisions, and these boundaries include boroughs and townships where they are present. (Source)
US Counties
Administrative boundary data displaying the 2010 county boundaries. Counties and county equivalents are the primary legal divisions of most U.S. states.
US States
Administrative boundary data displaying the 2010 state boundaries.
USGS Watersheds
Depicts the geographic division of the United States into hydrologic units based on watershed boundaries. These divisions are sixth-level classifications identified by a 12-digit unique hydrologic unit code (HUC). Watershed boundaries have been updates to incorporate the NDHPlus v2 dataset. (Source)
USDA FS National Forests
A depiction of the boundary that encompasses a National Forest.
USDA FS Ranger Districts
A depiction of the boundary that encompasses a Ranger District.
US Federal Lands
Depicts the boundaries for lands owned and administered by agencies of the US federal government as distributed through The National Map. Categories (and related sub-categories) are provided for administrative agencies that control 1 million acres or more. Although this layer contains National Forests, these boundaries do not align with the USDA FS National Forests or Ranger District boundaries since they come from different sources.

Canopy & Land

Tree Canopy
Tree cover estimates are derived directly from 2011 National Land Cover Data (NLCD) or 2001 NLCD data in Alaska, Hawaii and Puerto Rico (as 2011 data are not available). These data estimate percent tree cover using satellite data with a 30 meter resolution (www.mrlc.gov). For areas where high resolution land cover data are available, that dataset will be displayed by default.
Plantable Space
Available planting space estimates are derived from National Land Cover Data (NLCD) where plantable space = land area - (canopy + impervious).
Total Basal Area
Forest Basal Area describes the extent to which an area is occupied by trees by estimating the relative size and density of tree trunks. Basal area is usually expressed in square feet per acre (ft2/acre), and can act as an indicator of forest volume and growth. No data means Basal Area was not measured at that location. The data can be found at the USDA FS Remote Sensing & Image Analysis site.
Forest Type
The FIA (Forest Inventory and Analysis) Forest Type data shows the extent, distribution, and composition (species type/group) of forested areas in the United States. The data can be found at the USDA FS FIA page National Forest Type Dataset.
Urban National Forests
A depiction of National Forest boundaries where one million or more people live within 50 miles. (Source)
Impervious
Impervious cover estimates are derived directly from 2011 National Land Cover Data (NLCD) or 2001 NLCD data in Hawaii and Puerto Rico (as 2011 data are not available). These data estimate percent impervious cover using satellite data with a 30 meter resolution (www.mrlc.gov). For areas where high resolution land cover data are available, that dataset will be displayed by default.
Land Cover
2011 and 2001 National Land Cover Database (NLCD) provides a synoptic nationwide classification of land cover into 16 classes at a spatial resolution of 30 meters.
Forest Type Groups
The USDA FS Forest Inventory and Analysis (FIA) Program's National Forest Type Dataset shows the extent, distribution, and forest type composition of the nation's forests.

Homer, C.G.; Dewitz, J.A.; Yang, L.; Jin, S.; Danielson, P.; Xian, G.; Coulston, J.; Herold, N.D.; Wickham, J.D.; Megown, K., 2015, Completion of the 2011 National Land Cover Database for the conterminous United States – Representing a decade of land cover change information. Photogrammetric Engineering and Remote Sensing. 81 (5): 345-354.

Forest Risk

Wildfire Potential
A map classified by the relative potential for wildfire that would be difficult for suppression resources to contain. The intended use of this layer is to help inform evaluations of wildfire risk or prioritization of fuels management needs across large spatial scales. This map layer was derived by the U.S. Forest Service by classifying the Wildfire Hazard Potential (WHP) continuous dataset values. The process entailed converting the WHP values to integers, evaluating the statistical distribution of WHP values and then classifying them into fire classes: very high, high, moderate, low, very low. WHP ranges for each class are unknown. The non-burnable and water values were incorporated from the LANDFIRE FBFM40 layer to produce the final classified WFP. (source)
Wildland Urban Interface
Documentation coming soon.
Hardiness
Hardiness zones are based on the average annual extreme minimum temperature during a 30-year period. The zones can be used to determine the threshold at which certain plantings can thrive. The dataset is available here: http://planthardiness.ars.usda.gov.
Riparian Zones
A Riparian Zone is an area within 108 meters around the edges of surface waters.  These corridors can help guide ecological and stream channel stability efforts, improving habitat for fish and protecting stream banks against erosion and gouging. In the data tables for area selections, values record both the area (in square meters) and the percentage of a given boundary that is classified as riparian. (Source)
Floodplains
Floodplains are the land areas adjacent to rivers and streams where the overflow is displaced during flooding. Floodplains provide several important ecosystem services. They store water during storm events, thereby reducing flooding in downstream communities. In addition, floodplains are high in biodiversity and are among the most species-rich environments, and they provide opportunities for recreation and ecotourism. In the data tables for area selections, the values record both the area (in square meters) and the percentage of a given boundary that is classified as floodplain. (Source)
Drought Severity Index

A measurement of the frequency and intensity across forest and rangelands in the U.S. Data is based on cumulative trends from 1987 - 2013; earlier information can be viewed here. Index values are from 0-250+, classified as follows:

  • < 50 (limited)
  • 51 - 100
  • 101 - 150
  • 151 - 200
  • 201 - 250
  • > 250 (chronic)
Disease - Forest Pests
Determined by whether the range of known pests appears within the boundary of a location area or not. Pest range maps are derived from the Forest Health Technology Enterprise Team (FHTET) and can be viewed at the Insect and Disease Detection Survey Data Explorer.
Insect - Forest Pests
Determined by whether the range of known pests appears within the boundary of a location area or not. Pest range maps are derived from the Forest Health Technology Enterprise Team (FHTET) and can be viewed at the Insect and Disease Detection Survey Data Explorer.

Health Risk

Street Walkability Index

A measurement of characteristics in the built environment that influence the likelihood of walking being used as a mode of travel. The higher the index value, the more likely people will walk in that area. The Index ranks each Census block group based on factors including the densities of street intersections, housing populations, and employment opportunities. (Source)

  • Walkability Legend Key
    • 1 – 5.0 (Least Walkable) - Orange
    • 5.1 – 10.0 (Below Average Walkable) - Yellow
    • 10.1 – 15.0 (Above Average Walkable) - Light Green
    • 15.1 – 20.0 (Most Walkable) - Green
EPA Impaired Waterways
Lines representing EPA-designated impaired waterways (including rivers, lakes, and estuaries) under Section 303(d) of the Clean Water Act, which established guidelines for the maximum amount of specified pollutants allowed in a waterbody, and serves as the starting point or planning tool for restoring water quality. The impaired waterways are a subset of the NHDPlus V2.1 medium resolution flowlines. (Sourece)
UV Index
Ultraviolet (UV) index values displayed as the average UV index at solar noon for all days between 2008 and 2012 and the maximum UV index at solar noon for all days between 2008 and 2012. The UV index scale was developed by the World Health Organization to more easily communicate daily levels of UV radiation and alert people to when protection from overexposure is needed most. (source)
Air Quality
Pollution concentrations are estimated for ozone (O3) and particulate matter less than 2.5 microns (PM2.5) and derived from the U.S. Environmental Protection Agency’s (EPA) Downscaler Model. Average and maximum values are estimated from the pollution concentration for all days in 2008. (source)
EPA Non-Attainment Areas

Indicates whether an area has received a status of Non-Attainment from the Environmental Protection Agency with respect to air quality standards for the following pollutants:

  • 8-Hour Ozone (2008 Standard)
  • PM2.5 (2012 Standard)
  • Sulfur Dioxide (2010 Standard)
  • Carbon Monoxide (1971 Standard)
  • PM10 (1987 Standard)
  • Nitrogen Dioxide (1971 Standard)

Information regarding standards and non-attainment evaluations can be found here: https://www.epa.gov/green-book.

Climate

Land Surface Temperature
Determining the difference between localized surface temperatures and regional mean temperatures can help qualify the impacts of land use. Generally speaking, areas with more impervious surface tend to be warmer than average, while areas with more canopy cover tend to be cooler than average. Land Surface Temperature data is derived from Landsat-8 Thermal Infrared Sensor Data. Temperature values are the difference from the median surface temperature for each Landsat scene available through landsat.usgs. Temperature differences were estimated for the United States based on data and standard procedures from the literature as described in the Data Land Surface Temperature section.

Base Maps

Google Streets
Street map provided by Google Maps.
Google Aerial
Aerial imagery provided by Google Maps.
Open Street Map
Street map provided by Open Street Map.
White Canvas
White base layer with no map data.
Black Canvas
Black base layer with no map data.

Publications

"Understanding i-Tree: 2021 Summary of Programs and Methods" https://www.fs.usda.gov/nrs/pubs/gtr/gtr_nrs200-2021.pdf (self-hosted copy).