Closer Look at the Layers List

Summary of Map Layers

Purpose: provides visual and geographical context for overlaid map layers at various scales.

Basemap Layers (Top section)

The National Map Base Layer:

• Vector-based map without imagery
• Displays, geographic names, boundaries, transportation, contours, hydrography, land cover, shaded relief, and bathymetry
• Covers the U.S. and territories
• Useful as a reference layer for identifying road and highway names, cities, counties, and the names of natural and human-made features  

Media

Sources/Usage: Public Domain. View Media Details

The National Map Imagery:

• Combines NAIP aerial photos (Continental United States) with High Resolution Orthoimagery and Maxar Technologies (Alaska, PR, HI)
• Resolution ranges from 6 inches to 1 meter
• Geometrically corrected to remove terrain and camera system distortions with map-level accuracy
• The preferred layer for ensuring correct symbol placement on buildings or within cemetery grounds

Media

Sources/Usage: Public Domain. View Media Details

The National Map + Aerial Imagery:

• Combines the first two map layers to provide visual and contextual information in one view with the spatial accuracy and reliability of a planimetric map
• Useful for assessing objects, patterns and nearby associative features to assist with feature collection

Media

Sources/Usage: Public Domain. View Media Details

Esri Imagery:

• Provides 1m or better satellite imagery and aerial imagery in many parts of the world and lower resolution satellite imagery worldwide
• Features high-resolution aerial photography from the GIS user community
• Useful for zooming in on building footprints or distinguishing boundaries for cemeteries in combination with NAIP imagery for proper point placement
• Citations can be accessed in the World Imagery with Metadata web map

Media

Sources/Usage: Public Domain. View Media Details

NAIP Imagery

• Combines NAIP aerial photos (Continental United States) with High Resolution Orthoimagery, and Maxar Technologies (Alaska, PR, HI)
• Primarily 0.6 meter resolution 4-band imagery presented in natural color
• Geometrically corrected to remove terrain and camera system distortions with map-level accuracy
• Useful for confirming the correct location of a point and final symbol placement  

Media

Sources/Usage: Public Domain. View Media Details

Summary of Map Overlays

Purpose: Map layer overlays add National Map features representing types of spatial information to the base layer; each can be toggled on/off and adjusted for transparency. 

Overlay Layers (Bottom section)

Structures:

• The National Map data which comprises the National Structures Dataset (NSD) and is editable via TNMCorps
• Point features representing locations, names, and details of structures (human-made facilities) across the U.S. and territories (e.g., Fire Stations, Schools, and Cemeteries)
• Useful for viewing existing data to ensure you’re not creating duplicate points, or toggling various structures on or off to narrow down a visual search

Media

Sources/Usage: Public Domain. View Media Details

Boundaries:

• Displays vector boundaries of states and counties
• Useful for researching cemeteries by county on Find A Grave or looking for parcel information

Media

Sources/Usage: Public Domain. View Media Details

Quad Index:

• Displays USGS quadrangle map grid, with names and publication years of maps
• In combination with topoView, search by quad name to access the historical topographic map collection to see landscape change over time
• Useful when editing cemeteries to identify existence/name on older maps

Media

Sources/Usage: Public Domain. View Media Details

USA Federal Lands:

• Shows location of U.S. federal lands for Bureau of Land Management, U.S. Fish & Wildlife Service, U.S. Forest Service, and National Park Service
• Legend available for different features within this overlay by agency by color
• Useful for identifying campgrounds, trailheads, and visitor centers located on restricted areas - federal public lands on which TNMCorps volunteers are not permitted to edit

Media

Sources/Usage: Public Domain. View Media Details

Historical Topo:

• A digital repository of maps printed between 1884 (the inception of the topographic mapping program) and 2006 at various scales
• A snapshot of physical and cultural features from a particular time
• Useful when editing cemeteries to see if the cemetery location and name were shown on an older map
• Maps available through the The National Map Downloader and via the topoView application

Media

Sources/Usage: Public Domain. View Media Details