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Dataset Names: San Mateo County Impervious Surfaces 

Version: 2/10/2021 

Download Location: ArcGIS Online (see table 1 below) 

Credits: Golden Gate National Parks Conservancy, University of Vermont Spatial Analysis Lab, Tukman Geospatial LLC, Santa Cruz Mountains Stewardship Network, Midpeninsula Open Space District, CAL FIRE, San Mateo County Parks, San Mateo Office of Sustainability, San Mateo Dept. of Public Works, San Mateo Planning and Building Dept., San Mateo Information Services Dept., San Mateo Dept. of Agriculture Weights and Measures, San Mateo City/County Association of Governments 

Access: Publicly Available 

Appropriate Scale Range for Use: 1:1,000 and smaller 

Dataset Summary: 

The San Mateo County Impervious Surfaces map is a 5-class land use and land cover map of San Mateo County. The impervious map is a fine-scale polygon vector representation of all artificial impervious surfaces in San Mateo County. There are over 780,000 features in the dataset. Non-impervious areas are not mapped and are not covered by polygons. The impervious map represents the state of the landscape in summer, 2018. This data product was produced by the impervious mapping team at the University of Vermont Spatial Analysis Lab. Table 1 lists download locations for the dataset. 

Table 1. Impervious surfaces availability 

San Mateo County Impervious Surfaces – Selected Federal Lands 2 

systems rulesets for impervious mapping included: orthophotography (2018), the lidar point cloud (2019), and Lidar derived rasters. 

After it was produced using Trimble Ecognition, the preliminary impervious map product was manually edited by a team of UVM’s photo interpreters. Manual editing corrected errors where the automated methods produced incorrect results. 

The impervious surfaces map reflects the state of the landscape in summer, 2018 when countywide high resolution imagery collection occurred. 

The impervious map has 5 classes, which are described below: 

• Buildings – Structures above 200 square feet in area. Structures fully occluded by vegetation will not be mapped. 

• Paved Roads – Roads that are paved and wide enough for a vehicle. 

• Dirt and Gravel Roads – Dirt or gravel roads wide enough for a vehicle. Non-ephemeral fire roads, ranch roads and long driveways. 

• Other Dirt and Gravel – Dirt or gravel surfaces that are highly compacted and used by humans and equipment, such as parking lots, road pull-offs, some dirt or gravel paths, and highly compacted areas around commercial activities. This class DOES NOT include natural turf playing fields, very lightly used dirt roads, livestock areas, naturally occurring bare soil or rock, or bare areas around ponds. 

• Other Paved – Includes parking lots, sidewalks, paved walking paths, swimming pools, tennis courts. 

Miscellaneous quality control and processing notes: 

• Zoom level used during manual quality control was no finer than 1 to 500. 

• Vector data was created with no overlapping polygons. 

San Mateo County Impervious Surfaces – Selected Federal Lands 3 

Data Limitations: 

This is not a planimetric data product and was created using semi-automated techniques. It provides a reasonable and useful depiction of impervious surfaces for planner and managers but does not have the accuracy or precision to support engineering. Appropriate uses of the data product include: 

• As an input to storm water models 

• For planners to assess % imperviousness in a parcel/watershed 

• To help identify areas of human infrastructure for fuels and fire management 

• As an input to fuel models that are used in fire behavior and fire spread models 

• For cartography and mapping 

• Generally for use at scales 1:1,000 and smaller 

Inappropriate uses of this product include: 

• Measuring exact square footage of structures or impervious features for building projects 

• Using the impervious as geographically precise information in transportation and public works 

Minimum Mapping Units: 

Related Datasets: 

The San Mateo County Roads, Trails, and Dozer Lines feature class includes centerlines for paved and dirt roads, trails, and CAL FIRE dozer lines in San Mateo County. 

The datasheet and download links are available at vegmap.press/san_mateo_centerlines_datasheet 

San Mateo County Impervious Surfaces – Selected Federal Lands 

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Aug 11th Don Bullard

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