Fundamentals of GIS Lecture 8: Selected Public Data Lecture notes by Austin Troy, University of Vermont © Using GIS--

Fundamentals of GIS ©2009 Austin Troy Part 1 US Geological Survey Data Sources

Fundamentals of GIS ©2009 Austin Troy DLG Digital Line Graphs; U.S. Geological Survey (USGS) Derived from either aerial photographs or from manual and automated digitizing methods. Digital representations of planimetric information: points, lines and areas Full range of attribute codes, full topological structuring, have passed quality-control.

Fundamentals of GIS ©2009 Austin Troy DLG Summary

Fundamentals of GIS ©2009 Austin Troy Transportation layerHypsography and Public land boundary layers

Fundamentals of GIS ©2009 Austin Troy DLG Users Guides DLG Standards documentation available at Download, user guides, abstracts and metadata available for each DLG product at : earthexplorer.usgs.gov earthexplorer.usgs.gov Three DLG layers: hypsography, vegetation cover and roads

Fundamentals of GIS ©2009 Austin Troy DLG Category and Attribute Coding Attributes come in coded for in PAT tables To know what these codes signify, see web page 3/3dlg0798.pdf 3/3dlg0798.pdf Example: Vegetation Cover Layer, Item “Identity_lab” in PAT Outside area Woods or brushwood Scrub Orchard or plantation Vineyard Scattered trees Void area

Fundamentals of GIS ©2009 Austin Troy DLG-Medium Scale Example

Fundamentals of GIS ©2009 Austin Troy DLG-Small Scale Example

Fundamentals of GIS ©2009 Austin Troy DLG Availability Go to This shows hypsography coverage at 1:24000

Fundamentals of GIS ©2009 Austin Troy DLG Availability This shows vegetative coverage at 1:24000

Fundamentals of GIS ©2009 Austin Troy Digital Elevation Models Raster-based data structure for storing terrain data Stores regular array of points in space with spot elevation values Available for free from USGS, EROS Data Center Continuous coverage of lower 48, Hawaii and limited portions of Alaska Made from vector hypsography and hydrography data Still used by some, but no longer maintained by USGS

Fundamentals of GIS ©2009 Austin Troy National Elevation Dataset (NED) New-generation Digital Elevation model; is a complement, not a replacement to DEM They are seamless (not tiled); can be downloaded as a single scene for a large area Avoids terrain errors/ discontinuities at border of tiles and that they Filtering process yields fewer “artifacts;” improves quality of slopes and hydro modeling

Fundamentals of GIS ©2009 Austin Troy NED Here is an example of errors generated in drainage channel interpolation with an old DEM vs a NED

Fundamentals of GIS ©2009 Austin Troy NED Referenced to NAD83 Downloaded from seamless server as ArcGrid files Comes in one arc-second pixel size (~30 meters) for entire US Comes in 1/3 arc second (~10 meters) pixel size for much of the US too In a small number of areas is in 1/9 arc second (~3 meters) Status maps available at

Fundamentals of GIS ©2009 Austin Troy NED 10 and 30 meter coverage: from Seamless.usgs.gov

Fundamentals of GIS ©2009 Austin Troy NED Download: rectangle-defined areas as seamless tiles from along with many other data types

Fundamentals of GIS ©2009 Austin Troy NED NED homepage : NED is free for FTP downloads of under 10 megabytes Larger areas either have to be downloaded separately, or purchased as a bulk order.

Fundamentals of GIS ©2009 Austin Troy NED For large areas, can purchase pre-defined zones on CD/DVD

Fundamentals of GIS National Land Cover Data ©2009 Austin Troy

Fundamentals of GIS National Land Cover Data ©2009 Austin Troy Available for 1992 and category land cover classification scheme based on 1992 Landsat data Comes in image format 30 meter square spatial resolution Available for free from

Fundamentals of GIS ©2009 Austin Troy NLCD classes are somewhat different from 1992 and are not designed to be compared for many class types. E.g. “developed-open space”; many areas classed as low density urban in 1992 Hence change analysis no recommended; however later 1992 will be reclassed to allow this comparison NLCD 2006 is under plans as NLCD moves from being a mapping to a monitoring program

Fundamentals of GIS NLCD 1992 and 2001 classification schemes ©2009 Austin Troy Descriptions at

Fundamentals of GIS ©2009 Austin Troy NLCD 2001 Also includes layers of percent canopy cover and percent imperviousness. These can be downloaded or viewed through a viewer online at imperviousness canopy

Fundamentals of GIS ©2009 Austin Troy NLCD:accuracy Improved accuracy in 2001 Accuracy tables for 1992 by region available at accuracy tables still under development 1992 regions (EPA regions) 2001 regions/ reference points

Fundamentals of GIS NLCD accuracy: 1992 ©2009 Austin Troy

Fundamentals of GIS ©2009 Austin Troy DOQs Digital orthophoto quarter quadrangle Also known as DOQQ Old version is scanned photos, from the National Aerial Photography Program (NAPP) One-fourth of a 7.5-minute USGS topographic map 1 meter spatial resolution

Fundamentals of GIS ©2009 Austin Troy Digital Orthophoto Quadrangles Comes in three extents: 3.75 minute quarter quad (140 megs for color) 7.5 minute quad: limited availability, 140 megs for BW Seamless DOQs from

Fundamentals of GIS ©2009 Austin Troy The difference between an aerial photograph and an orthophoto Aerial photo –image displacement caused by tilting of camera and terrain relief –scale is not uniform –cannot measure distances on a photograph Orthophoto –rectified to remove non- constant scale due to varying distance to camera –Also adjusts for elevation and tilt –Therefore possible to measure distances directly like on other maps –Can serve as a base map onto which other info may be overlaid Light travels longer distance at scene edge: magnification

Fundamentals of GIS ©2009 Austin Troy DOQ Documentation Download, metadata and user guides available at Standards Documentation available at

Fundamentals of GIS ©2009 Austin Troy Scanned image of a U.S. Geological Survey (USGS) standard series topographic map The image inside the map neatline is georeferenced to the surface of the earth and fit to the Universal Transverse Mercator projection. The map is scanned at a minimum resolution of 250 dots per inch Digital Raster Graphics

Fundamentals of GIS ©2009 Austin Troy Used on-screen to collect, review, and revise other digital data, especially digital line graphs, DLG. DRG’s are available at and at some state GIS repositories have them too for freewww.gisdatadepot.comwww.mapmart.com

Fundamentals of GIS ©2009 Austin Troy This database contains information about almost 2 million physical and cultural geographic features in the United States. The Federally recognized name of each feature described in the data base is identified, and references are made to a feature's location by State, county, and geographic coordinates. Point coordinates are given in latitude/longitude Often abstracts large features to a point USGS Geographic Names Information System (GNIS)

Fundamentals of GIS ©2009 Austin Troy Includes location, names and category of features such as: Schools/universities Churches/cemeteries Airports/ports Parks/recreation centers Shopping centers Stadiums/arenas Theaters/auditoriums/cultural facilities Country clubs/golf courses Marinas/yacht clubs Trailheads (some) Rural fire stations (some) Dams/reservoirs Cities/incorporated areas (as points) GNIS

Fundamentals of GIS ©2009 Austin Troy Information, downloads and a query engine available at: Files export as zipped text file. Can be imported into Excel The query engine can tell you the following about any named geographic feature you input: Latitude/longitude Elevation Estimated 1994 population of cities Feature type GNIS

Fundamentals of GIS ©2009 Austin Troy Part 2 Data from Other Sources

Fundamentals of GIS ©2009 Austin Troy Comes from both the USGS and the EPA Surface water features: lakes, ponds, streams, rivers, springs Nationally consistent Order of linkages coded to allow for flow path analysis Background info at Resolutions from 1:100k to 1:24k National Hydrography Dataset (NHD)

Fundamentals of GIS ©2009 Austin Troy NHD Many analysis tools designed for this data. For instance: can find the path upstream or downstream from any point using NHD data and network analyst; flow reaches are numbered sequentially in order of flow to allow path analysis Stream reaches encoded like addresses on a street Connections encoded using topology Other tools available at

Fundamentals of GIS ©2009 Austin Troy NHD Download at

Fundamentals of GIS ©2009 Austin Troy NHD Can extract by County/state. Click on radio button of geography for clip Use check marks to make layers visible in base map Then Click on clip boundary (e.g. Chittenden County) in the map viewer

Fundamentals of GIS ©2009 Austin Troy NHD Can then choose the resolution and the database type Must turn popup blocker off to use Then get an for custom download

Fundamentals of GIS ©2009 Austin Troy NHD Contents of Geodatabase: many feature classes with different purposes Many will often be empty

Fundamentals of GIS ©2009 Austin Troy USDA Data USDA houses a number of data layers at their new Geospatial data gateway nrcs.usda.gov/ nrcs.usda.gov/

Fundamentals of GIS ©2009 Austin Troy USDA Gateway Includes CLU farm boundaries (not any longer, but SAL has it for VT)) Hydrologic Units (8 and 12 digit) NED elevation Digital Raster Graphics High resolution color orthophotos from 2003, 2004, 2006 (National Agriculatural Imagery Program) Geographic Names Cropland data layer (for some areas) NRCS Soils data and soils tables Climate Data (precipitation and temp)

Fundamentals of GIS ©2009 Austin Troy USDA Gateway Includes

Fundamentals of GIS ©2009 Austin Troy USDA Gateway Includes Can Define clip regions by state or county Can also highlight a layer and get information

Fundamentals of GIS ©2009 Austin Troy Common Land Units Farm field boundaries representing smallest contiguous unit of cultivated land For farms in USDA programs Much more accurate that “agriculture” category in NLCD land cover Type of crop is unknown

Fundamentals of GIS ©2009 Austin Troy NAIP National Agricultural Imagery Program Digital Imagery, mosaiced by county, used by the NRCS and FSA to look at compliance with subsidy programs Ortho-rectified, Color, 1:40,000 scale 2003 and 2004

Fundamentals of GIS ©2009 Austin Troy SSURGO Soils Data SSURGO: Soil Survey Geographic Data from NRCS Soils data also at ult.aspx ult.aspx Metadata and standards available at RGOMetadata.aspx RGOMetadata.aspx Entails both a polygon layer showing soils area boundaries, but also an Access Database of numerous soil attributes

Fundamentals of GIS ©2009 Austin Troy SSURGO Soil Data Mart interface Access—sample tables; there are dozens

Fundamentals of GIS USDA Forest Service Data Gateway For each National Forest includes layers like: boundaries, trails, roads, ranges for certain tree and animal species, and ecological regions ©2009 Austin Troy

Fundamentals of GIS ©2009 Austin Troy National Wetlands Inventory From Fish and Wildlife Service Maps all class 1 and 2 major wetlands Available digitally for much of the country 1:24,000 or smaller Involves a complex taxonomy of wetlands codes available at Calculator at Includes marine, estuarine, riverine, lacustrine and palustrine types

Fundamentals of GIS ©2009 Austin Troy

Fundamentals of GIS ©2009 Austin Troy NWI Wetlands map interface at Allows you to view online data and download First shows status availability map:

Fundamentals of GIS ©2009 Austin Troy NWI Can make PDFs easily

Fundamentals of GIS ©2009 Austin Troy NWI NWI by wetland type overlaid on NHD streams layer

Fundamentals of GIS ©2009 Austin Troy Topologically Integrated Geographic Encoding and Reference System Automates the mapping and related geographic activities required to support the decennial census and sample survey programs of the census bureau starting with the 1990 decennial census. The Census TIGER ® system supports: Creation and maintenance of the digital geographic data base that includes complete coverage of the United States and its territories TIGER

Fundamentals of GIS ©2009 Austin Troy The TIGER system provides support for: Creation and maintenance of a nation wide digital geographic data base Production of maps from the TIGER ® data base for all Census Bureau enumeration and publication programs Allows for address geocoding Can be integrated with Census attribute databases easily

Fundamentals of GIS ©2009 Austin Troy Accuracy and Attribution: TIGER has good attribution, but poor accuracy They are based partially on 1:100,000 DLG Are often conflated This is often used to assign the attributes from TIGER ® data to 1:24,000 DLG data

Fundamentals of GIS ©2009 Austin Troy The TIGER files contain data describing three feature types: Line Features 1.Roads 2.Railroads 3.Hydrography 4.Transportation and Utility Lines Boundary Features 1.Statistical boundaries, such as census tracts and blocks 2.Local government boundaries, such as places and counties 3.Administrative boundaries, such as congressional and school districts Landmark Features 1.Point landmarks, such as schools and churches 2.Area landmarks, such as parks and cemeteries 3.Key geographic locations, such as apartment buildings and factories

Fundamentals of GIS ©2009 Austin Troy TIGER line files and the demographic files Direct linkage using keys built up from: State FIPS code County FIPS code Tract number Block group number Block number

Fundamentals of GIS ©2009 Austin Troy For geographic files ESRI: Download 2000 U.S. Census TIGER lines files and demographic data UC Berkeley Tiger Server: For attributes to 2000 and 1990 Census For data in intermediate years via the American Community Survey

Fundamentals of GIS ©2009 Austin Troy

Fundamentals of GIS ©2009 Austin Troy

Fundamentals of GIS ©2009 Austin Troy Introduction to GIS

Fundamentals of GIS ©2009 Austin Troy For continuing data updates, check the data links page at Here you’ll find links to many state level GIS online data repositories plus many of the ones mentioned here Another link is to map a network drive to \\zoofiles\gisdata where you’ll find: NAIP imagery, ortho photos, all VCGI data plus VTrans database, World data from ESRI, DRG topo maps, Street maps USA

Fundamentals of GIS ©2009 Austin Troy VCGI The web site offers many layers through a browser

Fundamentals of GIS ©2009 Austin Troy Includes an interactive map browser for “clipping and zipping” data

Fundamentals of GIS ©2009 Austin Troy Other sources for USGS data –Allows users to choose tiles and layers with a geographic interface –Most public data are free, but,any others available for a price –Gives status maps –Can also buy bulk public data for a fee –Not as user friendly –Just a plain old interface that is hard to navigate –However, many free data layers and lots of scripts and extensions