Data Sources

What are digital sources

Pre-digitized data

Why collect sources

Cost - someone has done the work for you. Speed - you can access them faster than you can develop your own data

How are they obtained?

Government, and to alesser extent private sources. Most are web-delivered.DATA SOURCES

NLCD - National Land Cover Data

land use

Digital Line Graphs (DLG) Digitized by

USGS using standard methods, littleaccuracy lost in conversion, available at well belowtheir production cost

Digital Raster Graphic (DRG)

A scanned image of a U.S.Geological Survey

250 dots perinch."

Digital Line Graphs (DLG)

Point and line locations from 1:24,000 and1:100,000 maps, e.g., county and state boundaries, road locations, structure locations, etc.

Digital Line Graphs (DLG) is delivered as

text or binary files (useconversion utilities to convert to vendor-specific data files)

DLG's provide

limited attribute data butconveys important topological andcategorical relationships (road type;major/minor road, unpaved)

DLG is represented in

Most often in UTM coordinate system

USGS Digital Orthophoto Quadrangles (DOQ) created by

scanning the diapositive (transparencyof the aerial photograph

USGS Digital Orthophoto Quadrangles (DOQ) delivered as

a compressed .JPG files withUTM coordinates.

Digital Soils Data National

-Natural Resource Conservation Service (NRCS) (Digitalsoil data sets at different scales and extents)
- National Soil Geography (NATSGO), national coverage,small scale

Digital Soils Data state

-State Soil Geographic (STATSGO) data intermediate scaleand resolution. (1:250,000)

-Soil Survey Geographic (SSURGO) data at a very largescale provides the most spatial and categorical detail.(used by land owners, farmers, planners - county level)

National Wetlands Inventory (NWI)

depict wetlands as interpreted from photostaken on a single (usually Spring or Summer) date

Digital Elevation Models are useful for

slope, aspect, visibility calculations

TIGER/Census data come in two parts:

Line files and Data files

TIGER/Census data are used to

define polygons, and summary attributes for those polygons

TIGER line files are valuable because

they may easily be combined with census data file

TIGER Line files contain data on

Line features, Landmark features, and Polygon features

Digital Floodplain Data

used for many purposes includingestablishing flood insurance rates through the National FloodInsurance Program (NFIP)

what is USGS Digital Orthophoto Quadrangles (DOQ)

- Photographic images that have been corrected for distortions due to camera tilt, terrain displacement,and other factors
-

what data source would i use for

-Establishing ground control points.
-Creating or updating roads data layers
Vegetation data layers
-Time series analysis (temporal changes such asUrban expansion)

NMI is intended for

use in management, not regulation;wetlands may be missing, or over defined

L in L1UBG

lacustrine (system)

1

for limnetic (subsystem)

UB

for unconsolidated Bottom (Class)

G

intermittently exposed

Wetland systems

Marine, Estuarine, Riverine, Lacustrine, and Palustrine

Wetland subsystems`

subtidal, intertidal, tidal, perennial, intermittent,limnetic (away from shore) and littoral (near shore)

Wetland Class

defines general bottom or vegetation conditions (e.g.,rock bottom, scrub-shrub wetland).

U on wetland maps

Uplands

OUT

out of the mapped area

Digital Elevation Models are

Raster data sets of elevation

Raster data sets of elevation are developed using

photogrammetric surveys

Line files for TIGER data

depicting county, state, census tract, or otherareas or boundaries

Data files for TIGER data

containing attributes on population, age, income,race, housing, or other important variables for the areas

Census data maybe summarized at several nested levels

State•Counties•Tracts•
Block groups

Congressional districts•FIPS zones (Federal Information Processing Standard zones)