Digital Line Graph (DLG) Large Scale Data Dictionary

 

Cell ID

• Field Definition:  This number is assigned for internal NMD use only.

 

Coordinates - Decimal Degrees

• Field Definition:  The latitude and longitude are provided in decimal degrees for the following fields:

          Values:

          Scene Center Latitude and Longitude

         Northeast (NE) Corner Latitude and Longitude

         Northwest (NW) Corner Latitude and Longitude

         Southeast (SE) Corner Latitude and Longitude

         Southwest (SW) Corner Latitude and Longitude

 

          Latitude Format Decimal Degrees: -90.000 through 90.000

          Longitude Format Decimal Degrees: -180.000 through 180.000

 

          Number of decimal places will vary by dataset – check collection in EE.

 

Coordinates - Degrees, Minutes, Seconds

• Field Definition:  The latitude and longitude are provided in degrees, minutes, and seconds for the following fields:

          Values:

          Scene Center Latitude and Longitude

          Northeast (NE) Corner Latitude and Longitude

          Northwest (NW) Corner Latitude and Longitude

          Southeast (SE) Corner Latitude and Longitude

          Southwest (SW) Corner Latitude and Longitude

          Longitude Format:

          DDDMMSS.SSH

          DDD = Degree(s) with a range of 0 through 180

          MM = Minute(s) with a range of 0 through 59

          SS.SS = Second(s) with a range of 0 through 59.99

          H = Hemisphere with E for east and W for west

 

          Latitude Format:

          DDMMSS.SSH

          DD = Degree(s) with a range of 0 through 90

          MM = Minutes(s) with a range of 0 through 59

          SS.SS = Second(s) with a range of 0 through 59.99

          H = Hemisphere with N for north and S for south

 

Coordinate System

• Field Definition:  Code indicating which coordinate system was used when capturing the digital information.

 

Coordinate Zone

• Field Definition:  Zone of the UTM coordinate system

 

Create Date

• Field Definition:  Creation date for the product

          Values:

          Format:

          YYYY = Year

          MM = Month

          DD = Day

 

Data Format

• Field Definition:  The data format can be either Native or SDTS. Spatial Data Transfer Standard (SDTS) is a language for communicating spatial data which was developed to allow Federal agencies to share spatial data among projects that use different hardware, software, and operating systems. The SDTS is a flexible and comprehensive standard that offers the data encoder many options.

 

Digitizer

• Field Definition:  A reference to persons or organizations who perform digitized work.

 

Entity ID

• Field Definition:  This field is used to uniquely identify data which can be ordered in any combination of unique products.

          Example:

          Entity ID: DL514200BD079276

          Where:

          DL = Data Set Identifier for DLG

          51420 = Quad Sequence Number

          0BD = Boundary Layer

          079276 = Sequence number within data set.

 

Horizontal Units

• Field Definition:  A reference for horizontal measuremen (feet or meters).

 

Horizontal Datum

• Field Definition:  A geodetic reference for horizontal control. Five quantities are known: latitude, longitude, azimuth of a line from the point, and two constants that are the parameters for the reference ellipsoid (NAD27, NAD83).

 

Level

• Field Definition:  DLG level code of data quality depending on the specific production process used, such as:

           Values:

           Digital Line Graph - 3 (with all categories of hypsography, hydrography, ridge line, break line, drain files,and all vertical and horizontal control networks.)

 

Map Name

• Field Definition:  This is the quadrangle map name defining a geographic area.

 

Overlay

• Field Definition:  This field is the two character overlay category defining a geographic area. This field uniquely identifies individual overlay categories for digital line graphs which can be ordered in any combination of unique products.

          Values:

          Following are the overlay categories available and unique codes for each:

         BD = Boundaries

         HP = Hypsography

         HY = Hydrography

         MT = Misc.Transportation

         MS = Man-Made Features

         NV = Non-Vegetative Features

         RD = Roads

         RR = Railroads

         PL = Public Land Survey System

         SC = Vegetative Surface Cover

         SM = Survey Control

 

Product Group

• Field Definition:  This field describes the specific type of data available for this collection.

           Values:

           Valid types:

           7.5-min DLG hydro

           7.5-min DLG hypso

           7.5-min DLG veg

           7.5-min DLG nonveg

           7.5-min DLG bound

           7.5-min DLG survey

           7.5-min DLG trans

           7.5-min DLG manmade

           7.5-min DLG plss

           15-min DLG hydro

           15-min DLG hypso

           15-min DLG veg

           15-min DLG nonveg

           15-min DLG bound

           15-min DLG survey

           15-min DLG trans

           15-min DLG manmade

           15-min DLG plss

 

Quad Sequence Number

• Field Definition:  This number is assigned for internal NMD use only.

 

Resolution X

• Field Definition:  Measure of the sharpness of an image or feature

 

Resolution Y

• Field Definition:  Measure of the sharpness of an image or feature

 

Revision Date

• Field Definition:  Date indicating the most recent revision/inspection

 

Revision Type

• Field Definition:  Identifier to describe type of revision such as:

           Values:

           D = Digital Revision

           I = Photo Inspected

           L = Limited Revision

           P = Photo Revision

 

Scale

Field Definition:  The scale is the ratio of the distance on the image compared to the equivalent distance on the ground.

 

Source Date

• Field Definition:  Source date from Header (default)

 

Standards Version

• Field Definition:  Detailed information on the Standards Version specifications can be found in the USGS National Mapping Program's Standards for Digital Line Graphs.

 

State

• Field Definition:  Two character state abbreviation

 

Status Type

• Field Definition:  "H" stands for Historical (revised by a newer version) data and "A" stands for Recommended (current) data.

 

 

Version Number

• Field Definition:  The version number is based on the cell ID, product group, and overlay. If only one product exists per cell ID/product group/ overlay, the version value is 1. If there are more than one product per cell ID/product group/overlay, then for DLG data the following fields are considered in the order listed below: Source Date (Most recent date takes precedence) Revision Date (Most recent date takes precedence) Level (Highest number takes precedence)

 

Vertical Datum

• Field Definition:  Any level surface used as a reference from which to reckon elevations, usually mean sea level.