Location Documentation Table Structure

L_BASE C / 3 Base map type code
L_ACC_EST I / 4 Location accuracy estimate measurement
L_TYPE C / 4 Location type code
L_METH C / 4 Location method code
L_SRC_1 C / 30 Primary source material code
L_SRC_2 C / 30 Secondary source material code
L_SRC_3 C / 30 Tertiary source material code
L_DATE C / 8 Date of automation

Description of Items

L_BASE (Location Base Map)
The standard MassGIS base map is the 1:5,000 digital orthophotography (DOQ).  Point data development at DEP should whenever possible conform to the 1:5,000 standard.  Since DEP has significant historical data developed at smaller scales (1:24,000 and 1:25,000), it is important that base scale be documented.

The L_BASE field contains a code that represents both the type of base map and/or the technique used for digitizing the location. (See Appendix A for a current set of DEP PDDS location base map codes).

L_ACC_EST (Location Accuracy Estimate)
Horizontal accuracy refers to the quantitative measurement of the deviation from a coordinate position to the actual position (on the ground) that the coordinate represents.  The DEP’s horizontal accuracy goal for point locations is +/-16.4 feet (approx. 5m).  This goal reflects the accuracy capabilities of the DEP’s GeoExplorer (GPS) receivers, which under optimal mapping conditions are capable of providing horizontal accuracy typically in the order of 2-5 meters.  The DEP’s horizontal accuracy goal exceeds the +/-25 meter (approx. 82ft) horizontal accuracy goal recommended by the EPA’s Locational Accuracy Task Force (LATF).  Like the EPA’s recommended accuracy goal (+/-25m), it is important to remember that DEP’s accuracy goal (+/-16.4 ft) is simply a goal and not a standard.  Most DEP point locations are estimated to be within +/-100 feet (30.5m), and the coarsest allowable horizontal accuracy for DEP production data is  +/-1,000 feet (305m).

The L_ACC_EST field contains an integer code representing the estimated horizontal accuracy of the location in feet, according to the data developer.  (See Appendix B for a current list of DEP PDDS location accuracy estimate codes.)

L_TYPE (Location Type)
The location type (L_TYPE) field contains a spatial reference code, indicating what the point represents.
(See Appendix C for supported location type codes.)

L_METH (Location Method)
The location method (L_METH) field contains an alphanumeric code defining the method used to locate the feature.  The location method is determined by the primary source used.
(See Appendix D for supported location method codes.)

L_SRC_1 (Primary Location Source)
The L_SRC_1 field contains a code indicating the primary source material used to locate the feature.  Relevant date information should be recorded in L_SRC_1_DATE.  (See Appendix E for supported location source codes.)

L_SRC_2 (Secondary Location Source)
The L_SRC_2 field contains a code that indicates the secondary source material used to locate the feature. Relevant date information should be recorded in L_SRC_1_DATE.  (See Appendix E for supported location source codes

L_SRC_3 (Tertiary Location Source)
The L_SRC_3 field contains a code that indicates any tertiary source material used to locate the feature. Relevant date information should be recorded in L_SRC_1_DATE.  (See Appendix E: for supported location source codes

L_DATE (Automation Date)
The L_DATE field contains the date the feature was located/automated in GIS.  The date of automation is automatically populated through the PDT.  When using an automation methodology other than the PDT, automation date should be entered as follows: 20010403 for April 3, 2001.  When editing locations outside of the PDT the L_DATE should be modified to reflect the date the point was last edited.

Appendix A:

L_BASE (Location Base Map) Codes
DOQ Digital orthophoto base map (DOQ)
DTQ USGS digital topographic quadrangle (DTQ)
DVB Digital vector base (DVB) map
PTQ USGS paper topographic quadrangle (PTQ) base map or stable mylar overlay compiled from USGS topographic quad using traditional tablet digitizing technique
NA Not applicable (NA), automation based on address match technique or Coordinate input from source such as external database or GPS.
UNK Unknown

Appendix B:

L_ACC_EST (Location Accuracy Estimate) Codes
16 Estimated horizontal accuracy is 0 - +/-16 feet
100 Estimated horizontal accuracy is +/-16 - +/-100 feet
500 Estimated horizontal accuracy is +/-100 - +/-500 feet
1000 Estimated horizontal accuracy is +/-500 - +/-1,000 feet
9999 Estimated horizontal accuracy is greater than 1,000 feet
0 Horizontal accuracy estimate unknown

Appendix C:

L_TYPE (Location Type) Codes
AA Perimeter of assigned area POLYGON
AB Administrative building POINT
AM Address-matched location POINT
AMS Air monitoring station POINT
ARV Air Release Vent POINT
CA Center of site investigation activity POINT
CB  Center of a building footprint positively associated with the facility/site POINT
CB2  Center of a building footprint, NOT positively associated with the facility/site POINT
CF Center of a facility POINT
CL  Center of property lot or parcel associated with a facility/site address POINT
CS Center of site or area of known contamination POINT
CT  Center of individual tank or cluster of tanks (AST or UST) POINT
CWA Center of Waste (approximate/presumed) POINT
CWK Center of Waste (known) POINT
EL Estimated location POINT
EWA Extent of Waste (approximate/presumed) POLYGON
EWK Extent of Waste (known) POLYGON
FR Center of Firing Range (rod & gun clubs) POINT
FD Approximate location of front door or main entrance to a facility/site POINT
FDF Facility/Site Entrance (Freight) POINT
FDG Facility/Site Entrance (General) POINT
FDP Facility/Site Entrance (Personnel) POINT
FDU Front door or main entrance to a facility/site (Unspecified) POINT
FEN Fence-Line Visible on Source Map/Image POLYGON
GW Water supply well POINT
INC Incinerator POINT
IW Irrigation well POINT
LAG Lagoon or settling pond POINT
MW Monitoring well POINT
PB Parcel Boundary POLYGON
PD Point of discharge (NPDES) POINT
PH Pump house associated with PWS well POINT
PR Point of release (Ch 21E) POINT
RES Center of PWS reservoir POINT
RW Center of receiving water body POINT
SC  Source of contamination POINT
ST Emissions stack POINT
SW PWS surface water intake POINT
TF Center of trap field (rod & gun clubs) POINT
WF PWS Well field POINT
WMS Water monitoring station or sampling point POINT
WP PWS wellfield well point (TWF) POINT

Appendix D:

L_METH (Location Method) Codes
AM_1 Address matched to number and street or parcel
AM_2 Address matched to nearest intersection
AM_3 Address matched to midpoint of street segment centerline
AM_4 Address Matched to Zipcode Centroid
AM_5 Address Matched to Town Centroid
DD_1 Location snapped to point feature in an existing digital data source
DD_2 Location snapped to the centroid of an existing area digital data source
GP_1 GPS Survey Grade Carrier Phase Signal Data
GP_2 GPS Coarse Acquisition Code:  DGPS (1-5 meter accuracy)
GP_3 GPS Coarse Acquisition Code:  DGPS (sub-meter accuracy)
GP_4 GPS Coarse Acquisition Code: Uncorrected, positions averaged
GP_5 GPS Coarse Acquisition Code: Uncorrected, single position
GP_6 GPS: Unspecified Device, DGPS Unknown
GR_1 Digitized from Georeferenced map, registered with survey grade coordinates
GR_2 Digitized from Georeferenced map, registered with DGPS (2-5 meter) coordinates
GR_3 Digitized from Georeferenced map, registered using digital orthophoto
IN Interpolation based on primary source material (L_SRC_1)
DDS Interpolation - Digital Map Source
MAP Interpolation - Map
MSS Interpolation - MSS
OTH Interpolation - Other
PHO Interpolation - Photo
SAT Interpolation - Satellite
SPOT Interpolation - SPOT
TM Interpolation - TM
XY_1 Coordinate pair derived from traditional survey techniques
XY_2 Coordinate pair unverified or reported by regulated community, includes undocumented coordinate data
UNK Unknown

Appendix E:

L_SRC_(N)  (Location Source) Codes
DB_BOH Massachusetts Board of Health
DB_EPICS DEP Environmental Protection Integrated Computer System
DB_EPA United States Environmental Protection Agency - System Unspecified
DB_DFS Massachusetts Department of Fire Services (DFS)
DB_DOE Massachusetts Department of Education
DB_SSEIS DEP BWP Stationary Source Emission Inventory System
DB_RCRIS EPA Resource Conservation and Recovery Information System
DB_WMA DEP Water Management Act
DB_WPP DEP Water Permitting Program Database
DB_OTH Other Database Source
DD_21E DEP BWSC Chapter 21E Tier Classified Oil or Hazardous Materials datalayer
DD_BAS MassGIS watershed/basin data
DD_ESRI ESRI Data and Maps media
DD_FAC DEP BWP Regulated Facilities datalayer
DD_GDT Geographic Data Technology (GDT) streets Geocoding datalayer
DD_GWP DEP Permitted Discharge to Groundwater datalayer
DD_HOSP MassGIS Hospitals and Emergency Room Facilities datalayer
DD_LU MassGIS Land Use datalayer
DD_MMR Massachusetts Military Reservation
DD_NPL US EPA National Priority List datalayer
DD_OS MassGIS Open Space datalayer
DD_PAR       Digital Parcel Data
DD_PWS DEP Public Water Supply datalayer
DD_SCHL Schools datalayer
DD_SW DEP BWP Solid Waste Facilities datalayer
DD_SWAP Contracted data developed through DEP SWAP
DD_TIGER US Census Bureau TIGER Line Files
DD_UNK Unknown
DD_UST DEP Underground Storage Tanks datalayer
DD_OTH Other Digital Data Source
MS_LMTQ Locus map based on USGS topographic quadrangle map
MS_LMST Locus map based on street information (ex. Street Atlas)
MS_LMOT Locus map other (ex. Trail map)
MS_MCP DEP MCP Site Scoring Map
MS_PIM DEP Pre-inspection Map
MS_SITE Detailed Site plan or map 
MS_SKCH Hand sketched map
MS_SURV Survey grade map of site derived from traditional survey techniques
MS_TAX Tax assessment map
MS_USGS USGS topographic quadrangle map
MS_WWW Internet map source (use L_COMM to record web URL)
MS_OTH Other Map Source
AP_CIR DWW Color Infrared photography 1:12,000
AP_DOQ MassGIS 1:5,000 digital orthophotography
AP_GE General Electric (GW) Project
AP_PC Pictometry Community Oblique
AP_PN Pictometry Neighborhood Oblique
DS_GPS GPS Data Sheet
FMSR Field Measurement (tape and compass bearings)
KNOW Located by DEP staff through knowledge gained in the course of their professional activities
OTH or OTHER Other
TEXT Textual information
UNK Source Unknown
VERB Verbal information
WWW Website Information
EDEP Submitted via eDEP Application, Source Unknown
AP Other aerial photo source
MSS Multi Spectral Signature Image
SAT Other Satellite Image
SPOT SPOT Corporation Image
SV Site visited for the purpose of field verification and/or site inspection
TM Thematic Mapper Image

Last Updated 6/22/2012