Minnesota Public Land Survey System Section Corner Database: SECTIC-24K, Version 1.1a

This page last updated: 10/04/2013
Metadata created using Minnesota Geographic Metadata Guidelines


Go to Section:
1. Overview
2. Data Quality
3. Data Organization
4. Coordinate System
5. Attributes
6. Distribution - Get Data
7. Metadata Reference

Section 1 Overview
Originator Minnesota Geospatial Information Office (MnGeo)
Title Minnesota Public Land Survey System Section Corner Database: SECTIC-24K, Version 1.1a
Abstract SECTIC-24K is a digital file of the Public Land Survey (PLS) section corners of Minnesota as recorded on the most recent edition of the U.S. Geological Survey's 1:24,000 7.5-minute quadrangle maps. The database attempts to best fit the section corner locations shown on the published 1:24,000 maps, even though better 'real world' data for the location of the section corner might be available elsewhere. The SECTIC-24K data set also includes a program which has the following utilities:

Utility A: Section corner extraction from the SECTIC-24K database by county, 1:24,000-scale quad, or township.

Utility B: Conversion among PLS, UTM, or LAT/LONG coordinates, either interactively or by file conversion. It also allows NAD27 - NAD83 conversions.

Utility C: Creation of a dBASE output file from SECTIC-24K.

***This program does not run on Windows 7 - 64 bit computers (it does run on Windows - 32 bit). There is also a web service that generates much the same info as the sectic program. See geoint.lmic.state.mn.us/pete/pls.html . The main differences are it may not do NAD27/NAD83 shifts and it doesn't have a batch mode. A batch mode could be created using the web service and the scripting code of your choice.***
Purpose This database was developed to provide section corner locations for mapping applications which use the U.S. Geological Survey's 1:24,000 7.5-minute quadrangle as a base map.
Time Period of Content Date
Currentness Reference Section corner locations were recorded from the most recent edition of the U.S. Geological Survey's 1:24,000 7.5-minute quadrangle maps that were available at the time the dataset was created. Map dates ranged from the late 1940s to the late 1970s.
Progress Complete
Maintenance and Update Frequency None Planned
Spatial Extent of Data Minnesota
Bounding Coordinates -97.25
-89.50
49.40
43.50
Place Keywords Minnesota
Theme Keywords location, U.S. Public Land Survey, PLS, PLSS, PLS section corners, USGS 1:24,000 7.5-minute quadrangle
Theme Keyword Thesaurus ISO 19115 Topic Category
Access Constraints None.
Use Constraints Redistribution Conditions: In obtaining this data from MnGeo, it is understood that you and/or your organization have the right to use it for any purpose. If you modify it, you are encouraged to apply responsible best practices by documenting those changes in a metadata record. If you transmit or provide the data to another user, it is your responsibility to provide appropriate content, limitation, warranty and liability information as you see fit.
Contact Person Information Pete Olson,
Minnesota Geospatial Information Office (MnGeo)
658 Cedar Street, Room 300
St. Paul, MN  55155
Phone: 651-201-2467
Fax: 651-296-6398
Email: clearing.house@state.mn.us
Browse Graphic Click to view a data sample
Associated Data Sets Control Point Generated PLS (quarter-quarter section)
The land survey information in this database is constructed using section corner coordinates (and other PLSS corners if available) from the Control Point Inventory as well as information from the original surveyors' notes and plat maps. Quarter-quarter section and government lot boundaries and meander corners are proportioned using Cadastral Measurement Management software from the U.S. Bureau of Land Management. Meander lines are added with ArcCOGO using the bearings and distances from the original survey notes. The section lines and Indian reservation boundaries are extended across water bodies, but the smaller subdivision lines are not. Attributes are included. See deli.dnr.state.mn.us/metadata/pls_fortypy3.html

Minnesota Public Land Survey System: TRS (Township, Range, Section)
This dataset contains all PLSS section and township boundaries as well as county boundaries for Minnesota. The data were digitized from USGS 1:100,000-scale maps. All lines were extended across water bodies. Attributes are included. A statewide file is available online. See www.mngeo.state.mn.us/chouse/metadata/trs.html

Minnesota Public Land Survey System: TRSQ (Township, Range, Section, Quarter-quarter)
This dataset contains county, township, range, and section boundaries digitized at LMIC (now MnGeo) from USGS 1:100,000-scale maps. Quarter-section and quarter-quarter section subdivisions were calculated using the digitized sections. All lines were extended across water bodies. Attributes are included. See www.mngeo.state.mn.us/chouse/metadata/trsq.html

MnDOT BaseMap
Section lines digitized from USGS 7.5-minute quadrangle maps. The dataset does not include attributes. See www.dot.state.mn.us/maps/gdma/data/metadata/plss.htm

Control Point Inventory, Minnesota Department of Natural Resources (MnDNR)
This is a multi-agency effort to create a database that provides a comprehensive public land survey point referencing system. It is intended to hold the most current and accurate set of coordinate points which can be used as a GIS base layer. A coordinate value for each PLSS section corner was obtained by digitizing 1:24,000 USGS quad maps. SECTIC 24K was used as one source of information to construct the Control Point Inventory. As available, more accurate coordinates and PLSS points to the 40 corner or the government lot level are added.

Section 2 Data Quality
Attribute Accuracy Unknown (see Lineage element for description of tests performed during data set creation).
Logical Consistency Not applicable
Completeness Section corner locations are complete statewide. Corner locations were projected in cases where the corners were not printed on the source map.
Horizontal Positional Accuracy Locational accuracy for points derived from USGS 7.5-minute quadrangles cannot be assumed to exceed National Map Accuracy Standards for 1:24,000 scale maps (+/- 40 feet). (See Lineage element for description of tests performed during data set creation.)
Vertical Positional Accuracy Not applicable
Lineage HISTORY OF THE SECTIC-24K DATABASE:

In the early 1980s, the Minnesota Land Management Information Center (LMIC) (now MnGeo) created a data file of the location of the State's Public Land Survey (PLS) section corners. The file, which was given the name 'GISMO', was created by digitizing the section corners from the U.S. Geological Survey topographic quadrangle maps. These maps were the most detailed set of base maps available statewide at that time. For most of the state, 1:24,000 scale maps were used. However, for nearly 20% of the state, only 1:62,500 scale maps were available.

All section corners shown on the published maps were recorded. Because of the use of this original database, all four corners of a given section needed to be digitized. Therefore, section corners were 'projected' to complete any section not completely shown on the quadrangle maps. Section corners were 'projected' by extending the published section line segments into areas such as meandered waters, at survey base changes and across the state border.

Some things to keep in mind about the original GISMO data:

1. It must be remembered that the section corner locations on the quadrangle maps were only as good as the information available when the map was made. The maps used for this project were published from the late 1940s to the late 1970s. National Map Accuracy Standards for 1:24,000-scale maps is plus or minus 40 feet for identifiable objects. In many cases, section corners are not easily located during map compilation. Therefore, section corner locations from this source might be described as a 'caricature' of the land net and are highly generalized. The GISMO database was designed to best approximate the location of the section corner 'map feature' as shown on the published quadrangle map, even though more precise data might have been available from other sources for selected section corners.

2. The digitizing was done from printed paper maps. Because of changes in temperature and humidity conditions, the paper maps could shrink or expand up to 1/8 of an inch which is not uniform in all directions across the map. Thus, error in the digital file of this magnitude could be expected.

3. The digitizing technology of that time was 'blind'; that is, the person digitizing could not visualize and verify the data interactively. Later, the data was visually checked by the creation of plots to overlay on county maps of that vintage (scales of 1:126,720 for most of the state and 1:63,360 for the Twin Cities metro area). However, the data was never systematically checked at the 1:24,000 scale with the original quadrangle map.

4. The data was captured on a township-by-township basis. It took anywhere from one to four quad maps to display an entire township. The section corners in a township were captured as one of 49 points. Because of this format, common corners along a township border were digitized two, three, or even four times. The data for these points was later processed to establish the same coordinate values for the multiple records representing a specific section corner.

5. The data was captured in UTM meters, NAD27 in UTM Zone 15 extended. These values were calculated for each section corner based on the digitized latitude/longitude coordinates from the corners of each quadrangle base map. The statewide data file was organized by county, township and range. Conversions can be made to other units of measurement, NAD83, and other projections. However, the accuracy of those conversions will only be as good as the conversion program allows. And of course, these programs cannot improve the quality of the coordinate values from the original data.

In spite of all these shortcomings, the data set is still very useful. Many people in various county, regional, and state-wide inventory programs use the 1:24,000 quad as a base map. Many mapping applications require the section corners or lines for reference. This database will be very adequate for this purpose.

UPDATES TO THE GISMO DATA

Since the completion of the GISMO file in the mid-1980s, some section corner values have been edited and updated to better reflect the published 1:24,000 quadrangle maps. Most of these updates have occurred in the forested area of Minnesota. In 1992, LMIC systematically analyzed the approximately 20% of the state that was originally digitized from old 1:62,500 quads. The resulting file, SECTIC-24K, is a better representation of the section corners as shown on current 1:24,000 quad maps.

During the first half of 1992, about 20% of the old GISMO points in the state were reviewed and many were revised as part of the Control Point Inventory Project using the following process:

1. Plot the GISMO points for old 1:62,500 scale map areas

A 1:24,000-scaled plot was made for 333 quads which showed the following information: United States Geologic Survey (USGS) quad tics and an identification code; USGS quad outline; the GISMO points (as digitized from 1:62,500 maps); and the GISMO code which consists of county, township, range, direction and corner.

2. Visually edit the plot

For these 333 quads, the old GISMO section corner location was plotted as a circle with the radius of .05 inch at the 1:24,000 scale (this is about 100 feet in ground scale). The method used to check positional accuracy was to overlay the plot on the published USGS quad map and use a 'best fit' of the published quad boundary to the plotted quad boundary. If the section corner tic shown on the current USGS 1:24,000 quad map did not fall within the .05 inch circle, the point was then highlighted for revision. The GISMO and county codes were also checked and highlighted where changes were needed.

As stated previously, the computer processing for the GISMO effort required complete sections (4 corners). If a corner was not shown on the quad map, 'projected' points were added to build a complete section. 'Projected' points were added to the file when a corner needed to complete a section was:

A: in a meandered water body
B: beyond the state's border
C: across a county line (e.g., along the Mississippi River)
D: across the Prime Meridian line from the original land survey, or
E: no clear intersection shown on USGS quad for any other reason

3. Correct the section tics to the 1:24,000 quads

Section corner tics beyond a .05 inch locational tolerance shown on the check plot had been highlighted in the visual editing. The highlighted tics were redigitized and coded to show that the locational values had been changed from old GISMO values. Then any other observed coding problems, such as county code, were resolved statewide. Note: multiple records for some points still exist in some cases because of the reasons stated in item #2 above.

4. Verify changes on 1:24,000 quads

On quads where changes had occurred, the data was re-plotted at 1:24,000 to verify that all the positions were corrected and that any coding corrections were done.

5. Proof entire state file

Two steps were used to review the final file. First, LMIC plotted the whole state as a set of 1:100,000 map sheet blocks and compared them to published USGS 1:100,000 quad maps to proof county boundaries and projected points. This also served as a double check for any other problems that might have been in the original GISMO points.

A second proof was done with the help of MN-DNR's Division of Minerals staff. They compiled a complete statewide section line mapping file by connecting the SECTIC-24K corner tics. A few problem areas were identified and have been revised.

6. Translate to NAD83

All of the section corner data points were translated into NAD83 using the National Geodetic Survey's NADCON program. This conforms to state law requiring use of the 1983 datum. The final master SECTIC-24K database is housed at LMIC. It is organized as a state file containing about 120,000 records and is sorted geographically (county, township, range, section).

NOTE - The location values for all revised points were collected as 'double precision' values. In addition, all other points carried over from the old GISMO file were converted to double precision values. However, for the SECTIC-24K file, the locational data has been truncated to the nearest whole meter. Remember, the locational values in the SECTIC-24K database should never be assumed to be that accurate. This data file only attempts to reflect the published quad maps with all the faults listed above. Other sources of data should be used to produce maps reflecting the best 'real world' location of these section corners.

7. Fix two bugs in Version 1.1

Version 1.1 contained two known bugs: 1. the option to convert a file of coordinates from UTM NAD83 to Lat/Long NAD83 did not work correctly, and 2. a problem with the runtime compiler resulted in a 'Runtime Error 200' message when trying to start SECTIC on computers that are 200 megahertz or faster (the program would not run). Version 1.1a fixes these two problems.

Section 3 Spatial Data Organization (not used in this metadata)

Section 4 Coordinate System
Horizontal Coordinate Scheme Universal Transverse Mercator
UTM Zone Number 15E
Horizontal Datum NAD83
Horizontal Units meters

Section 5 Attributes
Overview The SECTIC-24K data set contains the following files:

1. SECTIC.DAT: A compressed version of the statewide database containing NAD27 and NAD83 values of the section corners, indexed by PLS coordinates

2. TOWN: File of township names

3. COUNTY: File of county names

4. Q24: File of 24K quad names

5. Q100: File of 100K quad names

6. Q250: File of 250K quad names

7. SECTIC.EXE: A program which includes the following utilities:

Utility A: Section corner extraction from the SECTIC-24K database by county, 1:24,000-scale quad, or township.

Utility B: Conversion among PLS, UTM, or LAT/LONG coordinates, either interactively or by file conversion. It also allows NAD27 - NAD83 conversions.

Utility C: Creation of a dBASE output file from SECTIC-24K

8. SECTIC.HLP: Help file for SECTIC-24K program

9. SECTIC24K.PDF: Documentation file (also in Word and WordPerfect 5.1 formats, with graphics in .EPS or in high or low resolution .TIFF formats)

10. READ.ME: Installation instructions

11. SHAPE.TXT: Instructions for converting SECTIC output to shapefile format using Excel and ArcView3.x.

Note: If the dBase file creation option is chosen, the resulting three databases will have the following fields:

1. SECTIC.DBF contains the following fields for each section corner:

CNTY -The county number of the section corner. Corners on county borders appear once for each county.
TOWRAD - 6 digit identifier concatenated from 3 digit township, 2 digit range and 1 digit direction. Used to index into TOWNSHIP.DBF name file.
TIC - Corner number in township, from 1 to 49.
UTMX27, UTMY27 - NAD27 coordinates for UTM X and Y.
LAT27, LONG27 - Latitude and longitude in NAD27, in decimal degrees.
UTMX83, UTMY83, LAT83, LONG83 - NAD83 versions of above.
QUAD - Index into QUAD.DBF; file of quad names.
CODE - PJ = projected; CR = corrected; NC = No Change


2. TOWNSHIP.DBF contains the following fields:

CNTY - 2 digit county number.
TOWRAD - 6 digit TOWRAD identifier as in SECTIC.DBF above.
TOWNNAME - Township name


3. QUADS.DBF contains the following fields:
QUAD - Index number, as in SECTIC.DBF
NAME24K - USGS 24K quad name
NAME100K - USGS 100K quad name
NAME250K - USGS 250K quad name
Detailed Citation SECTIC24K.PDF
Table Detail:

Section 6 Distribution
Publisher Minnesota Geospatial Information Office (MnGeo)
Publication Date 1999
Contact Person Information Nancy Rader, GIS Data Coordinator
Minnesota Geospatial Information Office (MnGeo)
658 Cedar Street, Room 300
St. Paul, MN  55155
Phone: 651-201-2489
Fax: 651-296-6398
Email: clearing.house@state.mn.us
Distributor's Data Set Identifier sectic
Distribution Liability MnGeo's data disclaimer is online: www.mngeo.state.mn.us/chouse/disclaimer.html
Ordering Instructions This data set is distributed on the internet by clicking below after Online Linkage. Doing so will tell your browser to start downloading a compressed 'zip' file which will contain the following:

- The SECTIC-24K data set, associated conversion utilities and documentation described in Entity and Attribute Overview element.
- Documentation (.html)
- NOTICE.TXT, the disclaimer.

After downloading this 'zip' file, uncompress (unzip) it to extract the files described above. For help, see: www.gda.state.mn.us/resource.html?Id=16253#compress

***This program does not run on Windows 7 - 64 bit computers (it does run on Windows - 32 bit). There is also a web service that generates much the same info as the sectic program. See geoint.lmic.state.mn.us/pete/pls.html . The main differences are it may not do NAD27/NAD83 shifts and it doesn't have a batch mode. A batch mode could be created using the web service and the scripting code of your choice.***
Online Linkage I AGREE to the notice in "Distribution Liability" above. Clicking to agree will either begin the download process or link to download information. See "Ordering Instructions" above for details.

Section 7 Metadata Reference
Metadata Date 10/04/2013
Contact Person Information Nancy Rader, GIS Data Coordinator
Minnesota Geospatial Information Office (MnGeo)
658 Cedar Street, Room 300
St. Paul, MN  55155
Phone: 651-201-2489
Fax: 651-296-6398
Email: clearing.house@state.mn.us
Metadata Standard Name Minnesota Geographic Metadata Guidelines
Metadata Standard Version 1.2
Metadata Standard Online Linkage http://www.mngeo.state.mn.us/committee/standards/mgmg/metadata.htm


This page last updated: 10/04/2013
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