INTRODUCTION:
This CD was created to disseminate survey
information in Burnett County. Burnett County has had an ongoing
program to map PLSS corners into the county coordinate system.
This has been accomplished by compiling conventional survey traverse work
into large least squares adjustments. The work of compiling
traverse and maintaining the adjustments has been performed by North Country
Surveying, Inc. under contract with Burnett County. The software
selected to do this is Star*Net-Professional Edition V6.0 from StarPlus
Software.
The county coordinate system is a Lambert
conic conformal map projection using a custom ellipsoid that is at a design
elevation of 1000 feet above sea level. See the Land Information
Office for additional information regarding the county coordinate system
if you need it. For all practical purposes, surveyors can use the
county coordinates as ground coordinates. If the elevation of your
project is less than 800 feet or more than 1200 feet, you may want to consider
a a scale or grid factor to better match the coordinates.
The traverse data used in these adjustments
comes from many sources of differing quality. It is up to the user
of the data to determine if the information is suitable for their purposes.
No guarantee, as the to correctness or quality of this data, is made by
Burnett County, North Country Surveying, Inc., or any of the other contributors
of the data compiled. The data includes previous county surveyor
projects spanning more than 20 years, private survey data from all deputy
county surveyor firms, ongoing county projects, other private survey data,
state data from Wisconsin DOT and DNR, Minnesota DNR data, Baker 1938 remonumentation
work in Blaine, Polk County projects, Washburn County projects and others.
Instrument libraries that define different sets of standard errors are
used to weight the data of different quality.
Some the data that has been entered
is called "mod" data. This comes from former County Surveyor Gerald
Wagner's mod sheets. These mod sheets consist of drawings of
6 sections showing bearings or angles and distances around the sections.
In this data we do not know the underlying traverse information and only
know section line angles and distances. Based a statistical analysis
of mod data in Scott Township where we also had the underlying traverse,
we developed appropriate standard errors to associate with this data.
Some of the inverses shown on these mods are quite weak and this degrades
the quality of the mod data. Information based exclusively
on mod data will show up with large error ellipses and you should be careful
in what it is used for.
The networks are controlled by GPS and
conventional traverse measurements using the Burnett County Geodetic Control
Network as fixed control. This network of 123 stations was
completed in 1994. It was bluebooked to be included in the
National Spatial Reference System as a 10ppm or First Order Survey.
2ppm to 5ppm was actually attained in 95% relative positioning between
the monuments of this survey.
ADJUSTMENT ZONES
The county has been divided into 11
adjustment zones. All ACAD maps on this CD are available in
three formats. This includes ACAD2000, Release 14 DWG (appended
-R14) and Release 12 DXF (appended -R12). ACAD maps of
these zones are included on this CD. As an added bonus, the background
map is Burnett County's base map used for county wide plots.
It originates from the 1:100,000 USGS DLG data, but has been editted in
many areas for road centerline and possibly hydrography information where
ortho photos are available. This map is on the county county coordinate
system.
Point numbers are planned to be between
1 and 10,000 in each zone. This will allow for appending the
zone number to the front of the zone point number to create a unique county
wide numbering system. Within a zone it is not necessary to use more
than a four digit point number.
The seam lines between zones have been
designed to be along roads (or open areas) that have PLSS corners, whenever
possible. We hope that this will allow for GPS shots to be
done on these PLSS corners and the resultant coordinates used in both zones.
This will solve the problem of different coordinate values for seam line
points. Significant progress on this has been made in some
areas of the county since 1994. The seam lines are not always
accurate boundaries of the data available in a zone. There
are times that a particular project spills over into an adjoining zone.
We have not always had time or sometimes it is not possible to sever the
data at the planned seam line. If you are near a seam line,
check the adjacent zone. While the zones do not exactly follow
town lines, the following list shows roughly what townships are in which
zones:
0.) Union, Oakland, Jackson,
Sand Lake North, Meenon North, Lincoln
1.) Swiss, West Blaine
2.) Webb Lake, East
Blaine
3.) Rusk, Scott
4.) Dewey, Roosevelt
(Note the only significant part of county above 1200 feet is in
Roosevelt.)
5.) LaFollette,
Sand Lake South
6.) Siren,
Meenon South
7.) Daniels,
Lincoln South
8.) Trade
Lake, Anderson
9.) Grantsburg
10.) West Marshland,
Union
DATA INCLUDED ON THIS CD
1.) Subdirectory - STAR This directory includes Star*Net
files for each adjustment zone. The data for each zone begins
with BCZ##, where ## is the zone number. All Star*Net files are ASCII
text files and can be read with a text editor that can handle large files.
The following list shows the file extensions for the different types of
Star*Net Files:
a.) *.DAT = This is an input
data file
b.) *.LST = This is an output
listing file
c.) *.PTS = This is a points
file in county coordinates (PNED in columns)
d.) *.POS = This is a points
file in Lat-Long NAD83(91) (PLLD in columns)
There are many items that need to be examined in these files to determine
the quality of the final coordinate values. A review and discussion
of some of the items is found below in the Star*Net section.
2.) Subdirectory - BC LAND PROJECTS This subdirectory
includes ACAD Land Development Project Files for each Adjustment Zones.
The projects are compatible for both LDD Release 1 and 2. The
projects and drawings are named Z##YYMM.DWG, where ## is the zone number,
YY is the year created and MM is the month created. These drawings
provide a snapshot of the adjustment at a particular point in time.
You can expect that the coordinates will change as data is added and upgraded
in the future. Under each project, you will find a subdirectory
named DWG. This contains the AutoCAD drawings for each zone.
All ACAD drawings on this CD are available in three formats.
This includes ACAD2000, Release 14 DWG (appended -R14) and Release 12 DXF
(appended -R12). In the future, we are hoping to use the new
LDD features for external point databases. This could
be used to splice in elevation data from a separate adjustment or list
or provide a connection from the points in a drawing to a proposed county
survey point database that would contain a lot of additional information
about the survey points.
3.) Subdirectory - LEVEL This directory contains
information from various countylevel projects. Reports
contains the reports for the Yellow River Flood Study Control Project.
Levels contains reports on the Gandy Dancer Level Project.
Levels were run from STH77 bridge over the St. Croix, into Danbury, to
the Danbury Dams, and south on the Gandy Dancer to the Burnett County Airport.
Lev-adj contains Star*Lev files for the Gandy levels, the BC Level Net
(run down STH 70 from Washburn Line east into Siren, with side runs
up Dongola and beyond and to Stellrecht GPS station), and other various
smaller runs. These are all based on work done by Mike
Norton. The field notes are available at the Burnett County
Office of Land Information. COE contains Star*Lev files
for the entry of Corps of Engineers data from their Flood Study.
We attempted to get this data into a Star*Lev readjustment so we could
use it to build into our county level nets. This had
vary degrees of success. See the report for more info. An ACAD
map of benchmarks has been included in the BC Land Projects subdirectory
called BMMARKS.DWG. The elevations shown are NGVD 29 and the
points may not have high quality horizontal coordinates.
4.) Subdirectory - PNTSFRMT This contains the points file
for each zone formatted for use with other software. The files are
named Z##.PTS, where ## is the zone number. The format is comma delimited
with PNEZD. Z = -99999 for invalid elevations on 2D points.
5.) Subdirectory - SURVINDX This contains the Burnett County
Survey Index in a DBase III format. This is the entire index
of surveys in the card file at the county surveyor's office. It was
updataed within the last month. There is a DBF file containing the
main database and a DBT file with the memo fields. See
the Land Information Office for information on the fields, although they
are quite self explanatory. Note the older section surveys
of Conner and other earlier surveyors are not listed in this index.
For these older surveys, it is necessary to check the WPA index of surveys
that was created by WPA and maintained up through County Surveyor Buggert,
circa 1970. There is additional information in this directory.
The Survey Index is provided as a MDB or Microsoft Access Database File.
To the best of my knowledge, I believe that it is an Access 97 file.
A Release 14 AutoCAD map named PARCORTHOKEYMAP shows which sections in
the county have ortho photos available and which sections have been parcel
mapped. DIGORTHO.DBF is a Dbase III file of the digital ortho photos.
6.) Subdirectory - TAXROLL This contains the Parcel Assessment Database
maintained by Burnett County. This is a Dbase III+ file format.
The creation of this CD has been delayed to approximately March 1 to allow
inclusion of the latest updates and splits for the current year.
A file named FORMAT.TXT in this subdirectory describes the field names
and structure. The field names are quite self explanatory.
This data is being released to surveyors using this CD with the following
understanding: It is not allowable to give or sell this database
to anyone else. It is intended to be used to help surveyors in their
research.
7.) Subdirectory - METADATA I tried very hard last
year to create standard metadata files with several different methods.
This attempt is enough to drive a person completely mad. The error
output from the program MP is impossible to comprehend and when I attempted
to fix the errors, it got worse. The file BCPLSDAT.TXT is as
close as I could get last year and I have manually editted it to reflect
this years data. This still contains over 20 errors and MP would
not create the HTML or SGML files.
8.) Subdirectory - BLAINE PROJECT - This contains reports on using
CMM to adjust Baker's WPA remonumentation survey in Blaine into the County
Coordinate System. See this report for information on the project
and the quality of the results. ACAD drawings of both
townships are included in the BC Land Projects Subdirectory.
9.) Subdirectory - PARCEL MAP - This contains all the 149 parcel maps
presently completed or prelmininary in Burnett County. Each
drawing is of a section. This are all saved as ACAD R14 drawings.
See the README file in this directory for information about the parcel
maps.
STAR*NET DAT FILES AND HOW TO DETERMINE CONNECTIONS
The DAT file contains all the measurements
in the adjustment. Some data could be included using
INCLUDE statements, which includes an external file. We have attempted
to eliminate all these types of files that contain measurement data.
Each adjustment uses an INCLUDE file which is specified at the top of the
DAT file. This is an approximate coordinate file that is used
to make the adjustment run faster. These approximate coordinate files
have not been included on this CD. Lat-Long values represent control
points, usually NGS stations or other points with GPS data available.
All control stations that are followed by "!" are fixed coordinates and
usually are stations of the BCGCN. Other points that have numbers
after the Lat-Long values have Standard Error Values assigned to the coordinate.
These generally are GPS shots to PLSS corners or traverse points and are
held partially fixed in the adjustment.
You should use a text editor to search for
every occurrence of a point number that you plan to use. This
is a method to determine how a corner is connected to the network.
You can determine if it has GPS coordinates or if it is based on a single
stub line. This is the best way to determine the redundancy
involved in computing a corner's coordinates at this time. If you
cannot find a point you need to look for include files and search in them.
We are hoping to develop a database of survey
points in the future that will allow us easier access to the status of
a point. For each section of data in the DAT file, a header
has been added at the start of the section to specify where the data came
from, the date and other pertinent info that we might have decided to include.
It will also list the instrument library of standard errors assigned to
that data.
It is extremely important to determine if
a corner that you are relying on has redundant measurements connecting
it to the network. If it is based on a single measurement, it is
possible that undetected blunders can be in the coordinate for that point.
There can be blunders in measurements, recording of the measurements, or
in data entry for computations. We are attempting to create as much
redundancy as possible for every corner in the county. However there
are many corners that are based on stub line traverses or single measurements.
We still enter the single measurement or stub traverse to the corner and
hope that in the future we can add redundant measurements to verify the
position.
It is not possible in these traverse adjustments
to determine if a GPS position has redundancy or not. As far
as the NCS GPS work for Burnett County, we try to make two independent
measurements into a point if the there are no traverse connections to the
point. If there is a traverse connection, we will make only one measurement.
There are times that one measurement works and we cannot get the second
one to resolve, or we get two measurements that don't come to the same
point. In these instances, there may be a single shot GPS coordinate
entered into the traverse adjustment. We are not able to perform
an adjustment with both the GPS vectors and the traverse data together
because so much of our data is 2D. GPS adjustments are required
to be 3D. In the future, our survey point database could tell
you how the point is connected. We hope to compile all the GPS shots
for mapping corners into GPS adjustment for each zone and make that available
on future updates of this CD.
STAR*NET LST FILES AND HOW TO DETERMINE THE QUALITY OF COORDINATES
The LST file shows the listing of the results
of the adjustment. A list of what is in the LST file follows:
1.) Adjustment Date
2.) Files Used
3.) Adjustment Options
4.) Input Standard Errors Used for different
Instrument Setups
5.) Optional Input Data File
6.) Stress or Residuals on Partially
Fixed Stations
7.) Adjusted Coordinates
8.) Results and Statistical Evaluations
of Adjustment
9.) Adjusted Observations and Residuals:
Coordinates, Angles, Distances,
10.) Adjusted Bearings and Distances
of Observations and Lines Specified for Relative
Ellipses. This includes the section lines.
11.) Convergence Angles and Grid Factors
at Each Station in the Network
12.) Traverse Loop Closures
13.) Station Coordinate Standard Deviations
14.) Station 95% Error Ellipses
15.) 95% Relative Error Ellipses
There are many items to look at in this file. Residuals show
how much an observed value has been changed in the adjustment.
You need to look at the residuals of coordinates, angles and distances
in the area you are working to know how well the original data is fitting
together and the resultant stress. We don't use the traverse
type data entry anymore and so the traverse loop closures only show up
on some of the older entered data. These loop closures don't
mean much in a full network like we have here. The Station Coordinate
Standard Deviations express how well we know the coordinates of a point
in relationship to monuments of the BCGCN. Standard deviations are
evaluated at a 68% confidence interval. The station error ellipses
show a similar thing, except they are evaluated at 95% and are expressed
with a azimuth showing the computed direction of the maximum possible error.
This maximum computed possible error is the semi-major axis of the ellipse
and the semi-minor axis is perpendicular. Remember that there
is still a 5% chance that the true coordinate could fall outside the ellipse.
Our checking of these error ellipses with GPS shots has confirmed that
our weighting of the input data has produced realistic 95% station error
ellipses.
The 95% relative error ellipses show how well
a point is know in relation to another point. There are many times
where we don't have the best location of the points in an area within the
county coordinate system, but we have good measurements between them.
In this instance, you will have large station error ellipses with a small
relative error ellipse between them. This situation tells us
that while the coordinates will probably move around with subsequent adjustments,
the points are correlated and will move together.
We have attempted to calculate relative error
ellipses on all the PLSS lines that are in the system. The Traverse
Standards adopted by the County Surveyors Association, WSLS, and WLIB requires
that we attain a relative positioning accuracy of 1:10,000 over half mile
intervals between PLSS corners. This is calculated by dividing the
length of the semi-major axis of the 95% relative error ellipse of the
line by the length of the line. In other words for a half mile
line, you want the semi-major axis to be less than 0.26 feet. We
have attempted to use this criteria to determine if measurements used to
map a section are strong enough to parcel map.
AUTOCAD DRAWINGS
The AutoCAD drawings are created by bringing
the Star*Net points file into a drawing. All points are plotted
LDD or Land Developement Desktop Civil Point Objects showing point number
and descriptor. All the adjustments are 2D adjustments, so the elevation
attribute is frozen. Points are filtered to different layers depending
on their descriptor. These layers are described below with
the exception that some points are tagged as private data in the adjustment.
At the request of the contributor, these private data points are actually
erased from drawings before they are released.
We have decided to release drawings in Rel.
12 DXF along with Rel. 2000 and Rel. 14 drawings. The drawings
have been created in AutoCAD Land Development Desktop software.
Release 12 and 14 drawing were created by using the SAVEAS command.
The line work and error ellipses are brought in
with a DXF file from Star*Net. A script file processes these
entities into layers used in the county system and described below.
Relative error ellipse lines that are not direct observations are put on
the section line layer. If a section line has been observed directly,
the line comes in on the observation or trav layer and not on the section
line layer. A graphic determination of the quality of
a point can be determined by viewing the error ellipse around each point
in the drawing.
The following layer structure is used in these
network drawings:
a.) 83PTS =
Control Points and other monuments
83SYM = Control Point Symbols
b.) 33PTS =
PLSS points filtered to layer by PS descriptor with Romportl ID
33SYM = PLSS Points Symbols
c.) 23PTS =
Other Monuments or Points Tied In
23SYM = Monument Symbols
d.) 80TRAV =
Direction observations of distance or angle in the Adjustment
e.) 30SECLINE
= Line Connections between adjoining PLSS Corners unless the line
was measured directly
f.)
80ELLIPSE = Exaggerated Point Error Ellipse
g.) 80RELELLIPSE
= Exaggerated Relative Error Ellipse computed on PLSS lines.
Note the ellipse exaggeration is specified in the drawing title block.
This ellipse scale is 500x for all drawings this year.
These network drawings are large and
can be difficult to work in due to the large size in an older or smaller
computer. You will not be able to save any changes back to the CD.
We have found that you can use the AutoCAD WBLOCK command to block out
any section of the drawing that you want to a temporary file using 0,0
as the reference point, start a new drawing using your favorite prototype
and then insert the temporary file at 0,0. This allows you
to work in a much smaller drawing.
ITEMS TO BE CAREFUL OF
1. ) There are a lot of
double corners out there. If we can compute both positions, we do
it. This is because you may need to retrace a survey based on either
one. You need to examine the corner certificate sheets to identify
where double corners exist and you may want to check that the section line
is drawn to the correct point that you want to use.
2.) The section lines
are occasionally drawn to the wrong point. We have tried very
hard to do the best job we can on this, but we keep running into some that
are not correct. We are sure that we have not found them all.
In the event that you find one, please let us know so we can correct it.
If we get it corrected in the Star*Net data file, all subsequent maps will
be correct.
3.) Watch out
for corners based on single measurements and stub line traverses.
If you verify one, please consider submitting your data to Burnett County
to upgrade the network.
4.) Watch out
for corners that have large error ellipses. These can be based
on very loose data such as Baker 1938 work or other old data.
You need to check this data using the techniques suggested here to determine
if the data has sufficient quality to be used for your purposes.
5.) Due to the large
amount of time covered by the data that has been included in these adjustments,
points and corners have been destroyed and disturbed. You need to
be very careful to verify that you have found enough undisturbed monuments
to insure that you will fit with the system.
CONCLUSION
We hope that this provides you with useful
information for whatever project you are working on. We would consider
any suggestions that you have to improve the usefulness of this CD on future
releases.
We would also encourage you to submit any
survey data that you have to improve this program. The backbone
of this system has been built on contributed private data.
The advantages are that your control points would be integrated tightly
into the system. If two different surveyors have independently measured
around a section, the combination of all the measurements create a much
stronger system due to the redundant observations. In terms of quality,
it would be in the range of 2 to 5 times stronger than a single traverse
around a section. If you would like to consider submitting some data,
we would encourage you to contact us prior to beginning your project.
We may have new data not contained on the CD. We could correlate
point numbers by assigning you an open range of points. This
will make it easier for us to get the data entered and the final county
network points will agree with your field notes and computations.
BURNETT COUNTY OFFICE OF LAND INFORMATION
Kathy Swingle, County Surveyor
Burnett County
7410 County Road K
Siren WI 54872
Tel (715) 349-2599
Fax (715) 349-2102
E-mail: kswingle@win.bright.net
NORTH COUNTRY SURVEYING, INC.
Douglas R. Crane, Wisconsin R.L.S.#1511
7875 Big Doctor Lake Road
Siren, WI 54872
Tel (715) 349-5957
Fax (715) 349-7518
E-mail: doug@ncs-wi.com