The State PID Project – Final Report on State PID Conversion

Sometime at the end of the summer of 2016, I became aware of the need to provide our section corner latitude/longitude to the State Surveyor for inclusion into the state section corner database. After some preliminary investigation and discussion with the County Surveyor, it was determined that we needed to alter our local Lancaster County PID to the accepted state version, and supply our section corners with latitude and longitude positions that we have maintained in the Enterprise GIS database to the State for uploading. Rather than change our local Lancaster County PID, we would create and build the new State PID as another (separate) attribute in our data base and maintain both.

Example of GIS Control Layer Database

Description (column 1) Local Lancaster County PID and in the last column the appropriate State PID

Example of Mapped State PID and local Lancaster County PID

The State Surveyor Announcement:

The Nebraska PLSS Database is ready to accept corner information. Please visit the site and take a look around. Use a browser other than Microsoft EDGE as it doesn’t work with ftp sites which is where all the linked files currently reside. We will change that in the future.

If you want to contribute and you have information that has the observation frame, latitude, longitude, township, range and a description of the section corner that identifies the location in the township we can do all the formatting for you. Just send the files (txt, csv, xls, dbf, etc.) to one of the emails listed on the web page.

The project is intended to provide GIS users more accurate section corner positions and to help land surveyors locate existing monuments prior to commencing field work. The information is not intended to replace established field procedures for boundary surveying.

Nebraska State PLSS Database link: http://www.sso.nebraska.gov/nescdb/nesc.html

Because of the nearly 3000 points in Lancaster County that are involved, and the need to sort out some of the points that we maintain from section corners, we agreed to approach the project one township at a time. This would allow us more effective quality control in the process by creating maps for review based on the Excel data tables derived from the GIS Control layer.

GIS assumptions: adding the Township and Range attribute from the PLSS layer and manipulation of the attributes would allow us to reconstruct most of the State PID. Many point PIDs may need to be manually repaired or replaced. I was able to conflate MOST of the needed elements from the GIS PLSS layer that we maintain due to the excellent attributes maintained with the township level polygons.

County PID = F13N

State Required PID = 1176N13

GIS Spatial Join: Analysis Tools -> Overlay -> Spatial Join

After the Spatial Join, Excel was used to manipulate the points to the appropriate State PID requirement. Since I have had no formal training with Excel, website access to various examples and tutorials made this exercise somewhat easier. This was a bit time consuming and the most difficult part of the project.

Problems: Some points had unusual extensions - sur, as well as am, cc, ccc standard parallel points may require manual adjustment or deletion from the project. Other problems involved common township lines and points that had to be manually corrected for appropriate township and range. Excel manipulation and join of the new State PID was facilitated by trial and error.

After adding in the appropriate new State PID, corner points were extracted from the township and a point database file in Excel was created for the township. All the attributes normally maintained in the GIS were dropped except the local and state PID, and the latitude and longitude attributes. Points that we not part of the section corner needs were deleted and point latitude and latitude was displayed in ArcGIS for further review.

Example of Township T7N-R6E (Buda)

Points displayed by geographical attribute location

Display of the attributes allowed us to check the geographical location of each point relative to the appropriate position. (Note that two points were identified as having the inappropriate geographical attributes in this check and were calculated to the correct position from the County Grid coordinates - see the addendum).

Point maps and Excel files with a ArcGIS online map were provided to Jerry Penry who checked the data for error in point file naming. There were about 5-6 points that had not been named correctly through the process described above. Jerry Penry provided a useful second Quality Control check on the PID process.

Sample Quality Control Check Map in ArcGIS Online

West Oak: T12N – R5E

Once the files passed this second check, they were attached as attributes to the GIS database via a ‘join by desc’ and calculate to the new StatePID attribute. We will maintain the new State PID as well as the local Lancaster County PID. As State Surveyor Steve Cobb uploaded the data we provided, we could perform a third check on the appropriate load of the townships by viewing the data in the State Surveyor database:

The State Surveyor Status Map February 2, 2017

ftp://ftp.sso.state.ne.us/nescdata/status.png

Final Map of the Lancaster County GIS Section Corner Control

Conclusion:

Along with providing the State Surveyor accurate positioning of the various section corners, this project allowed up to identify two errors in the geographical attributes of our data. These were corrected and replaced. I was also able to identify a singular section corner that was missing due to the lack of recent GPS survey along a section line that did not have an open road. One other point has some legal issues and its location is defined differently – this point was held back from the state database for now. (See the addendum).

Missing Section Corner – No Road Access

As the employee in charge of the maintenance of this data base for the last 25 years, my responsibility has ranged from data input from GPS latitude/longitude, coordinate geometry input of points derived from EDM survey and historical record research, as well as creating a wide range of maps and derived products that are based on this data. These corners and coordinates provide the foundation and base for the Enterprise GIS – nearly every user in the County at some level depends on the precision and accuracy of these points. Perhaps this was the most important job I have had in my tenure with Lancaster County Engineering – it has been my pleasure to be involved in this final upload of data to the State Database. I have maintained a series of files for each township when various points from various sources have been added to this GIS layer over the years.

Most of you are aware that there is a new datum that will incorporate height as well as horizontal positioning. My initial research into the new “reference frame” of 2022 indicate differential horizontal shifts of up to three feet for Lancaster County – this has some fairly serious repercussions for our positioning in the future – it is essential that someone from our office with a geodesy background monitor the progress of the new reference frame, and how it may be applied and how it may impact our positioning data.

I thank you for allowing me the time to complete this project, it was an enjoyable exercise that challenged me and my ability to use by GIS knowledge and experience.

Respectfully,

Scott C. Robinson, February 2, 2017

GIS Records Assistant II

Recognition of Project Assistance

Pamela L. Dingman, County Engineer – Guidance and Support

Steve Cobb – Nebraska State Surveyor

Ken Schroeder and Erik Hubl – Project Design and Coordination with State Surveyor

Jerry Penry – Project Quality Control: State PID

Jeffrey McReynolds – Enterprise Control Layer ‘join’ Assistance and Coordination with State Surveyor

Chad Kendall – Enterprise Control layer ‘join’ Assistance

Addendum

Two points with recalculated Geodetics that were incorrectly manually entered to the attribute data base:

Township Waverly T11N - R8E - A21X (E Corner of Section 35, or the W Corner of Section 36)

Township Nemaha : T8N – R8E - R15jsur (N Corner of Section 15, or the S Corner of Section 10)

Two section corners not supplied for the State PID project:

Township Lancaster: T10N – R 7E: (S Corner Section 22; or the N Corner of Section 27)

Township Nemaha: T8N – R8E: (E Corner Section 8, or the W Corner of Section 9)

Email Snip from State Surveyor