Effective: July 1, 2019
In an effort to standardize with other City of Grand Island departments, the City of Grand Island Public Works Department has adopted the Low Distortion Projection (LDP) coordinate system as the standard coordinate system for all spatial data housed in GIS and CAD. LDP was developed by the State Surveyor’s office with assistance from other registered land surveyors of Nebraska. The end goal for this project is to minimize grid to ground distortion and make a system (.prj files etc.) that is easy for surveyors and GIS professionals to use.
The LDP will create the best ground to grid solution with control established using recognized local control. This will eventually lead to better source data for all GIS horizontal calculations that improves all of Public Works’ spatial data sets.
One of the best reasons to use an LDP is that there's only one set of coordinates for each point in the county. No scale factors, no localizations as was the case with our previously used “modified” ground coordinate system.
The City of Grand Island Public Works Department requests that all Engineering firms doing business directly for Public Works, or for developers of subdivisions whose projects create infrastructure assets such as paving, storm water, sanitary sewer, etc. that will eventually become City assets, measure x,y coordinates using the Hall County LDP coordinate system. All elevations will continue to be based on the North American Vertical Datum of 1988 (NAVD 88).
Also, the City of Grand Island Public Works Department requests that in addition to the traditional construction plan sets delivered in PDF format (original design and final as-built versions), that corresponding CAD drawing or drawings provided to Public Works are registered to the LDP coordinate system. One CAD drawing submittal is requested at the initial approval for construction and another is requested representing the as-built condition of the project. CAD drawings shall be in .dwg format. These submittals greatly reduce time needed to input this data into the City GIS database.
Additional information about the LDP projection project is available at https://nebldpproject.blogspot.com including projection files, GPS equipment configuration procedures, etc.
We are requesting that all projects beginning in Grand Island July 1st, 2019 utilize this coordinate system. All projects that have started prior to this letter are ok to proceed with the coordinate system in which they were started. If you have any questions, please feel free to contact the City of Grand Island Public Works Department.
Thank you for your cooperation.
Public Works Department
City of Grand Island