In implementing a comprehensive GIS, the City of High Point has begun collecting thematic data for several departments and applications using global positioning system (GPS) technologies. For GPS data collection projects within the City, a set of minimum standards is being followed to assure consistency in resulting products. It should be noted that the City of High Point has adopted the GPS standards developed by the North Carolina Geographic Information Coordinating Council. For a complete review of the technology and standard elements, please refer to the full text of the NC GPS standard.
In April 2010 the Department of Justice issued an advisory opinion that the collection of GIS data by an employee of the State of North Carolina, any political subdivision of the State or a municipality while engaged in that activity in the course of their employment does not constitute surveying without a license. In a second advisory opinion, the Department of Justice stated that this conclusion also applies to regional councils of governments, so long as those entities are authorized by resolution of their member governments. Therefore, the collection of GIS data by local governments does not violate Chapter 89C of the General Statutes since local governments are exempt via the government exemption. For details on the background of this issue and the advisory opinions of the Department of Justice, please read progress on clarifying geographic data collection by local governments from the Surveyor's Model Law Working Group.
This document establishes the minimum GPS standards to be used by City personnel involved in mapping activities as well as individuals and groups submitting digital data to the City of High Point. Please refer to the NC GPS Standard document for field method guidelines as well as specific requirements for accuracy and precision. The following addresses only ground collected data and does not apply to aerial GPS procedures. The standards apply to current technology and are subject to revision as GPS equipment develops.
The City's enterprise GIS database contains data classified as having been located via GPS. These data are verified to be of "sub-meter accuracy" as described in the aforementioned standards and those detailed below. Features collected by any other method or by less accurate and precise means are not listed as GPS-located in the database.
GPS Receiver Standards:
- The GPS receiver must be of mapping-grade or better.
- The GPS receiver must produce and store data in a format compatible with the base station data used to perform the differential corrections or have the capability to receive real-time corrections from the base station.
GPS Data Collection Standards:
- Static Collection: We suggest standing at a collection location for 5-10 seconds to evaluate the quality of signal (PDOP and number of satellites) before gathering points.
- Kinematic Mode: Although kinematic collection will acquire points at lower positional accuracy, we accept line features collected with this method provided points are collected frequently.
- Elevation Mask: The elevation mask should be set to 10 degrees or higher.
- Horizontal Datum: NAD 83 (North American Datum 1983)
- Spheroid: GRS 1980
- Positional Dilution of Precision: Set your receiver to collect points only when PDOP is less than 6.
- Satellites: Set your receiver to collect points only when it has signals from 4 or more satellites.
- Units: Units will be in International Foot.
- Coordinate System: Data submitted to the City of High Point will be in North Carolina State Plane coordinate system.
- Elevation Mode: Use the Height Above Ellipsoid (HAE) as the elevation mode.
- Exchange Format: ESRI Shapefile (one file per theme).
- Metadata: .TXT file including collectors name, date collected, theme description, and receiver type.