National Geodetic Survey Control Stations

National Geodetic Survey Control Stations (NGSCS)

Radial Search

Requires Google Earth Version 4.3 or later.

NGSCS Radial Search creates a Google Earth network link that plots the approximate location of NGS control stations within a specified distance of the view center (Fig. 1). See NGS Datasheets for a list of supported locations.

Position the point of interest (POI) in the center of the view. One way to do this is to double-click an unmarked location. To precisely position the POI in the center of the view, add a placemark at the desired location; then edit the properties of that placemark and reset the view.
Check the box beside the Search Results network link. Range rings and station markers should appear within two minutes.
- H = Horizontal only
- V = Vertical only
- B = Both horizontal and vertical
On subsequent uses, reposition the POI and ensure that the network link is checked and selected. Then choose Refresh from the Edit menu, or right-click and select Refresh in the context menu.

Station markers are plotted at full-precision datasheet coordinates. Horizontal control stations typically have precise geodetic coordinates with five decimal digits of seconds, while vertical-only marks are usually scaled to whole seconds.

Figure 1. Radial Search
The radius, reference type, and station stability can be changed by visiting NGSCS Query Setup. Radii up to 10 miles are permitted, but the NGS server will not retrieve a list with more than 3000 stations.

Rectangular Search

Requires Google Earth Version 4.3 or later.

NGSCS Rectangular Search creates a Google Earth network link that plots the approximate location of NGS control stations within the viewer bounding box (Fig. 2). See NGS Datasheets for a list of supported locations.

Position the area of interest (AOI) in the viewer.
Check the box beside the Search Results network link. Station markers and the AOI rectangle should appear within two minutes.
- H = Horizontal only
- V = Vertical only
- B = Both horizontal and vertical
On subsequent uses, reposition the AOI and ensure that the network link is checked and selected. Then choose Refresh from the Edit menu, or right-click and select Refresh in the context menu.

Figure 2. Rectangular Search
The reference type and station stability can be changed by visiting NGSCS Query Setup. Areas up to 20' x 20' (arc minutes) are permitted, but the NGS server will not retrieve a list with more than 3000 stations.

County Search

Works with Google Earth Version 4.3, Google Maps, Bing Maps,
NASA World Wind Version 1.4, or ESRI ArcGIS Explorer Build 500.

When the Google Earth radio button is selected on the setup form, NGSCS County Search creates a network link that plots the approximate location of NGS control stations within a selected county (Fig. 3). See FIPS Codes for a list of supported locations. Google Earth must be installed as the default KML application when this option is selected.

The County Search network link is activated when it is first loaded. Station markers should appear within two minutes.
- H = Horizontal only
- V = Vertical only
- B = Both horizontal and vertical
To update the county search, ensure that the network link is checked and selected. Then choose Refresh from the Edit menu, or right-click and select Refresh in the context menu.

Figure 3. County Search
County searches do not currently recognize tanks or towers as horizontal marks. To visualize horizontal stations, plot all marks and uncheck the Vertical folder. Destroyed marks and marks with incomplete datasheets are not reported by county searches, nor do county searches assign vertical order to horizontal control stations with NGVD 29 heights.

Search results may be directed to Google Maps (Fig. 4) by selecting the Google Maps radio button on the setup form. Support for this feature depends on the availability and limits of the Google Maps server. The server will not accept more than 1050 stations, and a response of "File not found" indicates a server timeout.

Figure 4. Google Maps
Search results may be directed to Bing Maps (Fig. 5) by selecting the Bing Maps radio button on the setup form. Support for this feature depends on the availability and limits of the Bing Maps server. The server will not accept more than 200 stations, and a response of "This content is not available" indicates a server timeout.

Figure 5. Bing Maps 3D
Search results may be directed to a generic KML 2.1 document by selecting the Other radio button on the setup form. The resulting file is suitable for viewing in NASA World Wind (Fig. 6) or ESRI ArcGIS Explorer (Fig. 7).

Figure 6. NASA World Wind

Figure 7. ESRI ArcGIS Explorer
The county, reference type, and station stability can be changed by visiting NGSCS Query Setup.

See NGS Station List for source data. All data are retrieved from remote servers. Data errors, accuracy, and availability are beyond the control of this application.

NGSCS is a component of Google Earth
Survey © 2007-2009 Metzger & Willard, Inc.
Google Earth Survey is not affiliated with Google in any way. Google, Google Maps, and Google Earth are trademarks of Google, Inc.