What Are NGS Benchmarks?The USGS defines a NGS Benchmark as:
"A fixed, more or less permanent reference point or object of known elevation, the U.S. Geological Survey (USGS) installs brass caps in bridge abutments or otherwise permanently sets bench marks at convenient locations nationwide, the elevations on these marks are referenced to the National Geodetic Vertical Datum (NGVD), also commonly known as mean sea level (MSL), locations of these bench marks on USGS topographic maps are shown as small triangles, since the marks are sometimes destroyed by construction or vandalism, the existence of any bench mark should be field verified before planning work which relies on a particular reference point, the USGS or local state surveyors office can provide information on the existence, exact location and exact elevation of bench marks."
Can I see corresponding the NGS Data Sheets?Yes, click the Information Tool on the toolbar, then click on one of the NGS Benchmark symbols. The NGS Data sheet will appear. Options are giving for printing and saving the sheet.
How do I search for a NGS Benchmark?Open the Find menu and choose Browse Category, Benchmark. A list of all the Benchmarks in the state will appear.
When I export maps into my GIS application, I'd also like the NGS data sheets that correspond to the map. Does Terrain Navigator Pro offer an easy way to do this?Yes. When you export your maps (using File, Export Active Map or Export Multiple Maps) choose the NGS Data type and Extraction settings to match your specifications. A set of NGS sheets will be generated to match when the map(s) are exported.
Are regular updates to the NGS data sheets available?Yes - for "DVD" editions of the states.
As part of the annual subscription, NGS data sheets are updated roughly every 6 months. (If you have a specific need, please call and we can process an update.) The subscription also includes aerial photo access and software maintenance/updates.
To access the updated NGS data sheets, please log into your TNP Account.
Please note that we are unable to offer NGS data sheet updates for the older "Maptech" CD regions of states. (CD regions were sold prior to June, 2009.) If you have an older CD set and wish to receive updated NGS data sheets, please contact us to upgrade to the DVD set for your states.