The Search Published Control command allows you to search published control mark data freely available on the National Geodetic Survey (NGS) web-site (http://www.ngs.noaa.gov) and optionally store the retrieved information to the active coordinate file.
Map Tab: Use the Map tab to navigate to a location bounded by a viewing window no greater than 2 degree of latitude by 2 degree of longitude. The limits of the current view are shown at the lower right of the Map tab (see below). To navigate to the area of interest:
Type: Select the type of the NGS markers that are to be returned.
Order: Select the positional order of accuracy of the NGS markers that are to be returned.
Stability: Select the elevational stability of the NGS markers that are to be returned.
Symbol Size: Use the horizontal slider to adjust the symbol size of the
NGS markers.
Triangle = horizontal
control, elevation unknown
Circle = vertical
control (benchmark), hz position usually scaled
Triangle with circle = 3D
position, all dimensions measured.
Search for Control: Click on this
button to initiate the search for NGS control markers that satisfy
the search criteria.
Horizontal A-order stations have a relative accuracy of 5 mm +/- 1:10,000,000 relative to other A-order stations. Horizontal B-order stations have a relative accuracy of 8 mm +/- 1:1,000,000 relative to other A-order and B-order stations.Additional information can also be viewed at http://gpsinformation.net/main/ngs-accuracy.html.
Stability code A = expected to hold an elevation. Examples: rock outcrops; rock ledges; bedrock; massive structures with deep foundations; large structures with foundations on bedrock; or sleeved deep settings (10 feet or more) with galvanized steel pipe, galvanized steel, stainless steel, or aluminum rods.
Stability code B = probably hold an elevation. Examples: unsleeved deep settings; massive retaining walls; abutments and piers of large bridges or tunnels; unspecified rods or pipe in a sleeve less than 10 feet; or sleeved copper-clad steel rods.
Stability code C = may hold an elevation but subject to ground movement. Examples: Metal rods with base plates less than 10 feet deep; concrete posts (3 feet or more deep); large boulders; retaining walls for culverts or small bridges; footings or foundation walls of small to medium-size structures; or foundations such as landings, platforms, or steps.
Save selected stations to coordinate file? Indicate your preference if the opened NGS control marks should be saved to the current coordinate file.
Pulldown Menu Location: Points > Point Utilities
Keyboard Command: searchcontrol
Prerequisite: Internet connection