surveying iii (topographic and geodetic surveys) - Modern Prepper

and cultivated, or fields may have become overgrown or reforested. Gather and consider all availableinformation when searching for a station.(1) Trig lists, control cards, and control bulletins contain brief descriptions and sketches ofstations. The information may be outdated or insufficient for a final product but will permit surveyors tolocate the general vicinity of the station. The final step in locating the station involves the use ofdistances and azimuths from the reference marks (RMs) to the station.(2) Previous survey data may include survey schemes, overlays, or plots depicting the relativeposition of the stations in the general area. After one or more stations have been recovered, the otherstations may be roughly plotted and located using a magnetic compass and either intersection orresection methods.(3) Aerial photographs may be used if the station to be recovered can be identified in aphotograph. Using features that are permanent and prominent on both the photograph and the groundwill permit surveyors to reach the station site.(4) Maps with the station's plotted coordinates permit surveyors to identify the route of travel tothe station. Maps also assist surveyors in determining the station's accessibility.(5) Local information sources include local surveyors, public-service officials, constructioncompanies, and landowners. Local sources may be the only means of locating a station if the area hasdramatically changed since the other sources of information were published.c. Verify a station before using it. In a situation where only one other station is intervisible, acheck-distance measurement can be performed using the GPS or a conventional method. When two ormore stations are intervisible, check-angle observations or GPS measurements can be performed. Afterthe measurements and observations have been performed and reduced, they will be compared to thepublished information. If the results within the overall specifications for the survey project agree, thestations may be used.2-49. New Station Sites. New station sites will be selected after all existing stations have beenrecovered, described, and verified. The new stations will be placed where required to complete thescheme of the survey. The correct selection of a new station site will save time and expense and prolongthe life of the new station. Take the following factors into consideration when selecting a new stationsite.a. Monuments can be permanent or temporary.(1) Permanent monuments are set in a relatively stable material or structure for the purpose ofpreserving the location of either horizontal or vertical control. Consider another site if the proposed sitemight experience disturbance or land development. Since there is a wide variety of possible situationsthat may beEN0593 2-26