When most people think of field work, they often think of surveying. Of course, the term "surveying" can connote several things. Surveying can involve activities such as asking people questions during structured interviews. It can also mean that someone is simply looking around, taking stock of what she or he sees on the landscape. In its most common useage, however, and certainly the one most akin to geographic field work, it means mapping with sophisticated and complex instruments. The profession of surveying involves people with highly developed skills and expertise. Members who earn a living conducting cadastral surveys for the general public have to be licensed by the state.
Tools used by surveyors have changed over the years, and many "old" tools can still be purchased new, and are still used by some field workers for various tasks. Among the arsenal of such instruments are the level, a more elaborate and high-powered version of a hand level mounted on a tripod; the plane table and alidade, the former of which is a drawing board mounted horizontally on a tripod, the latter of which is similar to a level but is mounted on a flat base which is set on the plane table and used in the actual drawing of maps in the field; and the theodolite or transit which is used for measuring horizontal and verticle angles.
Thus far, this course has provided hands-on experience with the most basic and inexpensive of mapping, or surveying instruments-measuring tapes and the Brunton Pocket Transit. On one hand, it has all been rather elementary. On the other, the essential principles and theories of mapping have all been covered. Also, for a great deal of small area mapping for geographical and other purposes, Bruntons and tapes are about all one needs. To be sure, geographers rarely need to obtain the precision demanded of land surveyors, especially those measuring downtown properties that sell by the square inch, and those aligning the foundations of 50-storey buildings. When they do, however, when the job calls for very precise measurements, a high-tech instrument combining optics and computers has been developed recently, the Total Station.
Total Stations are so named because they do everything in one self-contained unit. They involve all the advantages theodolites and eliminate the need for measuring tapes. They do the latter by virtue of something called electronic distance measuring (EDM). The instument transmits an infrared laser beam that is reflected back off a mirrored prism. The time it takes for the beam to travel is converted by an on-board computer into units of spatial measure. Distances, angles, and other information so gathered can then be stored in a data recorder and later downloaded into computers loaded with software designed to convert measurements into maps. Total Stations which use lasers and have internal data recorders can cost over $20,000. Models using infrared light and relying on external data recorders cost about half as much.
Given the cost of a Total Station, the level of skill needed to operate one, and the comprehensive and introductory nature of this course, students will not be given some basic instruction and then turned loose to complete a job. Instead, one class period will be devoted to a participatory demonstration, and three will involve small groups of students actually working with a Total Station. Those students interested in gaining additional hands-on experience, may borrow the Total Station once they have demonstrated competency in its use.
Brief instructions for using a Nikon Top Gun total station. Page numbers in parentheses coincide with those in the instruction booklet included in the carrying case.
1. Set-up tripod.
2. Mount instrument and level (see p. 13). To change Initial Mode Settings see pp. 60, 56-59.
3. Press PWR (p. 18)
4. Rotate telescope 360 degrees+ (p.18)
5. Press 2nd (p. 22)
6. Press T-P (p. 22)
7. Press ENT to move cursor if necessary. To change temperature and pressure see pp. 22-23.
8. Press XYZ (p. 43)
9. Press ENT (p. 43)
10. Press ENT to move cursor to "HI" (p. 43)
11. Measure height of instrument with a measuring tape.
12. Set "HI" (see pp. 43-44), and change other Station Point Coordinate Settings if necessary.
13. Press ENT enough times to put "ZB" on top line.
14. Mount prism on pole and set at 2 meters.
15. Set prism at Coordinate Reference Direction, "arbitrary North" (see pp. 44-45).
16. Aim instrument at prism and focus.
17. Press ANG (p. 28)
18. Hold down RST (p.29)
19. Press MSR (p. 45)
20. Wait while readings are taken
21. Press XYZ (p.45)
22. Record X and Y.
23. Press XYZ (p.45)
24. Record Z.
25. Move prism pole to next point.
26. Repeat step 16.
27. Repeat steps 19-24.
If a data recorder is unavailable or the project is very small and does not call for one, field workers can record data in a traditional field notebook [example].
Created by William E. Doolittle. Last revised 2 August 2017, wed