DIFFERENTIAL – PROFILE LEVELING Ag 2373 Oct 27, 2003

Announcements Pre-registration starts this week. Exam II one week from Today (11/3) Lab This Week – finish up metal project and learn to read micrometer Other Announcements??

Introduction Leveling, one of several procedures used in surveying is an important skill for many different careers in Agriculture and Environmental Sciences. We will introduce two kinds leveling in this presentation: Differential Leveling Profile Leveling

Leveling In this presentation we will consider leveling as the surveying procedure used to determine: The elevation of points on the ground, the tops of stakes or any structure such as the slab or foundation of a building

Differential Leveling The process of finding the difference in elevation between two points.

Profile Leveling Is the process of determining the elevation of points at intervals (measured distances) along a line. A profile of the line is apparent when these elevations are plotted on a graph. Establishing grades is possible from this profile

Dumpy Level

Dumpy Level

Other types of Instruments used for Leveling Hand levels Tilting levels Transits Automatic levels Lasers and Electronic digital levels

Tripod Fixed Leg Tripods Adjustable Leg Tripods

Philadelphia Rod

Field Notes Field Notes, kept in a field book are considered a legal document and in some cases may be used to solve legal disputes in a court of law. Field notes are printed with a sharp hard leaded pencil. Ink pens should not be used except on the cover of the field book

Field Notes If mistakes are made in the field notes they should be crossed out and corrected. Erasers should never be used. Field notes and diagrams should be well laid out in an organized form so that they can be easily interpreted, even years later. Maps and sketches are kept on the right hand half of the page.

Field book Scan note form that David sent me One page of a typical Survey Field Book. Left and Right pages are considered one page. Right half for sketches.

Differential Leveling Terminology BENCH MARK, BM – Point of known or assumed elevation. Usually assume it to be 100.00 ft. Very seldom is it necessary to know Mean Sea Level, MSL of BM. Turning Points are temporary BMs upon which a foresight, FS and a backsight, BS are taken for the purpose of continuing the line of the survey. TP name comes from turning the Phil rod so instrument person can read a BS on it.

Differential Leveling Terminology Backsight, BS – are taken on known or assumed elevations. BS are added (+) to elevation of previous point to get instrument height. Foresights, FS – are taken on unknown elevations. FS are subtracted (-) from instrument height to find elevation of point FS was taken on.

Differential Leveling Terminology Height of Instrument, HI – is the elevation of the line of sight (cross hair) when the instrument is level. It is found by adding the BS reading to the elevation of the point on which the BS was taken. Closure – Procedure of differential leveling back to BM 1 or to another n BM with a known elevation to check for error.

Differential Leveling Terminology Allowable Error or Allowable Misclosure. Closure error allowed depends on degree of accuracy required. We will use a Third Order which is approximately: AE = 0.10 Traverse Distance in Miles Traverse Distance. Distance used to differential level from BM 1 to BM 2 and back to BM 1 or to another known BM. Traverse Distance in feet is converted to miles to use in formula above.

Differential Leveling Terminology Arithmetic or Page Check. Procedure used to check for any arithmetic errors in field notes. When differential leveling the sum “” of the BSs + or - sum of the FSs should be the same difference as BM 1 + or - BM 2 elevation. Note: Should have the same number of FS readings as BS readings when doing differential leveling.

Differential Leveling requiring TPs. 6.82 9.42 5.34 2.12 5.68 1.62 TP 3 4.34 2.34 BM 2 TP 2 TP 1 BM1 = 100.00 ft.

Differential Leveling Note Form STA BS HI FS ELEV DIST BM 1 100.00 Note form on the Left half of the page. Notice there are 6 columns.