4.2 Basic Definitions
| Site: | WERE ELEARNING PLATFORM |
| Course: | LEVELLING SURVEYING |
| Book: | 4.2 Basic Definitions |
| Printed by: | Guest user |
| Date: | Monday, 16 June 2025, 4:04 PM |
1. 4.2 Basic Definitions
• Vertical Line
• Horizontal Line
• Horizontal Plane
• Level Surface
• Level Line: A line that lies on the level surface.
• Difference in elevation b/w 2 points: is the
vertical distance b/w 2 level surfaces.
• Actual Line of Sight or Collimation: Neither
horizontal nor level. Affected by atmospheric
refraction.
4.2 Basic Definitions
• Bench Mark: A marked point whose elevation
has been accurately measured.
• Height of Instrument: The line of Collimation
above the datum after setting up the level above
a certain point.
4.2 Basic Definitions
4.3 Basic Principles of a Level
Differential Leveling Requires:
a) a device which gives a truly horizontal line
(the Level),
b) a suitably graduated staff for reading vertical
heights (the Leveling Staff).
Level consists mainly of:
a) Telescope for sighting and
b) A leveling device for maintaining the line of
sight in horizontal position.
2. 4.2 Basic Definitions
• Vertical Line
• Horizontal Line
• Horizontal Plane
• Level Surface
• Level Line: A line that lies on the level surface.
• Difference in elevation b/w 2 points: is the
vertical distance b/w 2 level surfaces.
• Actual Line of Sight or Collimation: Neither
horizontal nor level. Affected by atmospheric
refraction.
4.2 Basic Definitions
• Bench Mark: A marked point whose elevation
has been accurately measured.
• Height of Instrument: The line of Collimation
above the datum after setting up the level above
a certain point.
4.2 Basic Definitions
4.3 Basic Principles of a Level
Differential Leveling Requires:
a) a device which gives a truly horizontal line
(the Level),
b) a suitably graduated staff for reading vertical
heights (the Leveling Staff).
Level consists mainly of:
a) Telescope for sighting and
b) A leveling device for maintaining the line of
sight in horizontal position.