determining the relative locations of points (places) on the earth's surface by measuring horizontal distances, differences in elevation and directions
topos (Gr.): place; topographic maps give the locations of places (observable features); they serve as base maps
establishing vertical and horizontal control for accurately defining locations
General Principles
select a scale in advance; this determines the plotable error
work from the most accurate to the least accurate methods
orient each survey, preferably with respect to true north
the first stage of surveying is always establishing horizontal and vertical control: the distance, direction and difference in elevation between key fixed points
establish a survey plan that includes checks on accuracy, e.g. redundant points, pacing of measured distances, surveying between fixed positions, etc.
Methods
horizontal distance
tachymetry: a rapid optical means of measuring distance using a telescope with cross hairs and a stadia rod (one stadium = about 607 feet)
measuring slopes distance with a tape and reducing it to horizontal distance using the cosine of the slope gradient
difference in elevation
leveling with a level telescope and a stadia rod, or
measuring a vertical angles and a slope distance (height is the product of the distance and sine of the angle)
Leveling is more accurate since elevation differences are measured not calculated. Two readings are taken at each position of the automatic level: a backsight towards a station located before the level on the traverse and a foresight to the next station on the traverse. Thus the stadia rod occupies two stations, before and after the level on the survey. The difference in elevation between successive stations if the difference between the backsight and the foresight read from the stadia rod. For each position of the level, the lengths of the foresights and backsights should be approximately the same since accuracy is a function of the distance of a sighting. The level operator should anticipate the distance to the next station and set up the level midway along this distance (note: the distance that can be sighted decreases with increase in slope, since the stadia rod will disappear above or below the level line of sight). The lengths of backsight and foresight can be paced by the rod person or measured by the interval between the upper and lower cross hairs (tachymetry).
yes it is real, Arnel, I collect this photos.
I can' remember where I got this one but it is some students running a level loop on a volcanic plain somewhere....
Survey Photos by Tag or CategoryEarth's Largest Survey Photos Collection
Since 2007, Land Surveyors around the world have shared their best Surveying Photos from the field. Inside this collection you can transport yourself to virtually any location on Earth and see how Land Surveyors work, types of equipment being used and environmental challenges associates with being a land surveyor in that location.
Location Based Chapter Hubs also have photos specific to the locations they represent. You can use our Surveyor Apps for quick sharing of your photos from the field.
Note: Members who have uploaded their photos of surveying to this collection can also move their photos to location based hubs. To see how, follow this tutorial.
Survey Photos by Tag or CategoryEarth's Largest Survey Photos Collection
Since 2007, Land Surveyors around the world have shared their best Surveying Photos from the field. Inside this collection you can transport yourself to virtually any location on Earth and see how Land Surveyors work, types of equipment being used and environmental challenges associates with being a land surveyor in that location.
Location Based Chapter Hubs also have photos specific to the locations they represent. You can use our Surveyor Apps for quick sharing of your photos from the field.
Note: Members who have uploaded their photos of surveying to this collection can also move their photos to location based hubs. To see how, follow this tutorial.
Thoughts
Where is this Luke, and what are the circumstances?
Keith
Topographic Surveying
Use of topographic surveying in geography:
General Principles
select a scale in advance; this determines the plotable error
work from the most accurate to the least accurate methods
orient each survey, preferably with respect to true north
the first stage of surveying is always establishing horizontal and vertical control: the distance, direction and difference in elevation between key fixed points
establish a survey plan that includes checks on accuracy, e.g. redundant points, pacing of measured distances, surveying between fixed positions, etc.
Methods
Leveling is more accurate since elevation differences are measured not calculated. Two readings are taken at each position of the automatic level: a backsight towards a station located before the level on the traverse and a foresight to the next station on the traverse. Thus the stadia rod occupies two stations, before and after the level on the survey. The difference in elevation between successive stations if the difference between the backsight and the foresight read from the stadia rod. For each position of the level, the lengths of the foresights and backsights should be approximately the same since accuracy is a function of the distance of a sighting. The level operator should anticipate the distance to the next station and set up the level midway along this distance (note: the distance that can be sighted decreases with increase in slope, since the stadia rod will disappear above or below the level line of sight). The lengths of backsight and foresight can be paced by the rod person or measured by the interval between the upper and lower cross hairs (tachymetry).
I can' remember where I got this one but it is some students running a level loop on a volcanic plain somewhere....