Happy National Surveyors Week 2018 Everyone!
The purpose of Surveyors Week (NSPS) is to bring visibility to the profession. During Surveyors Week, land surveyors across the nation celebrate by educating the public on what they do & why it is important; encouraging students to consider surveying as a career choice; and participating in activities that promote and bring awareness to the surveying profession. All licensees, governmental agencies, technical professional organizations and citizens groups are encouraged to join the celebration.
**Due to such large participation in 2014, we are currently in stages of planning 2015 International Surveyors Week June 14th- 21st so stay tuned...Of course you also have Survey Earth in a Day 4D to look forward to..
Add SEIAD To Your Calendar:
Now onto the Importance of Surveyors
Like many of you, I am constantly asked what exactly do surveyors do? And although this question is rarely asked on this network, if at all, i have noticed that there are many surveyors out there who may not be able to explain this themselves. The truth is Surveyors are of enormous importance to the public and without surveyors, land ownership, land development and construction would be absolute chaos. So, I am going to layout some useful information about what surveyors do and invite all of you to add to my notes in the comments below.
I am learning, just like many of you, so the following notes are for teaching each other what we have learned along the way. Please feel free to correct me if I am wrong and add your own notes to keep this discussion going.
Without Surveyors, Engineering would be Chaos
All engineering projects are a puzzle. The planning and design of all Civil Engineering projects such as construction of highways, bridges, tunnels, dams etc are based upon surveying measurements. Without these professionally calculated measurements, we would not know how the puzzle looks when put together.
Moreover, during execution, project of any magnitude is constructed along the lines and points established by surveying.
Thus, surveying is a basic requirement for all Civil Engineering projects.
Other principal works in which surveying is primarily utilized are
• to fix the national and state boundaries;
• to chart coastlines, navigable streams and lakes;
• to establish control points :Control points : Stations having known position.
• to execute hydrographic and oceanographic charting and mapping; and
• to prepare topographic map of land surface of the earth.
Objectives in Surveying
• To collect field data;
• To prepare plan or map of the area surveyed;
Plan : Orthographic representation of features on or near the surface of the earth in Large Scale on a horizontal plane.
Map : Graphical representation of features on or near the surface of the earth in small scale on a horizontal plane and is constructed using a projection system other than orthographic.
• To analyse and to calculate the field parameters for setting out operation of actual engineering works
• To set out field parameters at the site for further engineering works.
Divisions of Surveying
The approximate shape of the earth can best be defined as an oblate tri-axial ovaloid.
Oblate (spheroid) : An oblate (spheroid) is a surface of revolution obtained by rotating an ellipse about its minor axis i.e., having equatorial radius greater than the polar radius.
Ovaloid : A pear shaped figure having dimension of one hemisphere larger than the other for earth, southern hemisphere is larger than the northern.
However, most of the civil engineering works are concerned only with a small portion of the earth which seems to be a plane surface. Thus, based upon the consideration of the shape of the earth, surveying is broadly divided into two types.
In this branch of surveying, the true shape of the earth is taken into consideration.
This type of surveying is being carried out for highly precise work and is adopted for surveying of a large area.
In this method of surveying, the mean surface of the earth is considered to be a plane surface. This type of survey is applicable for small area (less than 200 square kilometer). So, for most of the Civil Engineering projects, methods of plane surveying are valid.
Fundamental Assumptions in Plane Surveying
• All distances and directions are horizontal;
• The direction of the plumb line is same at all points within the limits of the survey;
Plumb line : The direction of the lines of force of earth's gravity field. In field surveying, it is defined by the direction of a freely suspended plumb-bob.
• All angles (both horizontal and vertical) are plane angles;
• Elevations (The vertical distance of a point from a datum.) are with reference to a datum (A levelled surface taken as reference for the determination of elevations of points.)
Classifications of Surveying
Based on the purpose (for which surveying is being conducted), Surveying has been classified into:
• Control surveying : To establish horizontal and vertical positions of control points.
• Land surveying : To determine the boundaries and areas of parcels of land, also known as property survey, boundary survey or cadastral survey.
• Topographic survey : To prepare a plan/ map of a region which includes natural as well as and man-made features including elevation.
• Engineering survey : To collect requisite data for planning, design and execution of engineering projects. Three broad steps are
1) Reconnaissance survey : To explore site conditions and availability of infrastructures.
2) Preliminary survey : To collect adequate data to prepare plan / map of area to be used for planning and design.
3) Location survey : To set out work on the ground for actual construction / execution of the project.
• Route survey : To plan, design, and laying out of route such as highways, railways, canals, pipelines, and other linear projects.
• Construction surveys : Surveys which are required for establishment of points, lines, grades, and for staking out engineering works (after the plans have been prepared and the structural design has been done).
• Astronomic surveys : To determine the latitude and longitude (of the observation station) and azimuth (of a line through observation station) from astronomical observation.
• Mine surveys : To carry out surveying specific for opencast and underground mining purposes.
Principles of Surveying
The fundamental principles upon which the surveying is being carried out are
- working from whole to part.
- after deciding the position of any point, its reference must be kept from at least two permanent objects or stations whose position have already been well defined.
The purpose of working from whole to part is
- to localise the errors
- and to control the accumulation of errors.
This is being achieved by establishing a heirarchy of networks of control points. The less precise networks are established within the higher precise network and thus restrict the errors. To minimise the error limit, highest precise network (primary network) Figure 1.1 of control points are established using the most accurate / precise instruments for collection of data and rigorous methods of analysis are employed to find network parameters. This also involves most skilled manpower and costly resources which are rare and cost intensive.
The reference of any point, say X, has to kept with respect to, at least, two permanent objects or well defined points, say Y and Z. Generally, this has been achieved by taking measurement of two parameters.The location of a point, say X can be done as shown in the figures below.
(d) Angles YZX and ZYX.
The point of intersection of the two measured parameters defines the position of the point.
Stages of Operations in Surveying
• the methods to be adopted for surveying;
• the resources (instruments & personnel) to be used;
• the control points / stations to be used ( those already available and/ or to set up).
The planning operation needs a-priori field visit and this is known as reconnaissance.
• Collection of field data by making necessary measurements;
• Recording of observed data in a systematic manner. Before starting any field observation, the permanent adjustments of all the instruments need to be checked thoroughly by trained personnel and if required, it must be adjusted.
• Processing, analysing and calculation of observed data;
• Preparation of necessary data (for making plan or map of the area);
• Making of a plan or map of the area;
• Computation of relevant field parameters as per design for setting out engineering works at site.
Setting Out Works
To locate and establish different parameters / dimensions at the site as per design for further engineering works.
I know that this is a lot to digest and the truth is it is only the tip of the iceberg. You can learn a lot about surveying within the pages of this network and from your fellow professional surveyors. Ask, learn, share your stories and improve through communication. You have close to 13,5000 other experienced minds to consult right at your fingertips on Land Surveyors United.
Did I miss anything? Now over to you..