Topographic Survey: a survey that measures the elevation of points on a particular piece of land, and presents them as contour lines on a plot. The purpose of a TOPOGRAPHIC SURVEY is to gather survey data using Total Stations, Auto levels, GPS etc., about the natural and man-made features of the land, as well as its elevations. From this information a three- dimensional map may be prepared. You may prepare the topographic map in the office after collecting the field data or prepare it right away in the field by plane table. The work usually consists of the following:
- Establishing horizontal and vertical control that will serve as the framework of the survey
- Determining enough horizontal location and elevation of ground Points to provide enough data for plotting when the map is prepared.
- Locating natural and man-made features that may be required by the Purpose of the survey.
- Computing distances, angles, and Elevations.
- Drawing the topographic map Topographic surveys is commonly identified with horizontal and or vertical control of third and Higher-order accuracies.
CADASTRAL SURVEYS: are conducted to establish the exact location, boundaries, or subdivision of a tract of land in any specified area. This type of survey requires professional registration in all states. Presently, land surveys generally consist of the following chores
- Establishing markers or monuments to define and thereby preserve the boundaries of land belonging to a private concern, a corporation, or the government.
- Relocating markers or monuments legally established by original surveys.
- This requires examining previous survey records and retracing what was done. When some markers or monuments are missing, they are re -established following recognized procedures, using whatever information is available.
- Rerunning old land survey lines to determine their lengths and directions. As a result of the high cost of land, old lines are premeasured to get more precise measurements.
- Subdividing landed estates into parcels of predetermined sizes and shapes.
- Calculating areas, distances, and directions and preparing the land map to portray the survey data so that it can be used as a permanent record.
The term Route survey refers to surveys necessary for the location and construction of lines of transportation or communication that continue across country for some distance, such as highways, railroads, open-conduit systems, pipelines, and power/telecom lines. Generally, the preliminary survey for this work takes the form of a topographic survey.
- Locating the center line, usually marked by stakes at required intervals called Stations
- Determining elevations along and across the center line for plotting profile and cross sections
- Plotting the profile and cross sections and fixing the grades
- Computing the volumes of earthwork and pre paring a mass diagram
- Staking out the extremities for cuts and fills
- Determining drainage areas to be used in the design of ditches and culvert
- Laying out structures, such as bridges and culverts. Locating right-of-way boundaries, as well as staking out fence lines, if necessary.
Utility agencies need extensive data collection related to their assets and consumers, for efficient distribution management and service delivery. We undertake large scale measurement and contact surveys to create comprehensive geospatial databases for consumer indexing and asset management. Realizing the critical need of meeting cost, speed and accuracy requirements simultaneously, we have designed innovative solutions, employing a judicious blend of technologies.
All types of mapping require establishment of an accurate control framework on the ground. We establish ground control employing differential GPS and/or total stations. Such control surveys are conducted by us for the following requirements.
- Creation of geodetic framework
- Field contouring and topography
- Site surveys for real estate and housing developers
- Route plans and profiles for power line and pipe line Corridors
- Engineering surveys
- Property and cadastral surveys
GPS&DGPS CONTROL SURVEY
GPS (Global Positioning System) GPS is the U.S. Global Navigation Satellite System (GNSS). A network of 24 satellites continuously transmits high-frequency radio signals, containing time and distance data that can be picked up by any GPS receiver,
Allowing the user to pin point their position anywhere on Earth.
A Differential Global Positioning System (DGPS) is a system designed to improve the accuracy of Global Navigation Satellite Systems (GNSS) by measuring infinitesimal changes in variables to provide satellite positioning corrections. Two or more receivers observe the same set of satellites, taking similar measurements that produce similar errors when positioned closely together. For Control Points, These are carried out to establish network of points called Control Points or Control Stations. These points can be used for the subsequent measurements that are to be recorded at the site. Establishing the control points calls for most precision, as this will have direct bearing on the accuracy of the final survey to be carried out at the project site. For Land Surveying, It enables larger surveys to be performed by a one-man crew with minimal moves and less operational downtime. For land and topographic survey easy-to-use mapping features include point, line and area mapping, real-time area calculation, offset measurement also well accurately.
The resultant processing generates the following data: Position: latitude, longitude, altitude with respect to a user selectable datum
Setting-out / relaying on the ground for all types of construction work and as -built surveys On-the-ground alignment, cross section & L-section generation and demarcation of physical infrastructure and utility corridors
TRANSMISSION LINE SURVEY:
The work of the Program for Coordination of Actions to Establish sites, with an Initial objective of determining the route of the transmission line and beginning the topographical survey.
In order to minimize the project’s impact on rural and urban populations that own Property in areas to be crossed by the transmission line, the Program for Coordination of Actions to Establish responsible for developing criteria and basic procedures for agreements and/or compensation in order to guarantee easements to build the line after proper application of measures to guarantee fair compensation and protect the current living conditions of the affected population.
Hydrographic surveying deals with the configuration of the bottom and adjacent land areas of oceans, Lakes, rivers, harbors, dams, and other water forms on Earth. In strict sense, it is defined merely as the surveying of a water area; however, in modern usage it may include a wide variety of other objectives Such as measurements of tides, current, gravity, earth magnetism, and determinations of the physical and chemical properties of water. The principal objective of most hydrographic surveys is to obtain basic data for the compilation of nautical charts with emphasis on the features that may affect safe navigation. Other objectives include acquiring the information necessary for related marine navigational products and for coastal zone management, engineering, and science.
The purpose of hydrographic surveying:
To collect, with systematic surveys at sea, along the coast and inland, Georeferenced data related to Shoreline configuration, including manmade infrastructure for maritime navigation i.e. all those Features on shore that are of interest to mariners. Depths in the area of interest (including all potential hazards to navigation and other marine Activities)
Principle: Electrical resistivity survey is being proved to be an excellent tool for the identification of horizontal and vertical variations of sub-surface litho units. The electrical prospecting method consists of measuring the potential at the surface which results from a known current flowing into the ground. A pair of current electrodes, A and B, and a pair of potential electrodes, M and N are used. The apparent resistivity (a) is given by a=K V/I where K denotes a geometric coefficient dependent upon the electrode array, V the measured potential difference and I the current intensity. By expanding the current electrode array, the depth of investigation can be increased. Such a dataset provides a vertical log of apparent resistivity. It can be achieved by the two successful techniques of profiling and sounding.
Resistivity Profiles: Resistivity surveys can be employed to detect lateral variations in resistivity. Profile surveys having fixed electrode spacing and the center of the electrode spread is moved for each reading. These experiments thus provide estimates of the spatial variation in resistivity at some fixed electrode spacing. This method used to examine groundwater contamination, corrosion ratio and some engineering properties of layers.
DDR1 model of IGIS Resistivity Meter is very useful instrument for resistivity and self-potential measurements. The design of circuitry incorporates the principles of digital technology to provide measuring accuracy and operational convenience during data acquisition. This is a single unit system with two digital displays one used for reading the current sent into the ground and the other to read the voltage across the potential electrodes directly. It can send current upto 1999 mA into the ground and measure the resulting voltage with accuracy of 0.1 mV upto a maximum potential value of 1999 mV.
Sensitive in potential measurement : 0.1 mV
Sensitive in current measurement : 0.1 mA
Potential Rangeaaaaaa : 0 to 1999 mV
Maximum input voltage : 450 V
Maximum input current : 199 mA
Good depth of investigation : 300 Mts.
- Identification of groundwater bearing formations
- Delineation of fresh and saline water zones in the coastal areas
- Water quality studies
- Well logging studies for well construction
- Delineation of effluent contaminated zones
- Identification of ground water contaminated zone
- Estimation of overburden in granite quarries
- Thickness and extend of mineralized zones
- Bedrock investigations
- Pipeline investigations
- Corrosion Studies
- anal investigations