Unit - 3

Modern Field Survey Systems

• EDM is electronic distance measurement survey which is used to find the distance of two point or object. This technique provides precise and more faster surveying than the old and conventional instruments that are used earlier. In old and conventional surveying, in linear measurement, chain and tape are used while in angular measurements   compass are used, Dumpy level and a leveling staff are used in work of leveling. With this instrument, survey work become tedious
• Hence in this case, the modern surveying instruments are used and this technique are replacing the old surveying instruments such as Dumpy level, chain, tape and compass. With the help of this modern techniques, survey work will be more, faster and precise.
• Electronic distance measurement is the way of finding the length between two points by using electronic energy waves by taking the time and velocity.
• Planks give the principle in which electromagnetic radiation travel with speed of light and time travel by waves can be noted which colloids with target .and hence distance can be finding out by the below given formula: -

• Missing line measurement (MLM}
• Control Survey (Traverse).
• Archaeologists use total station to record excavations and its details
• Height measurement (Remove elevation measurement- REM).
• Resection are easy by total station.
• Remote Distance Measurement (RDM)
• General purpose of angle and distance measurement
• Detailed maps

• Road Survey
• Rail Survey
• Canal Survey
• Mine Survey
• Engineering Survey
• Large Scale Survey

• Field work is very fast as compared to conventional survey.
• Calculation is also fast and accurate.
• Accuracy is very high.
• Manual errors can be eliminated.
• Computers can used for map making and contour and its cross-sections

• Detail survey is carried out easily by this technique.
• Missing Line Measurement (MLM)
• Plotting of contours
• Carrying out controlled surveys
• Used to fix the missing pillars and column.
• Area calculations

• The satellite constellation consists of 24-satellite constellation. The satellites are placed in six Earth cantered orbital planes with four satellites in each plane.
• The nominal orbital period of a GPS satellite is one-half of a side real day. The orbits are circular and equally spaced about the equator at a 60°separation with an inclination relative to the equator of nominally 55°.
• The orbital radius (i.e., nominal distance from the center of mass of the Earth to the satellite) is approximately 26,600km. This satellite constellation gives a 24-hr global user navigation and time determination capability.
• Similarly, for the Earth’s equator, it is like a ring that has been opened and laid on a flat surface. The slope of every orbit represents its inclination with respect to the Earth’s equatorial plane, which is nominally 55°.
• The orbital plane locations with respect to the Earth are defined by the longitude of the ascending node whereas the location of the satellite within the orbital plane is defined by the mean anomaly.
• The longitude of the ascending node is point of intersection of each orbital plane with the equatorial plane.
• The Greenwich meridian is the reference point where the longitude of the ascending node has value of zero. Several different notations are used to refer to the satellites in their orbits.

1. GPS Cables & Antennas,
2. GPS Cases,
3. GPS Chargers & Adapters,
4. GPS Maps,
5. GPS Mounts

1. Space segment
2. Control segment
3. User segment

• It is an important segment since it comprises the orbiting GPS satellites or space vehicles (SV) in GPS parlance. The GPS design originally called for 24 space vehicles, eight each in three circular orbital planes. However, it is modified to six planes with four satellites each.
• The orbital planes are centered on the Earth and these planes are not rotating with respect to the distinct stars. The six planes have an inclination of 55° approximately with respect to Earth's equator and these planes are separated by 60° right ascension of the ascending node. 60° right ascension means the angle along the equator from a reference point to the intersection of the orbit. These orbits are arranged in such way that at least six satellites always remain within the line of sight from almost everywhere on the surface of earth.
• Satellites are orbiting at an altitude of 20200 km approximately with the orbital radius of 26600 km. Each satellite vehicles performs two complete orbits on each sidereal day and hence the ground track of each satellite repeats each sidereal day.
• The ground track repeat can be used the ensure good coverage in combat zones.

• The track of satellite is well decided and the flight paths of the satellite are tracked by US air force monitoring the stations in Hawaii, Kwajalein, Ascension Island, Diego Garcia and Colorado Springs, Colorado along the monitor stations operated by the National Geospatial- Intelligence Agency (NGA).
• The tracking information is sent to the air force space command's master control station at Schriever air force base in Colorado Springs which is further operated by the two-dimensional (2d) space operations squadron of the United States Air force. Two space operations squadron contacts each GPS satellite regularly with a navigational update by using antennas.
• This updates synchronize the atomic clocks on the board of satellites within a few nanoseconds of each other and adjust the ephemeris of each internal model of each satellite.
• The updates are produced by Kalman filter which uses inputs from the ground monitoring stations, space weather and information and also the various other inputs.

• This is the segment in which GPS receivers are made of an antenna tuned to the frequencies transmitted by the satellites, receiver-processors and a highly-stable clock.
• It provides location and speed information on display to the user. The number of channels signifies how may satellite the receiver can monitor simultaneously.

• It generates and transmit code, carrier phases and navigation message.
• Here input is navigation message and output is P code C/A code, L, and L, which carries navigation message.

1. It produces GPS time.
2. It predicts ephemeris
3. It manages space vehicle

• Here input is P code observation and time and output is navigational message. It works out satellite orbit and clock parameter and passes the results to ground antennas.

1. It gives the navigation solution
2. It also gives the surveying solution

1. This system is based on Triangulation from satellites.
2. For Triangulation, the GPS receivers measure the distance, for which the travel time of the radio message from the satellite is used.
3. It needs to use a very high precision clocks, to measure the travel time (to measure the distance)
4. After the measurement of the distance the location of the satellite becomes important.
5. There is a time lag as the GPS signals travel through the ionosphere (upper layer of the atmosphere above the stratosphere layer) from transmitting the signal by satellite and receiving the same by the receiver.

1. Ionospheric error
2. Tropospheric error

• Satellite based position system signals travel with a speed of light. The upper layer of atmosphere termed as ionosphere containing charged particles which slow down the code and speed up the carrier. Range of ionospheric error is from 0.4 m to 5 m. Error is low for satellite when elevation angle is 90 and high for satellite at the horizon when elevation angle is zero.
• The impact of the ionosphere on electronic signals depends on the intensity of the frequency of the signals. If the frequency is more, impact is less.
• Hence using two different frequencies simultaneously, the patterns are transmitted and the ionosphere effects is removed.
• In short ionosphere effects can be removed by transmitting information in two frequencies L1and L2 or dual frequencies receivers remove the ionosphere effects.

• The lower part of the atmosphere consist of water vapour is termed as troposphere. Due to tropospheric effect; code and carrier becomes slowing down. In such case the effect of slowing down the code and carrier cannot be removed by using two different frequencies system or dual frequency system.
• The effect of troposphere can only be removed by measuring its water vapour content, its temperature and its pressure and applying a mathematical model.
• Range of troposphere errors varies from 0.2 m to 0.5 m.

• Satellite clock errors range is about 1.5 m. The errors and drifts of the satellites clock are computed and added in the messages which are transmitted by the satellite.

• Receivers can introduce some errors by itself in measuring code and carrier. Design of receiver and antenna can make influence on the receiver noise.
• In such case, error in absolute or point positioning is 0.3 m and error in differential positioning is also 0.3 m.
• The magnitude of receiver error is proportional to the wavelength and chip length of code and carrier measurements.
• These errors are zero for carrier phase and a few centimeters for code phase in case of high-quality receivers.
• Receiver clock error –

• Receiver clock error can range up to few metres depending upon the quality of the receiver clock.
• Clock error is estimated along with co-ordinates while positioning and hence do not affect the accuracies.

• Geographic Information System (GIS) is computer software which gives information of any discipline.
• GIS can present many layers of different information. Hence GIS technology is latest and one of the hottest new research tools in academia today.
• Surveyors and engineers understand the importance of geographic data.
• A Geographic Information System (GIS) is not one thing, nor a single analysis, but rather a collection of hardware, software, data organizations and professionals that together help people to represent and to analyse geographic data.
• A GIS can combine geographic and other type of data to generate maps and reports, enabling users to collect, manage and interpret location-based information in a planned and systematic way.
• The maps are limitation of time and the area and upto dateness, on the other hands, this new techniques of G.L.S. Has all the advantages of maps plus it has corrected the limitations of map, i.e., G.I.S. Can give all the details, of any area (from a small village to a nation. It provides the upto date information with no human error (which can be found in maps based on the field observation, through the actual field surveys carried by the persons).
• G.I.S. Is a complete system having Accuracy, capacity of verification, compilation and storage of both spatial and Alltribute data. It is capable of upto dating the information; changing, managing and exchanging data with the capability of manipulation (if required).
• G.I.S. Can retrieve and can present space related information which is coupled with attribute data, as and when required. With all these advantages of G.L.S., the most important function of G.I.S. Is that it incorporates the space in the analysis, with the top most level of Accuracy.
• G.I.S. Is defined as, "It is an organized collection of hardware, software, spatial data and personnel, designed to capture, to store, to update, to manipulate, to analyse and to display all the forms of geographically referenced data and information."
• G.I.S. Is neither special software nor a map producing method. It is associated different activities which are involved with the digital geographically referenced data. G.I.S. Cannot be purchased ready-made, it has to be built up within the organization, step-by-step as the various facts of G.I.S. Are inter-lined.

1. Allowing quick updating of data of low efforts and cost.
2. Supporting research activities which involves spatial data.
3. Providing significant and efficient tool for collection, storage, recalling, analysis integrating, manipulation, overlaying the spatial data from single sources or many sources.
4. Generating the information which is important for better logical decision making of complex analysis or queries involving geographical reference data to increase the efficiency of planners and decision makers.
5. Eliminating redundant database and minimizing duplication.
6. Answering the query by presenting the information in a format required by user.

1. GIS is used to improve organizational integration. A GIS can link data sets together by common location of data, such as addresses, which help department and agencies to share their data. By creating a shared database, one department can get benefit from the work of another. In GIS, data can be collected once and used many times.
2. GIS is used to make better decision. The old adage "better information leads to better decision" is true for GIS. A GIS is not just an automated decision-making system but a tool to analyse and map data in support of the decision-making process.
3. GIS is used for making maps. GIS is flexible enough to map of any kind of terrain; even the human body. GIS can map any data we wish to make. For example, GIS is used for mapping in which one can find individual feature of any object the land like building antennas, towers and landscape etc.
4. GIS is used for every organization of the defense industry is many nations around the world.
5. Surveyor precise instruments, procedures and use computations to accurately locate and define geographic features while conducting field survey that range from cadastral to engineering construction layout.
6. GIS is used as an interface for integrating and accessing massive amounts of location-based information in the public safety market.
7. GIS software to study epidemiology; look at health care facilities and map any system that is visual or spatial including inside a patient body.
8. GIS helps students and teachers engage in studies that require and promote critical thinking, integrated learning and multiple intelligences at any grade level.
9. Architect makes the design, planning in proper and precise way quickly with the help of GIS.
10. GIS provides the analytical capabilities that form the hub of successful precision agriculture system. GIS lets farmers perform site-specific analyses of agronomic data.
11. GIS technology enables telecommunications professionals to integrate location-based data into analysis and management processes in network planning and operations, marketing and sales, customer care, data management and many other planning and problem-solving tasks.
12. GIS is used in libraries and museums, in education, in conservation of water and wastewater, in transportation, in universities, in mining and earth sciences and in other so many institutions and organizations.

1. Geographic data
   1. Spatial data
   2. Non-spatial data
   3. Hybrid data

1. Method or procedure
2. Hardware
3. Software
4. People

• The geographic data includes the data related to the various types of features such as houses, population, rivers, mountains, climate, soil, streets, state boundaries, oceans, forest etc.
• The geographic data can be collected from the various sources like public agencies, satellite images, manual field surveys etc. and this collected data is then stored in the forms of digital maps. These digital maps can store the maximum information and provide more details related to any features than the paper maps.

1. Spatial data
2. Non-spatial data
3. Hybrid data

• The spatial data depicts the geographical features of a place using symbols like a point on a map can able to give the location of a college in an area.

• It is also termed as 'attributes'. It depicts the additional information about the spatial data such as amenities in the college, facilities in the school and the number of rooms in the school which depicted by the spatial data.

• It is a combination of spatial data and non-spatial data.
• Hybrid data = Spatial data + Non-spatial data.
• Location in case of spatial data and features of a school and population covered under this school are combined together and named as hybrid data.

• After collecting the geographic data, next step is method in which data is organized in a structured way for easy retrieval, editing and analysis.
• The method of organizing data is known as a data model. Data model can be organized just like the books are arranged on bookshelf in a library. The method of data structuring may be different from project to project.
• While handling and analysing large volumes of data, it is more essential to maintain the accuracy of data for correct analysis.
• Data structuring in method can be illustrated by giving the example in which unorganized the books are organized by keeping them properly in bookshelf.

• Hardware is also key components of GIS; which require powerful computer hardware which can support its massive database and huge images.
• Processing speed of a CPU must be more enough to run the software for GIS use and also ram requirements in GIS should be more higher due to very large size of database and images. The recommended size of ram is 128MB.
• To store the GIS data, secondary memory must be large. System can also be supported with external storage media such as CD-ROMS and tape drives. The main input devices which are required for GIS are as follows:
  • Monitors
  • Plotters
  • Printers
  • Film recorders
• Proper installation and configuration of each hardware component is important since the hardware is an important component for the performance in GIS.

• The software is needs for GIS. Software comprises the operating system and GIS application software.
• Windows 9x and later and UNIX are the two main operating system in GIS. Software gives the several mapping and analysing tools in GIS application.
• Types of GIS software are available in market are:

1. Auto CAD map from Autodeck Inc.
2. PCI Geomatics, Geomedia and TNT
3. Arc view, Arc / Info and Arc Ims from ESRI Inc.
4. Free software such as GRASS
5. Manifold from Manifold corporation
6. MapInfo professional and MapXtreme from MapInfo corporations.

• People are the most important component because of the most valuable resources which help GIS so as to achieve the variation applications.
• People are responsible to set the framework for computer hardware, software and process data for analysis for GIS which is applicable in a university, business or government organization.
• A group of people conduct surveys and collects data. Another group of people analyses the raw data, digitizes it, checks for errors, and edit it. Another team give support to protect data, troubleshoot and find the solution for complex analysis.
• Next team of people provides software support and updates of the software whenever the new and improved methods and techniques are employed.
• There are trained programmers who develop and provide user interfaces for the end users. Another team specializes in the study of systems design.

1. Vector Data
2. Raster Data

• It is a zero-dimensional presentation of on object shown by single X, Y co-ordinate. Each point is independent of every other point and shown by a separate row in database model. A point generally shows a very small geographic feature displayed as a line or area. Points can represent two generic types of features in a GIS.
• Any or each point of any objects has a unique location, in the space, which is fixed by two or three numbers in the coordinate system. As already said on the map these coordinates are the latitudes (horizontal lines) and longitudes (the vertical lines) which form a grid or graticule.
• The digital representation of the spatial data, in this model is based on individual points and their respective coordinates. In this, the lines are described the mathematical function like ellipse or circles and so the radii of these circles are also considered as lines.
• In GIS data, the instructions are given (entered) with the coordinate data about the point to be connected and the points which are not to be connected. By such instructions, the lines and polygons (areas) are developed. Vector can be expressed mathematically as, "It is straight line, in digital map, having both, i.e., the magnitude and the direction; which joints two data co-ordinates." In the vector model, points lines and polygons are homogeneous and are discrete units which hold the information.

• It is a set of ordered co-ordinates which shows the shape of geographic features like contours, streams, street centre lines etc, which is very narrow displayed as an area at the given scale.
• Some examples of line features are infrastructure networks of highway and railways.
• The points lines and polygons are graphically represented by the coordinate data. The location of such data is expressed in terms of x, y coordinates or Eastings and Northings. The points are identified by these coordinates and the lines by the end points coordinates. The series of lines are used to identify the polygons, the lines loop back to the starting point i.e., the starting coordinates.

• Points are shown by the coordinates like, 4-2 i.e., 4 is the location of point in the casting and 2 is the location of the point in the northings.
• The lines are shown by joining these points like, 1.8, 4.6, 5.4, 9.3 where in the first figure is always eastings and the second is always the northing, the lines are referred by giving the starting and ending coordinates i.e., 1.8 to 9.3.
• The polygones, let us assume that the starting point of this polygone is 4.7 if we join all the points by lines and came back to the starting point it makes the polygone such as 4.7, 5.8, 7.9, 11.7, 8.6 and back to 4.7.
• The points lines and the polygones are used to represent the entities from the real-world.
• For creating vector data, the field data is used to give the accurate coordinates. In case of getting the data from the map or the drawing of the region, following factors are needed to be considered.

• As already discussed, the scale of the map vary as per the purpose of the map. So, the digitizing can be a factor to limit the accuracy of the co-ordinates.

• In case of giving the coordinates of a feature which is an irregular shape; there may be some errors in giving the accurate coordinates.

• In this model the data is represented by pixel i.e., the picture elements. They have the structure of multi-celled grid. It comprises of a matrix of rectangular grid cells. Each one of the cells represents a given specific area.
• Its resolution (the scale) is defined by the ground area which is represented by the raster grid cell. On the basis of the scale a cell can represent 10 m², 100 m² or 1000 m area.
• For higher resolution, more cells are necessary to cover up the given surface area. The resolution of the raster is generally the function of the scale of the map, from which, the spatial data have been digitized (or scanned).

• The pixels are the result of computing the data through aerial photograph or throughout the satellite imaging. The colours and tones (shades) of the image are computed by assigning the unique numerical codes. The digital number (DN) values of each one of the pixels and a cell has only one DN.
• At present eight-bit data is used by the new software. It allows up to 256 numbers i.e., from 0 to 255.

• It is associated with specific real-world models, to represent the real world.

• It has the digital scans of maps and drawings, which is created with the methods of compilation.

• It does the compilation of the digital satellite image data.

• In this model, the reality is represented by regular, uniform, square or rectangular cells. The squares, look like grid of squares. So, they are also called as 'a grid model.
• The cells are identified in rows and columns (location is expected of any cell by column and row numbers. The 'zero' row and column is at the upper left of the raster grid (this location is defined in different ways in different software’s. These cells represent 'area' and not a point on the earth surface, so they are not be used for giving precise measurement.
• By giving the real surface values to the pixels, the model is produced. These values are comprised of the attribute objects which are represented by the cells. Any single cell is assigned only one single value, so the dissimilar objects are assigned to different raster layers.
• Each of this layer, represents a group of objects, with a specific theme like settlement or gross land or water bodies etc. Because the raw and column numbers are fixed, the location of neighbouring cells can be calculated very easily.

• Some time it is necessary to convert the Faster format into the vector format or the vector formal into the raster format. Many softwares are available in the market, for such conversions. Some GIS softwares also provide an inbuilt conversion facilities. The process of such conversion is called as vectorization (for conversing vector format into raster format) and rasterization (for conversing the raster format into the vector format).

• In the vector model, points lines and polygons are homogeneous and are discrete units which hold the information.
• In the vector models, the points lines and the polygons are used to represent the entities from the real world.
• In the vector models, the vector data is in the form of points; lines and polygons and objects can be identified either in the form of points, lines or areas (polygons).
• In raster model, the model data is represented by pixel i.e., Picture elements and provide a structure like multi-celled grid.
• In raster model, the pixels are the results of computing the data through aerial photograph or throughout the satellite imaging.

• For creating vector data, the field data has to use to give the accurate co-ordinates.
• For getting the data from the map, the factors such as the scale of the map and shape of the features has to be considered.
• In raster model, the colours and tones or shades of the image has to be computed by assigning the unique numerical codes.
• In raster model, the digital number (DN) values of each one of the pixels and a cell has only one DN.

1. Street and highway data GIS system such as name, number, width, length and location of streets and highways in an area can be used for the purpose of town planning.
2. Land information system of GIS consists of land use patterns in different pockets of land, types of soil, profiles of the population dependent on the land and such other related information which can be used by surveyors.
3. Planning information system consists of geographic as well as non-geographic data such as roads, buildings and sewage which can be used to help the town planning agencies.
4. Environmental information system is a part of civil Engineering and this system consists of data related to habitat, animals, plant and other related information in case of civil engineering field can be properly used by civil engineering and forest agencies.
5. There is a maximum use of GIS in the field of surveying, advanced surveying, geology, town planning, transportation engineering, hydraulics etc.