Lesson Note On Topographic Map

Reading Topographic Maps

 Interpreting the colored lines, areas, and other symbols is the first step in using topographic maps. Features are shown as points, lines, or areas, depending on their size and extent. For example, individual houses may be shown as small black squares. For larger buildings, the actual shapes are mapped. In densely built-up areas, most individual buildings are omitted and an area tint is shown. On some maps, post offices, churches, city halls, and other landmark buildings are shown within the tinted area.

The first features usually noticed on a topographic map are the area features, such as vegetation (green), water (blue), and densely built-up areas (gray or red).

Many features are shown by lines that may be straight, curved, solid, dashed, dotted, or in any combination. The colors of the lines usually indicate similar classes of information: topographic contours (brown); lakes, streams, irrigation ditches, and other hydrographic features (blue); land grids and important roads (red); and other roads and trails, railroads, boundaries, and other cultural features (black). At one time, purple was used as a revision color to show all feature changes. Currently, purple is not used in our revision program, but purple features are still present on many existing maps.

Various point symbols are used to depict features such as buildings, campgrounds, springs, water tanks, mines, survey control points, and wells. Names of places and features are shown in a color corresponding to the type of feature. Many features are identified by labels, such as “Substation” or “Golf Course.”

Topographic contours are shown in brown by lines of different widths. Each contour is a line of equal elevation; therefore, contours never cross. They show the general shape of the terrain. To help the user determine elevations, index contours are wider. Elevation values are printed in several places along these lines. The narrower intermediate and supplementary contours found between the index contours help to show more details of the land surface shape. Contours that are very close together represent steep slopes. Widely spaced contours or an absence of contours means that the ground slope is relatively level. The elevation difference between adjacent contour lines, called the contour interval, is selected to best show the general shape of the terrain. A map of a relatively flat area may have a contour interval of 10 feet or less. Maps in mountainous areas may have contour intervals of 100 feet or more. The contour interval is printed in the margin of each U.S. Geological Survey (USGS) map.

Bathymetric contours are shown in blue or black, depending on their location. They show the shape and slope of the ocean bottom surface. The bathymetric contour interval may vary on each map and is explained in the map margin.

Lesson Note On How To Used Theodolite/EDM Equipment

Theodolite/EDM Topographic Survey

Description: Using EDM instruments and optical or electronic theodolites, locate the positions and elevations of all topographic detail and a sufficient number of additional elevations to enable a representative contour drawing of the selected areas. 

Equipment: Theodolite, EDM, and one or more pole-mounted reflecting prisms.

Procedure:

• Set the theodolite at a control station (northing. easting, and elevation known), and backlight on another known control station.

• Set an appropriate reference angle (or azimuth) on the horizontal circle (e.g., 0°00'00" or some assigned azimuth).

• Set the height of the reflecting prisms (HR) on the pole equal to the height of the optical center of the theodolite/EDM (Hi).

• Prepare a sketch of the area to be surveyed.

• Begin taking readings on the appropriate points. Entering the data in the field notes and entering the shot number in the appropriate spot on the accompanying field-note sketch. Keep shot numbers sequential, perhaps beginning with 1,000. Work is expedited if two prisms are employed. While one prism-holder is walking to the next shot location. The instrument operators can be taking a reading on the other prism-holder.

• When all field shots (horizontal and vertical angles and horizontal distances) have been taken, sight the reference backsight control station again to verify the angle setting; also, verify that the height of the prism is unchanged.

• Reduce the field notes to determine station elevations and course distances, if required.

• Plot the topographic features and elevations at scales.

• Draw contours over the surveyed areas.

Lesson Note On How to used total station

Total Station Topographic Survey

Description Using a total station and one or more pole-mounted reflecting prisms, plot all topographic features and any additional ground shots that are required to accurately define the terrain. See Figure D.l0.

Equipment:Total station and one, or more, pole-mounted reflecting prisms.

Procedure:

• Set the total station over a known control point (northing, easting, and elevation known).

• Set the program menu to the type of survey (topography) being performed and to the required instrument settings. Select the type of field data to be stored (e.g., N, E, and Z, or E, N, and Z, etc.). Set the temperature and pressure settings-if required.

• Check configuration settings, for example, tilt correction, coordinate format, zenith vertical angle, angle resolution (e.g., 5"), c + r correction (e.g., no.), units (ft/m, degree, mm Hg), and auto power off (say, 20').

• Identify the instrument station from the menu. Insert the date, station number coordinates, elevation, and Hi.

• Backsight to one or more known control point(s) (point number, north and east coordinates, and elevation known). Set the horizontal circle to 0°00'00" or to some assigned reference azimuth for the backsight reference direction. Store or record the data. Measure and store the reflector height.

• Set the initial topography point number in the instrument (e.g., 1,000), and set for automatic point number incrementation.

• Begin taking I.Ss. Most total stations have an automatic mode for topographic surveys, where one button-push will measure and store all the point data.

• Put all or some selected point numbers on the field sketch. These field notes will be of assistance later in the editing process if mistakes have occurred.

• When all required points have been surveyed, check into the control station originally back sighted to ensure that the instrument orientation is still valid.

• Transfer the field data into a properly labeled file in a computer.

• After opening the data processing program, import the field data file and begin the editing process and the graphics generation process.

• Create the TIN (Triangulated Integrated Network) and Contours.

• Either finish the drawing with the working program or finish it on a CAD program.

• Prepare a plot file and then plot the sheet on scale.

Reference: Surveying with Construction Applications Seventh Edition

Barry. F. Kavanagh pages: 616-620 

What is a DEM (Digital Elevation Model

What is a DEM (Digital Elevation Model)?



Digital Elevation Models are data files that contain the elevation of the terrain over a specified area, usually at a fixed grid interval over the surface of the earth. The intervals between each of the grid points will always be referenced to some geographical coordinate system. 

This is usually either latitude-longitude or UTM (Universal Transverse Mercator) coordinate systems. The closer together the grid points are located, the more detailed the information will be in the file. The details of the peaks and valleys in the terrain will be better modeled with a small grid spacing than when the grid intervals are very large. Elevations other than at the specific grid point locations are not contained in the file. As a result peak points and valley points not coincident with the grid will not be recorded in the file.

The files can be in either ASCII or binary. In order to read the files directly you must know the exact format of the entire file layout. Usually the name of the file gives the reference location to some map corner point in the file. The files usually contain only the z value (elevation value) and do not contain the actual geographical location that is associated with that point. 

The actual location associated with that elevation data is calculated by software reading the actual DEM file, knowing the precise location of the data value inside the DEM file. In addition, there will be some needed reference information in the header (first part) of the file. When an elevation is calculated at locations other than the actual grid points, some method of interpolation from the known grid points is used. Again, this is done in software that is external to the actual DEM file.

The DEM file also does not contain civil information such as roads or buildings. It is not a scanned image of the paper map (graphic). It is not a bitmap. The DEM does not contain elevation contours, only the specific elevation values at specific grid point locations.


Some companies chose to encrypt their DEMs, thereby prohibiting you from making your own files, converting data from other sources or allowing you access to data files that were provided from anyone other than that software vendor. SoftWright maintains an open architecture on all our data files. Details for all DEM file formats that SoftWright supports are available to any of our customers. 

Heroizu Tech Services LTD

History : The Nigerian Institute of Quantity Surveyors (NIQS)

The Nigerian Institute of Quantity Surveyors (NIQS)

 

The Nigerian Institute of Quantity Surveyors was founded in 1969 by Nigerians who had trained, qualified and practised quantity surveying in the United Kingdom but who returned to Nigeria and felt the need to develop the profession in Nigeria.

The regulated and other Provisions) Act of 1978 recognised quantity surveying as one of the scheduled professions. Decree No. 31 of 1986 gave legal backing and recognition to the quantity surveying profession and also established the Quantity Surveyors Registration Board of Nigeria (QSRBN) to regulate the profession.

The vision of the NIQS is “To be the profession in Nigeria responsible for total cost and procurement management, for the achievement of client’s objectives in all types of capital projects and developments, from conception to commissioning and maintenance, in all sectors of the economy, for the attainment of sustainable national development and goals.”

The aims and objectives of the institute are:

(      a)  To promote the science and practice of the quantity surveying profession in all its ramifications.

(b) To provide a platform or forum for meeting and discussing matters of mutual interest to quantity surveyors in Nigeria and to preserve and further the interest of quantity surveyors.

 (c) To promote and stimulate the improvement of the technical and general knowledge of persons engaged in the profession of quantity surveying.

(d) To organize continuing education and professional training of those seeking to become professional quantity surveyors and assist and procure its members to be registered by the QSRBN.

(e) To undertake research study and to collate information from any quantity surveying bodies from any part of the world on the latest developments and technologies in the practice of quantity surveying and to make available such information to its members.

(f) To cooperate with the QSRBN in training of quantity surveyors and regulating and controlling the practice of quantity surveying in Nigeria.

(g) Generally to disseminate information and promote understanding of quantity surveying among members of the public and to cooperate with other professional bodies in Nigeria.

 (h) The maintenance of the highest standards of discipline and professional conduct.

The services offered by the quantity surveyor include:

(a) Feasibility studies of capital projects         (h) Facilities management

(b) Cost modelling              (i) Direct labour project procurement and management

(c) Contract documentation and procurement

(j) Arbitration           (d) Contract administration and management

(k) Expert witness              (e) Monitoring of capital projects

(l) Fire insurance assessment        (f) Preparation of cost reports, pricing of bills etc

(m) Dilapidation       (g) Project management

13 Duties of the Quantity Surveyor

Duties of the Quantity Surveyor

1.     Preliminary Cost Advice The quantity surveyor gives practical advice on:

• The likely cost of the scheme – however complicated or unusual it may be.

• The comparative costs of alternative layouts, materials, components and methods of construction. • The likely duration of project.

• The likely cost of future maintenance and operating costs. The quantity surveyor can, from the client’s brief, prepare a realistic budget and a cost plan showing the distribution of costs over the various elements.

2. Cost Planning Cost planning is a specialist technique used by quantity surveyor’s, which aims to help all members of the design team to arrive jointly at practical and efficient designs for the project and to keep within the budget. Once a realistic estimate is set from the cost plan, constant monitoring reduces the risk of overspending by noting problem areas at an early stage and applying prompt corrective action.

3. Contractual Methods The quantity surveyor can advise on the best type of tendering and the best form of contract that will best suit a specific project. The quantity surveyor prepares the documents for obtaining the tenders and arranging the contract.

4. Bill of Quantities Competitive tendering remains a common basis for selection of contractor and bills of quantities are fundamental to the process. Bills translate the drawings into a document listing in detail all the component parts required for a project so that each contractor can calculate tender prices on exactly the same basis as his competitors. During construction, the bill forms the basis for preparing interim valuations, pricing of variations and effective cost control.

5. Choice of contractor The quantity surveyor analyses tenders and makes recommendations to the client for contractor selection after taking into consideration other factors such as the contractors reputation and past performance.

6. Contract Administration The quantity surveyor acts with the architect or engineer to ensure that the financial provisions of the contract are properly interpreted and applied so that the client’s financial interest is safeguarded and that the builder is paid the proper price for the work. He also exercises control during construction so that the cost is not exceeded without authority.

7. Valuation of construction work The quantity surveyor prepares interim valuations, values variations and prepares financial statements during construction. He will also settle the final accounts at project completion. He may also prepare statements of expenditure for tax or accounting purposes and assess the project’s replacement value for insurance purposes. Other services of the quantity surveyor include:

8. Construction management Construction management uses latest management techniques and other applications of programming, network analysis, risk analysis, cash flow forecasting, budgeting and other control mechanisms.

9. Building maintenance management Building maintenance management involves planning, programming, controlling and costing of maintenance and repair work.

10. Dilapidations The quantity surveyor prepares schedule of conditions at the beginning of a tenancy or lease and a schedule of dilapidations at the end giving details of an outgoing tenant’s liability.

11. Arbitration This is a formal process for settling disputes

12. Facilities management This involves all aspects of providing, operating, maintaining, developing and improving facilities which are property where people are accommodated and work.

13. Contractor Organisations The quantity surveyor may work in a contractor’s organisation.