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. 

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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.

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