Specification for Topographic Surveys

 

Topographic Surveys

A topographic or topographical land survey shows the height, depth, size and location of any manmade or natural features on a given parcel of land, as well as the changes or contours in elevation throughout the parcel. While boundary surveys focus on horizontal measurements, topographic surveys are about elevation.

Following topics to be discussed here for Specification for Topographic Surveys.

1. SCOPE
2. REFERENCES
3. DEFINITIONS
4. FIELD SURVEY REQUIREMENTS

4.1 General
4.2 Field Surveys
4.3 Survey Control
4.4 Drawings
4.5 Survey Instruments

5. AERIAL PHOTOGRAPHY
6. COMPUTER GRAPHICS DATA

6.1 General Data Requirements
6.2 3-D Data
6.3 Data Category Levels
6.4 Scale
6.5 Text
6.6 Working Units
6.7 Global Origin
6.8 Symbols and Patterns

7. SURVEYOR’S CERTIFICATION
8. PROJECT SITE
9. SUBMITTALS

FIGURE 1 – Permanent Monument 7
TABLE – I Tolerances for Survey Features in Industrial Mapping 8

1. Scope

This specification details the field survey, photogrammetry, and office work required to compile a topographic map of a project site.

2. References

3. Definitions

For the purpose of understanding this specification, the following definitions apply.

Plant Grid (PG).

Is a plane grid system established by the Royal Commission. All land and facilities shall be located based on the PG system or any authorized agency’s system.

True Coordinate Position.

The position of a point as determined by field survey originating from a known control survey marker or any authorized agency, and performed to the precision and adjusted as required for second order surveys (that is, the horizontal error of closure shall not exceed 1 in 10,000 and the angular error of closure shall not exceed six seconds times the square root of the number of instrument stations in the traverse, all before adjustment).

4. Field Survey Requirements

4.1 General

4.1.1 Reports, mapping and drawing text, dimensions, and elevations shall be in English and shall be in the metric system.
4.1.2 The following surveys shall be conducted and the information obtained shall be submitted to SABIC as detailed in the requirements of 4.2 to 4.4 and sections 6 and 9.

(i) Boundary Survey
(ii) Topographic Site Survey.

4.2 Field Surveys

4.2.1 Survey shall be made by a licensed surveyor.

a. The survey shall be based on Plant Grid (PG) system established by Royal Commission and covered in Chapter 3 of Engineering Manual or any authorized agency’s system.
b. Table I shows the permissible tolerances applying to monument, contours, locations of improvements, structures, facilities, plotted locations and map scale.

4.2.2 Survey data is required for the design and construction of the project contained in the project documents and drawings. Boundary survey and topographic site survey are required. The levels shall be taken based on 25 meter grid laid across the site. The topographic survey shall be of sufficient detail to show the location, elevation and
configuration of all site features that may be located within or bordering the site as shown on project documents and drawings. Features shall include but not be limited to the following:

(i) Existing Buildings
(ii) Concrete Slabs
(iii) Structures
(iv) Roads
(v) Electric Poles
(vi) Utility Lines

(vii) Pipeway Columns (Piperacks)
(viii) Drainage Ditches
(ix) Culverts
(x) Railroads
(xi) Fencing
(xii) Other Obstacles
(xiii) Manholes
(xiv) Drains
(xv) Sewer Lines
(xvi) Underground Cables with Manholes.

4.3 Survey Control

4.3.1 Survey for a new site shall be tied to Royal Commission’s Plant Grid (PG) system and datum or any authorized agency’s system.
4.3.2 Survey for an expansion site shall be tied into the existing plant coordinate system and datum using existing coordinating monuments. The location and elevation of these monuments shall be shown on the survey drawings. The  survey drawings shall also show all property lines in the areas indicated in the project documents/drawings and tie them into the existing coordinate system.

4.3.3 New permanent monuments (permanent pillars) shall be set within the expansion project site or new project site and shall be tied into existing monuments.

a. Permanent monuments and major control points along primary traverse lines shall be set in concrete and prominently marked for identification.
b. Required number and location of permanent monuments shall be determined by SABIC. Permanent monuments shall be as detailed in Figure 1.

4.4 Drawings

4.4.1 Two sets of drawings will be required, one showing the boundary survey and the other showing the topographic survey data. The reproducible drawings required for the finished map drawings shall be made in durable, precision drafting film of double matte washoff mylars or stable base film of minimum 3 mil thickness. The document size shall be ISO standard A1 (840 mm x 594 mm).

4.4.2 Boundary drawings shall locate property lines, including bearings and distances, locations of rights-of-way and the locations of monuments and property corners. The topographic drawings shall be prepared as specified in 4.4.3 to 4.4.11.

4.4.3 A contour map shall be produced at a scale of 1:500 and a contour interval of 0.5 meter where the slope of the terrain exceeds 4 percent within the contract area. Spot elevations shall be taken at 25 meter grid intervals, where the contours are felt inadequate to present the true lay of the land. Names, numbers, dimensions, centerlines, and distance ties shall be given for structures directly affected by proposed new work. For a bigger site, the drawing scale and grid shall be mutually agreed by SABIC and surveyor.

4.4.4 Provide ditch invert elevations and any other grade breaks at top of cuts, toes of fills, and other similar site features.
4.4.5 A plane coordinate system shall be used for horizontal control with locations in meters. The horizontal grid shall be tied to the existing plant grid and existing monuments or to Royal Commission’s grid and monuments. Location and description of existing monuments used shall be provided.

4.4.6 Verify and tie the location of buildings, structures (including those bordering on the construction area), concrete slabs, asphalt pavement, centerlines of roads, fences, telephone and power poles, pipeways, railroads, railroad rights-of-way, and other physical features in the proposed construction area.

4.4.7 Vertical control shall be based on existing bench marks located within the plant boundaries. Descriptions of existing benchmarks and the elevation of each above mean sea level (for example Geodetic Survey datum) shall be provided if available and within project property.

4.4.8 Information obtained shall be recorded on drawings and computer graphics data as described in section 6. The drawings and computer graphics data shall become the property of SABIC.

4.4.9 A true north point, plant north and ‘Makkah’ direction shall be provided on each drawing, whether covered by grid lines or not.
4.4.10 Elevations shall be shown for building floors, inverts of drains and culverts, crowns of roads, tops of rails (each rail), ground or pavement surface at building corners, tops of curbs, flowlines of gutters, tops of manholes and vaults and other identified features.

4.4.11 Elevations of soil boring locations shown on reference drawings shall be located and established.

4.5 Survey Instruments

4.5.1 Surveyor shall furnish instruments, equipment, and personnel to accomplish the field survey. Survey instruments shall be the latest industry technology.
4.5.2 Surveying instruments shall be calibrated as specified in manufacturer’s recommendation.

4.5.3 Auxiliary tapes (cloth or fiberglass) shall only be used for rough measurements where precision is not important, for example determining ditch width, location of excavations or other irregular features. Tapes of this sort shall not be used to measure distances in excess of 30 m.

4.5.4 Latest calibration certificates shall be provided to SABIC prior to start of survey.

5. Aerial Photography

5.1 General. The topographic mapping may be accomplished by aerial photogrammetric methods using precision aerial mapping cameras. The applicable requirements of this specification and the other contract documents shall be satisfied. If aerial photography is used, 2 sets of complete prints and 1 set of negatives of all photographs shall be provided for SABIC.

5.2 Flight Plan. When aerial topographic methods of obtaining topographic data are to be used, the surveyor shall prepare a proposed flight plan showing the flight lines to be flown and the ground control points to be utilized. Each flight line will be flown continuously across the project area. The principal points of the first two and the last two exposures of each flight strip shall fall outside the boundaries of the area to be mapped. The flight plan shall be submitted for SABIC approval prior to carrying out aerial photography.

6. Computer Graphics Data

6.1 General Data Requirements

Data shall be provided on magnetic media suitable for use on Intergraph, Microstation or AutoCAD as described below.
a. Write data to the magnetic media in its native and uncompressed format as: *.dgn or *.dwg files. The data may be provided on compact disc (CD).

b. An electronic design file shall be provided for each of the final topographic maps. A composite of the total mapped area shall be produced in one electronic *.dgn (Intergraph or Microstation) or *.dwg (AutoCAD) design file in addition to the individual topographic maps. Additional survey data required by the contract document shall be incorporated into final electronic *.dgn or *.dwg design file and provided in ASCII file format as follows:

Point Number, Northing, Easting, Elevation, Description P,_,N,_,E,_,Z,_DESC

6.2 3-D Data

3-D elements representing contours, breaklines, faultlines, and centerlines shall be at the actual Z value. The contour elements may have reasonable gap due to the digitizing process but shall not touch or overlap. The surveyor shall furnish Triangular Irregular Network (TIN) files, as produced by Intergraph/Microstation based Inroads product (for example *.dgn, *.tin) electronic data files, or equivalent in AutoCAD based software, for use in preparation of earthwork volumetric calculations and ground surface modeling. 

6.3 Data Category Levels

Map data shall be recorded in separate data category levels in accordance with industry practice, and submitted for SABIC approval.

6.4 Scale

Scale dependent data (for example text, cells, and symbols) shall be recorded at a scale factor suitable for display at the specified map scale.

6.5 Text

Text shall be a minimum of 2.5 mm in height when plotted.

6.6 Working Units

Data files shall be set up on the basis of the following working units:
(MU) Master Units = 1 m
(SU) Sub-Units = 1000 mm
(PU) Positional Units = 80

6.7 Global Origin

Global origin of design files shall be at the center of the Integraph/MicroStation or AutoCAD design cube.

6.8 Symbols and Patterns

Symbols and patterns incorporated into the map shall be appropriate cells (Intergraph/Microstation) or blocks (AutoCAD) available to the surveyor either of his own creation or other SABIC approved software packages. Symbols and patterns used shall be clearly identified in the map legend on each drawing delivered.

7. Surveyor’s Certification

Each survey drawing shall be affixed with the surveyor’s license number, signature, seal and date of signature.

8. Project Site

8.1 Access to the Project Site. Surveyor shall give notice to SABIC of commencement of field surveying or aerial photography operations a minimum 2 weeks prior to entering the project site.

8.2 Field Contract. For additional information pertaining to the site and for permission to enter the site, SABIC shall be contacted.

9. Submittals

The following shall be submitted on completion of the topographic survey.

(i) Field Data. Original field books, computations, sketches and related survey data, which shall become the property of SABIC.
(ii) Topographic Maps.

(1) The topographic maps shall be produced based on the requirements of 4.4.
(2) Each map or survey drawing shall be certified, as detailed in section 7.
(3) Maps shall be drawn to scale 1:500 and for Master Plan, the scale shall be 1:5000.
(4) Plant grid system (existing) shall be shown with a 100 meter spacing.
(5) Utility and pipeline cross-section drawings with elevations shall be shown at 1:100 scale.

(iii) Electronic Files

(1) Computer aided drawings shall be at 1:500 scale unless noted otherwise.
(2) Electronic design files shall be in conformance with section 6.

(iv) Records. Documents based on survey services carried out, shall be the sole property of SABIC. The surveyor shall have no right to use, reproduce, or pass on to third parties any data, drawings, or information without prior permission from SABIC.

FIGURE 1 – Permanent Monument

Specification for Topographic Surveys

Specification for Topographic Surveys

TABLE I – Tolerances for Survey Features in Industrial Mapping

TABLE I - Tolerances for Survey Features in Industrial Mapping

TABLE I – Tolerances for Survey Features in Industrial Mapping

paktechpoint.com

You may also like...

Leave a Reply

error: tected !!Content is pro
%d bloggers like this: