Chapter 4: Design Surveying

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Section 1: Descriptions and Definitions of Survey Types

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Overview

Information contained in this section is the result of discussions of the Standing Committee on Surveying (SCOS), or is excerpted in its entirety and/or adapted for this manual from the Texas Society of Professional Surveyors, Category 6.

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Topographic Survey

A topographic survey is a survey performed to determine the configuration, relief or elevations of a portion of the earth’s surface, including the location of natural and/or man made features thereon. A topographic survey is necessary in order to prepare an accurate topographic map and requires the expert skill of a Registered Professional Land Surveyor (RPLS) well versed in maintaining accuracy and precision in detail mapping. Unless noted to the contrary, a topographic survey is not intended as a boundary survey, although some boundaries may necessarily be defined.

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Topographic Map

A topographic map is a two-dimensional (2-D) map that presents the horizontal and vertical positions of the features represented; distinguished from a planimetric map by the addition of relief in measurable form. A topographic map usually shows the same features as a planimetric map but uses contours or comparable symbols to show mountains, valleys, and plains.

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Planimetric Map

A planimetric map is a map that presents the horizontal positions only for the features represented; distinguished from a topographic map by the omission of relief in a measurable form.

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Digital Terrain Model (DTM)

A digital terrain model (DTM) is a mathematical model of a project surface that becomes a three- dimensional representation (3D) of existing and proposed ground surface features. Critical calculations and processes based on the DTM include contouring, cross sections and quantities, drainage models, watersheds, hydraulics, water catchment areas, and cross sections sheets.

A DTM is created through the construction of a Triangulated Irregular Network (TIN) and is based on modeling the terrain surface as a network of triangular facets that are created by simply connecting each data point to its nearest neighboring points. Each data point (having x, y and z coordinates) is the vertices of 2 or more triangles. The advantage of the TIN method is its mathematical simplicity- all DTM calculations are either linear or planar.

The processes and the resulting DTM offer many advantages over a topographic survey. Field data for a DTM is collected in a way that allows TxDOT to use the latest in automated survey technology. Traditional data collection (for a topographic survey) involves taking cross sections, typically every 100 feet, along a horizontal control line or in a grid pattern. Digital terrain modeling has virtually eliminated this practice.

Data points (shots) are taken at every break in elevation with no particular pattern being required. The emphasis is on identifying all features and changes in elevation within project limits. Data is collected using an electronic data collector with an electronic total station. The data points are assigned feature codes, attributes, descriptions, comments, and connectivity linking codes to add intelligence to a point at the time of data entry into data collector.

Information is downloaded from the data collector to a computer, either in the field or later in an office, and is processed using AASHTOWare® Survey Data Management System® (SDMS) software. A SDMS® calculated file is generated for importation into CAiCE or GEOPAK Survey for further review. The file is then imported into GEOPAK® for project design.

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Route Survey

A route survey is an application of the above described topographic or DTM survey along a determined linear ROW route, either existing or proposed, for a utility or roadway.

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Purposes

A topographic survey is made for the purpose of gathering relevant information that will be represented on either a topographic map or in a DTM. Typically, highway planning, engineering design and ROW design are the primary purposes.

Special Note For TxDOT Purposes. When this text discusses procedures or standards relating to either a topographic survey or survey for a digital terrain model, the accuracy, standards, equipment and basic procedural methods employed will be the same. A topographic survey will be performed and a DTM can be used for most all TxDOT applications where route design and engineering are required, whereas a topographic map may be better suited for large area site design and development.

This specification is intended for use in developing a design survey, a digital terrain model, or a topographic survey, with accuracy sufficient to meet TxDOT design needs and requirements.

A 3D model or a DTM may be preferred for purposes such as:

  • highway/roadway planning, design
  • ROW design
  • drainage studies
  • site development, planning
  • architectural planning, design
  • landscape design.

A significant advantage of a DTM is that it offers the ability to view, inspect, and smoothly navigate through, over and across a DTM in a 3D environment for the purposes of locating, editing, and correcting raw field data (points and chains) in 3D.

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Considerations - Other Technology

A computer model or a DTM is the ultimate work product of any of these newer methods of data acquisition. Depending on the critical factors of each project, including type, terrain, accuracy, precision required, cost, traffic conditions, and safety, such advanced methods may warrant serious consideration as a compliment to conventional data gathering or as a replacement of common or conventional surveying methods.

While conventional aerial photogrammetry may still be viable; however, as technology continues to advance, existing methods such as photogrammetry with airborne Global Positioning System (GPS) control become more accurate and even more cost effective. Other newer methods of terrain modeling are also available. One such method is airborne Light Detection and Ranging (LiDAR), which is a laser imaging scan done from a helicopter. Another, more advanced method is FLIMAP, or Fast Laser Imaging Mapping and Profiling, which employs laser scanning, incorporated with GPS for navigation and position. A DTM is produced as the deliverable.

Ground based LiDAR is an automated collection of data by reflector-less laser which involves high density scanning of an object or location to collect a “point cloud” of data points. The point cloud of data is further processed into a 3 dimensional computer model image. Typically done from a remote instrument location or multiple locations, 3D Laser scanning is especially good for sites or objects that are difficult to access, have high traffic volumes, involve extreme detail or have other extreme dangers or conditions associated.

This method has also been utilized in place of conventional topographic or digital terrain model (DTM) surveying with much success, especially where high traffic volumes or lane closure issues (safety) were critical factors. Presently the accuracy of the scanned data is said to equal or even exceed that of conventional survey methods, even electronic total station work, with the additional advantage of a greater number of data points all throughout the structure or project. Other methods or technology should be discussed with and approved by the district survey coordinator before use.

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Work Product

A DTM or Topographic Survey requires:

  • A control survey network, with horizontal and vertical positions on primary control points that are monumented, referenced, and placed near or on the project site.
  • Points of secondary control, which are based upon and supplement primary control to facilitate data acquisition within a project.
  • A description and location sketch of each control point.

See Chapter 3, Preliminary Surveying, for specifications on horizontal and vertical control networks and information on point descriptions, location sketches, and other pertinent information.

While a topographic map (2 dimensional) may be the typical end product of a topographic survey, for TxDOT purposes a processed computer file for a DTM (3 dimensional) is the primary deliverable product. Even when hard copy maps are specified as a part of the deliverable, electronic graphics files (2D and/or 3D) for the final product must be furnished to TxDOT for each project.

Required files include:

  • Computer files of collected raw data, as required by the respective TxDOT office. These computer files should at a minimum, consist of raw, unprocessed data as originally collected in the field by Survey Data Management System® (SDMS) or other approved, TxDOT supported data collection method and software.
  • Processed data in a form that is fully compatible and usable in TxDOT supported software programs such as CAiCE, GEOPAK®, and MicroStation®.
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Information Required

The Standing Committee on Surveying (SCOS) has adapted and approved information within this subsection from the Texas Society of Professional Surveyors, Category 6.

Information may be furnished to the surveyor by TxDOT, or the surveyor may be required to research TxDOT files and/or public records, if so directed and agreed upon. Information should include the following:

  • project or site location shown on a map
  • ROW maps depicting current ROW width(s) and other land, ownership and survey information
  • ownership information of adjacent tracts
  • intersecting road ROW information, documentation
  • construction plans of existing facilities if available
  • intended use of the survey and required form of deliverable, files required, etc.
  • accuracy required and method of display (contours, spot elevations, etc.)
  • horizontal and vertical datum upon which the survey should be based if this varies from the TxDOT standard. Example: match existing project datum instead of NAD 83 or NAVD 88
  • availability and need of special data, whether current or historic, which may include: Existing data or mapping from other agencies, county, flood control/drainage district, FEMA, Corps of Engineers, etc.
  • for state forces and all consultants, permission must be secured prior to entry on private property to survey outside of state ROW
  • research on subject tracts/parcel ownership also includes name(s) of tenants or parties in charge and special conditions or considerations required or requested by the owner
  • existing National Geodetic Survey (NGS) and/or United States Geological Survey (USGS) survey control information and data sheets for horizontal and vertical monumentation
  • recent aerial photographs (particularly for large sites), USGS quadrangle sheets, or computer files of the same.
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Monuments

Reference points and control monuments for a topographic survey may include temporary stakes, hubs, nails in pavement, iron rods, or reinforced concrete monuments.

A wooden hub or stake, nail or iron rod is considered as secondary control (temporary bench mark or control point) which only supplements primary survey control monumentation to facilitate data acquisition.

Primary control points, whether set by GPS or conventional survey methods, shall be of reasonable permanence and should conform to the requirements and specifications shown in Appendix C, “Monumentation” of this manual.

A “datum point” rod or a rock setting is required for GPS Level 1 control points, but the “standard” TxDOT concrete setting can be used for GPS Level 2 surveys. The standard concrete setting was formerly depicted in the old M-92 drawing for Right of Way (ROW) monuments.

Control monuments shall be well referenced, named according to district procedure, indexed in the project data or field notes and identified in the computer file final deliverable. Point names may be furnished for a state-wide or a district monument numbering system by the TxDOT District Survey Coordinator. A location sketch and data sheet for each monument should be furnished to the project manager prior to completion of work.

Example of a monument stamping: 000-0000

  • where, 000 refers to the County number
  • and 0000 refers to a discrete monument number for each district and is determined by district surveyor personnel.
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Monumentation for New Stations

All monumentation for new Level 1 points are to be in accordance with the following NGS publications:

Concrete Marks, from NGS Operations Handbook and Manual of Geodetic Triangulation, S.P. 247.

Setting a Survey Disk in Bedrock or a Structure from NOAA Manual NOS, NGS 1, Geodetic Bench MarksSetting a NGS 3-D Monument Based on Revised NGS 3-Dimensional (3-D) Rod Mark [Draft Version] by: Curtis L. Smith, National Geodetic Survey, July, 1996.It is recommended that new Level 2 points also follow these construction specifications, but the TxDOT surveyor in charge may call for less stringent requirements.

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Naming Convention for Level 1 and Level 2 Monuments

The recommended naming convention for Level 1 and Level 2 monuments is as follows:

Example: 1580032

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Digits

Indication

158

  • The first three (3) digits indicate the county in which the monument was set.
  • This is the standard county code used by TxDOT.

0032

  • The next four digits indicate the point number of this particular monument.
  • It is specific for this county and there can be no duplicates in the county.


Some districts use variations of this by including a prefix or suffix.

Figures 4-1 and 4-2 are sample data sheets for documenting the monuments likely to be used in the future. There must be a data sheet for all Level 1 and Level 2 monuments. Districts may use their own data sheet form; however, it must contain all the horizontal and vertical geodetic data of these sample data sheets. An RPLS signature and seal is recommended for data sheets for Level 1 and Level 2 GPS monuments.

The following table provides a list of the standard county designator codes used by TxDOT.

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County

#

County

Name

County

#

County

Name

County

#

County

Name

County

#

County

Name

1

Anderson

65

Donley

130

Kaufman

193

Real

2

Andrews

67

Duval

131

Kendall

194

Red River

3

Angelina

68

Eastland

66

Kenedy

195

Reeves

4

Aransas

69

Ector

132

Kent

196

Refugio

5

Archer

70

Edwards

133

Kerr

197

Roberts

6

Armstrong

72

El Paso

134

Kimble

198

Robertson

7

Atascosa

71

Ellis

135

King

199

Rockwall

8

Austin

73

Erath

136

Kinney

200

Runnels

9

Bailey

74

Falls

137

Kleberg

201

Rusk

10

Bandera

75

Fannin

138

Knox

202

Sabine

11

Bastrop

76

Fayette

142

La Salle

203

San Augustine

12

Baylor

77

Fisher

139

Lamar

204

San Jacinto

13

Bee

78

Floyd

140

Lamb

205

San Patricio

14

Bell

79

Foard

141

Lampasas

206

San Saba

15

Bexar

80

Fort Bend

143

Lavaca

207

Schleicher

16

Blanco

81

Franklin

144

Lee

208

Scurry

17

Borden

82

Freestone

145

Leon

209

Shackelford

18

Bosque

83

Frio

146

Liberty

210

Shelby

19

Bowie

84

Gaines

147

Limestone

211

Sherman

20

Brazoria

85

Galveston

148

Lipscomb

212

Smith

21

Brazos

86

Garza

149

Live Oak

213

Somervell

22

Brewster

87

Gillespie

150

Llano

214

Starr

23

Briscoe

88

Glasscock

151

Loving

215

Stephens

24

Brooks

89

Goliad

152

Lubbock

216

Sterling

25

Brown

90

Gonzales

153

Lynn

217

Stonewall

26

Burleson

91

Gray

154

Madison

218

Sutton

27

Burnet

92

Grayson

155

Marion

219

Swisher

28

Caldwell

93

Gregg

156

Martin

220

Tarrant

29

Calhoun

94

Grimes

157

Mason

221

Taylor

30

Callahan

95

Guadalupe

158

Matagorda

222

Terrell

31

Cameron

96

Hale

159

Maverick

223

Terry

32

Camp

97

Hall

160

McCulloch

224

Throckmorton

33

Carson

98

Hamilton

161

McLennan

225

Titus

34

Cass

99

Hansford

162

McMullen

226

Tom Green

35

Castro

100

Hardeman

163

Medina

227

Travis

36

Chambers

101

Hardin

164

Menard

228

Trinity

37

Cherokee

102

Harris

165

Midland

229

Tyler

38

Childress

103

Harrison

166

Milam

230

Upshur

39

Clay

104

Hartley

167

Mills

231

Upton

40

Cochran

105

Haskell

168

Mitchell

232

Uvalde

41

Coke

106

Hays

169

Montague

233

Val Verde

42

Coleman

107

Hemphill

170

Montgomery

234

Van Zandt

43

Collin

108

Henderson

171

Moore

235

Victoria

44

Collingsworth

109

Hidalgo

172

Morris

236

Walker

45

Colorado

110

Hill

173

Motley

237

Waller

46

Comal

111

Hockley

174

Nacogdoches

238

Ward

47

Comanche

112

Hood

175

Navarro

239

Washington

48

Concho

113

Hopkins

176

Newton

240

Webb

49

Cooke

114

Houston

177

Nolan

241

Wharton

50

Coryell

115

Howard

178

Nueces

242

Wheeler

51

Cottle

116

Hudspeth

179

Ochiltree

243

Wichita

52

Crane

117

Hunt

180

Oldham

244

Wilbarger

53

Crockett

118

Hutchinson

181

Orange

245

Willacy

54

Crosby

119

Irion

182

Palo Pinto

246

Williamson

55

Culberson

120

Jack

183

Panola

247

Wilson

56

Dallam

121

Jackson

184

Parker

248

Winkler

57

Dallas

122

Jasper

185

Parmer

249

Wise

58

Dawson

123

Jeff Davis

186

Pecos

250

Wood

62

De Witt

124

Jefferson

187

Polk

251

Yoakum

59

Deaf Smith

125

Jim Hogg

188

Potter

252

Young

60

Delta

126

Jim Wells

189

Presidio

253

Zapata

61

Denton

127

Johnson

190

Rains

254

Zavala

63

Dickens

128

Jones

191

Randall

 

 

64

Dimmit

129

Karnes

192

Reagan

 

 



TxDOT Control Point Data Sheet. (click in image to see full-size image)

Figure 4-1. TxDOT Control Point Data Sheet.

Sample Project Specifications Control Point. (click in image to see full-size image)

Figure 4-2. Sample Project Specifications Control Point.

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Conditions

The effect of location, such as rural, suburban, urban, or urban business district, on conditions of a DTM or topographic survey will be minor and will be most dependent upon the purpose of the survey.

The need for appropriate control and tolerances will be the deciding factor when the purpose of the survey is for roadway or ROW design in determining reasonably accurate quantities of construction materials, such as water, spoil, fill, concrete, etc.

For TxDOT needs, the following shall be covered under Condition I regardless of location (rural or urban), unless TxDOT gives directed and prior approval:

  • roadway design
  • bridge design
  • ROW design
  • environmental site
  • historical site.

Extended area topography (i.e.: drainage area outside of a ROW) may fall under Condition II, but is subject to direction by the TxDOT project manager.

DTM and topographic survey tolerances are typically confined to the Condition I and II.

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Field Procedures

DTM or topographic surveys require a reliable horizontal and vertical control system based on acceptably closed and adjusted traverses and level loops. Attention should be given toward developing this control system before any detail work is begun.

Field work shall be performed to achieve the specified or intended accuracy and results as stated in this manual, in accordance with accepted technical methods, i.e.: TxDOT, NGS, or the TSPS Manual of Practice, and as directed by the manufacturer of the surveying instrument(s) or equipment used.

For GPS applications, the Federal Geodetic Control Subcommittee’s (FGCS) Geometric Geodetic Accuracy Standards and Specifications for Using GPS Relative Positioning Techniques shall be followed.

Field personnel shall be well trained in the technical aspects of surveying as related to their respective duties.

Surveying instruments shall be checked and kept in close adjustment according to their manufacturer’s specifications or in compliance with textbook standards.

  • Electronic distance measuring devices shall be compared against a standardized baseline at 6 month intervals, however a comparison check should always be done as needed, especially if an instrument has been dropped, damaged or is suspect of the same. A calibrated baseline certified by NGS is the preferred standard.
  • This comparison includes electronic total stations or any other electronic measuring instrument, and may be done by more up to date methods as agreed upon by TxDOT.
  • Total stations and theodolites shall be compared against a standard known angle at a 6 month interval; however, a comparison check should always be done as needed, especially if an instrument has been dropped, damaged or is suspect of the same.
  • Levels, auto or digital should be checked by the “2 peg test” or the reading the elevation difference between two reference points taken from 1.) a middle setup between points and also 2.) from an end setup. Failure to get the same difference of elevation indicates an out of adjustment condition, which usually requires a shop cleaning and adjustment.
  • Auxiliary tapes, cloth or fiberglass, shall only be used for rough measurements where precision is not important, such as determining the width of ditches, the location of excavations or other irregular improvements. Tapes of this sort shall not be used to measure distances in excess of 100 feet.

Field measurements of angles and distances shall be performed in such a manner as to attain the closures and tolerances as found in this manual and see Table 4.4 TSPS Manual of Practice Chart for Tolerances for Conditions, at the end of this section.

Surveys for vertical or horizontal monumentation for control of a DTM or a topographic survey shall refer to the following sources:

  • TxDOT Survey Manual
  • NGS special publications
  • NGS standards for horizontal or vertical control monuments that will be registered
  • Department of the Army ( Corps of Engineers).

Where aerial photogrammetry is to be used to compile the topographic map, the surveyor shall consult with the photogrammetrist as to specific requirements for the photo control and for additional supplemental information required by conditions of a specific project or location.

  • Horizontal and vertical photo control (picture points) shall be based on and looped to the control system.
  • Identification of photo control (picture points) must be precise and clear since these points will be used to build the network from which the photogrammetrist must work.
  • Photo control points, set before the aerial photography is made, shall be located from, and looped to the control system. The density and pattern for paneled picture points shall be determined through consultation and coordination with the photogrammetrist.

For TxDOT purposes, methods that are more modern are normally used such as the DTM survey that incorporates methods described in the section below.

Surveying procedures with electronic total station or with GPS shall incorporate control points that are tied to a primary control system network of an appropriate level of precision and accuracy for the project.

Acquisition of field data may require running secondary control and bench marks that begin and end at points on the primary control system.

The use of open ended legs or “spur” lines should be avoided whenever possible. When such lines are necessary, appropriate checks shall be made on all field data before leaving the vicinity.

Any field notes written in a field book shall be kept in a neat and orderly manner on all control points, primary or secondary. Appropriate annotations on location, description of point and reference to identifying specific features located during the DTM or topographic survey shall be made.

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Topographic Features

The perimeter limits of any unique or special features such as historical structures, cemeteries, burial grounds or grave sites known or found within the project limits or adjacent to and which may be affected (existing or proposed ROW) and shall be shown by actual location.

Buildings and improvements, including distance from proposed ROW up to 50'. See Chapter 5, ROW Surveying of this manual and the TxDOT ROW Manual Volume 1 - Procedures Preliminary to Release. The project manager and/or district surveyor may extend this distance in the following ways:

  • center lines of dry creeks, gullies or other confined intermittent watercourses
  • paths, car trails, pasture roads, etc.
  • borders, boundaries - city limits, county line or state line
  • additional data points shall be collected along such features, outside of state ROW, as required and directed by TxDOT. These additional features may include:
    • creeks, streams, rivers and water bodies, shown and identified by name. Water levels shall be determined and displayed by elevation, time, and date of observation.
    • drainage areas - field information on drainage area(s) of a project shall be collected in the same manner as other information to the extent as directed by the project manager and/or district surveyor.
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Electronic Data

In nearly all cases, field work is automated by the use of computer software and hardware for collecting, reviewing, editing and processing field data. A data collector may be connected to the instrument (total station, GPS receiver, digital level, etc.) to store the raw measurement data and perform coordinated geometry (COGO) functions while in the field. Original raw data must be saved as a file for retention, as a matter of record, before any data editing or processing is done.

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Data Collection

Field data in electronic form should be collected in the SDMS® collection form and processed in SDMS® Processor. This software was developed through the American Association of State Highway and Transportation Officials (AASHTO) and supported by TxDOT Technology Services Division. It is provided gratis to TxDOT consultants under TxDOT’s license agreement with AASHTO. Its purpose is to provide a more flexible and user definable method of recording horizontal angle, vertical angle and slope distance from most of the total stations and in a standard format recognized by the survey review or design software.

There are numerous ways to provide connectivity. When performing radial topography surveys for a DTM, points in the same chain such as edge of pavement, centerlines and ditch lines can be linked together. These survey chains can ultimately be ported to mapping files or to DTM files as DTM break lines. Standard TxDOT feature codes and cells have been developed for use in the field to insure standardization of line weight, color, levels, and symbology.

These feature codes also determine where the points and chains will go, either to a mapping file or a DTM file. Topographic surveys, traverses and level runs may be collected in Survey Data Management System® (SDMS) Collector software. The data can then be reduced to coordinates on a desktop PC using SDMS® Processor, which uses a least squares type of adjustment. There are a number of useful reports that can be generated in this software.

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Office Analysis

Survey review and DTM - In order to view the results of a survey for troubleshooting and delivery of a .dgn file, pre-design software will be used. TxDOT uses CAiCE Visual® Transportation, GEOPAK Survey, and SDMS® Processor to serve as the tool(s). This software will accept the SDMS .cal file as input with the TxDOT feature table attached, and will graphically display the project for analysis. Corrections and additions can be made and the DTM can then be created. Photogrammetry files, background maps, macros for visualization and other enhancements may be utilized before 2D or 3D graphics are exported as a .dgn file for GEOPAK® / MicroStation® use by the designer.

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TxDOT Deliverables - Computer Files, Maps, and Drawings

Printed maps or plan sets of topographic surveys or digital terrain model (DTM) shall be represented by neat, reproducible drawing sheets. These drawing sheets are plotted for urban projects at a typical scale of 1'' = 50' (Full Size or scale) or 1'' = 100'. Half size, scale, or rural projects may use a typical scale of 1'' = 100' and 1'' = 200', unless otherwise approved or directed and shall accurately depict the results and details of the field work, research, and computations as compiled and checked.

For initial submission, plotted drawings may be on paper, in the same sizes listed above, in a size prescribed by TxDOT graphics standards, the TxDOT ROW Manual Volume 1 - Procedures Preliminary to Release, or as requested by the TxDOT project manager. Information may also be submitted in electronic form according to district standards.

For the TxDOT final work product, all final drawings shall be plotted on Mylar film medium and other typed documents on a quality bond paper. All drawings and the information shown shall be plotted or printed on standard sizes and shall be according to TxDOT graphics standards, the TxDOT ROW Manual Volume 1 - Procedures Preliminary to Release, or standards contained in this manual, as may be applicable.

Typically, full size drawings shall be plotted on 22'' x 34'' medium. Half (½) scale drawings shall be on an 11'' x 17''size medium. Bond paper may be used for initial submittal. Mylar shall be used for all final drawings.

No plat, map or drawing shall be made on a sheet size smaller than 8 ½'' x 11''

All information, existing topographic features, monuments - ROW or control monuments, or property corners, whether found or set, etc. shall be represented on a map and in the computer file(s), in the proper dimensioned location by using the most current TxDOT cell library (example: TxDOT2K.cel) for symbol standardization. Some projects (i.e.: ROW acquisition) may require that other features are labeled and dimensioned as to size, height, width, or depth and referenced to the nearest ROW or property line. Site maps for architectural design may require other symbology.

All maps or drawings, whether printed, plotted or in a computer file shall have a north arrow and shall be oriented so that north is toward the top of the sheet unless otherwise directed by TxDOT.

The Texas Coordinate System, based upon NAD 83 (HARN), shall be used with the proper zone, adjustment factor, theta angle and reference monument information used shall be noted.

For TxDOT purposes, a statement containing the above information shall be placed on all drawings and/or included with all computer files that provide reference information or “metadata” on the control monumentation, NGS, or other that is used as a basis for all projects.

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Title Sheet

A title/cover sheet shall be prepared for each project (examples accessed from TxDOT ROW Manual Volume 1 - Procedures Preliminary to Release, and shall show the following items:

  • location of the route or project being mapped shall be shown on a title/cover sheet prepared for each project
  • appropriate location sketch
  • station numbers of the projects beginning and end
  • charge numbers (CSJ, both Construction and ROW)
  • stated scale of the drawing with a graphic scale
  • project description
  • survey date
  • larger projects, a sheet index may be preferred
  • statement of the basis for horizontal and vertical control, including information listed in sections below
  • if prepared by a consultant, the company name, address and phone number shall be shown.
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Horizontal Control

Horizontal control deliverables shall include the following:

  • For TxDOT purposes, the Texas Coordinate System of 1983/93 HARN adjustment shall be used.
  • Map coordinates and distances shall be in surface measurements and the combined adjustment factor (CAF) must be indicated to allow for return to state plane coordinates (SPC).
  • A statement shall also be made specifying the proper zone, referenced traverse or triangulation station(s), and the published coordinates of the station(s) used along with elevation.
  • The appropriate mapping angle (theta angle) for the site shall be shown on the map.

It should be noted that the TxDOT Surface Adjustment Factor (SAF) is the reciprocal of the CAF.

As mentioned, TxDOT works in surface coordinates, but project size/length, number of counties or SPC zones crossed or other factors may justify showing all information in grid coordinates.

Unless otherwise directed by TxDOT, all deliverables shall be fully compatible with CAiCE and/or GEOPAK® and be native MicroStation® files. Graphics standards are available from TxDOT.

Anchor: #i1003898

Vertical Control

Typically, TxDOT elevation basis is either 1.) an existing project (datum specified by project) or 2.) NAVD 88.

A statement of the basis of elevations shall be made in computer files and placed on all map prints similar to one of the following examples:

  1. Elevations refer to a BM set near the N. E. corner of the intersection of First St. and Ave. B (Location), an “X” on top of a concrete inlet (description). Elevation is 200.00 ft., and is referenced datum of Project CSJ 0000-00-000.
  2. Elevations are based upon NGS bench mark A1422, NAVD 88, Published elevation—326.042 ft. (1988 Adjustment).

Per TxDOT policy (see Contract for Surveying Services) and as agreed to in survey contracts with the state, all original work products become property of the state. A consultant performing work under contract with the state may keep a copy for company records.

Anchor: #i1191505

Control Point Data Sheets

A data sheet shall be provided for individual Level 1 and Level 2 control points. It should contain, at a minimum, the information noted below:

Anchor: #i1000055Table 4.3 Control Point Data Sheets

Established by

contractor company

Date established

date monumented

TxDOT Level of Survey

e.g. Level 2

Horizontal Datum

e.g. NAD83

Horizontal Adjustment

e.g. '93 HARN

State Plane Projection Zone

e.g. Tx South Central 4204

Vertical datum

e.g. NAVD88

Geoid model used

e.g. GEOID03 or GEOID99

Units

US Survey foot

County name

e.g. Bexar

Station name

e.g. 0150102

Latitude

Latitude to 5 decimal places

Longitude

Longitude to 5 decimal places

Northing

three decimal places

Easting

three decimal places

Elevation

two decimal places

Convergence angle

nearest second

Combined Adjustment Factor

eight decimal places

Survey method for vertical

GPS or leveling

General location

e.g. S Loop 1604 W & FM2790

To Reach description

how to get to station from a well known intersection

Type of Mark

iron rod, brass disc, etc.

Stamping

what is actually stamped on the disk

Stations directly tied

list up to three closest stations directly tied



Anchor: #i1003928

Certification

While TxDOT contract requirements call for supervision and monitoring by a Registered Professional Land Surveyor (RPLS) signing and sealing a topographic survey, a digital terrain model (DTM) or preliminary design survey is not usually required, but may be called for by district standards.

Anchor: #i1003938

Right of Way - Descriptions with Plats (Exhibit A) and ROW Maps

If descriptions and plats of parcels become necessary for ROW acquisition, all descriptions and plats (combined as property descriptions and labeled as TxDOT Exhibit A of the ROW Map package), shall be prepared according to Chapter 5, ROW Surveying of this manual and the TxDOT ROW, Volume 1 - Procedures Preliminary to Project Release. Any additional information needed or required by the district shall also be included as directed.

The following chart is excerpted from the TSPS Manual of Practice.

Anchor: #i1002535Table 4.4 TSPS Manual of Practice Chart for Tolerances for Conditions

Condition

I

II

 

 

Urban Business, District Urban, Suburban & Industrial

Rural & Broad Area General Mapping

Remarks & Formulae

Error in Traverse Closure

1:10,000

1:7500

System Control Loop

Unadjusted Level Loop Closure (ft.)

.04

.08

System Control Loop M=Miles

Secondary Traverse Closure

1:7500

1:5000

Between System Control Points

Secondary Level Loop Closure (ft.)

.05

0.2

Between System Control Points

Positional Error of Any Primary Monument (horizontal)

1:15000

1:10000

For monuments used for Triangulation or Radial Surveying in respect to another

Positional Error of Any Primary Monument (vertical)

± .03 ft.

± 0.15 ft.

For permanent bench marks

*Contour Interval

2 ft.

10 ft.

Or as needed by the State

Contour Accuracy

± ½ Contour Interval

± ½ Contour Interval

 

Positional error of any Photo Control Point (horizontal and/or vertical)

0.50 ft.

2 ft.

Or as recommended by Photogrammetrist

Location of Improvements, Structures, and Facilities during survey

± 0.05 ft.

± 0.50 ft.

± 0.1 ft.

± 1 ft.

Vertical (inverts, flow lines)

Horizontal

Plotted location of Improvements, etc.

± 1/40 in.

± 1/40 in.

Symbols may be used for large scale maps indicating Center point

Scale of maps sufficient to show detail, but no less than

1'' – 200'

1'' – 2000'

Drawings are to show location of survey monuments and bench marks



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