18VAC10-20-382: Minimum standards and procedures for surveys determining topography; field procedures; office procedures

A. The minimum standards and procedures set forth in this section are to be used for topographic surveys performed in the Commonwealth of Virginia pursuant to Chapter 4 (§ 54.1-400 et seq.) of Title 54.1 of the Code of Virginia. The application of the professional's seal, signature, and date as required by this chapter is evidence that the topographic survey is correct to the best of the professional's knowledge and belief and complies with the minimum standards and procedures.

B. Minimum field and office procedures. The following information must be shown on, or contained in, all plats, maps, or digital geospatial data, including metadata, used to depict the results of the topographic survey:

1. Physical improvements on the property, all man-made or installed structures, as well as visible evidence of underground features (e.g., manholes, catch basins, telephone pedestals, power transformers), and utility lines and poles must be shown or depicted when they are visible based on the methodology and scale. If the methodology or scale prevents depiction of the improvements as described in this section, then notice must be clearly stated on or contained in the map, plat, or digital geospatial data, including metadata, indicating the improvements that are not depicted.

2. Elevations must be provided as spot elevations, contours, or digital terrain models.

3. Onsite, or in close proximity, benchmarks must be established on site or in close proximity of the project and shown in the correct location, with correct reference to vertical datum, preferably North American Vertical Datum (NAVD), and shown in the correct location. Clearly state reference and basis of vertical datum. Elevations must be provided as spot elevations, contours, or digital terrain models.

4. The title of the topographic survey identifying the land surveyed and showing the state, county, or city in which property is located.

5. Name, address, and contact information of the individual or entity for whom the survey is being performed.

6. Name, address, and contact information for the land surveyor, surveyor photogrammetrist, or registered business.

7. Date, graphic scale, numerical scale, and contour interval of plat, map, or digital geospatial data, including metadata.

8. North arrow and source of meridian used for the survey.

9. Names or route numbers of highways, streets, and named waterways must be shown.

10. A distance to the nearest road intersection or prominent or well-known object. In cases of remote areas, latitude and longitude or state plane coordinates must be provided.

11. The horizontal and vertical unit of measurement, coordinate system, and data, including adjustments if applicable.

12. A statement, in the following form, must be shown on or contained in plats, maps, or digital geospatial data, including metadata:

This ________________ (provide description of the project) was completed under the direct and responsible charge of _______________________________ (Name of Professional) from an actual Ground/Conventional RTKGPS (or GNSS) or Remotely Sensed (check all that are applicable) survey made under my supervision; that the imagery or original data was obtained on ______________ (Date); and that this plat, map, or digital geospatial data, including metadata, meets minimum accuracy standards unless otherwise noted.

For the purposes of the certification above, remotely sensed data includes photogrammetry, airborne LIDAR, terrestrial and mobile LIDAR, and for hydrographic surveys, sonar or other acoustic type technologies for measurements.

C. Minimum positional accuracies must be met in accordance with the tables in subdivisions 1, 2, and 3 of this subsection. These tables are not intended to be acceptable in all situations, and the professional will be responsible to perform the work to the appropriate quality and extent that is prudent or warranted under the existing field conditions and circumstances. Metric or other unit of measurements must meet an equivalent positional accuracy. Map or plat scales, or contour intervals, other than those defined in these tables must meet an equivalent positional accuracy. The minimum positional accuracy tables are as follows:

1. Scale and contour interval combinations.

Map or Plat Scale

Contour Interval

1" = 20'

1 or 2 feet

1" = 30'

1 or 2 feet

1" = 40'

1 or 2 feet

1" = 50'

1 or 2 feet

1" = 100'

1 or 2 feet

1" = 200'

2, 4, or 5 feet

1" = 400'

4, 5, or 10 feet

2. Vertical accuracy standards.

Contours - Vertical Positional Accuracy

Spot Elevations - Vertical Positional Accuracy

Contour line 1' interval

± 0.60 foot

± 0.30 foot

Contour line 2' interval

± 1.19 feet

± 0.60 foot

Contour line 4' interval

± 2.38 feet

± 1.19 feet

Contour line 5' interval

± 2.98 feet

± 1.49 feet

Contour line 10' interval

± 5.96 feet

± 2.98 feet

Positional Accuracy is given at the 95% confidence level.

3. Horizontal accuracy standards.

Well defined ground points - Horizontal (Radial) Positional Accuracy

Map or Plat Scale

Absolute Horizontal Positional Accuracy

Relative Horizontal Positional Accuracy

1" = 20'

± 0.8 foot

± 0.20 foot

1" = 30'

± 1.1 feet

± 0.30 foot

1" = 40'

± 1.5 feet

± 0.40 foot

1" = 50'

± 1.9 feet

± 0.50 foot

1" = 100'

± 3.8 feet

± 1.00 feet

1" = 200'

± 7.6 feet

± 2.00 feet

1" = 400'

± 15.2 feet

± 4.00 feet

Positional Accuracy is given at the 95% confidence level.