Guidelines for the use of GNSS in surveying and mapping

Appendix D: Sample specification with
specific GNSS clause
The following extract could be part of a sample
survey specification, based on the RICS Measured
surveys of land, buildings, utilities – a guidance
note for surveyors.
The elements which are related to GNSS are
detailed:
2.1 Control network
The surveyor shall establish plan control at a
density sufficient to achieve the specified
accuracies. The main survey stations shall be of
stable construction. The surveyor should choose
the most appropriate marker for each location.
The final survey grid shall be arbitrary but related to
the national grid. A description of the grid system
used shall be quoted on each survey plan or upon
the index plan. The control stations shall also be
connected to the national grid values. The
maximum error ellipse at 95% shall not exceed
20mm throughout the main control network. For
this survey GNSS co-ordinates are required for the
control stations and static or fast static GNSS
survey shall be used for the control network.
The survey report shall include copies of the control
station sheets and a method statement describing
the survey technique used. Copies of the final
network adjustment report shall also be included.
2.2 Level network
The surveyor shall establish vertical control at a
density sufficient to achieve the specified accuracy
of less than 5mm. The main site control station
may be linked to the national vertical datum using a
static GNSS control survey. A principal control
station shall also be levelled to a national control
bench mark and the closure value stated.
GUIDELINES FOR THE USE OF GNSS IN LAND SURVEYING AND MAPPING |63