Guidelines for the use of GNSS in surveying and mapping

Table B: Detail survey guidelines
Guideline Explanation Pt. 2 ref.
Survey detail within the control framework. It is recommended that points of detail surveyed by GNSS are within the control framework for the project,
as outlined above. It is good practice to pick up the points from the control survey as a quality control
check during the detail survey.
7.2
Survey in areas where there is a good view of
the sky.
The same visibility constraint exists for detail points as for control points, although the accuracy
considerations which inhibit station location are not as stringent. It is recommended that the complete area
of detail survey to be surveyed has a clear view of the sky. Alternative methods should be considered for
areas that are very severely obscured.
5.2
5.3.4
7.3.1
Exercise extreme care when surveying in urban
areas.
In urban areas GNSS may not be the best technique for undertaking detail surveys due to obstructions that
interfere with GNSS signals, requiring longer occupations. There may be a requirement for some
conventionally surveyed work from local control points fixed by GNSS.
5.2
Use a dynamic survey method. For detail surveys it is recommended that a dynamic technique (see paragraph 1.3 above) should be used.
This affords maximum productivity for the rapid pick up of points.
4.3
4.4
When using a base and rover configuration,
use a base station at a project control point
during the survey.
It is best practice when using a base and rover system for detail survey using the dynamic method to use a
project control point as the base reference station.This is the best way of ensuring that survey detail is
correctly positioned in the project co-ordinate system.
7.3.4
When using dynamic methods, initialise in clear
open areas.
In this case it is best practice to perform the initialisation of the GNSS receiver system at a location within
the survey area where there are a minimum of obstructions. When a ‘loss of lock’ occurs and a new
initialisation is required, it is recommended that this point in the survey is noted on a booking sheet or in a
log file on the receiver.
7.4.4
7.4.6
Set accuracy and GDOP masks and check
values before logging point.
In real-time dynamic surveys, co-ordinate accuracy and GDOP masks can be set. Ensure these are set to
the value given within the specification for the survey. It is also good practice to periodically check the
displayed accuracy to ensure all logged points are within specification.
7.4.1
7.4.2
Log all raw observations in real-time surveys. This will allow the re-computation of survey results by post-processing if unforeseen problems arise and are
not identified during the real-time survey. This can be of extreme benefit if observation errors, antenna
height errors, transformation errors or communication/data malfunction occur during the survey. This data
should also be archived and can be submitted to the client if requested.
7.4
GUIDELINES FOR THE USE OF GNSS IN LAND SURVEYING AND MAPPING |9