Guidelines for the use of GNSS in surveying and mapping

Table F: Planning
Guideline Explanation Pt. 2 ref.
Ensure the client specification is read and
understood.
This will ensure that all requirements such as accuracy and any other specific issues that relate to logistics
are assessed. Any changes to survey design can also be incorporated in the survey planning at this stage.
7.1
When designing a control network, plan for
closed baseline loops.
This allows network closures to be computed for the survey. The GNSS receiver set-ups and antenna
heights for the survey can be checked by calculating closures around the closed loops. It is also important
to re-occupy the main control points to reduce any possible antenna height errors. Incorrect baseline
solutions due to multipath or other environmental considerations will also be highlighted.
7.2
Plan to observe independent baselines in the
network.
If three or more receivers are used in the survey, the independent baselines should be observed to remove
trivial lines in the survey. For a three-receiver set-up there will be two independent baselines per session.
This removes the possibility of highly correlated observations being present in the network adjustment.
7.2
7.3
Plan to over-determine the network design. Ensure that the network design is over-determined so that any baselines which do not process, or are too
noisy, can be deleted. This will ensure there is sufficient redundancy in the network for the final adjustment.
It will also reduce the likelihood of needing a return to site.
7.3
Make a contingency plan for the fieldwork. By their very nature, GNSS observations for control involve the receivers being at sites remote from each
other. This, coupled with the complex nature of the equipment, communications and logistics can lead to
unforeseen problems during the survey. It is wise to make a contingency or back-up plan, especially with
regard to the travelling time between points and unforeseen access problems that may occur.
7.1
Check all equipment prior to mobilisation to
site.
Due to the many constituent parts of GNSS receiver systems, especially real-time kinematic systems:
batteries, antennas, receivers, radios, data cards or loggers, associated cables and sundries, it is good
practice to check all equipment prior to mobilisation.
Order/check fundamental control station data. It is good practice to check that the co-ordinates or data for the fundamental control stations are available.
It is also recommended that back-up control is selected, as passive or fixed ground stations may have been
destroyed.
7.2
18 | GUIDELINES FOR THE USE OF GNSS IN LAND SURVEYING AND MAPPING