22/01/2021
SURVEY EQUIPMENT CALIBRATION
CALIBRATION OR VALIDATION WHAT DO WE MEAN?
The terms calibration and validation require some explanation.
First we need to define calibration in the context of survey equipment.
Calibration is a comparison between measurements – one of known magnitude or
correctness made or set with one device and another measurement made in as
similar a way as possible with a second device.
The device with the known or assigned correctness is called the standard. The
second device is the unit under test, test instrument, or any of several other names
for the device being calibrated.
From the EDM Calibration Manual we have:
These guidelines describe the four Electronic Distance Measurement (EDM)
calibration baselines in the province of Alberta as well as how to undertake an
EDM calibration baseline survey. They have been developed to assist users in
verifying that their EDM equipment is working within the EDM manufacturer’s
stated specification for scale error and constant error. The guidelines also include
requirements for submission of EDM calibration survey data to the Geodetic
Control Unit, Surveys and Technical Services Section for evaluation.
Further to the process of simply testing against a known value it is often possible and therefore
necessary to make adjustments to the equipment to bring it back into calibration. For the
purposes of this discussion the terms calibration and adjustment may both be used to describe
the process of bringing a piece of equipment into specifications.
The validation process differs significantly from calibration. Validation goes beyond
simple calibration. The validation process includes the following:
The equipment;
o Is it capable of achieving the required accuracy under project conditions;
o Are the resulting measurements within specifications, that is, is it properly
calibrated?
The procedures used in the field as well as in the office;
In some cases even the personnel become part of the process.
From the Edmonton GPS Validation manual we have:
The validation networks may also be used to evaluate proposals from GPS
survey contractors. A "validation survey" on a GPS basenet may be required to
assess the proposed GPS positioning system, and determine with confidence
whether it can meet contract accuracy requirements. A positioning system in this
context includes the equipment and procedures used for data collection as well
as the software and procedures used for the data processing and adjustment.
