Sect_10.1.1

10.1.1 GPS and Quality Issues

INTRODUCTION

A Question of Quality

Though "quality" is nowadays a much abused buzzword, there is nevertheless an unprecedented interest in measuring, assuring, verifying and improving the quality of products and services. Hence there is a headlong rush by the manufacturing and service industry sectors to embrace such concepts as "customer oriented business", "Total Quality Management", "transparent operations", "commitment to quality", etc., each representing (it is widely assumed) some aspect of that elusive and ill-defined issue of Quality. What does it all mean for the GPS surveyor?

In previous chapters many concepts that are related to "quality" were discussed, including network redundancy, biases and errors, appropriate field procedures, baseline accuracy and precision, and many more. This chapter deals with quality issues in GPS surveying in order to highlight the role of Quality Management as an integral part of the GPS surveying process, and not simply a set of adhoc procedures which are applied in order to "check" if the results are OK. The language of Quality Management is replete with terms such as Quality Control (QC) and Quality Assurance (QA).

Although the two terms are often considered synonymous, a good working definition is that: (a) QA refers to the set of practices and procedures which are intended to maximise the chances that the product or service will satisfy the client's requirements, at a reasonable cost, while (b) QC refers to the procedures used to verify the level of quality achieved, and if it is inadequate, to detect the source of the problem and remedy it, if possible.

Quality Management (QM), in the context of GPS surveying, is concerned with assuring an agreed level of accuracy and reliability for the station coordinate results. The focus is therefore on procedures for defining, measuring and verifying quality, from the commencement of a project to the delivery of the results to the client. This is not to imply that past surveys were of "poor" quality. On the contrary, the set of survey practices which are now accepted as "standard" are the product of many years of hard-won experience. What is proposed is that in future the procedures themselves, and even the bases for the procedures, be: (a) documented (which procedures were followed? what were the outcomes?), (b) "de-mystified" (why was a certain procedure used? can it be justified?), and (c) premeditated (what was done to assure a quality result?). In this era of Total Quality Management it is no longer acceptable for a survey organisation to present such responses as:

"I am a licensed/registered surveyor, all my work is of the requisite quality"

"The client doesn't understand, he/she is only interested in the numbers and in making sure his/her bill as low as possible"

"If I start charging extra for this Quality Assurance stuff, he/she will take
his/her business to someone else"

"I paid good money to buy the best equipment, the results certain to be good!"

So what is meant by Quality Management? QM is a management system which provides a framework for a consistent approach to managing all aspects of an organisation's operations. The intention is to "get it right first time, every time", rather than the historical quality approach of "let's check if we got it right -- if not let's fix it up". However, perhaps the defining characteristic of QM is that it promotes an organisational culture in which all quality procedures are subject to continual scrutiny and improvement, supported by a management system which encourages identified improvements to be put into practice.

In section 10.1.2 procedures and checklists are presented to demonstrate how QA may be implement at every stage of a GPS survey. Sections 10.2 and 10.3 deal with GPS "standards and specifications", which provide the basis by which "levels of service" may be defined. Although "rules-of-thumb" (and commonsense) generally suffice when it comes to GPS survey planning, modern survey techniques such as "rapid static" and "stop & go" present special problems because of the unusual deployment scenarios that are possible. For example, when three or more GPS receivers are used in a survey, will the use of two fixed base receivers result in an inherently stronger and more reliable network, than other configurations? In section 10.4, QC procedures for GPS surveying are presented and discussed.

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