Field Inventory - Do’s and Don’ts
Other project expectations
Client expectations from the inventory project are often not addressed. In order for the vender
to fully evaluate the project, the expectations should be explicitly stated. In addition to the
usual expectations for map products and a data base, useful issues to address would be a list of
applications that would need to be supported by the project data. Does the project need to
verify or use any internal records - if so explain. Should the project update record keys such as
pole numbers.
Locational Requirements
A major cost component of inventory is the accuracy level needed for the placement of facilities.
Historically, manual methods have been used. Today, advanced methods are available. The
advantages of each method should be evaluated.
Relative to land-base - specification
Facilities can be placed relative to mapped features in a landbase using traditional methods of
measuring in the field. Accuracy of actual placement, using this method, is a combination of
error in the landbase plus error due to placement. Given a landbase with a good selection of
features in urban areas, error due to placement can be a foot or so. This error is not
accumulated beyond the error inherent in the land and should be seriously considered.
GPS - specification
GPS is a hot item now-a-days which provides useful results given an accurate landbase. If GPS
is attempted to place poles and facilities in an inaccurate landbase, the graphic appearance of
the product will be unacceptable as facility locations may not be oriented correctly relative to
the map. Our proposals often suggest that the GPS information be provided as an attribute to
facility locations which have been placed manually. Many projects contain a requirement for
GPS initially, which is later dropped after prices are evaluated.
Accuracy of Data
Any of the several Field Inventory companies in business today can probably produce perfect
data. Not a single client would be willing to pay for it. The question is “What level of accuracy
is worth the price.”
Accuracy levels
Accuracy considerations should be made in terms of cost. Using 98.5?40as a reasonable level of
accuracy, perfect data would probably cost three times as much or more to produce. As the
accuracy level drops, costs decrease, but not commensurately. Data at a 97.0°/0 accuracy level
might come in at 90°/0 of the cost. We suggest that the best cost/value relationship be achieved.
Measurement procedure
If data can be counted as incorrect, it must be counted as correct when it is. The way to
measure accuracy is to use the count of data items collected as the base, for comparison against
the number found to be incorrect. If one hundred poles were inventoried and the data collected
contained 1700 individual fields needed to describe the facilities, a 98.5°/0 accuracy rate would
require that 1675 fields be correct. Conversly, the proposition that every forth pole could
contain an error is difficult for some to justify even though forty errors in 100 poles is the effect
of a 98.5°/0 accuracy specification.
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