3-Dimensional utility data conversion and utilization
Planimetric Map
Planimetric maps in the pipe utility industry typically have to serve two main purposes: 1) to
record the accurate location of utility facilities and, 2) to represent the operational network*, **. In
the hardcopy environment this is typically satisfied by two separate map sets at different map
scales. In the digital environment these two scales of maps can be produced from the single set of
planimetric data using generalization and scale-based symbology techniques. Since the
operational network map is, for the most part, simply 'less' information than the infrastructure
location record map (as built), this product can be generated by dropping detail from the as built
map and enhancing those devices of interest to an operations staff - 'Normally Open' valves for
example.
Profile
In the hardcopy records environment, profile drawings are typically located either 'above' or
'below' the plan drawing on the same map sheet (hence the term, 'Plan & Profile' drawing). This
enables the user to make the relationship between a valve or manhole on the profile drawing with
the same valve or manhole on the planimetric drawing by simply looking vertically 'up' or
'down' the sheet between the separate plan and the profile drawings. To replicate this scenario in
the digital environment would mean that fixed map sheets would have to be maintained with
some method of associating pre-generated profiles with a certain location on a map page. Since
this would not allow for the production of plan drawings with associated profiles for any area of
the digital utility database this approach would be overly restrictive.
To avoid this problem a method has to be developed to allow for the generation of profiles for
any area and for the profile to be placed anywhere on a plan map (or even separately) yet still
allow a user to visually associate facilities in the plan drawing with the same facilities in the
profile drawing. One method of accomplishing this is to ensure, during conversion, that unique
identifiers for valves or manholes (or whatever facilities are to be shown on the profile) are
captured and displayed on the plan drawing. When the profile drawing is generated from the plan
information, these unique identifiers are displayed so that facilities on two physically separate
outputs - one plan and one profile - can be visually associated using the unique identifiers.
An additional consideration for profile drawings is the potential for them to be available in the
field via handheld devices. Currently, for this to be realistically possible it is necessary to pregenerate
profiles and then make them available either simplistically through some sort of index
list with a descriptor identifying the location of the profile. Another indexing option would be
through the use of "profile polygons" as a separate layer in the utility database that when a
particular profile polygon was selected, the associated pre-generated profile would be displayed
(or plotted, dependant on the environment). While this does not necessarily have an impact on
* "Wire", or non-pipe utilities usually have facilities so closely spatially located to each other that the planimetric
map showing utility facilities at accurate locations is unable to show the operational network at a useful scale.
Typically, schematic maps are used at quasi-geographically accurate locations for this purpose.
** While the model of a utility network, using a system with sufficient graphic interface and output capabilities,
could represent the operational network, this is typically used instead for planning modifications or additions to the
existing network.
data conversion activities, it is yet another way that profile drawings can be made available to
users.
Another solution, and one that simply reduces, but does not totally eliminate the need for a
profile drawing yet still relays the necessary elevation information, is to display on the
planimetric map the depth of pipe endpoints where devices such as valves, manholes, catch
basins etc., are located. Since inverts and rim elevations (road surface) can be recorded in the
GIS with the pipes and devices respectively, by utilizing the connectivity of pipes to devices the
pipe depths at the devices can be determined. The difference between the pipe inverts and rim
elevations can be displayed as annotation on the map at a predefined distance from the pipe
endpoints (to reduce clutter given that at pipe endpoints typically utility devices are shown)
showing the depth of pipe at that location. For in-field use this information can be used as an
approximate guide for field users when digging in the vicinity of underground utilities.
Network Modeling
For the connectivity model of the network to be derivable from the infrastructure facility records,
at a minimum, it must be possible to export the data to the network modelling system of choice.
Ideally, and given that data model standards are now emerging in the GIS industry, network
modelling systems would be able to 'read' the GIS data directly. However, assuming that that
type of higher level of systems integration is not available, output routines must be able to format
the utility infrastructure data to suit the network modelling system. Of importance, from a data
conversion perspective however, is that the information required to adequately create the
network model is available in the GIS after loading it with the converted utility data. This
implies therefore that sufficient infrastructure information (other than the traditional pipe
diameter and material), from a 3-dimensional perspective, needs to be available. By converting
pipe elevations into the GIS and including this information in the infrastructure utility facility
data, pipe slopes and true utility facility connectivity can be derived.
Of importance here is that the network model needs to be able to be created easily and quickly so
that:
- network modifications are done on the source infrastructure facility records data in the GIS
and then exported to the network modelling system as opposed to modifications being made
directly in the network modelling system, and,
- The data in the network modelling systems is updated frequently (as the infrastructure facility
data changes) so that network operations engineers are always working with the most current
information. For this to happen, the transfer of the source infrastructure facility information
to the network modelling system (if that is even necessary), must be simple and fast.
All too often, after struggling to get infrastructure facility information into a network modelling
system and then struggling to correctly model the network, operators are reluctant to refresh the
information due to the amount of work involved in re-creating the network representation. The
utility network, modeled in the network modelling system, becomes a new 'source' of
information as changes to the network start to happen there as opposed to the 'true' source of the
information; that being the infrastructure facility records data in the GIS.
Data Conversion
The adage of "Garbage in, Garbage out" couldn't be more true when it comes to converting any
kind of data, however it is even more apparent when the data being converted comes from; 1)
many sources, and, 2) contains complexities not typically encountered. With data conversion
involving 3-dimensional information both of these are the case. It is for this reason that data
conversion must be approached in a systematic and controlled manner.
