AM/FM 101: The GIS Mind-Meld
Spatial Engine
The next key component is the Spatial Engine. Of the geographic tools provided by the ‘
software vendor, this may be the most important and most powerful. This engine allows
analysis to be performed based on geographic locations. This tool allows explicit
coordinate locations for points lines and polygons to be incorporated in implicit analysis.
Another example may be helpful. An airport maybe assigned a geographic location.
Depending on our scale requirements we might use a point or a polygon, but for now let’s
assume we use a point, (X, Y). We could then assign line locations for all transmission
lines. Using the spatial engine we could inquire for all transmission lines within one mile
of the airport.
The crucial difference in this analysis is that we made no additional explicit references
between airports and transmission lines. By assigning locations in the form of geographic
attributes, and employing the spatial engine, we have derived these relationships on the
fly - as needed - with no long-term explicit data to be maintained other than the
geographic components of each. -Connectivity
Model
The third key component is the connectivity model. Technically, this might be
considered part of the data base or possibly part of the vendor toolkit, but it is worthy of
separate discussion here.
The connectivity model is how we maintain connections between our facilities and our
customers - the things we need to run our business. Why? Because connection is a
fundamental part of the reason we are in business. It is vitally important to know that a
certain customer is connected to a certain waterline or electric transformer. If the
customer reports an outage we know where to start. Economics may also be associated
with feed paths (circuits), and the notion of profit becomes directly associated with
service.
This connectivity model may be expanded to include a direction attribute if needed.
Geographical User Interface
Finally, we get to the GUI - the geographical user interface. This is more than the
traditional “graphical user interface” because it allows the user to interact with the system
“geo’’-graphically. The GUI is typically used to maintain the geographic component of
the data base. It is also used to present the results of analyses to the user.
Often the GUI is a key part of application development since it is tailored to allow users
to efficiently uerform business functions. Communicating information geographically is
a very powerful and effective method.
Example
If we assume that the data base has been populated, the spatial engine is operational, the
connectivity model built and the GUI functions as needed, we may find it useful to step
through a sample application and discuss the functions of the key components.
Sample Business Problem
Let’s say that a tornado has been sighted in a certain area and we want to prepare a list of
critical customers which could be affected. We might place the sighting at an (X,Y)
point, then look for all substations within a five mile radius. From the substation list we
could find all circuits potentially affected, then trace all circuits to construct a list of
customers which could be affected. We could then select from that list those customers
designated as “critical”. We might then highlight those customers on the display and ask
if the user would like to save the file, print a report or produce a map with the streets and
critical customers plotted.
To solve this problem we have employed the critical components of the AM/FM/GIS.
Let’s examine each step:
Step 1: We used the GIS to place a point, then employed the spatial engine to find
substations within 5 miles of that point
Step 2: We used the data base to find circuits fed from those substations
Step 3: We used the connectivity model to trace each of those circuits until we
found all customers fed by those circuits
Step 4: We used the data base to select all critical customers from that list
Step 5: We used the GIS to highlight those critical customers on the geographic
reference and optionally produced that geographic information as a map
product.
Architectures
Finally, we must discuss the architectures - the pieces that make all of this possible. This
may be considered an overview only.
Network
At the very foundation is the network - the physical connection between the computers
and communications protocols used to transfer information between them. This might be
local area net (LAN), wide area network (WAN) or Internet.
Hardware
Next, we have the hardware -- the computer systems used for data base management,
applications and user workstations. We would also include such peripheral devices as
disk drives, plotters, monitors, etc. For simplicity we can loosely consider the Operating
System as part of the hardware group as well.
GIS Software
Then we have the GIS software - the graphic and geographic tools, spatial engine, etc.,
provided by the vendor. This will be the basis of a long-standing “love-hate” relationship
between you and the vendor you select.
Data Base Management System
Next we have the data base management system used.
Application Software
Then the Application Software which employs functions of the DBMS, GIS software and
even the Operating System as needed. Again, for sake of simplicity we will include the
GUI in this category.
Each layer or group must function on its own as well as in conjunction with all of the
others. A breakdown at any point carries the same result: no benefits gained until the
problem is resolved. This is a difficult issue in the face of unavoidable changes in every
category.
Conclusion
So, a GIS is an information system designed to store, maintain, manage and employ
corporate information by means of a geographic attribute or attributes. The key
components in a GIS are the data base, the spatial engine, the connectivity model and the
geoma~hical user interface. These components can be combined along with geographic
data from multiple sources to perform highly sophisticated applications and analyses.
The underlying architectures required for this kind of application are extremely intricate
and dreadfully complex but are capable of stable performance if implemented and
managed properly. In the face of the tremendous technologies involved, constantly
remind yourselves of the business problems to be solved. Always ask “WHY” before you
ask “HOW”. Don’t cheat your company - your project - or yourself - by letting your focus
be shifted to anything else.
