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| Subject: | [gislist] Linear Referencing, requirements as a topic of discussion |
| Date: |
12/22/2005 01:15:03 AM |
| From: |
DickBoyd .. aol.com |
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In a message dated 12/21/2005 3:45:45 PM Pacific Standard Time,
ahargis@co.boulder.co.us writes:
Thank you, everyone who emailed and phoned with ideas and thoughts about
getting started in linear referencing. The GIS community is truly
filled with some very generous people.
Can we review the bidding? The linear referencing question brings to mind
another question.
Is it "better" to teach a programmer the details of the discipline (land use,
emergency response, snow removal, the people using the "map") or is it
"better" to teach someone in the discipline enough programming (data manipulation)
to prepare the desired product?
The answer to the question is that it is better for both to work as a team
from a requirements document.
There are several decision trees to help in preparing a requirements
document. Focus on the intended audience.
The most difficult application of linear referencing is probably autonomous
navigation. The end product isn't a paper map. Although a paper map or computer
screen provides decision information. The end product is a steering algorithm.
Related to autonomous navigation is route selection. What is the shortest
distance between two points? What is the path of shortest time between those
points? What are the alternate paths between those points? What are the paths with
the greatest constraints? The customer for this product would be an emergency
control center, ambulances, police, fire and emergency responders.
Another factor to consider is that most of the GIS wheels have been invented.
How the wheels are put together depends on the project at hand. Dig around to
see what already exists. Does the county surveyor maintain a list of numbered
routes? Who gets to name roads and geographic features? Become familiar with
OMB Circular A-16 and derivative policy.
Do the people in the discipline know their audience?
At a recent presentation, the audience was shown a fairly detailed paper map
with extensive legend, several colors and several sets of shading. The amount
of detail suggested this was a final product. I believe the presentation was
intended to highlight the early stages of a decision process to locate fuel
reduction areas in a fire district.
In my opinion, the presentation would have been more effective if it had been
presented as a "cartoon". Something simple prepared with a draw program. A
rectangle schematic showing the neighboring jurisdictions and one identifying
geographic feature and two types of fuels reduction areas. One for immediate
protection of existing buildings and another to control spread. The presentation
was intended for fire planners to identify fuels reduction areas. People in
the audience got sidetracked, in my opinion, by the amount of detail. They took
the detail of the map to be an indication that the process was much more
advanced than it actually was. In my opinion, questions that the map should have
elicited from the audience were along the lines of the responsibilities of the
land owners and the planning and zoning authorities. The degree of detail
masked those questions. The degree of detail implied those questions had been
answered.
The requirements document should have identified the audience and stated the
reason for the map. Was it information only or were decisions expected? Would
any audiences other than the decision makers see the product?
One of the first things people do when presented with a map or aerial
photograph is to find their house. If a detailed map is presented, the presenter
should get that out of the way up front by identifying the geographic features
that the audience is familiar with. Roads, rivers, lakes, buildings, airports,
parks, fire stations, etc. Before starting with the spiel, ask everyone if they
have found their house. Another way to get this distraction out of the way is
to simplify the map to eliminate all but the desired discussion items. People
only need know that their house is in the area of discussion. If they need to
know how close they are to the planned fuels reduction area, the
identification should come in the next phase. the presenter should make note of that as a
requirement for the next iteration.
Geographers are familiar with latitude and longitude and other grid systems.
But if the audience is attuned to roads, lakes, rivers and mountains, the
presenter has to orient the audience to what the audience is familiar with.
In the presentation under discussion, location of houses to be protected,
location of ridges to serve as fire breaks and evacuation routes are the focus
points I would have concentrated on. One aspect of the presentation was a fire
break along a geographic boundary along the southern boundary of the fire
district. I think that fire break was in conflict with the original guidelines of
cooperation with neighboring jurisdictions. Implied in the presentation was t
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