Generating Information from Scanning Ohio Maps
(GISOM):
The Conversion of 7.5 Minute Quadrangles to DLG-3
Files for the State of Ohio
Introduction | Background
| Goals | Organization | Conversion
Model | Independent Contractors
Introduction
In October 1993, The Ohio State University, several Ohio State agencies,
and the U.S. Geological Survey (USGS) began a four-year cooperative agreement
to convert 700 of the 793 7.5-minute (1:24,000 scale) quadrangles covering
Ohio to the USGS Digital Line Graphic 3 (DLG-3) Standard format. Seventy-three
quadrangles already had partial-to-complete DLG-3 coverage. Information
layers being converted include boundaries, hydrography, hypsography, public
land survey system, and transportation (roads, railroads, and miscellaneous
transportation). At the end of the agreement, Ohio will be the first state
in the nation with such coverage. This project is known as Generating Information
from Scanning Ohio Maps (GISOM).
Background of the
GISOM Project
In 1990, the Center for Mapping (CFM) of The Ohio State University started
a pilot project to become familiar with the conversion of the 7.5-minute
quadrangles to DLG-3 Standard files. The director of the Center presented
this idea to the Ohio Geographically Information Program (OGRIP), the statewide
organization that coordinates spatially referenced data and Geographic
Information Systems (GIS) activities. OGRIP approved the project, which
was sponsored by The Ohio State University, four state agencies, and the
USGS. When this project began, no one at the Center had previous experience
in conversion of DLG-3. In 1991, the Center for Mapping acquired a high-resolution
scanner (12.5 microns), two workstations, and several computer programs.
A full-time researcher and two graduate students spent the next two years
learning about DLG-3 conversion and improvements. During the second semester
of 1992, these personnel and two volunteers produced the first DLG-3 files.
By August 1993, with additional personnel, sixteen complete quadrangles
(112 DLG-3 files) were converted and delivered to the USGS. During this
three-year effort, a great deal was learned about state-of-the-art map
conversion, and the need for an improved solution was apparent. As a result,
the CFM set two goals for its conversion effort.
GISOM Goals
| 1. |
To develop a cost-efficient conversion model to generate DLG-3 Standard
files for boundaries, hydrography, hypsography, Public Land Survey System,
and transportation (roads, railroads, miscellaneous) from 7.5-minute quadrangles.
|
| 2. |
To test this model in the State of Ohio by converting to DLG-3 files
all the 7.5-minute quadrangles without digital representation (more than
700). |
The nationwide status of the map conversion process heavily influenced
the development of these goals. It was clear that a major research effort
was needed to speed up the conversion process.
Map Conversion Status for 1:24,000 Scale in 1992:
| 1. |
There are 53,796 7.5-minute quadrangles covering the United States
of America (excluding Alaska). |
| 2. |
Less than 5% (2,850) have DLG-3 files for some or all of the layers.
|
| 3. |
For hypsography, less than 3% (1,710) have DLGs. |
| 4. |
This conversion effort has taken fifteen years. |
A plan was prepared to improve existing conversion methodology and develop
new solutions. Two types of tasks were planned: short-term tasks (those
that could be accomplished in less than six months) and long-term tasks.
High-payoff tasks were given higher priorities. Most of the short-term
tasks were completed during the second semester of 1992 and first semester
of 1993. Several long-term tasks have since been completed. In February
1993, the CFM presented a proposal to the USGS for the conversion to DLG-3
format of 700 7.5-minute quadrangles. In September 1993, the CFM was informed
of the USGS's acceptance of the proposal. The cooperative agreement started
on October 1, 1993.
Project Organization
The following partners are financially suporting the project: the Ohio
departments of Development (ODOD), Natural Resources (ODNR), and Transportation
(ODOT), Ohio Environmental Protection Agency (OEPA), and the USGS. The
GISOM project will be completed in four years with a cost of approximately
$4.9 million. A little more than half of the money is being provided by
OGRIP and the four state agencies and the rest by the USGS. The Ohio Department
of Administrative Services (ODAS) is storing the DLG-3 files once they
are accepted by the USGS. ODAS is the depository and distribution center
of these files for the State of Ohio. At the CFM, the GISOM project is
organized as follows. A project manager supervises the research and development
and conversion efforts. Research and development is carried out by the
project manager, who is also the principal investigator, with the cooperation
of a group of graduate students. Five graduate students are currently working
as graduate research associates (GRAs) for the GISOM project. The conversion
effort is supervised by three full-time senior project leaders under the
direction of the project manager. Two junior project leaders and two student
employees assist the senior staff members. The conversion effort is done
by twenty independent contractors working from their homes. Their work
is checked and approved by the CFM project leaders.
The Conversion Model
Each year of the project, the state agencies submit a list of quadrangles
to be converted. The CFM coordinates the selection of quadrangles from
these lists. The resulting priority list is submitted to the USGS for evaluation
(against other ongoing conversion projects and 7.5-minute quadrangles updating)
and the USGS either approves or recommends changes to the list. Once the
list is approved, the CFM orders the corresponding source material (up
to five chronopaque separates: hydrography, hypsography, cultural features,
photo-revisions, and fence roads) twelve weeks in advance of the conversion
starting date. It can take up to ten weeks for the CFM to receive the material
ordered from the USGS. Once the material arrives, it is examined at the
CFM. When obvious problems are evident (such as too many broken lines,
missing tic marks, etc.), new material is requested.
After the CFM accepts the source material, the conversion process begins.
Three major steps are followed: (1) generation of a raster image from the
source material; (2) generation of vector data files (from the raster images)
with the corresponding DLG-3 attributes (including elevations for hypsography),
and (3) quality evaluation. After the vector files are found satisfactory,
they are sent to the USGS for acceptance. After acceptance, files are returned
to ODAS to be archived.
Work-at-Home Program
for Independent Contractors
The Work-at-Home Program was developed at the CFM as an alternative
to conventional conversion programs existing in private or government agencies.
In planning the implementation of the GISOM project, it was clear that
traditional models based on full- or part-time employees could not be accommodated
in an efficient manner as part of the university structure. In the earlier
stages, the CFM considered dividing the conversion process among all or
some of the participating state agencies and the CFM, with the CFM coordinating
the effort. Once the USGS decided to go ahead with the GISOM project, however,
it was evident that the state agencies would have a hard time participating
in the conversion process. It was easier for the state agencies to support
the project economically, which left the conversion work to the University.
The Work-at-Home program is based on a contractual agreement between each
independent contractor and the CFM. Each independent contractor is assigned
a particular quadrangle to convert all the corresponding layers. The contract
stipulates that the independent contractor agrees to deliver the corresponding
computer files by a given date. When the files are accepted by the CFM,
the contractor is paid a set amount of money. Once the independent contractor
delivers the files, he or she receives the materials to convert another
quadrangle. This relationship continues until the independent contractor
decides to stop, the CFM runs out of quadrangles to be converted, or the
CFM finds that the independent contractor's quality of work has fallen
below standard. This approach shifts part of the overhead cost (space,
equipment, benefits, etc.) from the CFM to the independent contractors.
At the same time, this approach gives the independent contractors the unique
opportunity to work at their own pace from their homes. The contractors
are also paid an attractive amount of money per map.
Independent contractors are responsible for providing their own equipment
and place of work. The CFM provides them with conversion documentation,
the software needed for collection and correction of the data on PCs, the
ability to transfer files electronically between their own computers and
the CFM mainframe, and access to quality control software in the CFM mainframe.
The contractors also have access to the raster files for each layer, the
vector file for hypsography, a lithographic copy of the quadrangle, and
the plots of the raster files (if requested). Independent contractors have
been trained at the CFM. A total of twenty-four have been trained, and
twenty are currently working in the GISOM project.
Independent contractors' work can be divided into three major tasks:
(1) Heads-up digitizing and attribute tagging, (2) Contour correction and
elevation and attribute tagging, and (3) Error detection and correction.
The first two tasks are done on the contractors' PCs. Error detection is
done on the CFM mainframe. Heads-up digitizing and attribute tagging is
done using RETSAM_PC_CFM and Intergraph's Microstation software (version
5.0 or higher). This process consists of loading the raster file (.RLE)
into the design file (.DGN), selecting the icon of the layer to be converted
and the icon of the element type to be collected (node, line, or area),
displaying the corresponding DLG-3 codes, selecting codes by clicking the
mouse on the corresponding values, and then drawing the center line of
the element, following the DLG-3 specifications.
Please send Comments and Sugestions to Kosta Bidoshi
