The city of Devils Lake, North Dakota is on the shore of a
lake that is the lowest area of an enclosed basin. This basin has
no outlet such as a river so that the only way that surface water
can leave the basin is by evaporation or evapotranspiration.
After 4 consecutive wet years with above average rainfall and
snowfall the basin is full and due to the low topographic relief
of the area, Devils Lake has increased in size by nearly 1/3 in
the last 24 months.
The City of Devils Lake had created a database of property
polygons in AutoCad. The US Geological Survey with the US Army
Corps of Engineers created a database of 3 foot contour lines
that was in an AutoCad format. Cates Earth Science Technologies,
Inc., obtained the Digital Ortho Quadrangles for the area of the
This project required the integration of PC ArcInfo and
ArcView as well as the use of the Spatial Analyst Extension.
The objective was to convert property polygons and 3 foot
contours AutoCad files into a compatible ESRI format, attribute
the polygons with the proper Property Identification Number, link
to an ACESS properties database, georectify the various data sets
(and put them into a common coordinate system), create a map
showing the areas within the city that would be effected by
projected lake levels, create a data table that would include the
Property Identification Numbers and the approximate maximum and
minimum elevation within each property polygon.
Since all of the capability needed for this project was not
entirely available within ArcView, portions were done using PC
ArcInfo. The nearly simultaneous use of these two software
products was in many cases complimentary.
- An analysis of the raw Property Polygon DXF files was
done using ArcView.
- Make maps showing data problems (missing lines,
subdivided polygons, etc) that needed to be fixed in the
DXF source data by personnel of the City of Devils Lake.
- Use PC ArcInfo to convert USGS 100K Public Land Survey
and Roads Digital Line Graphs to ArcInfo coverages.
Reprojected these data into UTM, NAD83 horizontal
coordinates to fit clients technical specifications.
- Used ENVI image processing software to convert USGS
formatted Digital Ortho Quadrangles (DOQs) to TIFF files
that could be used in ArcView. Georectified these images
based on a 24K section line coverage by changing the
values in the TIFF world file.
- Converted the ArcInfo roads and PLS coverages into shape
files. Using the DOQs and the Digital Raster Graphics
(DRGs) which are raster images of USGS 7.5 minute
quadrangles, for background references edited (in
ArcView) the shape files to improve the accuracy of the
line work. Used PC ArcInfo to build section and township
polygons from the improved PLS data but used ArcView to
attribute those resultant polygons.
- Used ArcView to analyze the improvements made on the
Property Polygon DXF files by personnel of the City of
- Converted the Property Polygon DXF files an ArcInfo
coverage. Converted the AutoCad property identification
labels into a point coverage and did an overlay operation
to attribute the 2,074 property polygons.
- Used ArcView to analyze results and verify data quality
of the Property Polygon coverage. The ArcView table
statistics capabilities were used in this analysis.
- The 3 foot contour line data was in 29 huge AutoCad DXF
files. These were converted using PC ArcInfo into 29 Arc
covers. These Arc covers were converted to shape files
and merged in ArcView using a MergeThemes script to
create a single 3 foot contour shape file.
- It was required by the client that a maximum and minimum
elevation value be found for each property polygon.
Because not each property polygon have 2 contour lines
that fell within it a grid of values had to be generated
from the contour data and attributes assigned to each
polygon. With the 3 foot contour shape file as the active
theme the script pline2pt.ave was run. This script
converts a polyline theme into a point them, where each
point represents each vertex on all polylines.
- Using the Spatial Analyst Extension to ArcView, a surface
was interpolated. Then with the property polygon shape
file active and the grid derived from the 3 foot contour
data in the active view, the Summarize Zones option was
used from within the Spatial Analyst Extension Analysis
menu. The resultant information which included the
minimum and maximum grid values found within each polygon
was exported to a DBF file. The DBF file was subsequently
edited to have only the required fields of Property
Identification Number, Minimum Elevation, and Maximum
- The resultant MxMnEl.dbf file was joined to the property
polygon attribute table and analysis was done in ArcView
by visual comparison of the DRGs, DOQs, 3 foot contour
lines. An overlay of the 3 foot contours and the property
polygons was done in PC ArcInfo and those polygons
crossed by two contour lines were compared to the results
of the Zone Summarization process. The verification
analysis indicated that the results of this process was
sufficiently accurate to meet the client's criteria.