Database of Geographic Information: Topographic Map of Central Arizona
Publication date: 2004
Author(s):
- Alexander Buyantuyev, Arizona State University
Abstract:
This dataset has been created to meet the needs of the research community of
Arizona State University. Apart from purely vizualization purposes (i.e. displaying
the data on various maps) it can potentially be used for spatial modeling. The data
consist of engineering-quality contours, also known as isolines, created from the
NED 10-meter Digital Elevation Model subset to the extent somewhat exceeding Cetral
Arizona - Phoenix LTER. Contours ( lines connecting points of equal height above sea
level) are drawn at 15 meter intervals with the base set at 145 m of elevation.
Contours are an exact interpretation of the grid surface model and may sometimes
appear blocky looking, may cross, appear to intersect, or form an unclosed branching
line. All these are valid engineering-quality interpretations of the elevation
surface that cartographers typically modify (smooth) for aesthetic purposes.
Keywords:
Land-Use, Land-Cover and Land Architecture sonoran desert,
phoenix,
urban,
metropolitan area,
gis,
contours,
informatics,
database remote sensing gis applications,
remote sensing,
digital elevation model,
elevation,
isolines,
topographic urban,
geographic information systems,
maps,
deserts,
surveys,
remote sensing,
digital elevation model,
elevation,
modeling,
surface elevation table caplter,
central arizona phoenix longterm ecological research,
arizona,
caplter created,
az,
cap,
arid land
Temporal Coverage:
1954-01-01 to 1984-01-01
Geographic Coverage:
Geographic Description: Central Arizona Phoenix
Bounding Coordinates:
Longitude:-113.291341 to -111.26736
Latitude:33.909831 to 32.888377
Contact:
Information Manager, Global Institute of Sustainability, Arizona State
University,
Global Institute of Sustainability, Arizona State University, POB 875402,TEMPE
caplter.data@asu.edu
Methods used in producing this dataset:
Show
DEM preparation
The U.S. Geological Survey National Elevation Dataset (NED), which is
a seamless mosaic of best-available elevation data, was used to prepare
the DEM. Three separate areas consisting of multiple USGS quads were
obtained from the GIS lab and mosaicked in Erdas Imagine software. The
resulting raster was reprojected to the North American Datum 27 UTM Zone
12 coordinate system using bilinear interpolation resampling technique.
The final extent was derived by subsetting to the rectangular area that
runs from the Gila River on the south to the edge of the uplands (lower
border of the rim) on the north. The extent covers parts of Maricopa,
Yavapai, Gila, and Pinal counties. In an attempt to produce smoother
contours the raster data were subject to two additional processing
steps. Sinks were filled in ArcInfo to make sure that a drainage network
is continuous. The next step was to adjust Z values so that a contour
does no longer pass exactly through a mesh point. This was done by using
ArcInfo FOCALSUM function with WEIGHT option. The following 3X3 kernel
file was used: .005 .005 .005 .005 .960 .005 .005 .005 .005 Within this
neighborhood each value in the initial DEM grid is first multiplied by
the corresponding value and then summed up. The sum is then sent to the
corresponding cell location (the middle cell) in the output grid
Creating contours
The vector coverage was created in ArcInfo by using CONTOUR function.
The interval was set to 15 meters and the base was set to 145.0001
meters. The .0001 offset is an additional approach that is employed to
produce smoother contours. Because the offset is very small the accuracy
of resulting contours is not significantly affected. An additional
attribute, ELEV, was created in the arc attribute table (.aat). It is
populated by initial grid values converted into integer format, i.e.
rounded to the nearest integer value, and can be used for labeling
purposes.
Data Files (1) :
Spatial Vector:
CAP_topo_15contour
Description:
Horizontal Coordinate System:WGS_1984_UTM_Zone_12N
Geometry Type: MultiLineString
| Column |
Description |
Type |
Units |
| FID |
Internal feature number.
|
OID |
|
| Shape |
Feature geometry.
|
Geometry |
|
| LENGTH |
LENGTH
|
Float |
meter |
| CONTOUR |
Elevation in meters from cell values in the input DEM
grid
|
Float |
meter |
| ELEV |
Elevation in meters converted to integer
format.
|
integer |
meter |
