The Northern Ohio Data & Information Service (NODIS) in the Maxine Goodman Levin College of Urban Affairs at Cleveland State University is making available a series of geospatial data sets of parcel tax map information, parcel polygons, and parcel centroids for Cuyahoga County, Ohio. The methodology used to convert data from its original format to a latitude/ longitude coordinate system and to ArcInfoTM and MapInfoTM formats(1) is described below.
NODIS was asked by the City of Cleveland's Water Department to make certain computerized parcel map data files available to the public. The data in these files represent all lines and text as seen on the Cuyahoga County tax maps and were developed from files produced originally by the Cuyahoga County Auditor's Office in DGNTM (Intergraph) format. The City of Cleveland contracted Analytical Surveys Incorporated (ASI) to make refinements to the Auditor's data and to develop these files in InfoCADTM GIS format. The InfoCAD files are used by the City of Cleveland's Division of Engineering and Construction for project-specific engineering work. The files are current as of November 1994.
In order to make these data useful to other users of Geographic Information Systems (GIS), two obstacles had to be overcome. First, the geospatial files were developed using the Cleveland Regional Geodetic Survey (CRGS) as the coordinate system. This coordinate system is locally unique and prevents other potential users of the data to overlay (combine and relate) other geospatial data which are developed in more common coordinate systems such as latitude/longitude or state plane coordinates.
Second, many GIS users use ArcInfoTM and/or MapInfoTM software and may have difficulty importing and using DGN or InfoCAD data.
Thus, in their original format, the data are unavailable to many GIS users.
Therefore, NODIS undertook the task of converting the data to latitude/longitude coordinates and to ArcInfoTM and MapInfoTM formats. The original and the converted data are made available on CD-ROM.
ArcInfo software was used to build polygons from DXF(2) data exported from InfoCAD files by the Division of Engineering and Construction of the City of Cleveland. It is noted that during this automated process some portion (less than 2%) of the original parcels did not contain sufficient arcs to fully create the parcel polygons. These parcels had to be added as closed polygons by manual edits.
ArcViewTM v. 3.2 was used to define the CRGS custom projection. The CRGS parameters are based on the revised "McFadden Shift" method. McFaddden was staff member of the Cuyahoga County Engineer's Office. The "McFadden Shift" method and parameters are described in a series of reports produced by the Engineer's Office from the 1930's to the 1950's. Errors of up to 7 feet were observed at the northeastern edges of the county. The Cuyahoga County Planning Commission discovered a "Scale Factor" as well as some other parameter adjustments such as a Stereographic Projection to improve the CRGS projection accuracy. The Planning Commission defined the CRGS projection in MapInfoTM. NODIS created the CRGS projection in ArcViewTM 3.2 and ArcInfoTM Beta v. 8.02. The locational accuracy was very similar. The stereographic method was tested using 500 USGS monument and GPS control points that have known x and y coordinate values in CRGS and US State Plane NAD 83 meters. 78% of all the projected points were within 1 foot and 96% were within 2 feet of the known x and y locations of the control points.
(See Figure 1:
500 GPS and USGS Monument Control Points.)
The parcel polygon file contains parcels for all of Cuyahoga County and is provided in the latitude/longitude coordinate system since it is a projection-free coordinate system and since it may be difficult for some GIS users to use projection-based coordinate systems such as CRGS and State Plane.
Permanent parcel numbers (ppn) have been associated with the parcel polygons as an attribute. In addition, street addresses have been assigned to the parcel polygon records based on linking permanent parcel numbers in the map file to address and ppn data from the Auditor's property characteristics file. Approximately 95 percent of the parcels have associated street addresses.
The parcel polygon file is current as of November, 1994. There are 498,005 parcel polygon records in the file. The field ppn represents the permanent parcel number. Ppn is a unique field. If the field value begins with 888, 999, or contains the letters UN or UNK, the ppn value was unknown. If the ppn field value ends in #1, #2, …, or –A, -B, …, then the parcel polygon could be comprised of multiple polygons that are separated. This is similar to how Hawaii contains multiple polygons and are separated by water.
In the ArcInfo parcel file, only the ppn attribute is stored in the parcel polygon file. A dBase file (parcel_data.dbf) contains other attribute data about the parcel. The dBase file can be relationally joined to the parcel polygon file by linking the ppn field in both the ArcInfo parcel polygon file and the parcel_data dBase file. The link will be a one-to-one relationship since there are the same unique records (498,005) in both files.
The fields are:
Ppn- Permanent parcel number (unique or key field). Character field, length = 10
Primary_1- If the Ppn field value is the primary field that tax assessment is based, then the Primary_1 field will contain a value of 1. If the Primary_1 field value = 0, the ppn tax assessment is associated with another parcel number (which is shown in the Ppn_tax field). Numeric field
Ppn_tax- The parcel number that tax assessment is recorded Character field, length = 10
Address_st- The address of the parcel. The address was standardized using an address standardization package. If the address value is all capital letters, the address could not be standardized. Character field, length = 30
City_std- City name based on the mailing address field as determined by the standardization package. The parcel polygon may or may not be geographically located in this city. Character field, length = 20
Zip_std- Zip Code based on the mailing address field as determined by the standardization package. The parcel polygon may or may not be geographically located in this zip code. Character field, length = 10
In MapInfo parcel file, all attributes listed above were relationally joined and stored as attributes in one parcel polygon file.
NODIS does not guarantee the completeness nor accuracy of the data.
Potential errors may result from any combination of the following.
1. The original Auditor' data have some errors of unknown character.
2. Conversion of Auditor's data by ASI may have introduced additional errors while correcting others.
It is not recommended that these data be used for property applications concerning legal issues, nor in engineering and other applications requiring exact positional accuracy.
The data have been converted to ArcInfo export ("e00") and MapInfo formats. The original DGN and DXF version formats are also available on CD-ROM.
The attribute data field attached to each parcel polygon is the permanent parcel number (ppn). The ppn is in its native format; i.e., there are no dashes after the book or map number. Street name text labels were also extracted from the DGN files and imported into both ArcInfo (e00) and MapInfo annotation/ text formats.
The following figure can be used as an index map showing the County Auditor's tax book borders and city borders.
(Figure 2: Tax Book
Index Map shows the auditor's tax book areas and city borders.)
Parcel centroid point files are also available in both ArcInfo (e00) and MapInfo native formats. There can be more than one point per parcel polygon (i.e., multiple dissolved parcels but only one reference parcel).
Please provide the following credits in any published report or map
The Cuyahoga County Parcel Boundary Database was developed by:
Northern Ohio Data & Information Service The Urban Center Maxine Goodman Levin College of Urban Affairs Cleveland State University
from data supplied by:
The City of Cleveland and the Cuyahoga County Auditor as of November 1994.
1. ArcInfo (and its related ArcViewTM) and MapInfoTM are among the most commonly used Geographic Information System (GIS) software in the world.
2. DXF is an AutoCADTM format often used as a standard for data exchange.
Supplied by Northern Ohio Data & Information Services at Cleveland State University
Contact Jim Wyles at 216-687-2221 or wyles@urban.csuohio.edu
Source data for all files originated from Cuyahoga County Auditor, current as of November 1994.
NODIS cannot guarantee the completeness or accuracy of the source data.
Prices may change. Please confirm price when ordering. All data available only on CD-ROM.
1. ArcInfo export format files (e00): parcel polygon file (parcel.e00) with attached ppn; street name labels (str_name.e00); auditor primary parcel designation attributes and standardized address, city, and zip code attributes (par_data.dbf); and tax book index file (book_idx.e00)
Coordinate system: Latitude/ longitude NAD 83, Northern Ohio, units- decimal degrees (552 MB)
Cost:............................. $ 600
2. MapInfo native format files (.map,tab,id,dat,ind): parcel polygon file (parcel) with attached ppn, auditor primary parcel designation attributes, standardized address, city, and zip code attributes; street name labels (str_name); and tax book index file (book_idx.e00)
Coordinate system: Latitude/ longitude NAD 83, Northern Ohio, units- decimal degrees (161 MB)
Cost:............................. $ 600
3. Parcel centroid (point) files in ArcInfo .e00 format and MapInfo native
format: parcel points representing centroids (weighted center) of parcel polygons.
There can be more than one point per polygon (i.e., Reference parcels). Filename
is centroids. Attributes (columns): ppn, crgs_x (x coordinate value in CRGS),
crgs_y (y coordinate value in CRGS), primary- if primary parcel number- value
= 1, ppnaud- ppn to match with auditor's attribute data. Note: ppn does not
have dashes (-) between book, map, and page.
Coordinate system: Latitude/ longitude NAD 83, Northern Ohio, units- decimal degrees
(148 MB for uncompressed e00 files; 33 MB for MapInfo native files)
Cost:............................. $ 160