Frequently Asked Questions
About Digital Data and Hardcopy Maps
Go to section:
Hard Copy Maps
Digital Parcel Data
Digital Orthophoto Data
Digital Contours
Hard Copy Maps
How do you sell your maps?
Standard 1/2 section maps are available at 1-inch equals 200 feet (1:2400) for the entire county. It is important to note that in dense areas having a lot of detail, the 1-inch equals 200 feet version will have some of the information removed for clarity on the hard copy map. A note printed in the legend of the map points this out. For the denser areas of the county, we have maps at a scale of 1-inch equals 100 feet (1:1200). We also have county wide digital aerial photos and two-foot contour data, which allows us to produce the same 100 or 200 scale plots with an aerial photo background and contours. We have the ability to produce these plots on demand at our front counter and also have the ability to produce custom scale maps on an 11x17 size print with any combination of parcels, aerial photo, and/or contours.
What features are shown on your parcel map?
The features included on the parcel map include all lot lines, geocoded parcels (also known as assessor or tax parcels), plat boundaries, Public Land Survey System lines, right of way lines, major utility easements, municipal boundaries and water and wetland areas.
When does the map get updated?
We update and maintain all areas of the county in digital form on a monthly basis. With the one-month lag time, our entire digital parcel map database is never more than 60 days old. Updated versions of our maps are released on the first of each month. These updates are based on parcel geocodes available from the Washington County Property Tax System and documents from the County Recorder.
How was the map drawn?
The parcel mapping project was completed by mapping one Public Land Survey System section at a time; research was performed to collect all necessary property descriptions, plats, road plans and other documents. Coordinates were created with COGO software analyzing the legal descriptions. Coordinate points were brought into AutoCAD software for a reference frame to create all line symbols. Each feature comprises a different layer theme. All layers are then processed into Arc/Info where they are divided into unique coverages with a multitude of points and lines. As each section of land was completed, it underwent numerous quality control checks to insure full and complete accuracy with record information and map development standards.
What maps are available and how much do they cost?
A
price list
is available for all maps sold by our division.
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Digital Parcel Data
What is the average size of a section in megabytes?
The average size of a section of digital map information is 0.5 megabytes. This is in native AutoCAD format. The size of an export file would depend more on the format supplied, such as Arc/Info export, DXF, etc.
When does it get updated?
We update and maintain all areas of the county in digital form on a monthly basis. With the one-month lag time, our entire digital parcel map database is never more than 60 days old. Updated digital data is available on the first of each month.
How much do you charge for data?
The cost for our digital parcel information is based on a
sliding fee schedule
The charge for updated digital data is the same. Subsequent charges are based on the number of added parcels since the last purchase (there is a minimum order charge). When a purchase is made of updated information, the user automatically receives the entire database for the entire area of the original purchase. This is provided to make sure the user gets any enhancements or other corrections built into the data since the original purchase. Local government agencies are supplied data at 50% off the quoted price.
Is everything digitized (electronically traced)?
Actually very little of the information on our parcel map is digitized. Ownership limits are interpreted from legal descriptions and analyzed using coordinate geometry. Only those features for which we do not have a legal description are digitized. This might be an occasional road or easement where the location is not defined. In these situations features are captured by digitizing from interpretation of aerial photographs. Most of the water features are captured in this manner.
What software do you use?
We use Autodesk software for all of our coordinate geometry analysis and graphic work. Arc/Info and Arc/View are used for finalizing cartographic elements and adding the intelligence to the map database. These two ESRI software products are also used for viewing, analysis and checking.
What features are included in the digital data?
The features included in the digital data are: all lot lines, geocoded parcels, plat boundaries, Public Land Survey System lines, right of way lines, major utility easements, municipal boundaries, and water and wetland areas. For a complete listing see our
metadata.
How was the data compiled?
The parcel mapping project was completed by mapping one Public Land Survey System section at a time; research was performed to collect all necessary property descriptions, plats, road plans and other documents. Coordinates were created with COGO software analyzing the legal descriptions. Coordinate points were brought into AutoCAD software for a reference frame to create all line symbols. Each feature comprises a different layer theme. All layers are then processed into Arc/Info where they are divided into unique coverages with a multitude of points and lines. As each section of land was completed, it underwent numerous quality control checks to insure full and complete accuracy with record information and map development standards.
What coordinate system is used for your data?
The digital parcel maps are developed on the Washington County Coordinate System. This coordinate system is based on the North American Datum of 1983 (1986 adjustment) and the Minnesota State Plane Coordinate System, south zone (NAD83/86).
Do you have metadata or data dictionary complete?
Yes. We provide these items with each data sale. Our
metadata
follows the state standard prepared by the Minnesota Governor's Council on Geographic Information. We recommend acquiring metadata on all data purchased.
Are these maps copyrighted?
We do require a signed license agreement for all data sale purchases exceeding our minimum fee. This agreement generally provides for making one copy of the data for backup purposes. It allows for the licensee to create new and original electronic hard copy products that the licensee can use. The purchaser cannot reproduce the database for distribution or resale. We also ask that a source reference to the Washington County Department of Transportation & Physical Development be made on all hard copy items created.
What is your key link to tabular data files?
The parcel geocode. The geocode is a 13 digit number which in itself provides you with its location within a quarter mile. This identifier is very helpful when you must handle tens of thousands of geocodes. A typical geocode looks like: 21-032-20-43-0002. The sets of digits are grouped as follows: Public Land Survey System (PLSS) section number, Township number, Range number, Quarter section and Quarter-Quarter section number and the last set of 4 digits is the unique parcel number. This geocoding method is similar throughout the Twin Cities Metro Area. The PLSS numbering is common throughout most of the United States as it is the basis for describing the location of most land ownership.
Do you have topology?
Yes. Parcel polygon topology with attribute information is available in ArcView Shapefile format. No topology is associated with our AutoCAD data files, however all necessary labels and linework needed to create topology is included in the file.
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Digital Orthophoto Data
What is a digital orthophoto?
A digital orthophoto is an aerial photograph that has been scanned to create a digital image that is then corrected for distortion caused by tilt of the camera, curvature of the earth, and the ground's vertical relief.
Are the orthophotos in color or black and white?
Are the orthophotos in color or black and white?
What is the ground resolution of the digital orthophotos?
The digital orthophotos have ground resolution pixel size of 6 inches.
When were the aerial photographs taken?
April 6, 2000 (North 1/3 of Washington County)
April 20, 2000 (East 1/2 of South 2/3 of Washington County)
April 21, 2000 (West 1/2 of South 2/3 of Washington County)
Are the digital orthophotos georeferenced?
Yes. The digital orthophotos are georeferenced to the Washington County Coordinate System NAD83, the same coordinate system used for the county's digital parcel base map.
Are digital orthophotos available for all of Washington County?
Yes, the entire county is available. The data set contains approximately 500 orthophoto images covering Washington County, Minnesota. The coverage extends a minimum distance of 400 feet outside the county's boundary in areas where the county boundary is not determined by the St. Croix River or the Mississippi River. In areas where the county boundary is determined by the St. Croix River or the Mississippi River, the digital orthophoto coverage includes the river shoreline opposite of Washington County.
What format is the digital orthophoto data available in?
The digital orthophotos are available on CD-ROM in uncompressed TIFF image format, (approximately 115 Mb per square mile), and MrSID compressed format, (approximately 20 Mb per square mile).
What is the cost of the digital orthophoto data?
Please refer to the
pricing schedule
for information on the digital orthophoto data.
Do you have metadata?
Yes. We provide metadata with each data sale. Our metadata follows the state standard prepared by the Minnesota Governor's Council on Geographic Information. We recommend acquiring metadata on all data purchased.
Is this data copyrighted?
We do require a signed license agreement with all of our digital data sales. This agreement generally provides for making one copy of the data for backup purposes. It allows for the licensee to create new and original electronic hard copy products that the licensee can use. The purchaser cannot reproduce the database for distribution or resale. We also ask that a source reference to the Washington County Department of Transportation & Physical Development be made on all hard copy items created.
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Digital Contours
What types of topographic data are available for Washington County?
2-foot contours, with spot elevations, are available for the entire county.
Basic planimetric data was collected, including road edges, (urban and rural), paved trails, railroad centerlines, bridges, major culverts, dam structures, rivers and streams, lakes and ponds, towers, (water, communication, steel electrical).
A digital terrain model, (DTM), was created using break lines along changes in slopes and a mass point grid of 50ft for areas requiring contours.
Do you have topography for all of Washington County?
Yes, the entire county is available.
What was the source of the topographic data?
Aerial photography, at a scale of 1in = 833ft, was gathered at 5000 feet during 3 separate flights in April, 2000 to support the creation of this data set.
When were the aerial photographs taken?
April 6, 2000 (North 1/3 of Washington County)
April 20, 2000 (East 1/2 of South 2/3 of Washington County)
April 21, 2000 (West 1/2 of South 2/3 of Washington County)
Is the digital topographic data georeferenced?
Yes. The digital topographic data is georeferenced to the Washington County Coordinate System NAD83, the same coordinate system used for the county's digital parcel base map.
What format is the digital topographic data available in?
The digital topographic data is available on CD-ROM. All topographic data is available in AutoCAD Rel.14 drawing format. The data is tiled in PLSS Section tiles based on the Washington County parcel base map. The topographic data for each section tile is comprised of 3 separate AutoCAD files:
Contour & spot elevation data: approx. 1 Mb per section tile.
DTM data: approx. 1.5 Mb per section tile.
Planimetric data: approx. 0.25 Mb per section tile.
The contour & spot elevation data is also provided in Arc/Info format: approx. 0.7 Mb per section tile.
What is the cost of the digital topographic data?
Please refer to the
pricing schedule
for information on digital topographic data.
Do you have metadata?
Yes. We provide metadata with each data sale. Our metadata follows the state standard prepared by the Minnesota Governor's Council on Geographic Information. We recommend acquiring metadata on all data purchased.
What is the accuracy of the digital topographic data?
Digital 2-foot contours, in AutoCAD drawing format, are now available for all of Washington County. The data is current to April, 2000. Using the National Standard for Spatial Data Accuracy, the data set tested 0.6 feet vertical accuracy at a 67% confidence level and 1.2 feet vertical accuracy at 95% confidence level.
Is this data copyrighted?
We do require a signed license agreement with all of our digital data sales. This agreement generally provides for making one copy of the data for backup purposes. It allows for the licensee to create new and original electronic hard copy products that the licensee can use. The purchaser cannot reproduce the database for distribution or resale. We also ask that a source reference to the Washington County Department of Transportation & Physical Development be made on all hard copy items created.
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