Scott County Geologic Mapping Update
The Iowa DNR and Iowa Geologic Survey approached us in the Fall of 2007 to educate us on their geologic mapping program and to ask us for our support to map two USGS quadrangles (Davenport East and Davenport West). We provided a letter of support for that effort and they were subsequently able to secure approval (at no cost to Scott County). They recently completed that project and you can view the resulting maps in PDF format here:
Bedrock Geology, Davenport West (4.9 MB)
Bedrock Geology, Davenport East (8 MB)
Surficial Geology, Davenport West (5.4 MB)
Surficial Geology, Davenport East (8.3 MB)
We have not yet received the GIS format files, but expect they will be available shortly. This information will be valuable for planning and environmental analysis.
The Iowa DNR and IGS are now hoping to take the next step. They would like to continue mapping the rest of Scott County through the Iowa STATEMAP program! They have again asked us for a letter of support to demonstrate local interest and value. I believe the geologic data will be very useful, particularly to our Health and Planning departments.
Improved geologic data will be useful in a number of county applications. For example, our Health Department is interested in identifying the areas of the county susceptible to groundwater contamination and is investigating the use of sand point wells, nitrate levels and other important factors that contribute to this problem. Septic systems are also a concern.
The Scott County Planning and Development Department has recently updated the Scott County Comprehensive Plan. They can leverage geologic, land use, zoning and other related spatial data in GIS to improve decision making for land use and resource management.
There is potential to use the geologic data in Conservation, Secondary Roads and Solid Waste Management. We anticipate working in partnership with the IGS and Iowa DNR to find other uses for the information as our own local GIS layer development efforts continue and more data is added to the mix.
Section Corner GIS Data Update
Scott County maintains a GIS database of all section corners within the county. Corner certificates from the Recorder’s Office and tie sheets maintained by the Secondary Roads Department are published to GIS databases on a quarterly basis. The GIS data is packaged for use with ESRI’s free ArcReader application.
This update contains corner certificates and tie book sheets through September 30, 2009. The data package and additional information can be accessed here: Scott County Section Corner GIS Data – September 30, 2009
To download the free ESRI ArcReader software, click here.
To look for corner certificates recorded after September 30, please visit Scott County Land Records Online.
2005 orthophotos available for download
The 2005 digital orthophotos have been available for some time, but we’ve recently acquired an online storage solution which has allowed us to upload photo tiles and certain mosaic products to the web.
Currently, all 100 scale and 400 scale image tiles are available for dowload. They are organized into folders by tile row. Some mosaic products are available, however we will be working to create smaller mosaic files as the current countywide, Bettendorf and Davenport ones are prohibitively large (countywide sizes are 2GB for the 400 scale mosaic and 4GB for the 100 scale mosaic).
The 2009 flights will be available in late October. Check back as we continue to post more data online. Be sure to view the Scott County Tiling Grid Scheme located in the Planning area of the downloads to determine which tiles you need.
Link to orthophotos: 2005 Orthophotos
Scott County Address Project
The new Scott Emergency Communications Center and consolidated dispatch operation will implement a new dispatching solution from New World Systems that relies more heavily on spatial data. We’re in the process of selecting a firm to create the addressing databases that will feed the new CAD system.
These databases include a new countywide street centerline file, address point features and supporting data layers such as emergency service zones, cell tower coverage areas and others. Combined, this new GIS data will provide SECC and local governments with improved caller locations, better match rates with telephone company records, and new routing capabilities all of which will enhance emergency response and many other location based applications.
Scott County PLSS data
We’ve just added an ArcReader document (zipped) to our GIS data downloads page.
Link: Scott County PLSS data
It includes a data bundle with an index containing all of our known recorded corner certificates and the unrecorded Scott County Tie Book sheets maintained by the Secondary Roads Department. The positions of features in the PLSS Index are current to May 31, 2009 and are approximate only.
Also in the data bundle, we have included our 2005 Scott County Control Network GPS monument locations and a collection of over 500 survey grade coordinates of various section and 1/4 section corners. The section corners were collected as part of a survey grade GPS project to support our continued cadastral mapping efforts. Corners were occupied and adjusted to the Scott County Control Network. Complete NSSDA reports and supporting information from the survey is available on request.
We hope that the survey community and others find the data useful in supporting their monument research, reoccupying corner positions in the field and as a source of accurate reference information tied to Iowa State Plane coordinates (IASP South, NAD83 (HARN96), U.S feet).
Bathymetric Map
Just finished up a small bathymetric map for the Scott County Conservation Department. Bathymetric maps are basically underwater elevation contours. While we do have LIDAR data countywide from 2005, it doesn’t penetrate surface water (I believe different frequencies are used for that). So the elevation data came from spot depth checks provided by Conservation staff.
I used ArcGIS 3D Analyst and ArcGIS Spatial Analyst to create contours using mass points (spot depth data), breaklines (they provided some linear depth information, e.g. the lake is 6′ deep at a distance of 25′ from the shoreline from point A to point B), and the lake boundary as a hard clip. Fairly easy, though getting nice looking contours requires a multi-step process; TIN-generated contours are pretty jagged. I like to build a TIN, export to a raster, generate contours and then simplify the results.
I wonder if in the future, we could pair depth finders with GPS equipment to produce a much more dense and accurate underwater survey?
Orthophotography Update
The Scott County Board just approved a contract with Kucera International for the 2009 orthophotography project! Cost of the project is $140,100, which will come from GIS funds. Details include:
1. Flight will be collected entirely with push broom style digital camera systems (no film).
2. Ground Sample Distance (GSD) for these color photos will be 0.4 ft (better detail than the standard 0.5 ft GSD flights).
3. We will receive black and white 0.25 ft GSD photos as well; that’s twice as detailed as our original color spec!
4. In addition to the driveway features and building outlines on all structures, we will be getting height and elevation data for all structures which will be valuable for flood preparation and response.
5. Kirkwood Community College GIS students will be assisting us in creating and placing aerial targets over our GPS Control Network monuments. That helps us enormously and will provide them with good field experience.
Scott County 2009 Orthophoto RFP
On behalf of Scott County and several Quad City area municipalities, Bi-State Regional Commission released an RFP for photogrammetric services last week. We’re partnering with other local governments which reduces costs for all participants. This is the second digital orthophoto project for Scott County in which aerial products were acquired jointly as part of a local consortium; the first was in 2005.
We’re doing a few things differently this time around. We’ve specified six inch ground sample distance (GSD) pixel resolution orthophotos county-wide (the 2005 flight was split between six inch and one foot GSD in urban and rural areas respectively). We also plan to take on more responsibility for aerial targeting and horizontal accuracy reporting. Both will be done in house which is a departure from the 2005 flight where both tasks were done by consultants. This will save the county several thousand dollars and should be a good experience for the GIS and Secondary Roads staff involved. The hardest part about these jobs may be in finding or fabricating quality aerial targets! I’ve seen square targets for sale online but I prefer the cross and T-shaped “legged” targets.
Another twist in our 2009 flight is that we plan to request (optional) building foot print and driveway features. These features will support addressing and E-911 among other things. Last but not least, this marks the first time I have requested an image mosaic to be delivered in ArcSDE (MSSQL) geodatabase or file geodatabase format. I’m not optimistic that anyone will be able to deliver imagery in these formats, but more photogrammetry firms seem to offer GIS services these days so I think it’s worth a shot. We prefer to store and access our aerials in these formats but loading individual photo tiles into a seamless raster geodatabase is cumbersome so this could save us a ton of time.
Ray Weiser
Scott County GIS Blog
Hello bloggers,
This blog will be updated periodically with news and updates about the activities of the Scott County GIS program housed within the Scott County Information Technology department. The blog is currently not enabled for comments pending our review of this medium for sharing information. However, you may contact me at the official Scott County website. Use the feedback forms on the GIS page under the Information Technology Department heading or send me an email at: gis@scottcountyiowa.com.
Thanks for reading. We will be updating the blog soon.
