Iowa Statewide LiDAR… What Will I Do With It, When, & How?

Iowa Statewide LiDAR… What Will I Do With It, When, & How?
June 26, 2008 Walter Ertz

If you are part of the geospatial community in Iowa, you know in 2006 the Iowa Department of Natural Resources (IDNR) began a project to map the entire state of Iowa with Light Detection and Ranging (LiDAR) technology. Now that we are beginning to see select data appear in the public’s grasp, how can you use or expect to use this data? When will you see data for your areas? How will you work with it?

How Can The Iowa LiDAR Be Used?

Because it can acquire highly accurate elevation data, LiDAR data is useful for a number of tasks crossing various fields of interest. These disciplines include engineering, transportation, mapping/GIS, natural sciences (hydrology, geology, and biology), emergency management, and agriculture. The Iowa LiDAR data will be useful for all of these areas, but more so for some than others.

For instance, the specified 8″ vertical accuracy will allow natural scientists to do useful hydrology modeling. Flood maps can be more accurately drawn, new water management strategy can be tested, and other studies will be accurate.

On the other hand, the stated accuracies will be helpful, but not sufficient for other uses such as engineering and transportation design. The data will provide an opportunity to do initial site reconnaissance and planning, but when building roadways, structures, and infrastructure, either higher resolution design scale LiDAR or alternative mapping will likely be needed.

For firms like Aerial Services and their clients, the Iowa LiDAR will provide new elevation data which can be combined or substituted for the currently available DEM/DTM data. DEM/DTM data is currently taken from other public sources or is derived from new or existing photography. These methods will probably not be eliminated, but supplemented. This means your work with firms like Aerial Services may be more accurate and perhaps more affordable.

How Will I Process The Data; What Will Be The Computer Requirements & Software Needed?

The amazing thing about LiDAR acquisition is the massive amount of raw data the sensor acquires when scanning the earth. Without getting too technical, the laser pulse hitting the earth and the elements on its surface typically send back hundreds of millions of data points for a given area. This is excellent for accuracy, but creates special challenges when you attempt to use the data without specialized expertise, powerful computers, and large storage disks.

The raw data files, even over small areas, can be large. Because of this, the Iowa DNR will also be providing “bare earth” data along with the raw datasets public. “Bare Earth” files will include only the processed LiDAR points/data which indicate the ground and will exclude any above ground features (like vegetation, buildings, etc.). This “bare earth” data will not be as substantial as the raw, but will still require processing.

Regardless of which dataset you use, management of these files will require a high-end computer and specialized software like TerraSolid’s Terrascan. It can handle LiDAR data and parse it down using a grid that derives measurements from selected data points instead of all the points in the raw or “bare earth” file. Unfortunately, programs like Terrascan can be costly and require extensive training to use.

With these issues in mind, the Iowa DNR and the University of Northern Iowa (UNI) GeoTree program are providing an extension for ERSI’s ArcGIS software that will do select processing tasks to the LiDAR data. For instance, slope, aspect, hill shade, and other features may be calculated from the data using this extension.

When Will Data Be Available For My Area; Where Can I Get It?

At the writing of this article (May-June 2008), approximately one-sixth of the state was available on the official distribution site, UNI’s GeoTree. Areas were mostly in the north-west and south-central part of the state. Some spots in the north-east are listed as “In Progress” and presumably will be the next available areas. It is unclear when additional areas will be available. Hopefully the schedule’s pace will pick up to complete the project within a year or two of the initial anticipated 2007 collection goal.

The status of quality control is not yet determined as the U.S. Geological Survey (USGS), who is a key partner in the project, is still performing the testing. The distribution site currently notes: “While this testing is underway, this data [is] being provided as-is, with no guarantee of accuracy. If USGS testing indicates data [does] not meet accuracy specs, [that] data will immediately be removed from this site.” Until this changes, they are advising you check the accuracy of the data yourself. Therefore, you may wish to wait or have a professional check the data.

It is imperative users do not assume positional accuracies of this data. The measurements of elevations with LiDAR instruments does not automatically guarantee it meets positional accuracy criteria. The data must be tested before statements about accuracy can be made with any certainty.

Aerial Services’ Expert Take

As Iowa’s geospatial provider since 1967, Aerial Services’ experts have been following the Iowa LiDAR project closely over the last few years. Certified photogrammetrist, Mike Tully (President & CEO), stated it this way, “The opportunity created by this data is astounding. If the data meets expectations of positional accuracy and quality, its potential uses for Iowa citizens and business will be unprecedented.” He went on to note, “Regardless, if clients require high accuracies, Aerial Services has the expertise to enhance their data. We look forward to helping clients accurately supplement their existing geospatial information with this new data.”

More Details To Come

We are all waiting for more data, final accuracy reports, and other details. We encourage you to get a hold of Aerial Services if you have questions, but also check out the Iowa DNR website and the UNI’s GeoTree program’s site. They post new information regularly, including the status map where you can download the zipped datasets.

Need Help With Your LiDAR Data?

Once your area’s data is posted, call Aerial Services for help exploiting this rich source of geospatial information. If you have questions about this article or would like professional advice, feel free to contact Aerial Services, Inc.’s experts with no obligation.