Thought Leadership

Integrated Design Approach

By Robert Slipka
Feb. 6, 2015

Integrated design brings together a diverse team of design professionals on one project. Projects benefit from this approach because a wider range of experts is contributing throughout the project as a team, rather than acting independently.

Early integration is crucial to reduce the potential for expensive conflicts as design progresses or implementation begins. The integrated design approach involves all parties, including design professionals, clients/owners, permitting agencies, and others. Involvement may also include cost analysis specialists, construction managers, and contractors.

No matter what that project type, an integrated approach helps ensure a holistic outcome rather than a culmination of interdependent elements. Below are two examples of what teams could look like.

Example 1

A site development project is led by a landscape architect or civil engineer with direct integration of specialists such as environmental scientists, ecological specialists, engineers, building architects, electrical engineers, irrigation designers, and the client (including their operations and maintenance staff).

Example 2

A roadway corridor project is led by a transportation engineer and/or a planner. The team for this type of project may integrate urban designers/landscape architects, engineers, environmental scientists, right-of-way specialists, and representatives from numerous government agencies.

Design charrettes and brainstorming sessions are often utilized heavily in the beginning phases of project planning and design. This helps the team identify key goals, strategies, and desired outcomes of the project while also establishing areas of conflict or design implications. Including a diverse range of professionals means a better likelihood of achieving creative solutions that might not be explored in a conventional, non-integrated approach. As the project develops into the construction documents phase, continued collaboration is required to ensure compatibility of spatial character, uses, spaces, materials, and other factors. This approach can also identify conflicts that might not otherwise be identified until late in design or into construction, avoiding unanticipated costs or redesign.

Although an integrated approach provides better results, it is important for consultants and clients to judge how extensively integration needs to occur based on costs and benefits. Some projects are smaller in scale or fee, which can make an elaborate integrated approach difficult to justify. Clients should also be aware that the term “one-stop shop,” often utilized to describe multi-disciplinary firms, does not necessarily mean that an integrated design approach is used for projects. If it is unclear or unproven, clients should ask the consultant to describe how the various team members will be integrated throughout the design process. The ultimate goal is to achieve higher quality projects with increased cost effectiveness to clients.

Bridges – An Overview

by WSB Municipal Engineering
Dec. 22, 2016

What legal responsibilities do bridge owners have?

Any municipality that owns a bridge in Minnesota must appoint a bridge program administrator. This administrator needs to be a professional engineer with a bridge background, as they are responsible for ensuring their bridges are inspected, load rated, and load posted (if required) according to state and federal law.

What does a bridge safety inspection involve?

A bridge safety inspection is an evaluation of the physical condition of a bridge. The inspection involves a visual and hands-on evaluation of all bridge components. The inspector looks for issues such as corrosion, deterioration, settlement, damage, or scour, and the results are detailed in a report based on each component. Following a bridge safety inspection, the overall condition of the bridge is compiled in an online database. Bridges are required by law to be inspected either annually or biannually, depending on the bridge type and condition. Special inspections such as an underwater inspection may also be necessary for bridges with components that are not visible during low water conditions.

How does a bridge owner know when it is time to replace a bridge?

The answer to this question varies based on the volume and type of traffic over the bridge. Bridges should always be replaced before the safety of the traveling public is at risk. Every bridge is assigned a sufficiency rating score, which varies from 0-100 and factors in the condition of the bridge, traffic volume importance of the route, and load carrying capacity. A bridge’s sufficiency rating is used to determine when it should be replaced and when it qualifies for funding. Bridges are also replaced when they are no longer able to meet traffic needs. Bridge owners can significantly extend the life of bridges by performing routine maintenance such as painting, cleaning, and crack sealing.

What is a bridge load rating?

A bridge load rating is a calculation that determines the safe load carrying capacity of a bridge. Bridge load ratings are based on the original capacity of the bridge while factoring in any deterioration or changes to the bridge’s condition that have occurred over time. A bridge load rating calculation is required when the bridge is first constructed and whenever the condition or configuration of the bridge has changed. The results determine if a bridge should be load posted and if it is safe for special permit vehicles to cross the bridge.

Glossary

• Load Rating: A calculation to determine the safe load carrying capacity of a bridge.
• Load Posting: Restricting the weight of vehicles that cross a bridge in order to prevent overloading.
• Sufficiency Rating Score: A numerical value on a scale of 0-100 that considers a bridge condition, traffic volume importance, and load carrying capacity.

Co-authored by Jay Kennedy and Diane Hankee.

The text of this article contains general information and is not intended as a substitute for specific recommendations. Your professional staff is more familiar with your community and can provide specific recommendations. Guidelines and regulations change and may be different from when this article was published. 

Envision: The Age of Sustainable Infrastructure is Here

By Brandon Movall
Aug 1, 2016

With the state of America’s infrastructure declining due to climate change and limited funding, today’s engineers and scientists must adopt creative and sustainable solutions. In 2011, the American Society of Civil Engineers (ASCE), the American Council of Engineering Companies (ACEC), and the American Public Works Association (APWA) came together to revolutionize the way engineers plan, design and build. The result was Envision, a holistic rating system for sustainable infrastructure.

Envision is a rating system to help project teams incorporate higher levels of sustainability at each step of a project, from assessing costs and benefits over the project lifecycle to evaluating environmental benefits and using outcome-based objectives. Envision considers social, environmental, and economic factors of projects (a process called the Triple Bottom Line), rather than only focusing on economic factors. Envision uses a scorecard of 60 credits divided into five categories that reflect all aspects of the Triple Bottom Line:

• Quality of Life
• Leadership
• Resource Allocation
• Natural World
• Climate and Risk

By tallying the credits achieved throughout the project lifecycle, Envision is able to effectively rate proposed infrastructure options in a way that is easy to communicate to clients, consultants and owners.

While there are many sustainability rating systems out there, there are a few things that make Envision the best option:

1. Envision rates all types of civil infrastructure, such as transportation, water, energy, information, and landscape infrastructure.
2. Envision covers the entire life cycle of a project, from the first meeting of the project team to post-construction maintenance.
3. Envision is free to use. Anyone can sign up for an Envision account and have access to the guidance manual and scorecard. The only costs involved are if a project is registering for awards through Envision, or if you want to get special training and become an Envision Sustainability Professional (ENV SP). These are optional and are not necessary to use the Envision system on a project.

In addition to individual users, many companies and public agencies across the United States have implemented Envision into their planning, design and construction processes. Benefits to a company or agency include discounted ENV SP certification rates, discounted project award registration rates, exclusive content from the founding organizations, and more. As part of our commitment to bettering ourselves, our clients, and our world, WSB is proud to be recently certified as an Envision qualified company.

To change the world, we must change our practices. Envision is one large step toward planning, designing and building a sustainable future. For more information about Envision in general, visit www.sustainableinfrastructure.org. For more information about Envision at WSB, please contact Katy Thompson, Brandon Movall, Stephanie Hatten, or Ann Wallenmeyer.

References:

“2013 Report Card for America’s Infrastructure.” 2013 Report Card for Americas Infrastructure. ASCE, n.d. Web. 28 July 2016.

“Envision.” Institute For Sustainable Infrastructure. N.p., n.d. Web. 28 July 2016.

What Makes a Wetland a Wetland?

By Joe Handtmann
June 10, 2015

A wetland is a flooded area of land with a distinct ecosystem based on hydrology, hydric soils, and vegetation adapted for life in water-saturated soils. Wetlands are heavily protected by federal, state, and local policies due to their environmental benefits and the historical filling and dredging that removed more than 50 percent of them across the country. Wetland types vary based on their location. Mangroves are found along the shores of salty waterbodies while peat bogs are found in cool climates, where slow decomposition facilitates the accumulation of peat over long periods of time. Common wetlands in Minnesota include wet meadows, shallow and deep marshes, scrub-shrub wetlands, and bogs.

Requirements and delineation
To be considered a wetland, the site must have the presence of water, soils indicative of frequent and prolonged flooding, and vegetation suited to handle flooding or saturated soils. Determination of wetland boundaries must be done by a certified wetland delineator based on the Army Corps of Engineers Wetland Delineation Manual and appropriate regional supplements. Delineations are subdivided into levels. Level one means onsite inspection is unnecessary; level two means onsite inspection is necessary; and level three, which is a combination of levels one and two.

Hydrology
Identifying hydrology, or presence of water, can be as simple as noticing the sustained presence of water in boreholes or manually measuring surface water, or as difficult as requiring the use of continued monitoring wells and piezometers. Areas with a surface water depth of more than 6.6 feet are considered deepwater aquatic habitats and not wetlands.

Hydric soils
Soils that are saturated for a long period of time display common visual patterns identifiable in a soil profile. Soils developed in anaerobic conditions show unique colors and physical characteristics that are indicative of hydric soils. When water continuously saturates the ground, organic soils are likely to occur. Organic soils are referred to as peats or mucks and require more than 50 percent of the upper 32 inches of soil to be composed of organic material. Hydric mineral soils form under a range of saturated conditions, from permanently saturated to seasonally saturated. Indicators for hydric soils can be found in the Field Indicators of Hydric Soils in the United States guide, published by the USDA.

Hydrophytic vegetation
Wetland vegetation is classified by its ability to survive in saturated soil conditions. These classifications range from OBL (obligate wetland plants that usually occur in wetlands), to FAC (facultative plants that occur in wetlands and non-wetlands equally), to UPL (obligate upland plants that are rarely found in wetlands). When OBL, FACW, and FAC species make up the vegetative species at a site, then the site is considered to have hydrophytic vegetation.

Classification
Two main systems are used to classify wetlands in Minnesota – the Circular 39 and the Cowardin systems. Both systems are commonly used when writing permit applications or describing or writing about wetlands. A noteworthy exception is the case of the National Wetlands Inventory, for which the U.S. Fish and Wildlife Service exclusively used the Cowardin system.

Circular 39
The Circular 39 system was developed by the U.S. Fish and Wildlife Service in 1956, and divides wetlands into eight different types based on water depth and variety of vegetation.

• Type 1: Seasonally Flooded Basin/Floodplain Forest: Soils are flooded during variable seasonal periods. Often found in upland depressions, these wetlands are well-drained during the rest of the year. Vegetation can be quite variable.
• Type 2: Wet Meadow, Fresh Wet Meadow, Wet to Wet-Mesic Prairie, Sedge Meadow, and Calcareous Fen: Soils in these wetlands are usually without standing water, but saturated close to the surface. Vegetation includes sedges, grasses, rushes, and broad-leaved plants. These wetlands are notes for their wildlife habitat capabilities.
• Type 3: Shallow Marsh: Shallow marshes are covered with more than six inches of water throughout the year. Typical vegetation includes grasses, cattails and bulrushes.
• Type 4 – Deep Marsh: Similar to shallow marshes, deep marshes are covered in water from six inches to three feet deep. Cattails, reeds and lilypads are common.
• Type 5: Shallow Open Water: Water is present, but less than six feet deep and fringed with emergent vegetation. This type of wetland is often used for fishing, canoeing and hunting.
• Type 6: Shrub Swamp; Shrub Carr, Alder Thicket: Soils are heavily saturated and may be covered in up to six inches of water. Dogwoods, willows and alders are all common species.
• Type 7: Wooded Swamps; Hardwood Swamp, Coniferous Swamp: Typical trees in wooded swamps include tamaracks, white cedar, arborvitae, black spruce, balsam, red maple, and black ash. The prevalence of trees helps control water flow during flood events. Soils are saturated up to a few inches of the surface and may be covered by up to a foot of water.
• Type 8: Bogs; Coniferous Bogs, Open Bogs: Organic soils are prevalent in bogs, with continually waterlogged soils and a spongy covering of mosses. Shrubs, tamaracks, mosses, and black spruce are all common species.

Cowardin
The Cowardin system was developed in 1979 for the U.S. Fish and Wildlife Service to classify wetlands and deepwater habitats. This system was used in the National Wetlands Inventory to identify wetlands. Two major wetland types, coastal and inland, are identified. All Minnesota wetlands are defined as inland (palustrine), which is then subdivided based on vegetation classes and bed material.

 

Planned unit developments: Easing zoning ordinances in exchange for creative development

By Addison Lewis
October 21, 2016

What is a Planning Unit Development (PUD)?

A Planned Unit Development (PUD) is a zoning designation used to ease the strict application of a zoning ordinance in exchange for creativity in development. A PUD is often used to provide deviations from standards such as setbacks, height, density, uses, and other regulations. A PUD is used when planning for larger areas (one acre or more), planning for multiple contiguous sites, or accommodating multiple buildings on one site. The area should be under unified ownership at the time of a land use application for a PUD. In exchange for deviations from the zoning requirements, benefits such as additional greenspace, pedestrian or transit amenities, enhanced energy efficiency or stormwater management, affordable housing, mixed use, or enhanced architectural features are usually provided by the developer to achieve a higher quality development that might not otherwise occur.

When to use a PUD 

A PUD is used to implement development goals identified in a community’s comprehensive plan. PUD process is not just an alternative to variances – it should be considered for unique development projects where the public benefit or development goal is clearly understood, and when the project would not otherwise be permitted through strict application of the zoning ordinance.

What to consider when developing a PUD

When developing a PUD ordinance, be sure to identify amenities or conditions that will help achieve the goals and objectives of the community’s comprehensive plan. A PUD ordinance should only be used if these amenities or conditions are offered by the developer. You may want to specifically list in the ordinance which specific zoning standards were deviated from.

A PUD designation is a similar process to rezoning. Think of each PUD as a customized zoning district that specifically identifies the location of buildings, uses, architectural design, etc. A PUD is a great tool for encouraging creativity and providing flexibility from the zoning ordinance, but once it is adopted any future change could require an amendment, depending on whether it is a major or minor change. A minor change can be approved administratively, while a major change would need to follow the same process as a rezoning. The community’s ordinance should identify which changes are considered minor or major.

Tracking Santa: An ArcGIS Online case

By John Mackiewicz
February 6, 2015

ArcGIS Online connects maps, apps, data and people so you can make smarter, faster decisions. It gives everyone – both inside and outside organizations – the ability to discover, use, make and share maps from any device at any time. At its core, ArcGIS Online is a hosted cloud software as a service (SaaS) platform. Everything you need to create your own web maps and apps is available on ArcGIS Online. You can create maps from Microsoft Excel or upload your data from ArcMap to share your map and collect data in the field on your tablet or phone.

ArcGIS Online supports many users collecting data in the field at one time. This presents a problem for large workforces, as you may need to track where your collectors go when working in the field. Using Esri’s Collector for ArcGIS app, you can have it periodically report the location of data collectors back to a tracking layer on ArcGIS Online by publishing a tracking layer on ArcGIS Online and adding it to an Web Map with tracking enabled. When this Web Map is accessed within the collector app, the collector app sends its GPS location back to the tracking layer hosted on ArcGIS Online at a predefined interval.

At WSB, we view ArcGIS Online as a technology that:

• Can quickly be deployed for multiple uses
• Is flexible enough to handle diverse workflows without requiring any programming
• Has untapped potential for public outreach

Below is one of our favorite examples of how we used ArcGIS Online to help a client deliver immediate value to both the organization and the public.

Tracking Santa

For more than 25 years, firefighters in the City of St. Anthony, Minnesota, have helped Santa by collecting gifts for those in need. Santa rides in fire trucks throughout the city collecting gift donations from residents. In 2014, the city wanted to allow residents to track Santa’s location along his route.

The City of St. Anthony decided to utilize ArcGIS Online to track Santa, thanks to all the app’s capabilities.

Here’s how we did it:

1. A tracking layer was published on ArcGIS Online.
2. The tracking layer was added to a Web Map configured with the city’s custom Esri base maps with tracking enabled.
3. The city deployed an iPad with the Esri Collector for ArcGIS app to ride along with Santa with the Web Map open on the fire truck.
4. A custom web app was built using our DataLink platform to show Santa’s most recent location.

As the fire truck drove along its route, the collector app was configured to report the truck’s location every 30 seconds back to ArcGIS Online. Residents used DataLink to view Santa’s current location in relation to their house so they knew when Santa was arriving.

Tracking Santa’s location is certainly a unique use of ArcGIS Online, but it shows how extensible the ArcGIS Online platform is. With just a few clicks, you can begin to track real-time locations of users who are using the collector app.

Using NDVI to Generate Impervious Surfaces for Large Areas

By Bryan Pittman
Feb. 6, 2015

Calculating the area or percentage of impervious surfaces for a given spatial extent helps determine curve numbers, runoff rates, and pollutant loadings. Overlaying an impervious surface layer with drainage areas for a city can determine impervious percentage per drainage catchment. The issue is getting an impervious surface for a large enough area, for example a city or a Watershed Management Organization (WMO). Digitizing of an aerial can create impervious surfaces for small areas but is too time consuming on a large scale.

Fortunately, with the current availability of high-resolution Color-Infrared (CIR) aerial photography, there is a workaround that is far less time consuming. Since the reflectance of vegetation peaks in the near infrared, vegetation yields high returns on CIR photography. This can be used to generate a Normalized Difference Vegetation Index (NDVI). The NDVI is a ratio from the returns of near infrared and visible light, telling us how “alive” something is. A high NDVI ratio signifies healthy, growing, green vegetation, where a low NDVI ratio signifies something not living, say pavement or rooftops.

The typical NDVI value ranges from -1.0 to +1.0 (GIS software calculates a value from 0 to 200). In that range, there will be a cut-off point that separates vegetation from non-vegetation. The value is typically just above 0.0, but varies based on the CIR aerial photography being used. Classifying the NDVI surface into two groups from that cut-off point gives a result that shows the area of vegetation and non-vegetation. Since there is a very high correlation between areas of non-vegetation and impervious surfaces, this result shows what is impervious and what is pervious.

This method yields results that are about 90 percent accurate. First, the assumption is made that vegetation equals pervious surfaces, which is not always the case. A large area of open dirt is a good example. It is still pervious but shows up as impervious because it is not vegetation. Another issue is shadows cast by trees, houses, and other structures. Since shadows are blocking out the light return (both visible and near infrared), any shadow is interpreted as non-living and thus impervious, even though it may be a pervious surface.

Even with these minor disadvantages, the time saved is enormous. Instead of taking weeks to digitize all the impervious area within a city, this analysis can be completed in under an hour. It is necessary to perform quality control on the data and clean up any of the issues described above by reclassifying something as pervious to impervious or vice versa.

Forgotten cracks and sealing the joint

Sealing the joint

Over the years, both crack sealing and crack filling have proven to be very cost-effective tools in the preventive maintenance tool box. One area that has been overlooked when sealing streets and highways, however, has been the joints between two types of pavement – such as between an asphalt street and concrete curb or concrete pavement and the asphalt shoulder.

When a joint between two different pavements is left unsealed, water is unable to “jump the joint” and can end up saturating the underlying base materials and causing load-related failures. In areas where de-icing chemicals are used for snow removal operations, the flow of the residual brine can also cause the areas of infiltration to thaw earlier – increasing the likelihood of load-related damage during spring thaw.

Figure 1 – Asking Water to Jump Across a Joint

Where’s the proof that sealing these joints makes a difference in performance?

MnDOT recently did a study and published the Edge-Joint Sealing as a Preventive Maintenance Practice report, which showed that sealing the joint between concrete main line pavement and asphalt shoulders resulted in an 80% reduction in water infiltration. The assumption was that by keeping the base and sub-base drier, there would be better performance.

There are at least three methods of sealing the joints:

1. Rout and seal if the configuration of the joint will allow a router to be centered over it.
2. Clean and fill the joint if the concrete curbs have a pan that is too narrow to allow routing.
3. Apply a joint adhesive to the face of the concrete and pave the hot mix asphalt against it. Joint adhesive was developed specifically for application to cold paving joints to reduce water infiltration. It has a higher viscosity than a normal hot pour sealant, which allows a thicker layer to be applied to the face of the structure.

Figure 2 – Clean and Seal Joint

A best practices guide, called Recommended Performance Guidelines for Crack Treatment, can be found on the ISSA website.

Figure 3 – Two-year-old Joint Adhesive

When sealing cracks in pavement, don’t forget about the joints along the curb line or between the shoulder and pavements.

Reference:

Minnesota Department of Transportation. Edge-Joint Sealing as a Preventive Maintenance Practice. August 2003. (MN/RC 2003-26).

An overview of wetland/water permitting in Minnesota

Wetlands and other waters in Minnesota are regulated by a variety of agencies, including those at the federal, state, local or watershed level. Knowing who to contact and what type of approvals are needed is important and depends on the scope and location of the project.

Federal level

At the federal level, the U.S. Army Corps of Engineers (COE) regulates discharge of fill to waters of the U.S. and works within the channel of navigable waters as defined by Section 10 of the Rivers and Harbors Act. If work is proposed within a water of the U.S., a permit may be required through Section 404 of the Clean Water Act. Project impacts will fall into one of the following permit categories:

• Regional General Permit (GP): These permits are issued for projects that impact less than 0.5 acres of wetland and authorize a specific list of impacts, or authorize work that is regulated and approved by the Minnesota Department of Natural Resources (DNR) through the Public Waters program. It typically takes three to four months to obtain this permit. In Minnesota, approval with a GP automatically includes EPA/MPCA Section 401 Certification.
• Letter of Permission (LOP): These permits are issued for projects that impact wetlands between 0.5 to three acres (non-road projects) or 0.5 to five acres (road projects). COE performs an environmental assessment, taking four to 12 months to obtain this permit. In Minnesota, this approval automatically includes EPA/MPCA Section 401 Certification.
• Individual Permit (IP): These permits are issued for projects that exceed the thresholds for the GP and LOP. COE performs an environmental assessment, taking anywhere from nine months to two years to obtain this permit. EPA/MPCA Section 401 Certification must be obtained separately.

State level

At the state level, the DNR regulates areas below the Ordinary High Water (OHW) of wetlands and waters listed as Public Waters. (View maps of DNR Public Waters. Obtain the OHW elevation from the DNR Area Hydrologist.)

If work is proposed below the OHW of a public water, a Public Waters Work permit will be required, which typically takes 60 to 90 days to obtain. It can take longer to obtain the permit depending on the complexity of the project. The DNR also issues permits for other types of work within public waters, including docks, crossings, dewatering, dredging, and boat launches.

Local level

At the local level, the State of Minnesota issued MN Rule 8420, the Wetland Conservation Act (WCA). (Guidance can be found here.)

The objective of the WCA is to obtain no net loss of wetlands within the state. The rule is administered at the local level by a local government unit (e.g., the city, county, watershed district, or soil and water conservation district.

If a project will impact a wetland, an approval through the Wetland Conservation Act is likely necessary. There are several types of approvals that may apply to the project:

• No loss: Indicates that the wetland will not be impacted by the project (e.g., temporary impacts, impacts to incidental wetland).
• Exemptions: Various exemptions exist for projects that are required to maintain public health and safety but also may result in minor wetland impacts.
• De minimis: Allows a minimal amount of wetland impact to occur depending on the location of the wetland impact within the state.
• Replacement plan: Allows wetland impacts to occur given that no other alternatives exist, impacts have been minimized to the extent practicable, and impacts will be mitigated (e.g., replaced).
• Road bank replacement: Allows the state to replace for impacts to wetlands required due to the reconstruction of an existing serviceable public roadway to meet safety or design standards. This program is available to city, county, township, and other local road authorities. It is not available for Minnesota Department of Transportation projects.

To obtain any of the above permits, an applicant must provide project information that includes a project purpose and need, alternatives analysis, impact minimization measures, and a mitigation plan. Typically, mitigation is required at between a 1:1 to 2.5: 1 ratio.

Some watershed districts within the state also have regulatory authority over the waters within their watershed. Though each watershed district has their own specific rules, they typically cover impacts resulting from stormwater, erosion, dredging, wetland impacts, and floodplain fill. (Determine which watershed district a project is located within.)

What does this mean for a project?

If a project has the potential for water resource impacts, it is best to start coordinating with the applicable regulatory agencies as soon as possible (ideally a year in advance of construction). If you are unsure of whether your project will impact wetlands, begin by contacting your local WCA representative, Army Corps of Engineers regulatory department, and/or DNR Area Hydrologist.

Light Detection and Ranging (LiDAR) Elevation Data

What is LiDAR?

LiDAR, which stands for Light Detection and Ranging, is a combination of “light” and “radar.” It’s a remote sensing technology that uses lasers to detect and measure features on the surface of the Earth. Due to its high accuracy, LiDAR has become the de facto standard for creating elevation surfaces and measuring heights of features above the ground such as trees or buildings.

LiDAR in action

Minnesota completed a statewide LiDAR gathering project funded by the Clean Water, Land and Legacy Amendment, and spearheaded by the Minnesota Department of Natural Resources and the Minnesota Geospatial Information Office. The six-year project resulted in a seamless, high-resolution digital elevation map of the entire State of Minnesota. This data is completely free to download and offers a vertical accuracy of six inches. This project has enabled the flow of accurate topographic information between all organizations and the general public.

LiDAR deliverables

The deliverables of the project came in different formats. The simplest and most frequently used format is two-foot contours that were generated statewide. There is also a high-resolution Digital Elevation Model (DEM) that can be acquired as county tiles. The user can generate contours at varying intervals in this format, such as one-foot or even six-inch. Both the contours and the DEM use bare earth returns, meaning you only get surface elevation.

A third format is the raw LiDAR data, which is dense collection of points, or a point cloud. If you imagine the laser from an airplane hitting the surface, it’s the information at that contact point that is reflected back to sensors on the plane. The density of those points depends on the exact collection methods, but typically there will be 2 million points per square mile, or approximately 20,000 points for a typical city block. The point cloud gives access to all the returns and not just the bare earth returns; therefore, we can gather information about the heights of trees, buildings, water towers, etc. The point cloud is so dense that it is even possible to extract overhead power lines from the data. These multiple returns allow the data to be used for many different 3D analyses and visualizations. Certain 3D software packages allow the user to take the point cloud and turn it on its side, creating a vertical profile with accurate object heights and ground elevations.

LiDAR uses

There are many uses for LiDAR data beyond viewing ground elevation or object heights. Any kind of hydrologic flow analysis can benefit from the use of this data. Erosion analysis can be done by using slope estimates from LiDAR to compute the amount of erosion in certain areas, and that in turn can be used to calculate sediment accumulations. LiDAR has also been used for flood modeling, urban planning, oil and gas exploration, and coastline management. With the wide availability of free and highly accurate topographic data, many are reaping the benefits of LiDAR data and finding that its uses are far-reaching across many disciplines.