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Publicly available lidar in Illinois, June 2014. Quality level 2 or better meets 3DEP's requirements. USGS, from the U.S. Interagency Elevation Inventory.
Illinois already had lidar — laser-scanned elevation data — over much of the state by 2014, but mostly at quality level 3, below the standard of the USGS 3D Elevation Program (3DEP).
By the numbers
| Expected annual benefits | $85.44 million |
| Estimated total cost | $18.82 million |
| Payback | 0.2 years |
| Benefit/cost ratio (8 years) | 36.3 to 1 |
| Cost to buy up to quality level 1 | $11.98 million |
About 83% of the identified needs are in flood risk management, water supply and quality, and infrastructure and construction management. Since the survey, Illinois agencies have found larger benefits in farming, conservation and geologic hazards as well.
| Rank | Business use | Annual benefits (millions) |
|---|---|---|
| 1 | Flood risk management | $32.40 |
| 2 | Water supply and quality | 21.76 |
| 3 | Infrastructure and construction management | 16.61 |
| 4 | Agriculture and precision farming | 8.18 |
| 5 | Homeland security, law enforcement and disaster response | 3.21 |
| 6 | Natural resources conservation | 2.47 |
| 7 | Geologic resource assessment and hazard mitigation | 0.28 |
| 8 | Wildlife and habitat management | 0.16 |
| 9 | Aviation navigation and safety | 0.12 |
| 10 | Urban and regional planning | 0.09 |
| Other | 0.16 | |
| Total | 85.44 |
How Illinois uses lidar
- Roads and rivers. The Illinois Department of Transportation began collecting lidar systematically in 2008. It saves time on hydraulic surveys and pins down river and watershed problems no one had located before.
- Sinkholes. The Illinois State Geological Survey used a bare-earth lidar model to map karst sinkholes in Monroe County, in the southwest, which has more than 10,000 of them — the state's highest concentration — on soluble limestone. Many lie hidden under dense woods, some close to houses, and they pose risks of groundwater contamination and ground collapse. Lidar has become an important tool for geologic mapping across the state.
About 3DEP
The National Enhanced Elevation Assessment (Dewberry, 2011) found the best return from quality level 2 lidar for the conterminous United States and quality level 5 radar (ifsar) for Alaska, refreshed every 6 to 10 years. 3DEP, managed by the USGS, chose an 8-year cycle, with the data made public.
| Quality level | Pulse spacing | Vertical error (RMSEz) |
|---|---|---|
| QL1 | 0.35 m | 10 cm |
| QL2 | 0.7 m | 10 cm |
| QL3 | 2.0 m | 20 cm |
| QL4 | — | 139 cm |
| QL5 (radar, Alaska) | — | 185 cm |
- Goal: operational by January 2015, national coverage by the end of 2022, depending on funding and partners.
- Value: conservatively $1.2 billion a year nationally, potentially $13 billion a year.
- Why a national program: larger purchases cut costs by 25%; buying high quality once avoids "buying up" later; data stay consistent across boundaries; federal money eases state and local shares; and ready contracts simplify buying.
Sources
Based on William J. Carswell, Jr., "The 3D Elevation Program: summary for Illinois," U.S. Geological Survey Fact Sheet 2014–3086; a work of the United States government in the public domain. The map and tables are taken from the fact sheet's PDF; its sinkhole lidar images, courtesy of the Illinois State Geological Survey, are not reproduced.
Licens: CC0 1.0 (allmän egendom) · Bearbetat efter pubs.usgs.gov
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