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Publicly available lidar in Utah, March 2015. USGS, from the U.S. Interagency Elevation Inventory.
Why elevation data matters
In Utah, elevation data are most valuable for infrastructure and construction, natural resources conservation, geologic hazards, flood risk management and agriculture. High-density lidar is now the main source of elevation models, and federal, state, tribal and local agencies work together to replace older data and fill gaps, aiming for consistent statewide coverage.
By the numbers
| Expected annual benefits | $8.70 million |
| Estimated total cost | $28.37 million |
| Payback | 3.3 years |
| Benefit/cost ratio (8 years) | 2.5 to 1 |
| Cost to buy up to quality level 1 | $18.05 million |
Because not every benefit had a dollar value, the true total is likely much higher. About 80% of the identified needs fall in infrastructure and construction, conservation and geologic hazards.
| Rank | Business use | Annual benefits (millions) |
|---|---|---|
| 1 | Infrastructure and construction management | $4.42 |
| 2 | Natural resources conservation | 1.88 |
| 3 | Geologic resource assessment and hazard mitigation | 0.68 |
| 4 | Flood risk management | 0.67 |
| 5 | Agriculture and precision farming | 0.53 |
| 6 | Forest resources management | 0.27 |
| 7 | Renewable energy resources | 0.07 |
| 8 | Aviation navigation and safety | 0.06 |
| 9 | River and stream resource management | 0.05 |
| 10 | Water supply and quality | 0.05 |
| Other | 0.02 | |
| Total | 8.70 |
How lidar helps Utah
Faster, cheaper projects. Where lidar exists, traditional topographic surveys are largely unnecessary, saving the public time and money in planning. Lidar yields bare-earth elevation models, building footprints and estimates of solar energy potential for evaluating many sites at once; it feeds hydraulic models to reduce flooding; and combining geologic, engineering and environmental data speeds project reviews. A lidar applications video shows more.
Geologic maps. The Utah Geological Survey's maps underpin nearly all geology-related work — site studies for schools, roads and housing, and natural resources such as minerals, oil and gas. High-resolution elevation data sharpen the mapping of surface features and poorly exposed bedrock, especially faults and landslide boundaries under vegetation; the fact sheet shows fault traces along the Wasatch Front revealed by lidar shaded relief.
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 chose an 8-year cycle. The USGS runs it as the federal lead for land elevation data.
| Quality level | Pulse spacing | Vertical error (RMSEz) |
|---|---|---|
| QL1 | 0.35 m | 10 cm |
| QL2 | 0.7 m | 10 cm |
| QL3 | 1.4 m | 20 cm |
| QL4 | — | 139 cm |
| QL5 (radar, Alaska) | — | 185 cm |
- Goal: complete national coverage by the end of 2022, depending on funding and partners.
- Value: conservatively $1.2 billion a year nationally, with the potential for $13 billion a year.
- Why a national program: larger purchases cut costs by 25%; buying high quality once avoids paying to "buy up" later; consistent data across state and watershed lines; more federal money reduces state and local shares; and ready contracts and specifications simplify buying.
Sources
Based on William J. Carswell, Jr., "The 3D Elevation Program: summary for Utah," U.S. Geological Survey Fact Sheet 2014–3115, version 1.1 (2015); a work of the United States government in the public domain. The map and tables are taken from the fact sheet's PDF; its fault-map image, modified from one provided by the Utah Geological Survey, is not reproduced. Benefit figures come from Dewberry's National Enhanced Elevation Assessment (2011, revised 2012).
Licence : CC0 1.0 (domaine public) · Adapté de pubs.usgs.gov
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