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Publicly available lidar in Georgia, June 2014. None met 3DEP's quality level 2 standard. USGS, from the U.S. Interagency Elevation Inventory.
In 2014, none of Georgia's public lidar met the standard of the USGS 3D Elevation Program (3DEP): what existed was quality level 3 or lower, and large parts of the state had none.
By the numbers
| Expected annual benefits | $8.56 million |
| Estimated total cost | $19.69 million |
| Payback | 2.3 years |
| Benefit/cost ratio (8 years) | 3.5 to 1 |
| Cost to buy up to quality level 1 | $12.53 million |
About 72% of the identified needs fall in infrastructure, conservation and flood risk management. Not every benefit had a dollar value, so the true total is likely much higher.
| Rank | Business use | Annual benefits (millions) |
|---|---|---|
| 1 | Infrastructure and construction management | $2.23 |
| 2 | Natural resources conservation | 2.08 |
| 3 | Flood risk management | 1.84 |
| 4 | Agriculture and precision farming | 1.20 |
| 5 | Forest resources management | 0.46 |
| 6 | Water supply and quality | 0.29 |
| 7 | Aviation navigation and safety | 0.15 |
| 8 | Geologic resource assessment and hazard mitigation | 0.11 |
| 9 | Coastal zone management | 0.08 |
| 10 | Sea level rise and subsidence | 0.06 |
| Other | 0.06 | |
| Total | 8.56 |
How lidar helps Georgia
- Floods. Better elevation data are central to Georgia's Flood Mapping, Assessment and Planning program and FEMA's Risk MAP, which fill gaps in flood hazard data and lead to mitigation that protects lives and property.
- Stormwater. Runoff carries oil and grease, fertilizer, chemicals, pet waste and litter into the state's waters. Hydrologic models built on lidar can find places in a watershed to hold runoff temporarily, cutting peak flows and the sediment and nutrients reaching streams. In cities, the data help protect wetlands, measure impervious surfaces for stormwater planning, and model where water collects.
A tributary carrying sediment and nutrients into the clearer Chattahoochee River in Atlanta. USGS photo.
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 as the federal lead for land elevation data, 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 Georgia," U.S. Geological Survey Fact Sheet 2014–3058; a work of the United States government in the public domain. The map, photograph and tables are taken from the fact sheet's PDF. Benefit figures come from Dewberry's National Enhanced Elevation Assessment (2011, revised 2012).
Licencia: CC0 1.0 (dominio público) · Adaptado de pubs.usgs.gov
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