2. Outline • Accuracy • Specifications • Comparisons to Photogrammetry and cost considerations • Data storage, tiling and software considerations

3. Accuracy • Combination of two parameters • Positional accuracy of discrete points in digital elevation model • How well the data fits the form of the earth’s surface

4. Accuracy Precise, but not accurate Not Precise, not accurate Precise, accurate

5. Descriptive Statistics • Utilizes well defined independent checkpoints (differences between higher order surveyed coordinates and product test coordinates are calculated for each checkpoint component)

6. Error Statistics • Normal Distribution Function - A mathematical function describing the behavior of one-dimensional random errors whose graph is a bell-shaped curve that extends indefinitely in both directions.

7. Confidence Level and the Bell Shaped Curve • 1 sigma (1σ) level equals 68.26% of area under the curve • 2 sigma (2σ) level equals 95.44% of area under the curve • 3 sigma (3σ) level equals 99.74% of area under the curve

8. Accuracy Standards • National Map Accuracy Standards (1947) • USDOT Reference Guide Outline - Specifications for Aerial Surveys and Mapping by Photogrammetric Methods for Highways (1968) • ASPRS Accuracy Standards for Large-Scale Maps (1990) • National Standard for Spatial Data Accuracy (NSSDA) (1998) • National Digital Elevation Program (NDEP) (2004)

9. National Map Accuracy Standards (1947) • Dependent on Map Scale and Contour Interval • Accuracy Reporting • “This map complies with National Map accuracy standards.” • Accuracy Requirements at 90% confidence level • Sets Pass/Fail limits of product • Does not define testing method • Horizontal Accuracy • 90% of planimetric features are within 1/30” at map scale for map scales larger than 1:20,000 • Vertical Accuracy • 90% of elevations determined from contours are within 1/2 contour interval

10. USDOT Reference Guide Outline(1968) • Dependent on Map Scale and Contour Interval • Accuracy Reporting language not explicitly defined • Accuracy Requirements at 90% confidence level • Sets Pass/Fail limits of product • Does not define test method • Horizontal Accuracy • 90% of planimetric features are within 1/40” at map scale • Vertical Accuracy • 90% of elevations determined from contours are within 1/2 contour interval • 90% of spot elevations are within 1/4 contour interval

11. ASPRS Accuracy Standards for Large-Scale Maps (1990) • Dependent on Map Scale and Contour Interval • Accuracy Reporting • RMSE Class I, II, III • 1/3 CI and 1/6 CI spots • Sets Pass/Fail limits of product • Defines testing method • Accuracy Reporting (Testing) “THIS MAP WAS CHECKED AND FOUND TO CONFORM TO THE ASPRS STANDARD FOR CLASS 1 MAP ACCURACY.” • Accuracy Reporting (Procedure) “THIS MAP WAS COMPILED TO MEET THE ASPRS STANDARD FOR CLASS 1 MAP ACCURACY.”

12. Map Product Accuracy Table values are RMSE in feet

13. NSSDA (1998) • Independent of Map Scale and Contour Interval • Accuracy Reporting at 95% confidence level and is based on either Testing or Procedure • Does not set Pass/Fail limits, leaves it to the user to determine • Defines testing method • Accuracy Reporting (Testing) Tested ____ (meters, feet) horizontal accuracy at 95% confidence level Tested ____ (meters, feet) vertical accuracy at 95% confidence level • Accuracy Reporting (Procedure) Compiled to meet ___ (meters, feet) horizontal accuracy at 95% confidence level Compiled to meet ___(meters, feet) vertical accuracy at 95% confidence level

14. NDEP (2004) • Extension of NSSDA • Same statistical level • Specific to elevation data • Defines testing method • 20 (30 preferred) points per vegetation type • Located around features of interest • Land cover types in the area of interest • Open terrain • Tall weeds/crops • Brush lands and low trees • Forests • Urban

15. Project Example

16. Check Points Asphalt Gravel Concrete Grass Tall Grass Trees

17. Data Analysis

18. Summary

19. Linn and Sullivan

20. Topographic Data of Kansas

21. DEM Horizontal Resolution

22. Grid vs. Mass Points & Breaklines Mass Points Ground Surface Interpolated Surface Breaklines Mass Points Ground Surface Interpolated Surface

23. 1-arc-second (30 meters) 1/3-arc-second (10 meters) 1/9-arc-second (3 meters)

24. How do you define your specifications?

25. Horizontal Standards

26. Vertical Standards

27. Data Density?

28. Elevation Data Sample Distance

29. FEMA Specifications

30. Comparisons to Photogrammetry

31. Photogrammetric Process

32. Combined LiDAR and Photogrammetric Process

33. Estimated Time and Cost Savings • Highway Projects (Iowa DOT) • Time • Photogrammetric mapping – estimated two years to produce • LIDAR – five months (addt’l. photogrammetry work, eight months) • Result – eleven months time savings • Financial • Photogrammetry – est. $500,000 • LIDAR – est. $150,000 (addt’l photogrammetry $100,000) • Result - $250,000 savings (50%) over photogrammetry

34. Estimated Time and Cost Savings • Time • Photogrammetric mapping required 2,670 hours • LIDAR required 598 hours • Savings of 2,072 hours (71%) not including time for final design

35. Contour CostsPhotogrammerty vs LIDAR Dewberry and Davis

36. MNDOT LiDAR Study

37. File Size Considerations

38. File Formats • ASCII Text • .txt, .csv, … • Software • ESRI • Open • GeoTiff • USGS DEM • LAS • Binary • 35% - 80% file size reduction depending on attributes selected.

39. LAS Format

40. LAS Format

41. LAS Format

42. LAS Format

43. LAS Format

45. 1-arc-second (30 meters) 1/3-arc-second (10 meters) 1/9-arc-second (3 meters)

46. Specifications • Other

47. Deliverables