Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships IGIC - Indiana GIS LiDAR Applications for Surveyors 3. Accuracy and Limitations of using LiDAR, DEM and Derivative Products Robert N. Wilkinson, IDNR (GIS Bob)

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Accuracy and Limitations of using LiDAR, DEM and Derivative Products FGDC Metadata [and Published Accuracy] for Indiana’s LiDAR & DEM data products IN_2011_Statewide_East_LAS.txt IN_2011_Statewide_West_LAS.txt IN_2011_Statewide_East_IMG_DEM.txt IN_2011_Statewide_West_IMG_DEM.txt IN_2011_Statewide_East_Breakline.txt IN_2011_Statewide_West_Breakline.txt Published Accuracy: The LiDAR data vertical accuracy RMSE is Block cm (0.187 ft), Block cm (0.241 ft) and Block cm (0.215 ft). The data collected under this Task Order meets the National Standard for Spatial Database Accuracy (NSSDA) accuracy standards. IGIC - Indiana GIS LiDAR Applications for Surveyors

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships NSSDA Accuracy Testing View Here National Standard for Spatial Data Accuracy Issued by FGDC in 1998

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships NSSDA Objective The National Standard for Spatial Data Accuracy (NSSDA) implements a statistical and testing methodology for estimating the positional accuracy of points on maps and in digital geospatial data, with respect to georeferenced ground positions of higher accuracy.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships IGIC - Indiana GIS LiDAR Applications for Surveyors 3.C How to compute the vertical accuracy of your AOI and Derivative Data Products

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Independent Vertical Accuracy Testing (Using Existing DNR Survey Data) IDNR Projects from 2007 – 2010 Mostly from Work Done for FEMA MapMod Projects In Various Locations Around the State In One Location, More or Less in a County

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Independent Vertical Accuracy Testing Haw Creek 2010 Data 2003 Data not used in NSSDA Test

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Haw Creek 2010 Data Project from 2010 May have been some changes between survey and LiDAR - Road resurfaced, erosion, Cut/fill areas 3422 Total Points Too many points. NSSDA only requires 20 Some points on guardrails, bridge low structure etc. not suitable for checking LiDAR data.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Testing Methodology Data Producer will determine Geographic extent of testing area. 20 points required for area. Point placement  Better to spread through entire area  Evenly dispersed in four quadrants  10% across entire length of box Concentration can be heavier in specific areas User can concentrate more points in specified area when warranted by job requirements.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Points Needed for Modeling Bridge HEC-RAS 99 Total Points

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Typical Bridge Section

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Weeded Down to 3 Points Surveyed Value Left – LiDAR Value Right

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Results of Weeding Down Points 3428 Points were Weeded down to about 210 Points. Several more points weeded by looking at their attributes to confirm that they were not ground points. 203 Points Remain.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Add LiDAR Value to Point File with ArcMap

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Attribute Table

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Check Statistics in ArcMap

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships NSSDA Test in Excel NSSDA at 95% Confidence Level is RMSE times 1.96 E – D = F 2 F Square Root of MSE Average of G

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships NSSDA Test Results Bartholomew – 0.58 ft. Brown – 0.67 ft. Boone – 0.32 ft. Cass – 0.47 ft. Clinton – 0.33 ft. Elkhart – 0.81 ft. Howard – 0.30 ft. Johnson – 0.47 ft. Monroe – 0.72 ft. Morgan – 0.23 ft.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships IGIC would like to create a tracking system for public use that visually shows where LiDAR data has been checked against survey data. Using qualified survey data, either previously collected or specifically collected for running elevation checks:  Be willing to run checks through the process  Be able to describe the reasoning behind how the process was done with used points.  Be willing to share data sheets and description of area checked to IGIC (free of charge). Index for Accuracy Reporting

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Accuracy Reporting Will be included in index Metadata –  Index will be shapefile designed to visually depict area checked.  Shapefile attributed with pertinent data  Vertical datum  Date of check  Check performed by Example in metadata -  0.58 ft. at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 0.30 ft. in the open terrain land cover category (Note USGS V1.2 Specification).

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Hydro Flattening. HYDRO FLATTENING: Potential loss of some data.  Only the DEM’s derived from the LAS files. Breaklines digitized from the LAS files. Point clouds are not as sharp as the orthophotos. A little bit of land may accidently get flattened while a little bit of water may not. Should now be just ± 10 feet.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Questions?