Li DAR Quality Control Validating Li DAR Data

Li. DAR Quality Control Validating Li. DAR Data Tim Loesch Minnesota Department of Natural Resources GIS Section 10/7/2020 MN GIS/LIS Spring Workshop Series

Li. DAR QA/QC – Did I get what I paid for? Li. DAR = Massive quantities of data Li. DAR = Expensive acquisition costs Li. DAR = File upon file… Li. DAR = Very accurate information Li. DAR = Lots of room for error Client QA/QC is an critical part of the process 10/7/2020 MN GIS/LIS Fall Workshops

Li. DAR QA/QC – Did I get what I paid for? QA/QC Elements Validating file(s) existence l Li. DAR is delivered in tiles Validation of data Schema l Valid elevation values l Visual exam for data defects l Vertical accuracy 10/7/2020 verification MN GIS/LIS Fall Workshops l

Li. DAR QA/QC – Did I get what I paid for? Tightly defined data delivery structure Provides a basis for comparison Development of automated validation routines 10/7/2020 MN GIS/LIS Fall Workshops

Li. DAR QA/QC – Did I get what I paid for? Step by Step Checklist Helps with consistency Allows for distribution of effort Ensures consistency of validation Provides record of work 10/7/2020 MN GIS/LIS Fall Workshops

Li. DAR QA/QC – Did I get what I paid for? Initial File Check-in Automated routine checks for: File existence (GDB, LAS, DEM, etc) l Valid values l Field validation l Produces table of results 10/7/2020 MN GIS/LIS Fall Workshops

Li. DAR QA/QC – Did I get what I paid for? DEM Mosaic all DEMs to single raster Generate shaded relief Provides excellent product for visual examination Display techniques can reveal small irregularities 10/7/2020 MN GIS/LIS Fall Workshops We visually inspect every

Li. DAR QA/QC – Did I get what I paid for? Generate derived products 2’ Contours Building Polygons Can highlight problems that you cannot see Classification errors Overlap errors 10/7/2020 MN GIS/LIS Fall Workshops

Li. DAR QA/QC – Did I get what I paid for? Vertical Accuracy Assessment Validation Points Level ground away from breaks in topography l Open, visible sky l Five cover classes – 20 points per class (30 preferred) L 1 O – Open terrain l L 2 T – Tall Grass l L 3 B – Brush l L 4 F – Forested Minnesota Department of Natural l L 5 U - Urban l 10/7/2020 Resources

Li. DAR QA/QC – Did I get what I paid for? Types of Accuracy Fundamental Accuracy = Best Case Scenario l Open terrain tested to 95% accuracy Supplemental Accuracy for Cover Classes other than Open terrain Consolidated Accuracy l 10/7/2020 All Cover Class Accuracies Combined Minnesota Department of Natural Resources

Li. DAR QA/QC – Did I get what I paid for? 371. 93 Li. DAR points Interpolated Value 372. 115 10/7/2020 Minnesota Department of Natural Resources

Li. DAR QA/QC – Did I get what I paid for? Winona County Validation Points 10/7/2020 Minnesota Department of Natural Resources

Li. DAR QA/QC – Did I get what I paid for? RMSE Calculations RMSE(z) = Sqrt(sum(Zdata(i) – ZCheck(i))2 / n) NSSDA Vertical Accuracy 95% Rate = 1. 96 * RMSE 2 10/7/2020 MN GIS/LIS Fall Workshops

Li. DAR QA/QC – Did I get what I paid for? ----- Report Summary ----Error Mean: Error Range: Skew: RMSE(z): NMAS/VMAS Accuracy(z) (90% CI): ASPRS/NSSDA Accuracy(z) (95% CI): -0. 116 [-0. 435, 0. 143] -0. 305 0. 161 ± 0. 265 ± 0. 315 176 control points included in summary out of 176 - 0 control points turned off - 0 control points returned no-data ----- Control Points ----Name L 1 O 0 L 5 U 1 L 1 O 2 L 1 O 3 L 1 O 4 L 1 O 5 L 1 O 6 L 1 O 7 L 1 O 8 L 2 T 9 L 2 T 10 10/7/2020 Control X 604760. 340 608921. 294 610991. 353 607292. 402 622397. 772 626922. 206 631669. 497 635439. 901 625518. 897 621174. 012 620283. 975 Control Y 4878787. 629 4878065. 350 4876621. 369 4874401. 804 4873262. 387 4869248. 810 4863815. 331 4857649. 190 4864620. 423 4864494. 226 4857065. 579 Control Z Surface Z Error 201. 217 201. 389 -0. 172 201. 488 201. 806 -0. 318 200. 214 200. 397 -0. 183 233. 428 233. 606 -0. 178 207. 292 207. 356 -0. 064 202. 936 202. 969 -0. 033 200. 254 200. 333 -0. 079 375. 011 375. 070 -0. 059 385. 756 385. 722 0. 034 388. 359 388. 470 -0. 111 386. 810 387. 048 -0. 238 MN GIS/LIS Fall Workshops

Li. DAR QA/QC – Did I get what I paid for? Winona County Validation Report RMSE across cover Types 0. 250 0. 196 0. 200 0. 166 0. 150 0. 172 0. 161 0. 136 0. 127 L 1 O L 2 T L 3 B L 4 F 0. 100 L 5 U Overall 0. 050 0. 000 RMSE 10/7/2020 Minnesota Department of Natural Resources

Li. DAR QA/QC – Did I get what I paid for? Winona County Validation Report Vertical Error Distribution 0. 2 0. 1 0 L 1 O -0. 1 L 2 T L 3 B -0. 2 L 4 F -0. 3 L 5 U -0. 4 -0. 5 175 10/7/2020 225 275 325 375 Minnesota Department of Natural Resources 425

Li. DAR QA/QC – Did I get what I paid for? Then…. . If the data does not meet spec Vendor is notified and delivered QA/QC Checklist l Some issues are clear and some are not If the data is deemed to meet or exceed spec Packaging and Publishing l Metadata, Services, etc…. . l 10/7/2020 MN GIS/LIS Fall Workshops

Li. DAR QA/QC – Did I get what I paid for? National Accuracy Standards Specifications USGS Base Li. DAR Specifications V 13 NDEP Guidelines For Digital Elevation Data 10/7/2020 MN GIS/LIS Fall Workshops