Presentation on theme: "Geospatial Data Accuracy and the New Mapping Accuracy Standard: New Era Session #35 Dr. Qassim Abdullah, Woolpert, Inc. Pierre Le Roux, Aerometric, Inc."— Presentation transcript:
1 Geospatial Data Accuracy and the New Mapping Accuracy Standard: New Era Session #35 Dr. Qassim Abdullah, Woolpert, Inc. Pierre Le Roux, Aerometric, Inc. Becky Morton, Towill, Inc.
2 New ASPRS Positional Accuracy Standards for Digital Geospatial Data Drafting Committee: Chair: Douglas L. Smith, David C. Smith & Associates, Inc. Dr. Qassim A. Abdullah, Woolpert, Inc. Dr. David Maune, Dewberry Karl Hans Heidemann, USGS REVISION 7, VERSION 1 NOVEMBER 14, 2014 (FINAL BOARD APPROVAED Version)
3 New ASPRS Positional Accuracy Standards for Digital Geospatial Data Replaces:ASPRS Accuracy Standards for Large-Scale Maps (1990)ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data (2004)Developed by:ASPRS Map Accuracy Standards Working Group, PAD, PDAD and LIDAR joint committee for map accuracy standard updateIn Final Approved VersionREVISION 7, VERSION 1, Nov. 14, 2014Approved and adopted by ASPRS during the board meeting on Monday Nov. 17, 2014 in Denver during ASPRS 2014 PECORA conference
4 New Standard for a New Era Motivation Behind the New Standard:Legacy map accuracy standards, such as the ASPRS 1990 standard and the NMAS of 1947, are outdated. (over 30 years since ASPRS1990 was written)Many of the data acquisition and mapping technologies that these standards were based on are no longer used.More recent advances in mapping technologies can now produce better quality and higher accuracy geospatial products and maps.Legacy map accuracy standards were designed to deal with plotted or drawn maps as the only medium to represent geospatial data.
5 New Standard for a New Era Within the past two decades (during the transition period between the hardcopy and softcopy mapping environments), most standard measures for relating GSD and map scale to the final mapping accuracy were inherited from photogrammetric practices using scanned film.New mapping processes and methodologies have become much more sophisticated with advances in technology and advances in our knowledge of mapping processes and mathematical modeling.Mapping accuracy can no longer be associated with the camera geometry and flying altitude alone (focal length, xp, yp, B/H ratio, etc.).
6 New Standard for a New Era New map accuracy is influenced by many factors such as:the quality of camera calibration parameters;quality and size of a Charged Coupled Device (CCD) used in the digital camera CCD array;amount of imagery overlap;quality of parallax determination or photo measurements;quality of the GPS signal;quality and density of ground controls;quality of the aerial triangulation solution;capability of the processing software to handle GPS drift and shift;capability of the processing software to handle camera self-calibration,the digital terrain model used for the production of orthoimagery..
7 New Standard for a New Era These factors can vary widely from project to project, depending on the sensor used and specific methodology. For these reasons, existing accuracy measures based on map scale, film scale, GSD, c-factor and scanning resolution no longer apply to current geospatial mapping practices.Elevation products from the new technologies and active sensors such as lidar and IFSAR are not considered by the legacy mapping standards. New accuracy standards are needed to address elevation products derived from these technologies.
8 ASPRS Positional Accuracy Standards for Digital Geospatial Data Applicability:Defines specific accuracy classes and associated RMSE thresholds for digital orthoimagery, digital planimetric data, and digital elevation dataIntended to be technology independentLimited to accuracy thresholds and testing methodologies for any mapping applications, and to meet immediate shortcomings in the outdated 1990 and 2004 standardsIs not intended to cover classification accuracy of thematic mapsDoes not specify the best practices or methodologies needed to meet the accuracy thresholdsIncludes:Glossary, Symbols, examples, conversion to legacy standards
9 New Standard Highlights Positional Accuracy Thresholds which are independent of published GSD, map scale or contour intervaldigital orthoimagerydigital elevation dataAdditional Accuracy Measuresaerial triangulation accuracy,Ground controls accuracy,orthoimagery seam lines accuracy,lidar relative swath-to-swath accuracy,recommended minimum Nominal Pulse Density (NPD)horizontal accuracy of elevation data,delineation of low confidence areas for vertical datarequired number and spatial distribution of QA/QC check points based on project area
10 New Standard Highlights Positional Accuracy Thresholds which are independent of published GSD, map scale or contour intervaldigital orthoimagerydigital elevation dataAdditional Accuracy Measuresaerial triangulation accuracy,Ground controls accuracy,orthoimagery seam lines accuracy,lidar relative swath-to-swath accuracy,recommended minimum Nominal Pulse Density (NPD)horizontal accuracy of elevation data,delineation of low confidence areas for vertical datarequired number and spatial distribution of QA/QC check points based on project area
11 New Standard Highlights It is All Metric!Unlimited Horizontal Accuracy Classes:Horizontal Accuracy Standards for Geospatial DataHorizontal Accuracy ClassRMSEx and RMSEy (cm)RMSEr (cm)Horizontal Accuracy at 95% Confidence Level (cm)Orthoimagery Mosaic Seamline Mismatch(cm)X-cm≤X≤1.41*X≤2.45*X≤ 2*X
12 Common Horizontal Accuracy Classes according to the new standard Horizontal Accuracy Class RMSEx and RMSEy (cm)RMSEr (cm)Orthoimage Mosaic Seamline Maximum Mismatch (cm)Horizontal Accuracy at the 95% Confidence Level (cm)0.6188.8.131.52.251.82.53.12.503.55.06.15.007.110.012.27.5010.615.018.410.0014.120.024.512.5017.725.030.615.0021.230.036.717.5024.735.042.820.0028.340.049.022.5031.845.055.125.0035.450.061.227.5038.955.067.330.0042.460.073.445.0063.690.0110.160.0084.9120.0146.975.00106.1150.0183.6100.00141.4200.0244.8150.00212.1300.0367.2200.00282.8400.0489.5250.00353.6500.0611.9300.00424.3600.0734.3500.00707.11000.01223.91414.22000.02447.7Common Horizontal Accuracy Classes according to the new standard
13 Common Orthoimagery Pixel Sizes Associated Map ScaleASPRS 1990 Accuracy ClassAssociated Horizontal Accuracy According to Legacy ASPRS 1990 StandardRMSEx and RMSEy (cm)RMSEx and RMSEy in terms of pixels0.625 cm1:5011.32-pixels22.54-pixels33.86-pixels1.25 cm1:1005.07.52.5 cm1:20010.015.05 cm1:40020.030.07.5 cm1:60045.015 cm1:1,20060.090.0Examples on Horizontal Accuracy for Digital Orthoimagery interpreted from ASPRS 1990 Legacy Standard.
14 Common Orthoimagery Pixel Sizes Recommended Horizontal Accuracy Class RMSEx and RMSEy (cm)Orthoimage RMSEx and RMSEy in terms of pixelsRecommended use1.25 cm≤1.3≤1-pixelHighest accuracy work2.52-pixelsStandard Mapping and GIS work≥3.8≥3-pixelsVisualization and less accurate work2.5 cm≤2.55.0≥7.55 cm≤5.010.0≥15.07.5 cm≤7.515.0≥22.515 cm≤15.030.0≥45.0Digital Orthoimagery Accuracy Examples for Current Large and Medium Format Metric Cameras
15 Horizontal Accuracy/Quality Examples for High Accuracy Digital Planimetric Data ASPRS 2014Equivalent to map scale inEquivalent to map scale in NMASHorizontal Accuracy Class RMSEx and RMSEy (cm)RMSEr (cm)Horizontal Accuracy at the 95% Confidence Level (cm)Approximate GSD of Source Imagery (cm)ASPRS 1990 Class 1ASPRS 1990 Class 20.6184.108.40.206 to 0.631:251:12.51:220.127.116.11.63 to 1.251:501:318.104.22.168.25 to 2.51:1001:635.07.112.22.5 to 5.01:2001:1277.510.618.43.8 to 7.51:3001:1501:19010.014.124.55.0 to 10.01:4001:25312.517.730.66.3 to12.51:5001:2501:31715.021.236.77.5 to 15.01:6001:38017.524.742.88.8 to 17.51:7001:3501:44420.028.349.010.0 to 20.01:8001:50722.531.855.111.3 to 22.51:9001:4501:57025.035.461.212.5 to 25.01:10001:63427.538.967.313.8 to 27.51:11001:5501:69730.042.473.415.0 to 30.01:12001:760
16 New Standard Highlights Unlimited Vertical Accuracy Classes:Vertical Accuracy Standards for Digital Elevation DataVertical Accuracy ClassAbsolute AccuracyRelative Accuracy (where applicable)RMSEzNon-Vegetated(cm)NVA at 95% Confidence LevelVVA at 95th PercentileWithin- SwathHard Surface Repeatability(Max Diff)Swath-to-SwathNon-Vegetated Terrain(RMSDz)X-cm≤X≤1.96*X≤3.00*X≤0.60*X≤0.80*X≤1.60*X
17 Vertical Accuracy/Quality Examples for Digital Elevation Data Vertical Accuracy ClassAbsolute AccuracyRelative Accuracy (where applicable)RMSEzNon-Vegetated(cm)NVAat 95%Confidence LevelVVAat 95th PercentileWithin-SwathHard Surface Repeatability(Max Diff)Swath-to-SwathNon-Veg Terrain(RMSDz)1-cm1.02.030.60.81.62.5-cm22.214.171.124.5245-cm5.09.815810-cm10.019.63061615-cm15.029.4459122420-cm20.039.2603233.3-cm33.365.31002026.753.366.7-cm66.7130.720040106.7100-cm100.0196.030080160333.3-cm333.3653.31000266.7533.3
18 Vertical accuracy of the new ASPRS 2014 standard compared with legacy standards Vertical Accuracy ClassRMSEzNon-Vegetated(cm)Equivalent Class 1 contour interval per ASPRS 1990 (cm)Equivalent Class 2 contour interval per ASPRS 1990 (cm)Equivalent contour interval per NMAS (cm)1-cm1.03.01.53.292.5-cm126.96.36.199.225-cm5.015.016.4510-cm10.030.032.9015-cm45.022.549.3520-cm20.060.065.8033.3-cm33.399.950.0109.5566.7-cm66.7200.1100.1219.43100-cm100.0300.0150.0328.98333.3-cm333.3999.9500.0
19 Vertical Accuracy Class Recommended Maximum NPS7 (m) Examples on Vertical Accuracy and Recommended Lidar Point Density for Digital Elevation Data according to the new ASPRS 2014 standardVertical Accuracy ClassAbsolute AccuracyRecommendedMinimum NPD(pts/m2)Recommended Maximum NPS7 (m)RMSEzNon-Vegetated(cm)NVAat 95% ConfidenceLevel (cm)1-cm1.02.0≥20≤0.222.5-cm2.54.9160.255-cm5.09.880.3510-cm10.019.620.7115-cm15.029.4120-cm20.039.20.51.433.3-cm33.365.366.7-cm66.7188.8.131.520-cm100.0196.00.054.5333.3-cm333.3653.30.01
20 Horizontal accuracy requirements for elevation data Photogrammetric elevation data:, the horizontal accuracy equates to the horizontal accuracy class that would apply to planimetric data or digital orthoimagery produced from the same source imagery, using the same aerial triangulation/INS solution.Lidar elevation data: use the following formula:𝐿𝑖𝑑𝑎𝑟 𝐻𝑜𝑟𝑖𝑧𝑜𝑛𝑡𝑎𝑙 𝐸𝑟𝑟𝑜𝑟 𝑅𝑀𝑆𝐸 𝑟 = 𝐺𝑁𝑆𝑆 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝑒𝑟𝑟𝑜𝑟 tan (𝐼𝑀𝑈 𝑒𝑟𝑟𝑜𝑟) 𝑥 𝑓𝑙𝑦𝑖𝑛𝑔 𝑎𝑙𝑡𝑖𝑡𝑢𝑑𝑒 2
21 Expected horizontal errors (RMSEr) for Lidar data in terms of flying altitude Altitude (m)Positional RMSEr (cm)50013.13,00041.61,00017.53,50048.01,50023.04,00054.52,00029.04,50061.12,50035.25,00067.6
23 Accuracy requirements for aerial triangulation and INS-based sensor orientation of digital imagery Accuracy of aerial triangulation designed for digital planimetric data (orthoimagery and/or digital planimetric map) only:RMSEx(AT) or RMSEy(AT) = ½ * RMSEx(Map) or RMSEy(Map)RMSEz(AT) = RMSEx(Map) or RMSEy(Map) of orthoimageryAccuracy of aerial triangulation designed for elevation data, or planimetric data (orthoimagery and/or digital planimetric map) and elevation data production:RMSEx(AT), RMSEy(AT)or RMSEz(AT) = ½ * RMSEx(Map), RMSEy(Map)or RMSEz(DEM)
24 Accuracy requirements for ground control used for aerial triangulation Accuracy of ground controls designed for planimetric data (orthoimagery and/or digital planimetric map)production only:RMSEx or RMSEy = ¼ * RMSEx(Map) or RMSEy(Map),RMSEz = ½ * RMSEx(Map) or RMSEy(Map)Accuracy of ground controls designed for elevation data, or planimetric data and elevation data production:RMSEx, RMSEy or RMSEz= ¼ * RMSEx(Map), RMSEy(Map) or RMSEz(DEM)
25 Examples on Aerial Traingulation and Ground Control Accuracy Aerial Triangulation and Ground Control Accuracy Requirements,Orthoimagery and/or Planimetric Data OnlyProduct Accuracy (RMSEx, RMSEy, or RMSEz)(cm)A/T AccuracyGround Control AccuracyRMSEx and RMSEyRMSEz502512.5Aerial Triangulation and Ground Control Accuracy Requirements,Orthoimagery and/or Planimetric Data and Elevation DataProduct Accuracy (RMSEx, RMSEy)(cm)A/T AccuracyGround Control AccuracyRMSEx and RMSEyRMSEz502512.5
26 Reporting Horizontal Accuracy “This data set was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a ___ (cm) RMSEx / RMSEy Horizontal Accuracy Class. Actual positional accuracy was found to be RMSEx = ___ (cm) and RMSEy = ___ cm which equates to +/- ___ at 95% confidence level.”“This data set was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a ___ (cm) RMSEx / RMSEy Horizontal Accuracy Class which equates to +/- ___ cm at a 95% confidence level.”
27 Reporting Vertical Accuracy “This data set was tested to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a___ (cm) RMSEz Vertical Accuracy Class. Actual NVA accuracy was found to be RMSEz = ___ cm, equating to +/- ___ at 95% confidence level. Actual VVA accuracy was found to be +/- ___ cm at the 95% percentile.”“This data set was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a ___ cm RMSEz Vertical Accuracy Class equating to NVA =+/-___cm at 95% confidence level and VVA =+/-___cm at the 95% percentile
28 Recommended Number of Check Points Based on Area Project Area (Square Kilometers)Horizontal Accuracy Testing of Orthoimagery and PlanimetricsVertical and Horizontal Accuracy Testing of Elevation Data setsTotal Number of Static 2D/3D Check Points (clearly-defined points)Number of Static 3D Check Points in NVANumber of Static 3D Check Points in VVATotal Number of Static 3D Check Points≤50020525103015403550604570805590100
29 New Standard Highlights Not Yet Addressed:Methodologies for accuracy assessment of linear features (as opposed to well defined points)Rigorous total propagated uncertainty (TPU) modeling (as opposed to -- or in addition to – ground truthing against independent data sources)Robust statistics for data sets that do not meet the criteria for normally distributed data and therefore cannot be rigorously assessed using the statistical methods specified hereinImage quality factors, such as edge definition and other characteristicsRobust assessment of check point distribution and densityAlternate methodologies to TIN interpolation for vertical accuracy assessment
30 Example on Applying the New Standard User asked for orthoimagery with GSD =10 cm ortho, what specifications he/she needs to ask for?Answer:1) According to the legacy standard of 1990, most probably will be: Horizontal Accuracy RMSE = 20 cm (2 pixels) class I, Map scale = 1:8002) According to the new Standard:- RMSE = 10 cm (highest obtainable/"highest accuracy work“, entails ground controls accurate to 2.5 cm and very accurate workflow)- RMSE = 20 cm ( comparable to 1990)Practical specs: RMSE = 15 cm, no scale to be assigned
31 The Standard Web SiteThe final standard document is posted on the web page: