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# Evaluating the Height of Regional Dikes of HH Rijnland with LiDAR using ArcGIS 10 by Grontmij

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Presentation on how ArcGIS was used to perform an in-depth analysis of the height of regional dikes of HH Rijnland using AHN2 (LiDAR) data.

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### Evaluating the Height of Regional Dikes of HH Rijnland with LiDAR using ArcGIS 10 by Grontmij

1. 1. 2 AHN2 2010 – interpolated AHN2 2008 – interpolated AHN2 2008 – not interpolated Location of dikes
2. 2. 3 AHN2 dataset consists of over 7 billion pixels ( 30GB) Querying the pixels values becomes slower when the size of theraster increments There are 1212 km of dike, every 0.5m 11 pixels are queried ( 27million points) and evaluated against 2 reference heights For each point on a dike there should be al least a length of 1.5mconnected within a class No standard tools available for this specific task
3. 3. 4 Merge AHN2 tiles to 1 raster dataset loop through dikes  fetch height every 0.5m  evaluate against two reference heights (A and B)  AHN2<B or B<=AHN2<A or AHN2>=A or NoData  Combine points with same class together to form a line  next point on dike next dike(repeat validationfor reference heights C and D) > 1.5m, it does meet the criteria
4. 4. 5 For each class (AHN2<B, B<=AHN2<A, AHN2>=A) register thenumber of consecutive points that fall inside that class The highest class with at least 3 consecutive points is assigned In the example below the resulting class is B<=AHN2<A, basedon points 4 to 9 which are higher that B, but not all above A (thelower limit of a class is used for validation) 6 7 A 2 4 5 8 9 B 3 10 11 1 Dike center
5. 5. 6
6. 6. 7ClassPoint >= AB <= Point < APoint < BNoData
7. 7. 8ClassAHN2 >= AB <= AHN2 < AAHN2 < BInsufficient dataNoData
8. 8. 9ClassAHN2 >= AB <= AHN2 < AAHN2 < BInsufficient dataNoData
9. 9. 10ClassAHN2 >= AB <= AHN2 < AAHN2 < BInsufficient dataNoData
10. 10. 11More than 1.5m, AHN2 > A More than 70% NoData AHN2 < BInsufficient data, less than 70% NoData, More than 1.5m, B <= AHN2 < Abut no 3 consecutive points with data
11. 11. 12Correct method of processing solitary points
12. 12. 13AHN2 >= A AHN2 >= AB <= AHN2 < A B <= AHN2 < AAHN2 < B AHN2 < BInsufficient data Insufficient dataNoData NoData
13. 13. 14AHN2 >= A AHN2 >= AB <= AHN2 < A B <= AHN2 < AAHN2 < B Bmin10 <= AHN2 < BInsufficient data Bmin20 <= AHN2 < Bmin10NoData Bmin30 <= AHN2 < Bmin20 Bmin40 <= AHN2 < Bmin30 AHN2 < Bmin40 Insufficient data NoData
14. 14. 15
15. 15. 16 Calculate percentage of total length per class per dike Sums 100% Explanation of the column names:  “KL” stands for class  “X” represents AHN2 value  “lt” is less than “<“  “le” is less equal “<=“  “ge” is greater equal “>=“ So “KL_BleXltA” means: Class where B <= AHN2 < A
16. 16. 17Percentage per class (based on A and B) Percentage per class (based on C and D)
17. 17. 18 The 1212 km of dike has been processed into classified pointsand lines and additionally aggregated per dike Processing time has been reduced to 12 minutes for the entirearea based on the 30 GB raster. For each point information about:  %NoData (indicates reliability)  elevation (min, max, mean)  classification For each polyline information about:  elevation (min, max, mean)  classification
18. 18. 19 After the height test, the results were combined with knowninstabilities and observations from previous research andfieldwork, in order to derive those locations with the highestpriority.
19. 19. 20 indicating the percentage of adike with sufficient stability tosafeguard the surrounding area
20. 20. 21 Sufficient height Height shortage between 0 and 10 cm Height shortage between 10 and 20 cm Height shortage between 20 and 30 cm indicating the amount of lacking Height shortage more than 30 cm NoDataheight to safeguard the Insufficient data to quantifysurrounding area
21. 21. http://twitter.com/#!/XanderBakker http://nl.linkedin.com/in/xanderbakker Xander Bakker Senior GIS Advisor Xander [DOT] Bakker [AT] Grontmij [DOT] NL http://software.grontmij.nlGrontmij Netherlands BV :: GIS & ICT – GIS Team :: http://www.Grontmij.com :: +31 30 220 79 11