Hamilton County Enhances GIS Base Mapping with 1-foot Contours

Transcription

1 Hamilton County Enhances GIS Base Mapping with 1-foot Contours Presented by Larry Stout, Hamilton County GIS Manager Brad Fugate, Woolpert Inc. Today s Presentation Hamilton County s 2004 Base Mapping Project Why LiDAR? What is LiDAR? Performing QA/QC: LiDAR Imagery: Color vs. Black and White Contours: 1 foot vs. 2-foot How the 2004 Base Mapping data can be used to enhance the County s GIS 1

2 Hamilton County GIS Policy Committee Barry McNulty Health Department Administrator BJ Casali - Information System Services Director Christine Altman Commissioner Chuck Kiphart - Plan Commission Director Debbie Folkerts Assessor Doug Carter Sheriff Jim Neal - Highway Engineer Judy Levine Councilor Kent Ward - Surveyor Robin Mills Auditor 1996 to 2001 Base Mapping Projects County Wide Black and White Digital Orthophotos 1 = 100 scale at 0.5 foot pixel resolution County Wide Digital Terrain Model (DTM) 2-foot contours County Wide Planimetrics Roads, Hydro, Building Footprints 2

3 Project Needs Assessment for 2004 Auditor Tax Mapping County & Township Assessors Property Assessment Health Department Well, Septic, and Vector Control Highway Engineer - Road, Bridge, and ROW Planning Commission - Community Development Sheriff E911 Addressing Surveyor - Drainage responsibilities GIS - Data Design, Maintenance, and Distribution Determined the need for new Color digital orthophotography and DTM with an increased accuracy Base Mapping Project New Color Digital Orthophotos o 1 = 100 scale County wide at 0.5 foot pixel resolution New County Wide Digital Terrain Model (DTM) o 1-foot Contour Generation Planimetric Features o Update Building Foot Prints o New 3-D hydro Water modeling Complete Connectivity Direction of flow Accurate elevations 3

4 How can we improve base mapping accuracy, and speed delivery while maintaining our budget? New advancements in technology since 2001 should provide a solution. Aerial Photography - Large Format Digital Cameras will provide an advantage, however they have just become available and beginning to be implemented. Digital Orthophotography Technology - has not seen dramatic improvement since 1996, however color imagery cost have become more affordable. DTM Acquisition - LiDAR a recent technology, claiming to produce an accurate surface model at a significant cost savings over traditional methods. LiDAR Research GIS, Photogrammetry, and Surveying publications had recently featured LiDAR GIS conferences and Seminars where presenting LiDAR workshops and presentations Many GIS vendors where providing LiDAR services Checked references of public and private organizations who obtained LiDAR After many inquiries, the county decided to use LiDAR to create our DTM. However, with all new technology you need confirmation that it can fulfill its promises: o Produce an accurate surface model o Provide a significant cost savings over traditional methods o Faster than traditional methods 4

5 What is LiDAR? Light Detection and Ranging Laser Scanner Mounted Vertically in Aircraft Integrated with Airborne GPS Captures Digital Terrain Model (DTM) Captures an extremely accurate DTM in almost any field condition Not only captures a 3-D model of the surface, but of vertical structures as well, such as, vegetation, buildings, and other structures What Equipment is Needed? Aircraft with Airborne GPS LiDAR unit with IMU (Inertial measurement unit) GPS base stations Data Acquisition hardware and software Post processing hardware and software And a lot of computer storage space 5

6 What is the Process? Cessna 404 Gathering Data Factors to consider How will the data be used? Contour generation,water modeling-flood plane, engineering,volumetric computations Accuracy Vertical accuracy of 1.0 Terrain Type Low, medium, high vertical relief and land use Woodland, cropland, wetland, urban, suburban Schedule How quickly can we deliver the orthophotos? 6

7 Hamilton County, Indiana Region - Central Indiana Size 400 Sq. Miles Terrain Type 3/4 low vertical relief 1/4 medium vertical relief Land Use 1/2 crop land, 1/4 woodland and 1/4 urban Major Cities Noblesville, Carmel, Fishers Several major lakes, rivers, and tributaries Hamilton County, Indiana 7

8 Aerial Photography LiDAR Flight Plan 8

9 LiDAR Supported Compilation Set Stereo model LiDAR Supported Compilation Compile Planimetric Data 9

10 LiDAR Supported Compilation Input LiDAR Data Perform QA/QC Compile limited breaklines LiDAR Compilation Generate Contours 10

11 LiDAR/DTM/Contours Deliverables Raw LiDAR Data Bare earth model Vertical Canopy model Stereo compiled DTM data QA/QC d LiDAR mass points Breaklines Contours and Spot Elevations 1-foot cartographic contours and labels Published Spot Elevations Quality Control and Quality Assurance Using a systematic approach to perform Quality Control to the LiDAR/DTM/Contour data 11

12 Field Survey Test Points Follow FEMA guidelines for Field Testing. Direct Point Comparison Provide a minimum of 20 test points for the following Land Use Classifications o Bare Earth and Low Grass o High Grass, weeds, and crops o Brush Lands and low trees o Urban Areas o Forested Bare Earth and Low Grass 12

13 Point Comparison Results LiDAR vs. Field Survey Points +/- 0.4 Deviation High Grass,Weeds, and Crops 13

14 Point Comparison Results LiDAR vs. Field Survey Points +/- 0.4 Deviation Brush Lands and Low Trees 14

15 Point Comparison Results LiDAR vs. Field Survey Points +/- 0.5 Deviation Urban 15

16 Point Comparison Results LiDAR vs. Field Survey Points +/ Deviation Forested 16

17 Point Comparison Results LiDAR vs. Field Survey Points +/- 0.4 Deviation Point Comparison Results LiDAR vs. Field Points +/ Deviation 17

18 LiDAR Data DTM Data 18

19 LiDAR Contours vs. DTM Contours LiDAR/DTM/Contour QA/QC Results Field Test Points vs. LiDAR Field Test Points vs.dtm/breaklines Field Test Points vs. Contours/Spots +/ at 90% confidence level 19

20 2 Foot Contours 1 Foot Contours 20

21 1 Foot vs. 2 Foot Contours B/W vs. Color Imagery 21

22 Black and 0.5 foot pixel 0.5-foot pixel 22

23 Planimetrics: 3-D Hydrology Water Modeling Complete Connectivity Direction of flow Accurate Elevations How the data will be used GIS - accurate base map for county GIS applications, such as parcel mapping, addressing/911, incident mapping, etc. Engineering - produce a surface model capable of contour generation for engineering applications, such as design and construction. 23

24 How the data will be used Planning - use orthophotography as base map instead of using traditional renderings. Orthos bring accuracy to the concept - and the image itself enhances visualization of the concept. Augment this by bringing in captured vertical heights and you have 3-D planning in a spatially correct environment. Transportation - use digital imagery as a base map for route selection, feasibility studies and design. Need to generate contours for grading plans, cut and fill calculations, and infrastructure plan and profile sheets. How the data will be used Water Management - use the new surface model for water modeling and watershed analysis. Reduce the need for field surveyors to manually collect cross-sections on rivers, streams and tributaries. New surface model to determine the floodplain, flood hazards, and impact zones. Airport Facilities need ground and the non-ground model to obtain heights on vertical obstructions. This is essential for determining the slope mapping for approach and departure zones. 24

25 LiDAR Shaded by Elevation Orthophoto Draped On LiDAR 25

26 Questions? 26