Image Services for Elevation Data

Transcription

1 Image Services for Elevation Data Peter Becker Need for Elevation Using Image Services for Elevation Data sources Creating Elevation Service

2 Requirement: GIS and Imagery, Integrated and Accessible Field Users Decision Makers Analysts Data Managers GIS Actionable information and knowledge Unified geospatial workflows Imagery + + Sensor Networks Knowledge Base Base Maps & Globes Georeferenced Content

3 Uses of Elevation Data As Elevation 3D Visualization Shaded Relief cartographic Aspect Agriculture Slope Land subsidence, off-road mobility analysis Profiles Planning pipelines, drainage Viewshed Visibility analysis Orthorectification Difference/Volume Tree Height Change Ground movement

4 Traditional Elevation Management Analyst work on individual projects Merge together different sources Similar to how imagery was managed

5 Elevation Data Requirements Multiple: Resolution Global to Local Source SRTM to Lidar Format Many formats used Projection Multiple Horizontal and Vertical Datums

6 Sources GTOP 30-arc second (1km) SRTM Shuttle Mission Topography Mission - 3-arc second (90m) ASTER GDEM 1-arc second (30m) NED 1-arc second (30m) & 1/3-arc second (10m) Intermap, SPOT,. Photogrammery Correlation or point capture Lidar Bathymetry Sonar From Contour, vector sources Varying accuracies (VE90 CE90)

7 Demo Using Image services for elevation

8 Formats Irregular LAS ASCII XYZ 3D SHP CAD Gridded TIFF ESRI Grid ASCII DTED IMG JPEG2000

9 LiDaR (Light Detection and Ranging) Laser based High Density, High Accuracy Partially penetrates foliage LAS ASPRS Include classification

10 Terrain Dataset Multi-resolution surface created from measurements stored in feature classesc MassPoints (Lidar), breaklines, spot heights, polygons, Stored in the geodatabase Schema: Defines feature class participation On-The The-Fly TIN Multi-resolution Highly scalable Attributes Editable, Versioned Points and Breaklines Terrain Pyramids High Resolution Medium Resolution Low Resolution

11 Raster / Grid For Elevation Generally a Derivative Advantages Simplest representation Highly scalable Fast access Disadvantages Loss of original point data Require multiple rasters for different classifications, attributes Terrain can be exported as Raster Use Terrain to Raster Consider exporting at multiple pixel sizes

12 No Data Areas Areas with No Valid values Where possible interpolate values Consider Accuracy Implications Clip using Footprints Define as No Data Value Define Mask Selection of Pixels by footprint intersect Selecting of Pixels by Analyzing transparent pixels Profile View

13 Lidar to Raster Conversion Via Terrain Point File Information (Average point spacing) Terrain Wizard With Terrain, holes are filled by TIN Terrain to Raster Interpolate to Raster LAS to Multi-point Point to Raster Set Point Set cell size to 4x avg. point spacing Filter to remove holes Con(IsNULL([inputraster]), FOCALMEAN ([inputraster], RECTANGLE, 3, 3, data), [inputraster]) 3 rd Party Tools Eg LP360 (QCoherent) Considerations Have overlap in tiles (20 pixels) Obtain extents of Lidar

14 Conversion of Raster Conversion sometime required for optimization Optimal format TIF LZW compressed, 16 or 32bit Internal overviews or.ovr ArcGIS Copy Raster GDAL (FWTools.org) GDALTranslate -of Gtiff -co COMPRESS=LZW -co PREDICTOR=2 input output.tif GDALAddo -r r average --config COMPRESS_OVERVIEW LZW --config USE_RRD NO --config PREDICTOR 2 output.tif

15 Image Services Optimized Access to Imagery New at ArcGIS Server 9.3 Serves all supported raster data (TIF, IMG, MrSID, ) Web accessible via SOAP, REST, OGC (WMS, WCS, KML) Accessible as image and pixel values Server side rendering enables, client definition of: Projection Compression for transmission Sampling methods Can be used to serve elevation data

16 ArcGIS Server - Image Extension Extends ArcGIS Server for Large Numbers of Images Manage large collections of images Provide single point of access Dynamic mosaicking On-the the-fly processing Maintain source information for every pixel Simplified data management Combines processing with serving Keep imagery in native form Author service definition (catalog) Properties and processes Publish as Image Service Client controllable properties Use Serve Author ArcGIS Server Image Extension Service Definition Service Definition Service Definition

17 Dynamic Mosaicking Fuses images as they are accessed Resolves Issues with Traditional Image Management Processing Time Time consuming Overlapping Imagery Loss of information Disparate Datasets Large NoData areas t1 t2 t3 t4 t5 Additional Storage Mosaicking requires storage Multi-resolution Data Need to sample up or down Maintenance Difficulty making changes Loss of Image Quality Sampling degrades quality Loss of Metadata Valuable information Very applicable for Elevation Data

18 On-The The-Fly Processing Create Multiple Products from a Single Source Processing can be applied to raster or service level Processes Enhance Extract Bands Orthorectify PanSharpen Vegetation Index Classify Shaded Relief Crop to Footprint Visualize Elevation... Enable the creation of derived products with no additional storage or pre-processing processing

19 Using Image Extension with Elevation Data Create Single Image Service Of all raster Elevation Sources Multi-Resolution Create Derived Service that define multiple products Slope Aspect Shaded Relief Hill Shade Accessible to a wide range of applications Usable in GeoProcessing

20 Considerations when Creating Services Possibly Optimize Imagery Do NOT Reproject or sample data (will be done OTF) Recompute footprints to remove NoData Use Calculate to Set MinPS and MaxPS Use DispOrder or SysOrder to force order Consider location of processes Use Edit Raster Properties Consider adding attributes to define accuracy

21 Demo Create Image Service Definition from GTOP SRTM NED 30m NED 10m Rasterized Lidar Data

22 Creating Derived Services Enable Multiple Service from same source Enables rendering: EG for WMS Enables high compression for transmission Simplifies data management Use SaveAs, or reference using ISRefs Developer can use client defined processes

23 Using Multiple Services Height = (First Return Bare Earth) Correct Geoid

24 GeoProcessing In ArcGIS Desktop Export AOI at required resolution In Geoprocessing Tools Use Make Image Server Layer

25 9.3.1 Limitations With Image Services Transparency of No Data not handled well Use footprints Black lines at edges of export with focal processes Source Vertical Datum Different renderer then ArcGIS Solution: Use as Layer on ArcGIS Server

26 ArcGIS 10 Improvements for Imagery and Elevation Management Mosaic Dataset Stored in GeoDatabase Access More formats Improved No Data Support Image Analysis Window Access OTF processing in Desktop Spatial Analysis Direct use of multiple formats Improved speed

27 ArcGIS The Platform for Fully Integrated GIS and Imagery Integrating Imagery as core to GIS Management, Dissemination, Visualization and Analysis Solution for wide range of user requirements Maximizes the value of imagery including Imagery Single Source for all elevation Multiple Products from a single source Maintainability GIS + +

28 Learn More Instructor-Led Training Introduction to ArcGIS Server Image Extension ArcGIS Server: Web Administration Using the Microsoft.NET Framework Free Web Training Seminar Serving and Managing Imagery with ArcGIS ESRI Training keep critical skills up to date