Low-Cost Orthophoto Production Using OrthoMapper Software

Transcription

1 Low-Cost Orthophoto Production Using OrthoMapper Software Rick Day Penn State Cooperative Extension, Geospatial Technology Program, RGIS-Chesapeake

2 Air Photos Historical air photos are available from a variety of sources Very useful to evaluate changes in land use and land cover Georeferencing air photos for use in a GIS can be difficult

3 GeoReferencing Methods Global Least Squares Regression rubbersheeting polynomial transformations control points ArcGIS Georeferencing Local Area triangulation methods control points ArcGIS Spatial Adjustment (vectors only)

4 Air Photo Georeferencing Rubbersheeting and local area methods generally do not accurately align air photos in a GIS..especially in areas of moderate to high relief

5 Spatial Errors In Air Photos Not Critical Earth curvature Radial lens distortion Critical Film deformation Tilt displacement Relief displacement

6 Film Deformation Physical distortion of photo due to stretching and shrinking of film during processing and handling

7 Tilt of Air Photo Tilt of focal plane of camera during flight Three axes of tilt (X,Y,Z) Every photograph different

8 Tilt Displacement Displacement of features on an aerial photograph due to the tilt of the focal plane at the time of exposure Amount of displacement depends on lens position

9 Relief Displacement Displacement of features on an aerial photograph due to topographic relief Amount of displacement depends on lens position Every photograph different

10 Ortho-Rectification Method Adjusts for: Film deformation Tilt displacement Relief displacement By solving for: Interior Orientation Exterior Orientation

11 Interior Orientation Relative orientation of camera focal plane to resulting photograph Determined by measuring coordinates of fiducial points Camera Focal Plane Aerial Photograph

12 Exterior Orientation Orientation of photo at instant of exposure Need minimum of 3 ground control points (GCPs) with known x,y,z coordinates GCPs must be clearly visible on photograph

13 Exterior Orientation Results in equations that can determine photo coordinates for any ground location Need X,Y, and Z (elevation) ground coordinates Digital terrain model used for elevations

14 OrthoMapper Software

15 What do you need? Scanned air photo Camera calibration file, if available Terrain model of photo area Georeferenced imagery of photo area

16 Example State College area Centre County 1938 digital aerial photos USGS 10-m Digital Elevation Model USGS DOQQ imagery

17 Example Data Three 1938 digital air photos obtained from PennPilot (

18 PennPilot

19 Test Sites Pine Grove Mills State College

20 Example Data Pine Grove Mills 10M Terrain Model

21 Example Data Pine Grove Mills DOQQ

22 Step 1: Interior Orientation Digitize fiducial points

23 Step2: Exterior Orientation

24 Control Points

25 Control Points

26 Results: Pine Grove Mills DOQQ

27 Results: Pine Grove Mills 1938

28 Results: Pine Grove Mills 1938 Image DOQQ

29 Results: State College DOQQ

30 Results: State College 1938

31 Results: State College 1938 Image DOQQ

32 Results: State College 1938 Image DOQQ

33 Accuracy Assessment

34

35 Original Photo Deformation

36 THANK YOU VISIT OUR EXHIBIT AREA Rick Day, Director Penn State Cooperative Extension, Geospatial Technology Program, RGIS-Chesapeake