1. Field Data Introduction to Remote Sensing Instructor: Dr. Cheng-Chien LiuCheng-Chien Liu Department of Earth Sciences National Cheng Kung University Last updated: 27 October 2004 Chapter 5

2. Outline  Introduction  Information of field data  Field radiometry  Tutorial/demonstration of handheld spectroradiometer  Basic radiometric quantities and definitions  Location information  Tutorial/demonstration of handheld GPS  Geographic sampling

3. Introduction  Field data Necessary for remote sensing  Establish relationship between ground truth and imagery  Validation  Evaluation Expensive Purpose-oriented  Content  Method

4. Information of field data  Attributes/measurements of ground conditions Nominal data  e.g. crop identification, land use, … Biophysical data  Moisture content, Leaf area index (LAI), … Radiometry data  Location and size  Time and date  Ancillary data Weather, illumination, calibration of instrument, persons who collect data

5. Field radiometry  Handheld spectroradiometer Constitution (Fig 1.14a or see Campbell 2002 Fig 12-4)  Pointing device  Fiber-optical cable  Measuring unit  Detector  Filter  Display unit  Data log Measurement  Radiance  Reflectance

6. Tutorial/demonstration of handheld spectroradiometer  Software installation  Hardware installation  Calibration  Data log  Data processing  Implementation (Fig 1.14b and Fig 1.15, or see Campbell 2002 Fig 12-9)

7. Basic radiometric quantities and definitions  Spherical coordinate Spherical coordinate Spherical coordinate  Measurement of radiance L  Definition of L  Measurement of planar irradiance E  Definition of E  Measurement of scalar irradiance E 0  Definition of E 0  Definition of reflectance R = E u /E d  Definition of remote sensing reflectance R rs =L u /E d

8. Locational information  Observations need locational information  Method Reference to distinctive landmarks  Valid for well-mapped regions Global Positioning System (GPS)

9. Global Positioning System  Satellite  Orbit  Working principle  Receiver  Accuracy Selective availability (SA)

10. Geographic sampling  Terminology Observation Sample  Three considerations Number of observations Sampling pattern Spacing of observations

11. Geographic sampling (cont.)  Number of observations The larger the sample size, the closer to the actual values Minimum number assigned to each class  Sampling pattern Simple random sampling pattern Stratified random pattern Systematic patterns Systematic stratified unaligned pattern Cluster sampling  Spacing of observations

12. Homework  We are going to employ the handheld spectroradiometer and GPS receiver to collect field data of vegetation in the watershed of Chen-Yo-Lan River. Please help us to integrate these instruments on (1) Shoulder (2) Suzuki grand Vitara (3) unmanned helicopter

13. Homework (cont.)  The reflectance of a standard white board is given in Table 1. The field measurements of the standard white board and the sample are shown in Table 2, respectively. Please use this information to calculate the reflectance of the sample. Wavelength (nm)400.26450.33500550.23600.21650.19700.04 White board352.265838.2652607.9522902.2652397.9521751.9521015.265 Sample12.93429.93484.929254.934124.92956.92991.934 Wavelength (nm)400450500550600650700 Reflectance0.455 0.4580.4610.4640.4670.471 Table 1 Table 2

14. Source

15. Fig. 2.3.1 Definition of the polar coordinates ( ,  ) and of the upward (  u ) and downward (  d ) hemispheres of directions. Reprint from Figure 1.3 in (Mobley 1994). Fig 2.3.1

16. Fig. 2.3.2 Fig. 2.3.2 Schematic design of an instrument for measuring un-polarized spectral radiance. Reprint from Figure 1.5 in (Mobley 1994).

17. 2.3 Basic radiometric quantities and definitions (cont.)  Radiance L:

18. Fig. 2.3.3 Fig. 2.3.3 Schematic design of an instrument for measuring un-polarized spectral downwelling planar irradiance. Reprint from Figure 1.6 in (Mobley 1994).

19. 2.3 Basic radiometric quantities and definitions (cont.)  Downwelling planar irradiance E d :

20. Fig. 2.3.4 Fig. 2.3.4 Schematic design of an instrument for measuring un-polarized spectral downwelling scalar irradiance. Reprint from Figure 1.7 in (Mobley 1994).

21. 2.3 Basic radiometric quantities and definitions (cont.)  Downwelling scalar irradiance E 0d :