Chapter 5 Field Data Introduction to Remote Sensing

Outline § Introduction § Information of field data § Field radiometry § Tutorial/demonstration of

Introduction § Field data • Necessary for remote sensing v. Establish relationship between ground

Information of field data § Attributes/measurements of ground conditions • Nominal data ve. g.

Field radiometry § Handheld spectroradiometer • Constitution (Fig 1. 14 a or see Campbell

Tutorial/demonstration of handheld spectroradiometer § Software installation § Hardware installation § Calibration § Data

Basic radiometric quantities and definitions § § § § § Spherical coordinate Measurement of

Locational information § Observations need locational information § Method • Reference to distinctive landmarks

Global Positioning System § Satellite § Orbit § Working principle § Receiver § Accuracy

Geographic sampling § Terminology • Observation • Sample § Three considerations • Number of

Geographic sampling (cont. ) § Number of observations • The larger the sample size,

Homework § We are going to employ the handheld spectroradiometer and GPS receiver to

Homework (cont. ) § The reflectance of a standard white board is given in

Fig 2. 3. 1 Fig. 2. 3. 1 Definition of the polar coordinates (q,

Fig. 2. 3. 2 Schematic design of an instrument for measuring un-polarized spectral radiance.

2. 3 Basic radiometric quantities and definitions (cont. ) § Radiance L:

Fig. 2. 3. 3 Schematic design of an instrument for measuring un-polarized spectral downwelling

2. 3 Basic radiometric quantities and definitions (cont. ) § Downwelling planar irradiance Ed:

Fig. 2. 3. 4 Schematic design of an instrument for measuring un-polarized spectral downwelling

2. 3 Basic radiometric quantities and definitions (cont. ) § Downwelling scalar irradiance E

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

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

Introduction § Field data • Necessary for remote sensing v. Establish relationship between ground truth and imagery v. Validation v. Evaluation • Expensive • Purpose-oriented v. Content v. Method

Information of field data § Attributes/measurements of ground conditions • Nominal data ve. g. crop identification, land use, … • Biophysical data v. 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

Field radiometry § Handheld spectroradiometer • Constitution (Fig 1. 14 a or see Campbell 2002 Fig 124) v. Pointing device v. Fiber-optical cable v. Measuring unit Ø Detector Ø Filter v. Display unit v. Data log • Measurement v. Radiance v. Reflectance

Tutorial/demonstration of handheld spectroradiometer § Software installation § Hardware installation § Calibration § Data log § Data processing § Implementation • (Fig 1. 14 b and Fig 1. 15, or see Campbell 2002 Fig 12 -9)

Basic radiometric quantities and definitions § § § § § 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 reflectance R = Eu/Ed Definition of remote sensing reflectance Rrs =Lu/Ed

Locational information § Observations need locational information § Method • Reference to distinctive landmarks v. Valid for well-mapped regions • Global Positioning System (GPS)

Global Positioning System § Satellite § Orbit § Working principle § Receiver § Accuracy • Selective availability (SA)

Geographic sampling § Terminology • Observation • Sample § Three considerations • Number of observations • Sampling pattern • Spacing of observations

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

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

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. Table 1 Table 2 Wavelength (nm) 400 450 500 550 600 650 700 Reflectance 0. 455 0. 458 0. 461 0. 464 0. 467 0. 471 Wavelength (nm) 400. 26 450. 33 500 550. 23 600. 21 650. 19 700. 04 White board 352. 265 838. 265 2607. 952 2902. 265 2397. 952 1751. 952 1015. 265 Sample 12. 934 29. 934 84. 929 254. 934 124. 929 56. 929 91. 934

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Fig 2. 3. 1 Fig. 2. 3. 1 Definition of the polar coordinates (q, f) and of the upward (Xu) and downward (Xd) hemispheres of directions. Reprint from Figure 1. 3 in (Mobley 1994).

Fig. 2. 3. 2 Schematic design of an instrument for measuring un-polarized spectral radiance. Reprint from Figure 1. 5 in (Mobley 1994).

2. 3 Basic radiometric quantities and definitions (cont. ) § Radiance L:

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).

2. 3 Basic radiometric quantities and definitions (cont. ) § Downwelling planar irradiance Ed:

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).

2. 3 Basic radiometric quantities and definitions (cont. ) § Downwelling scalar irradiance E 0 d: