GB/T 33988-2017 in English

1. Standard Overview

GB/T 33988—2017 specifies the spectral reflectance measurement requirements for urban objects in the visible-shortwave infrared wavelength range ($380\mathrm{nm\sim2500\mathrm{nm}$), including measurement conditions, basic measurement requirements, special measurement requirements, measurement records, measurement result processing and measurement summary. This standard is applicable to the spectral reflectance measurement of typical objects in urban areas that have been developed and utilized as non-agricultural land.

2. Measurement conditions

3. Measurement technical requirements

The measurement process includes measurement preparation, measurement implementation and data recording. The installation and parameter setting of the spectrometer must ensure that the observation field covers the ground object and is unobstructed. The standard reference plate should be placed horizontally and as close to the ground object as possible.

4. Data processing and quality control

The measured data must be screened and calculated to ensure that abnormal data is eliminated. The calculation formula of spectral reflectance is: $$\rho(\lambda,\theta,\varphi,\theta_{0},\varphi_{0})=\frac{L(\lambda,\theta,\varphi,\theta,\varphi_{0})}{L_{\mathrm{s}}(\lambda,\theta,\varphi,\theta_{0},\varphi_{0})}\times\rho_{\mathrm{s}}(\lambda,\theta,\varphi,\theta_{0},\varphi_{0})$$where $\rho$ is the spectral reflectance (%) and $L$ is the reflected radiance.

5. Implementation Suggestions

In order to ensure the accuracy of the measurement results, it is recommended in actual operation:

• Regularly calibrate the spectrometer and standard reference plate.
• Record detailed weather conditions and surrounding environment information.
• Choose appropriate measurement methods for different types of objects (such as buildings, vegetation, and water bodies).
• Ensure that the battery of the measurement device is fully charged to avoid performance changes during transportation.