# Landsat Surface Product Validation Instrumentation:
## 7 Summary/Conclusions/Path Forward
### Conclusions  
BigMAC was conducted with the specific purpose of understanding how various surface reflectance and temperature measurement methodologies might be used to monitor surface reflectance/temperature in an operational manner to validate Landsat surface temperature and reflectance products. In particular, our study emphasized accuracy, precision, and deployability.  
A large aspect of the campaign was the evaluation of handheld portable spectroradiometers that are normally deployed via a small team of people. Results from BigMAC are similar to those obtained in other campaigns [14; 15]. From the perspective of accuracy and precision of measurement, this approach to surface reflectance has become a recognizedstandard in the community with regard to field campaigns. However, the deployability of this methodology remains expensive, requires multiple personnel, and can be quite time consuming.  
UAS-based measurements of the surface reflectance were hampered by the target size in the BigMAC campaign, and due to the traceability of their calibration, the exhibited accuracy and precision predictably were slightly lower compared to the ground-based spectroradiometer method. Additionally, deployability typically involves several personnel and often has trailer-sized transportation requirements.  
Thermal instrument accuracies of 1 K were obtained with the UAS/FLIR combination over land, as well as with the water-based TidbiT instruments. These are with respect to the \(\mu\)FTIR, with a laboratory-tested accuracy of 0.5%. Both of these methodologies are more than adequate with respect to accuracy for the validation of surface temperature products. However, deployability is substantially different: UAS deployment involves teams of people as well as support equipment, while TidbiTs can be left in a water environment for months unattended. However, additional data would be needed to fully understand the relations between water temperature measured by the TidbiT and surface temperatures of water recorded by a satellite-based instrument.  
The MELM results show that this methodology can produce the repeatability and accuracy needed for surface reflectance product validation, as was demonstrated over a distance of several kilometers. However, further studies are needed to ensure that mirrors are properly designed and deployed and background subtraction is properly completed before the MELM is fully operational for validating surface reflectance products. Portable mirror systems are currently being designed and developed to address these issues.  
The Arable Mark 2 radiometer can be used in conjunction with ground truth information to validate surface reflectance products. Two years of deployment by SDSU have demonstrated that the Arable Mark 2 radiometers can be fully automated in all but the most extreme environments; they are not able to withstand the extreme cold in South Dakota winters. However, they appear to be stable, characterizable instruments that can provide highly repeatable measurements with traceable accuracy over the course of a growing season with minimal maintenance through the visible and near infrared wavelength range.