Smart networks of autonomous in-situ soil sensors

Abstract

The article describes a modern system of control and communication integrated in an in-situ soil sensor to make it autonomous in operation, energy and data transfer at low cost. Network of such sensors can monitor continuously soil moisture over a catchment with low maintenance. A recent industrial standard of radio communication, Long Range Wide Area Network (LoRaWAN) is presented. It permits rapid deployment of a sensor in a remote observatory, and the transfer in real time of sensor data to a central web-accessed database, via a LoRaWAN receiver, or gateway, 12 km away. In this situation transmission loss can reach a rate of 30%. Good quality antenna can lower it below 5% without extensive cost. Double messaging and other transmission algorithms are a possibility, taking into account consumption. Currently, sensors measuring one point every ten minutes can last seven months with four cheap AA alkaline batteries. Further gains would increase lifetime in same conditions by 30%.

Keywords:

• autonomous in-situ soil sensors
• information and communication technology
• Long Range Wide Area Networks (LoRaWAN)
• battery
• energy consumption
• web-accessed database

Acknowledgements

We are grateful to engineers of Live Objects, in particular Mr L. Chivot, and those of Objenious to help us to set up our prototypes in their respective LoRa network, and to give useful information on their functioning. We are equally grateful to Mr S. Klotz of INRAE, supervisor of Draix observatory in French southern Alps.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work is supported in part by the grant ANR11EQPX0011 of the Agence Nationale de la Recherche allocated to the program “Critex”—Challenging equipment for the temporal and spacial exploration of the Critical Zone at the catchment scale—(20 March 2013). It won the calls to submit projects for the “2012 Facilities of Excellence” competition named Equipex. The program Critex is a French national project, which groups together 21 laboratories from more than 20 universities and four research organizations. It will allow the study of surface and underground water relating to the characteristics of the natural environment and surrounding human activities. It will thus contribute to a better management of water resources in varied contexts. IPGP contribution number