Distributed sensing systems are spatially distributed autonomous sensing  devices  for  environmental  observation purposes  in large areas. In recent years, the innovation of embedded sensing devices and  wireless  communication  have  been  developed  rapidly.  It allows  for  improving  the  capability  of  processing  and  reducing energy  consumption  for  a  long  time,  wireless  sensor  networks (WSNs)  in  order  to  meet  a  wide  range  of  applications.  Besides wide-range coverage, LoRa technology also provides the benefits of low power consumption, scalability and interference immunity for wireless links. This paper proposes a support tool for the rapid deployment  of  large  scale  distributed  sensing  systems  based  on LoRa technology.  The  major  motivation behinds this work is to help designer select the proper set of parameters for improving the performance  of  LoRa  systems  taking  into  account  the  strong impact of geographic topology. The experiments on a star LoRa network  for  environmental  data  dissemination  was  done  to evaluate the effectiveness of the tool on the reduction of packet transmission time, known as time-on-air (ToA).