Specifications include, but are not limited to: a. Six (6) modular multiple frequency survey grade (8 mm +1ppm RTK and 3 mm +0.5 ppm static horizontal accuracy) GPS/GNSS (L1/L2/L2C/L5) receivers with all available channels (500+) and signal tracking capabilities for GPS/GLONASS/Galileo/Beidou constellations, internal digital UHF tx/rx radios (440-470 MHZ frequency range and a minimum of one (1) watt output power), & internal cellular modem (Verizon). Internal radios shall have a capability to broadcast corrections from a base position to rovers situated up to 1 mile away, under normal conditions. Receivers must also have USB and RS232 serial ports for data download and configuration. b. One (1) battery chargers for each GPS receiver. c. Two (2) spare batteries for each receiver.