Download our Network NTRIP Caster ​​

New version
Now reassembles partial TCP data from bases
Fixed crash in



Advanced Tech Specs
Back 40’s caster program uses a proprietary algorithm to calculate multi frequency code and phase measurements to create an accurate model of the current ionospheric layer. The majority of the systems in ag only calculate to the first order. Back 40 stands out as being the ONLY company that has integrated 2nd and 3rd order error terms. This innovative breakthrough significantly reduces range error during high solar activity.
During average solar activity 2nd and 3rd order terms are negligible and account for less than a few millimeters of error. However, during solar flares the second and third order terms, when left unaccounted for, can add up to 25 cm additional error.
Our reference stations exclusively use the most up to date technology. 
Back 40 currently utilizes the following signals:
GPS                      L1            CA & P
                             L2            P & C
                             L5            I
Glonass                L1            C & P
                             L2            C & P
Beidou                  B1            I              
                             B2            I
                             B3            I
Satellite Range Measurement Resolution:    1 mm
Data Output Accuracy Filter Rating:              3 Sigma
Available DataStreams from Caster:
Manual Selected Single Baseline: Selected by the user
Automatic Selected Single Base: Caster finds the closest base to the user
Individualized Master Auxillery Concept Network: Network bases are used
to correct for ionospheric effects at the user's actual reported location.
Master Auxillery Concept Network: Caster sends data from the Master Station
and the differences between several Auxillery bases and the
Master station measurements.
The images below are recorded positions called a "scatter plot" of various correction data stream types. These were recorded
in "REAL WORLD" circumstances. All three plots were recorded at the same location. The location was chosen to illustrate the differences. The closest reference station was 44.3926 miles away. The antenna was mounted on a vehicle parked close to a brick building. The parking lot was flanked on both sides with trees. There was a metal roof structure behind the vehicle. These factors combine to produce realistic partial shading and increased multipath error potential.
The left scatter plot was using "single baseline". Over half of the points were within 4cm the remaining points were within 6cm. This is equivlent to being within 2.5" repeatable.
The center scatter plot is iMAC (individualized MAC). This version receives modified messages from the "master" or closest station. All of the points remained within 2cm. This remained sub-inch horizontal position.
The right scatter plot is MAC (master auxillery concept). All of the points remained within 2cm. Upon close inspection it is found over half of the points remain within a 1cm circle. The majority of points remained within a 1/2" circle.
This test was performed with a Raven IndustriesTM, Phoenix 300 rover receiver. This unit uses a NovatelTM OEM628 GNSS processor inside. The antenna was a dual frequency Maxtenna minture helix antenna. Correction data types were transmitted over internet. For single baseline and iMAC streams the following message types were transmitted: RTCM3.1 1004, 1012, 1005, 1008, 1013. For the MAC datastream the following messages were sent: RTCM3.1 1004, 1012, 1017, 1039, 1005, 1008, 1013, 1014.
single baseline