How does GPS work and what GPS signal fits my operation?
How does GPS work?
Our Precision Farming Systems use the USA satellite system to operate tractors, sprayers, combines and other implements in the field. In addition to the USA satellite system we can view other satellite systems for example Russian (Glonass), Galileo and BeuDou. Not all receivers are able to view multiple satellite systems. Within the US satellite system, we can read multiple signals per satellite. We can read L1, L2 and L5 signals. The more signals per satellite we can read and the more satellites we have in view allow us to maintain our signal longer. Maintaining GPS signal is key to reliability while in the field, which is what our receivers excel at.
We need 5 satellites to receive our initial correction signal and need to maintain at least 4 satellites to continue to operate in the field. We also need to maintain our correction signal.
The correction signal allows you to operate within inches of accuracy or down to 1-inch accuracy while in your fields. The closer the correction signal is to your farm the more accurate you can be with your GPS system. The correction signal can be delivered different ways to your GPS receiver. What correction signal you are on determines the accuracy you are operating at while in your fields. The WAAS correction signal is a satellite delivered correction signal. Your antenna needs to be able to view the WAAS satellite which is over the equator. The PLM RTK+ correction signal comes from a Base Station at our store location that is connected to the internet and is downloaded to your tractor over the internet. In our area where ever we have cellular data coverage we can have a PLM RTK+ correction signal. Verizon has proven to have the most reliable coverage in our area and we sell them at our store. We use a modem to download the PLM RTK+ correction signal to the GPS display or now a device with a data plan and hot spot ability.
Having the internet in the Tractor cab gives you your RTK correction signal as well as allows for remote diagnostics and data transfer wirelessly to your personal devices or home computer.
What GPS signal fits my operation?
With the different GPS signal options which signal will work for you? What do you want to use GPS for in the field will help determine which signal will work for you. As you have seen above you have pass to pass and repeatable accuracy. As you increase accuracy up to RTK the pass to pass and repeatable accuracy get more accurate.
Operations in the field like mowing hay, spraying, yield mapping, tillage and spreading fertilizer maintaining a few inches pass to pass accuracy will work. Terrastar L, Rangepoint RTX and WAAS will work well for these operations. Terrastar L and Rangepoint RTX have proven to be very reliable and run at a higher accuracy than WAAS. Terrastar L, Rangepoint RTX and WAAS are all satellite 7500 GPS Receiver 6000 WAAS Receiver Nav. 900 GPS Receiver Nav. 500 WAAS GPS Receiver delivered signals. Terrastar L and Rangepoint RTX do not have as much drift in your guidnace lines like WAAS does. Note that Terrastar L and Rangepoint RTX use multiple signals per satellite and use multiple satellite constellations.
Operations in the field like planting corn, strip tilling, tramlines and drilling the PLM RTK+ signal gives the highest repeatable accuracy. Pass to Pass and Year to Year your guidance lines are with and inch.
The higher the level of accuracy the more overlap is eliminated which is your return on your investment by saving you inputs in time, seed and seed placement and fertilizer.
For our tiling systems RTK with a base station is the most accurate for vertical GPS accuracy.