What is a fixed solution?


I recently conducted a lab in my surveying course using Emlid Flow and had a few questions that I would be grateful if someone could assist me with them. Firstly, could you clarify the concept of a “fixed solution” for a point? What does it really mean? Additionally, I’m curious about methods to guarantee that all the data points I gather are fixed. Any insights would be greatly appreciated. Thank you.

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RTK uses a complicated mathematical formula or algorithm to calculate the exact number of radio wavelengths between the satellites and the base station antenna – a process known as ambiguity resolution – and yield either a fixed or float solution. In a fixed solution, the number of wavelengths is a whole number, or integer, and the algorithm is constrained to yield a whole number.

In practical use there is a source of corrections usually called a base station that has an established position that feeds these messages to a rover which can be another receiver or something like a drone. The two ends need to have enough satellites in common and a good connection to achieve and maintain a good fixed solution. There are different factors that can interrupt this communication depending on whether you are doing local radio or network (NTRIP).

Radios are susceptible to interference, distance restrictions and line of sight whereas NTRIP is subject to data connectivity. We typically use radio only when we have can have good LOS and baselines shorter than 10,000ft and the drones always use local NTRIP which means it is either connecting directly to the base or networked through a local hotspot like your phone. This method is restricted by the distance of the Wi-Fi connection but 99% of the time I have a special point set feet away from where I am operating.


Thanks Michael, that was pretty helpful.


Hi @absolute,

Welcome to our community!

The solution of your position is about how the ambiguities are resolved in calculating the position. Based on this, you can obtain a SINGLE, a FLOAT or a FIX solution.

As Michael said, if you use a base station, it can stream corrections to your receiver via radio or the Internet to help you obtain a FIX solution. If the conditions are proper, there are enough satellites in view, and all the ambiguities are resolved, you’ll be able to get a FIX solution - equal to centimetre accuracy.

If you have a plan for your survey, feel free to share it, and I can help you with the necessary steps to obtain a FIX solution.