Originally published at: https://emlid.com/single-band-vs-multi-band-how-to-choose-a-receiver-suitable-for-you/
When it comes to choosing the right receiver, it can get tricky. It is easy to get lost in various options and features and get a slight kick into the budget. However, if you know your workflow, you can get a clearer image of what kind of receiver you need for your particular case.
Before we proceed with options for existing receivers, let’s take a brief look at the way GNSS receivers work.
The main idea behind the GNSS receiver work is, logically, receiving signals from satellites. Each satellite transmits radio signals in one or more frequency bands. Satellites in different constellations use different frequencies.
In the main, all receivers can be divided into two categories: single-band and multi-band. The core difference is that single-band receivers only work with one frequency, while multi-band receivers fetch several frequency bands.
Single vs Multi: What’s the Difference
Getting slightly ahead of ourselves, let us say that in this case, “the more, the better” motto is an uncompromising solution. It means that the multi-band receiver is, in general, easier to use, as it has fewer limitations in its operation. However, your specific project and your budget have the last word—multi-band receivers are more costly than single-band ones.
So, the main difference between single-band and multi-band receivers is the number of frequencies they can work with. Other differences technically are the consequences of it.
RTK Initialization Time
Several factors affect the time required to obtain a fix. This is where the number of tracked frequencies matter.
A multi-band receiver is capable of finding a fix solution much more quickly. Since multi-band receivers can work with more than one frequency band, they can use more satellite signals to establish the fix solution. The more signals that are available, the less time is needed to obtain the fix. TTFX for Reach RS2 is ~5 seconds.
Single-band receivers require more time since they can only process one kind of frequency—the L1 frequency. Reach RS+ needs a few minutes to get a fix solution. It doesn’t mean you need to wait for several minutes every time you collect a point. This time is only required at the beginning of the survey or in the case where the fix solution was lost.
For different projects, you might need a different distance from the rover to the base. Working near a city, you are more likely to have a base nearby. However, if you mostly work in rural areas, base stations are likely to be further away.
Multi-band receivers can work at a longer baseline. Reach RS2, as a multi-band receiver, can operate with the baseline up to 60 km for RTK, while Reach RS+ single-band receiver’s baseline is limited to 10 km in RTK mode.
Both single-band and multi-band receivers are capable of cm-level absolute accuracy. The main difference is that more factors can influence the stable fix solution in the single-band receiver. Thus, when using a single-band receiver, you can obtain the same absolute accuracy, but only if you have reasonable working conditions.
Sky View Conditions
In the case of a blocked sky view, the more signals, the better, meaning the more signals you can catch, the sooner you get the fix solution. Due to their ability to process several frequencies and mitigate the multi-path impact, multi-band receivers can keep the reliable fix solution even in urban areas.
Single-band receivers need the open sky to work their best. Otherwise, it might be harder and take longer to establish a fix solution.
Which One to Choose
The ultimate factor that influences your choice of the receiver is the type of project you have and your budget. Both single-band and multi-band receivers obtain the same level of accuracy in their perfect conditions – so, first of all, you need to analyze your case.
Single-band receivers are perfect for working in the field with shorter baselines and a clear sky view. Say, you’re working in agriculture and you need to divide your field into equal sectors or determine the position for trees in an orchard-to-be, a single-band receiver is enough. They also make a great base for PPK or drone mapping. For example, a single-band Reach RS+ receiver was used to set the ground control points for a drone in creating an avocado orchard. Moreover: in this case, Reach RS+ helped to stake out each tree’s position in the orchard-to-be.
Multi-band receivers make a perfect fit for PPP, such as OPUS or NRCan, and high-accuracy surveying in tougher conditions. If you’re working in the city and you have a longer baseline, or the base station is too far, plus you want the job to be done fast, a multi-band receiver is your choice. It gets the fix solution faster despite the possible obstacles and distance from the base.
Choosing Reach for Your Application
Emlid offers single-band and multi-band receivers: RS+ and RS2. Both these receivers obtain the same level of cm accuracy. Reach RS+ and RS2 are suitable for working in bad weather conditions: whether it’s -20º C or showers, Reach won’t let you down. Both receivers have LoRa radio available for transmitting and receiving corrections.
However, Reach RS2, besides being a multi-band receiver, also has a SIM-card slot, which means it can work with NTRIP though the 3.5G modem. In general, Reach RS2 is considered to be more advanced and designed for professional applications.
Compare the two options side-by-side based on the main technical parameters and choose the one that suits your particular case better.
Side-by-side comparison of Reach RS+ and Reach RS2
Highlighting the Core
When selecting the right type of receiver, it is easy to get confused. It’s too scary to end up with an under-featured device, but you also don’t want to spend twice your budget on features you don’t need.
In the majority of cases, the single-band receiver is enough to perform an accurate survey and collect reliable data. It also helps you save yourself a penny budget-wise. However, if you are not sure your working conditions will be perfect or you simply don’t want to worry about possible technical limitations, stick to the multi-band receiver. It will be a more reliable option.
If you have any questions or still have doubts about whether you need a single-band or multi-band receiver, do not hesitate to contact the Emlid Support Team. We’ll answer your questions within one working day.