Coverage maps (or signal maps) are graphical interpretations of some networks expected coverage area. The map is made utilizing information such as transmitting power, geographical formations and used technologies. Because nearly all such maps are just computer generated models which do not for instance include radio weather or other such things, these maps are not 100% reliable and should be used for reference in determining whether or not an area has correct coverage in the location you seek.
Operators use the marketing term 4G for the new LTE (Long Term Evolution) network. Sometimes 4G might also be used to refer to 3G's newest technology, DC-SHPA (normally they are 3G Dual Carrier). ITU's (International Telecommunication Union) original definition defines that 4G stand for a mobile network, where the data transmission speed from the network to the client device is 1Gbit/s when the client device is in slow motion, for instance a cellphone in a pedestrians pocket. When moving fast, such as in an express train 100Mbit/s connection speed is required. A lot of Finnish ISP:s (and probably in other countries too) use the 4G term for networks which can't reach that, though. That's why one should always call these networks by their real names, LTE 800Mhz, 1800Mhz and 2600Mhz. Especially calling a 3G DC-HSPA network a 4G network is very misleading, since such a network only means combining two 2100Mhz cells, while the network technology itself is still 3G.
When interpreting a coverage maps it is vital to understand that the information provided by the map is only referential. On the spot the signal quality can differ greatly from the expected values, as it goes with radio communications. In many map applications it is possible to make a coverage query using a precise address, which is probably the easiest way to find out the (referential!) coverage of for instance your new home. Depending on the system, you might also be able to get summarized information about the network coverage in your queried location, Elisa/Saunalahti has this kind of functionality, for instance. Final and the most accurate information can only be achieved with testing the network physically. On the edges of calculated coverage areas one should be prepared for greatly dampened coverage indoors, especially if the walls are thick, windows are multi-layered/spectrally selective glass or if the house has a metal roof. The further you are from a base station, the weaker your coverage becomes and any geographical / mechanical obstructions will have even greater effect on the functionality of the network.
In Sonera's map it is possible to select between excellent and good coverage. A good rule of thumb is that in "excellent" coverage areas your cellphone will stay on the network constantly. On "good" coverage areas you might experience some breaks and the phone might transition into 3G network, if LTE signal drops too weak. You can still get a stable and functioning network connection on areas with "good" coverage by uising external antennae and a quality LTE router. For cellphone / mobile use the signal is often too weak and the user experience poor.
Coverage maps for different operators in Finland
In this article we go through the coverage map functions and information for different operators who provide mobile/LTE networks in Finland. Links to the maps included!
DNA's map In DNA's coverage map it is possible to distinguish between LTE 800Mhz and LTE 1800Mhz networks. The map's resolution is quite low though and the raster is single coloured, so judging the realistic coverage is difficult. On the 3G and 2G side the map is nearly the same as other operators. One downside is that the DC network which is on the UMTS900Mhz, 2100Mhz are pictured with the same raster, thus making it impossible to differentiate what is provided in either area.
Sonera's map, newer, plain Sonera's map has all of the LTE network only decipted by one colour, thus making it impossible to know the frequency. They also claim that the entire network is capable of speeds up to 150Mbit/s, which is not even possible in an LTE 800Mhz network. On the 3G side the map can display speed, but not network technology. The has a selection between "excellent" and "good" coverage for coverage to be displayed. The most realistic data is under "excellent" coverage, since "good" coverage is just their word VERY POOR to use indoors without extra antennae / equipment.
Sonera, old user interface, more information This map has more widely selectable frequency ranges. The biggest upside is on the 3G side though, where 900Mhz and 2100Mhz networks are separately displayed. You can also view, what areas are supported with 21Mbit/s speeds and Dual Carrier feature. The maps usage is a bit weaker though, the site loads very slowly and moving around on the map often causes it to stop responding.
22.8.2015 We have noted, that the old map's functionality can be defective. As you browse the map you can get random error messages.
In Elisa's coverage map it is possible to single out 2G, 3G and LTE networks for closer inspection. In all networks the rasster's colour doesn't change by frequency or signal strength though, so for instance the LTE network -looks- like it successfully covers a very wide area.
The map also tells you the speeds of the networks. The map claims 3G to be able to reach speeds up to 42Mbit/s, but in reality the speed is only achievable in 3G DC-HSDPA networks. 3G DC-HSDPA is found in parts of the 2100Mhz regions, but all base stations have not been upgraded with the technology. That is why 3G speeds usually vary from 1-20Mbit/s, depending a lot on network load and technology used.
In the map it is possible to inspect the signal quality by "stars". If you give an address into the application, it will give you a signal quality expectation in stars. It is pretty different to judge what these stars actually mean in the environment itself, as the amount of stars is unable to be compared with any values got from the network.