CellMapper is a free resource and one of the most useful tools available for pre-install IoT site planning in the UK. It does not replace on-site signal testing — its data is historical and crowd-sourced, and signal conditions vary — but it significantly improves the quality of pre-visit planning and helps avoid wasted site visits.
Pre-visit workflow using CellMapper
- Go to cellmapper.net
- Search for the site postcode
- Select network type (LTE) and operator (EE, Vodafone, Three, O2)
- View tower locations — note direction from the installation site to the nearest towers
- Switch to B20 (800 MHz) first — this is the most important band for UK IoT coverage
- Note the PCI (Physical Cell ID) of towers within 2–5 km of the site
- Repeat for B3 (1800 MHz) — likely to be the best throughput band at the site
- Identify which operators have coverage from towers you can see clearly from the site
PCI matching technique
After running a CellTester sweep on site, the PCI reported by the modem identifies the specific cell sector being served. Match this PCI in CellMapper to confirm:
- Which physical tower the router is connected to
- The direction from the site to that tower
- Whether a different tower on the same operator might give better performance with a directional antenna
This technique is particularly useful when a site shows adequate RSRP but poor SINR — the modem may be connecting to a distant tower behind competing cells. CellMapper lets you identify a more suitable cell and aim an LPDA antenna to force selection of the better sector.
CellMapper limitations
- Data is crowd-sourced — some UK areas have very few measurements
- Tower data can be outdated — operators add and remove sectors regularly
- Indoor or roof-mounted signal levels are not represented in crowd-sourced data
- CellMapper shows phone-level signal, not router-level signal
Use CellMapper for planning, not commissioning. CellTester with the actual router and antenna is the commissioning tool.