Signal strength is a factor of the sensor strength of the probe, the signal size of the target
Accuracy is determined by several factors where the most important RuneScape Gold is the probe type and signal strength (see advanced section for formulas). Longer range probes give larger max deviation from the target.
There is also some randomness involved here so a new scan might give a more accurate result (or worse). If you can get the Signal Strength above 1.0 with 1 probe you will always get 0m accuracy and can warp in right on top of the target.
Signal strength is a factor of the sensor strength of the probe, the signal size of the target, the range from the probe to the target and any skills you might have.
As long as you are using ship probes you should never get an accuracy result above 20.000 km.
If the accuracy is not good enough to get inside the same grid as the target you might need to launch and scan with a shorter range probe. Warp to the result by right clicking on it and choose warp to. Click new scan and right click on the probe you used and choose “destroy probe”.
The reason for this is the fact that you can not launch a probe within the scan radius of another probe. Now launch a 5au (snoop) probe and scan with that. Worst case scenario with that probe will land you just 200km away, most likely a lot closer.