If it is only a couple of resonators, it is actually ok, landmarks are very often the walls of big buildings like churches, so there is always a chance a couple of resonators will land inside it and will be only partially accessible.
You can always blow it up with high level xmp, unfortunately high level players are well aware of this exploit and try to place their strongest resonators at the blocked side of a portal.
If you on the other hand cannot access a portal itself, report it to ingress and suggest coordinate adjustment. https://support.google.com/ingress
gaming.stackexchange.com/users/11420/BanditoBunny
Yes , get as close as you can.
If you want to get tricky turn off your wifi, you will now determine your position solely by satelites, this can vary depending on if it's raining, if you're under a tree, or if you're next to a wall.
E.G.
you might want to go into a city block, but be up against the wall not able to get to that resonator;
try crossing the street and get up against the other wall, you might accidentally mirror off the wall a little, ending up closer than you could get before.
gaming.stackexchange.com/users/13937/dlamblin
For now, yes.
But you have the option of reporting the portal as not being publicly accessible on the website.
gaming.stackexchange.com/users/38213/aliencam
This happens way too frequently for Google to adjust coordinates for every instance of this.
You are going to have to accept that tactical placement of resonators can make it difficult to attack.
The problem swings both ways.
There is no reason for google to address it.
Take note of the placement, because when you do get it down you are going to want to place it in the exact same place!
Try moving to windows within the building.
You may not be able to get right on top of it
but you may get closer.
gaming.stackexchange.com/users/44611/Dan Daughtry
You don't need to stand exactly on the top of a resonator.
You may stand 8-10 meters from the resonator for L1-L3 xmps and still hit it with full effect.
The xmp effect is decreased in steps of the distance.
For a full detailed explanation see the Google+ group here:
Decode Ingress (Help/Game)
gaming.stackexchange.com/users/47813/Jan Rou
I was trying to attack a portal today, but I couldn't destroy the last few resonators because on the map they exist in the middle of a city block.  I tried going in the building, but the gps signal is gone at that point and it didn't get me any closer to those resonators.  How do I destroy resonators I can't get close to?  Do I just need to launch a ton of xmps from a distance and do around 1% - 2% damage at a time?
How can I attack resonators in the middle of a city block?
gaming.stackexchange.com
<ingress>
gaming.stackexchange.com/questions/95733
gaming.stackexchange.com/users/22491/mmrobins
Turn off your wifi to determine your position only by satellites and move to windows within the building. You can also blow it up with high level xmp. It seems that this is a common problem and most players just use tactics that include proper positioning.
The community proposes few tactics to tackle the problem. A user is suggesting to report it as a problem.