I have a dji phantom v1.1.1 which runs on 2.4 ghz. I Will be flying indoors without gps. the place is an office with lots of wifi routers. I just want to know that if i lose the signal due to WiFi interference, where will my phantom land?

Dont fly

On top of a wifi router I think

Dude, pls don't fly your quad in crowded areas such as an office - if you still want to fly indoors, chose a large hall, auditorium, or even a indoor stadium - and avoid Interference zones.

The place is large and I will be hovering it at one place. I just want to know what happens when there is no gps and I lose the signal will it start descending on the same spot?

UNPREDICTABLE.

Quote from: quadcptr on January 03, 2015, 12:07:20 PM
The place is large and I will be hovering it at one place.

What ever you do, avoid flying indoors where there are people and valuables .

The phantom may crash if gps is not enabled in such places.2.4ghz routetes can interfere in its transmission.

@sooraj if you dont know say dont know please dont misguide people just because you like to post in every thread

Its not unpredictable
If you fly without gps and the radio link breaks your copter will crash

YOU SHOULD NEVER FLY IN SUCH SITUATION

@Chintal sir, I agree that on losing radio link, the quad will finally crash, but can we predict, what will be its attitude and direction of flight ? It may go on full throttle sometimes (Have experianced),
And I am extremely sorry, if my deeds hurt somebody .

It will stop the motors mid air and crash down

If your quad doesnt have gps, you wont be able to use gps failsafe for sure, and RTL for that matter as its stated on Naza V2 wiki "(3) When GPS signal is bad or GPS is not working, failsafe will not work".

Im not sure how updated that wiki is, but if it is then then you will never be able to fly in any gps mode . You would be able to fly in atti mode only and it wont enter failsafe mode.

Now in case you loose radio link without GPS then,depending on your radio...

If your radio has failsafe feature, then you can get the quad to land in case of link failures by setting minimum throttle which would lead to landing in controlled decent but you will never know where it would land since it doesnt have gps.

If the radio doesnt have failsafe then the rx usually repeats the last received signal when it looses link, which will lead to a flyaway and crash! Now just imagine if your quad was to loose signal while you were doing a fast climb!

Phantom 2 vision plus has the feature wherein the copter would land in radio failsafe if it doesnt have gps, Arducopter too has similar feature. But again cant predict where it would land. Similar feature should have been there in your FC too. You should check your firmwares change log to see if its there.

Yet whatever the case is, an office, however big is absolutely a no flying zone, because there is no guarantee where your copter would land even in case of a working gps failsafe! GPS signals multipath inside buildings hence the quality wont be usable either so even flying with GPS inside building is a strict no-no.

Thanks for the info guys. I'll drop the plan

I have practically tried it (phantom)
Goes up to the ceiling touches it flips and drops like a stone and disarms the motors
Doesn't go into failsafe
Did it twice
(It was a controlled crash ) 
Its a bad idea to fly indoors
Dont do that when their is public
I am sure it wont happen anymore with the inspire 1 having optical sensor for indoors

there are two options that you can set when the signal is lost .
i case of loss of signal , your quad will enter failsafe mode.
you can  either configure failsafe to land wherever it is OR go home and land (this is naza feature - should be there in phantom too)
i've personally never tried failsafe yet . >> and i suggest you dont fly in the place with interference <<.

(ive accidentally left wifi of my gopro on while flying my naza quad and dint have any problem - my luck)

chintal you are right, it went up because in >go home and land< feature , quad rises to 20 meters and starts its journey back home. this shouldnt happen in the other failsafe feature that is land direct.