send this:
paste here what they send you:

check

your value with their hash:
result:

Explanation:
You have a hash. Then you write a text. You concatenate both, it gives you a hash.
You send this hash to someone. He can compare with what he calculates. So that way, you can know you wrote the same text, without sharing the text.

Here it works this way: the page generates a random salt (but you can override it, whatever).
Then, you write a text.
Then, you click on the button "calculate hash".
This is a hash you will send to the other one, along with the salt
They will do as well.
You enter their salt and hash on the new section that appeared.
You click on compare, the page will check if the hash you calculate is similar to their with their salt.
So this way, you know you have the same text. Also you know none of you cheated and pretend to have the same while it's not true, because both of you checked

Now, GPS:
If you enter some gps coordinates, format google. For example: 45.6356,2.3123123, then the page will detect it, and actually calculate 4 hashes, for a box around these coordinates of approx 50m (i guess).
If you received 4 hashes, it's also detected. And the comparaison consiste of finding how many points you have in common.
That way, you can tell if you're pinpointing approximately the same place.
The idea was to delimit the world in squares. And to know if two coordinates are around the same place, they have to be in the same square, or an adjacent one.