Geohash: the algorithm inside and out - Part 1

Most videos only show you how to use a geohash-not how to create one. I'm changing that. Geohashes are everywhere. Twitter's "Algorithm" keeps track of location solely with geohashes. Why are they so powerful?
Part 1 of 2
GM Morton's original geohash: dominoweb.drac...
Slides: josiahparry.gi...
Written notes: josiahparry.gi...
0:00 - introduction

[@cakcakcak]

i just watched this video start to finish and when i went to subscribe i couldn’t BELIEVE how few subscribers you have. this was really well-made and i have a feeling your numbers are gonna start to take off pretty soon

[@josiahparry]

Thank you, Christopher! If you have any requests for topics, please let me know here or in a github issue :) github.com/JosiahParry/youtube-tutorials/issues/1

[@Veezkox]

This video is well made. I've looked into others and they just confused me. This one and part 2 contain everything you need to understand and implement on your own. Key points make it easy to understand and how to apply it to the real world. One thing I would add is about corner cases - 2 points very close to each other could end up in a different grid ending with a different last character in hash (I don't think there are other cases?). Please keep it going and grow the channel! Thank you so much!

[@HorrorInsides-dm8fc]

Keep up the good work Josiah. This is fantastic. Hope to see you hit the 100K subscriber soon.

[@mukulbhave9376]

super clear ,easy and concise walkthrough. Amazing

[@dcnnvtr]

Elegant, well done! I had no idea what was going on under the covers!

[@raist78231]

This was fantastic! It was an excellent explanation. I'm going to build a geohash function for full understanding. Thanks!

[@monishchhadwa777]

Great explanation! I am surely going to be a strong hire if they ask this to me in the interview :D

[@haraldurkarlsson1147]

Excellent! Very nice explanation of how geohash works.

[@AutomateAaron]

This is a fantastic video!

[@amitkrthkr]

Liked the explanation of this subtle concept. At 11:46, the longitude decimal value used for example is not clear. It is not same as 19, as used in 10:46. Further, at 13:52, the sequence in the video is of 30 bits, in contrast to 32 bits in the audio. I guess we pad extra bits to make a combination of 5 bits for mapping.

[@stefanstefanov00]

I'm about 6 mins into the video and I gotta say this is pretty neat.

[@shobhitarya1637]

Very well explained.Thank you

[@elbarzwalid7344]

amazing content

[@asmitarai845]

This question may sound dumb, but want to know so after interleaving the total number of bits are going to be 64, we are splitting that into combination of 5 bits to generate a number which we will then look into BASE32 to get the character, 12*5 =60 , what about the remaining 4 bits if we include that is going to be 13 character long geohash. Am i missing something?

[@josiahparry]

Not dumb! You ignore the last 4.

[@ElonTusk..]

subbed, keep up dwag

[@HorrorInsides-dm8fc]

Hi Josiah - do we know why interleaving is being done?

[@josiahparry]

The interleaving is done to create a z-coordinate in a z-order curve (en.wikipedia.org/wiki/Z-order_curve#Coordinate_values) which helps identify a 2 dimensional position with only one value

[@crookeddream]

i may sound stupid. but i dont undrestand how you truncated it. i mean output is vastly different from input. and other algorithms say that we should interleave the actual binary values

[@josiahparry]

You don't interleave the actual binary values. That tripped me up quite a bit at the beginning. There's a way to do the geohash algorithm using bit-shifting but that's not the way it was initially designed as i'm showing here. You need to create the binary values your self as described around 10:35. Then after you've encoded longitude and latitude, you interleave those results. Then you truncate the resultant interleaving.

[@crookeddream]

@@josiahparry now i understand. tnx

[@josiahparry]

@@crookeddream dope! lmk if you end up writing it from scratch your self :)

[@crookeddream]

@@josiahparry definitely

[@wyattstevens8574]

2:17 You forgot Plus codes!

[@josiahparry]

Never heard of them! They sound like an S2 derivative of placekeys! Thanks for sharing

[@wyattstevens8574]

​@@josiahparryI don't think that's what it's from, but Google Maps uses it. It could be an S2 variant, but I don't know.