Second in the mobile series. Our mobile application takes shape as we build out a schema to support geo-specific data and friend finding. Learn how to use MongoDB geo-indexing for real-time proximity matching and gather analytics with the aggregation framework.

1. What’s My Place in the Universe?
Using Geo Indexes to Solve Existential Crises
Building a Mobile App with MongoDB Part 2

2. 2
The Scavenger Hunt App
Users create
scavenger hunts by
“pinning” waypoints

3. 3
The Scavenger Hunt App
Players search for a
scavenger hunt
near their current
position

4. 4
The Scavenger Hunt App
Basic Requirements

5. 5
The Scavenger Hunt App
Basic Requirements
• Mark target points

6. 6
The Scavenger Hunt App
Basic Requirements
• Mark target points
• Identify our users

7. 7
The Scavenger Hunt App
Basic Requirements
• Mark target points
• Identify our users
• Mark users’ progress
during hunts

8. 8
Waypoint
{ _id: ObjectId(),
user: UUID,
tour: UUDI
name: "Doug's Dogs",
desc: "The best hot-dog",
clues: [
"Hungry for a Coney Island?",
"Ask for Dr. Frankenfurter",
"Look for the hot dog stand"
],
"geometry": {
"type": "Point",
"coordinates": [125.6, 10.1] }
};

9. 9
Waypoint
{ _id: ObjectId(),
user: UUID,
tour: UUDI
name: "Doug's Dogs",
desc: "The best hot-dog",
clues: [
"Hungry for a Coney Island?",
"Ask for Dr. Frankenfurter",
"Look for the hot dog stand"
],
"geometry": {
"type": "Point",
"coordinates": [125.6, 10.1] }
};
Geospacial Index:
ensureIndex(
{ geometry: “2dsphere” }
)

10. 10
Waypoint
db.waypoints.find(
{
geometry: {
$near:{
{ type : "Point" ,
coordinates :
[ -173, 40.7 ]
},
$maxDistance : 100
}
}});

11. 11
GEOJSON
• Point
• MultiPoint
• LineString
• MultiLineString
• Polygon
• MultiPolygon
• GeometryCollection
http://geojson.org/

12. Crisis 1:
The sense of being alone
and isolated in the world

13. 13
The Checkpoint Document
{
_id: ObjectId(),
user: UUID,
huntId: UUID,
timestamp: ISODate(),
geometry: {
type: "Point",
coordinates: [125.6, 10.1]
}
}

14. 14
The Checkpoint Document
{
_id: ObjectId(),
user: UUID,
huntId: UUID,
timestamp: ISODate(),
geometry: {
type: "Point",
coordinates: [125.6, 10.1]
}
}
db.checkpoints.ensureIndex(
timestamp: -1,
geometry: “2dsphere”
);

15. 15
The Checkpoint Document
db.checkpoints.find(
{
date: {$gt: <10mins ago> }
geometry: {
$near:{
{ type : "Point" ,
coordinates :
[ -173, 40.7 ]
},
$maxDistance : 100 }
}});
{
_id: ObjectId(),
user: UUID,
huntId: UUID,
timestamp: ISODate(),
geometry: {
type: "Point",
coordinates: [125.6, 10.1]
}
}

16. 16
The Checkpoint Document
db.checkpoints.find(
{
date: {$gt: <10mins ago> }
geometry: {
$near:{
{ type : "Point" ,
coordinates :
[ -173, 40.7 ]
},
$maxDistance : 100 }
}});
{
_id: ObjectId(),
user: UUID,
huntId: UUID,
timestamp: ISODate(),
geometry: {
type: "Point",
coordinates: [125.6, 10.1]
}
}

17. 17
The Scavenger Hunt App

18. 18
Polygon

19. 19
Polygon
Data Driven Decision
• How many people live around this area
• How many of my customers are around this distribution center
• What time of the day do they actually get in front of the shop
• Where are my competitors located
• How much time does it take get from A -> B

20. 20
Polygon
{
"type": "Polygon",
"coordinates" : [
[
[ -73.969581, 40.760331 ],
[ -73.974487, 40.762245 ],
[ -73.977692, 40.763598],
[ -73.979508, 40.761269 ],
[ -73.982364, 40.762358 ],
[ -73.983692, 40.760497 ],
[ -73.972821, 40.755861 ],
[ -73.969581, 40.760331 ]
]
]
} Defines a business service area

21. 21
Polygon
Defines a business service area
{
"type": "Polygon",
"coordinates" : [
[
[ -73.969581, 40.760331 ],
[ -73.974487, 40.762245 ],
[ -73.977692, 40.763598],
[ -73.979508, 40.761269 ],
[ -73.982364, 40.762358 ],
[ -73.983692, 40.760497 ],
[ -73.972821, 40.755861 ],
[ -73.969581, 40.760331 ]
]
]
}

22. 22
Polygon

23. 23
$geowithin
{ geometry: {
$geoWithin: {
$geometry : {
'type': "Polygon",
'coordinates': [
[
[ -73.975181, 40.758494 ],
[ -73.973336, 40.760965 ],
[ -73.974924, 40.761663 ],
[ -73.976748, 40.759160 ],
[ -73.975181, 40.758494 ]
]
]
}}}}

24. 24
$geoIntersects
{
$geoIntersects: {
$geometry: {
"type": "Point",
"coordinates": [
-73.975010,
40.760071
]
}
}
}

25. 25
Complex Polygons

26. 26
Complex Polygons
{
"type": "Polygon",
"coordinates" : [
[ [ -73.969581, 40.760331 ],
[ -73.974487, 40.762245 ],
[ -73.977692, 40.763598],
[ -73.979508, 40.761269 ],
[ -73.982364, 40.762358 ],
[ -73.983692, 40.760497 ],
[ -73.972821, 40.755861 ],
[ -73.969581, 40.760331 ]
],
[[ -73.975181, 40.758494 ],
[ -73.973336, 40.760965 ],
[ -73.974924, 40.761663 ],
[ -73.976748, 40.759160 ],
[ -73.975181, 40.758494 ]]
]
}

27. 27
Complex Polygons

28. 28
Complex Polygons
{
$geoIntersects: {
$geometry: {
"type": "Point",
"coordinates": [
-73.975010,
40.760071
]
}
}
}

29. 29
Rendering Geo Elements
{ type: "GeometryCollection",
geometries: [
{ type: "Point",
coordinates: [
-73.975010,
40.760071
]
},
{ type: "Polygon",
coordinates: [[
[-73.975181, 40.758494 ],
[-73.973336, 40.760965 ],
[-73.974924, 40.761663 ],
[-73.976748, 40.75916 ],
[-73.975181, 40.758494 ]
]]
}
]
}

30. 30
Complex Polygons

31. 31
Complex Polygons
{ "type": "Polygon",
"coordinates" : [
[
[ -73.969581, 40.760331 ],
[ -73.974487, 40.762245 ],
[ -73.977692, 40.763598],
…
],
[
[ -73.975181, 40.758494 ],
[ -73.973336, 40.760965 ],
[ -73.974924, 40.761663 ],
..
],
[
[ -73.979437, 40.755390 ],
[ -73.976953, 40.754362 ],
[ -73.978364, 40.752448 ],
…] ]
}

32. 32
Complex Polygons
{ "type": "Polygon",
"coordinates" : [
[
[ -73.969581, 40.760331 ],
[ -73.974487, 40.762245 ],
[ -73.977692, 40.763598],
…
],
[
[ -73.975181, 40.758494 ],
[ -73.973336, 40.760965 ],
[ -73.974924, 40.761663 ],
..
],
[
[ -73.979437, 40.755390 ],
[ -73.976953, 40.754362 ],
[ -73.978364, 40.752448 ],
…] ]
}
$err : Can't canonicalize query
BadValue Secondary loops not
contained by first exterior loop -
secondary loops must be holes

33. 33
Complex Polygons
{ "type": "Polygon",
"coordinates" : [
[
[ -73.969581, 40.760331 ],
[ -73.974487, 40.762245 ],
[ -73.977692, 40.763598],
…
],
[
[ -73.975181, 40.758494 ],
[ -73.973336, 40.760965 ],
[ -73.974924, 40.761663 ],
..
],
[
[ -73.979437, 40.755390 ],
[ -73.976953, 40.754362 ],
[ -73.978364, 40.752448 ],
…] ]
}
$err : Can't canonicalize query
BadValue Secondary loops not
contained by first exterior loop -
secondary loops must be holes

34. 34
{ "type": "Polygon",
"coordinates" : [
[
[ -73.969581, 40.760331 ],
[ -73.974487, 40.762245 ],
[ -73.977692, 40.763598],
…
],
]
}
{ "type": "Polygon",
"coordinates" : [
[
[
[ -73.979437, 40.755390 ],
[ -73.976953, 40.754362 ],
[ -73.978364, 40.752448 ],
…] ]
}
Complex Polygons

35. 35
Complex Polygons
‘$or’ : [ {
"geometry" : {
"$geoWithin" : {
"$geometry" : {
"type" : "Polygon",
"coordinates" : [
...
]
}…,
{
"geometry" : {
"$geoWithin" : {
"$geometry" : {
"type" : "Polygon",
"coordinates" : [
...
]
}…

36. 36
Complex Polygons

37. 37
Complex Polygons
{
$geoIntersects: {
$geometry: { "type": "LineString",
"coordinates": [
[-73.979543, 40.761132],
[-73.974715, 40.759127],
[-73.973363, 40.760969],
[-73.970059, 40.759600]
]
}
}

38. Crisis 2:
Shattering of one's sense of reality,
or how the world is.

39. 39
Honolulu to Tokyo

40. 40
Honolulu to Tokyo

41. 41
Honolulu to Tokyo

42. 42
Honolulu to Tokyo

43. 43
Coordinate Reference System
• A system to locate geographical entities
• WGS84 datum
• Geoid - the shape of the surface of the oceans
• EGM96 gravitational model
"crs": {
"type": "name",
"properties": {
"name": "urn:ogc:def:crs:OGC:1.3:CRS84"
}
}

44. 44
Geoid
Credit: ESA

45. 45
Am I inside or outside the box?

46. 46
The Correct Interpretation

47. 47
Right Hand Rule

48. Crisis 3:
Anew-found grasp or
appreciation of one's mortality.

49. 49
BigPolygon in Action

50. 50
BigPolygon in Action

51. 51
BigPolygon in Action

52. Crisis 4:
Awareness of one's freedom
and the
consequences of accepting freedom.

53. Questions?

54. Thanks!
{ name: ‘Bryan Reinero’,
title: ‘Developer Advocate’,
twitter: ‘@blimpyacht’,
code: ‘github.com/breinero’
email: ‘bryan@mongdb.com’ }