how to set coordinates for ibeacons?

Question

I will be mapping longitude and latitude for ibeacons and then using the coordinates from the server and the distance between ibeacons and the device, I know that I can calculate the location of the "user" much faster and more precisely (at least more precise than GPS). However, I don't know what coordinate system to use. Do I use the global longitude and latitude (like the ones used in GPS) or do I create my own local coordination system for the beacons?

Answer 1

There is no right or wrong answer here -- this is a design question. Here are the tradeoffs I can think of:

Use Latitude and Longitude

Pros:

• Standardized system
• Easy to share with other data sources expecting latitude and longitude (e.g. plot on Google Maps)
• Easy to fold in location information from other data sources. (E.g. GPS)

Cons:

• Difficult for humans to comprehend numbers
• Difficult to get an accurate reference points for part of your building

Use a Custom Coordinate System

Pros:

• Easy to measure against a local reference point
• Easy for humans to comprehend numbers

Cons:

• Non-Standard
• Difficult to integrate with other systems

You may wish to do both. You can have conversion functions that switch between the two. Whichever you use as the native internal system is entirely up to you based on the pros and cons above. So long as you have conversions to go either way, and implement these in methods on your classes, it really might not matter what you use internally.

Answer 2

In your case I would consider the UTM coordinate system. Today it is the official standard projection for paper maps. Such paper maps have a latitude longitude markers and the UTM grid printed on.

The big advantage of the UTM coordinates are:

• The unit is meters, not degrees and it behaves like cartesian school coordiantes, so one unit in x- direction is the same as 1 unit in y-direction which is 1 meter. For lat/lon this is not true.
• there is src code available for lat/lon to UTM and reverse conversion
• you only have to measure one point in the building to know the UTM,x,y coordinate, then use a house floor map, or a ruler to set up the coordinates.

Consider buying a hiking map of your region with UTM coordinate grid printed on.

Somewhere in the house (or floor plan) you need to mark a South to North line, and one east to west. This two lines are the axes of your grid; You also can use your own grid, e.g take the point in the house most south and most west as (0,0). This can be your referecne point. Measure from there, and later determine the offset from UTM.