Question

I am working on indexing for multidimensional objects (location based services: long/lat/time for eg.) and experimenting with hilbert curve. The problem is, the java code i have works good upto 64 bits. For example:

value ( long, lat, time ) = H(bits)

if the number of bits > 64 , the algo fails.

So i just need to know what is the feasible range of long and lat values should i consider for real world applications?? Is it : -180 to 180 for longitude and 90 to -90 for latitude??

Thanks

Answer 1

Yeah, it is typical to define longitude to be between -180 and 180 and latitude between -90 and 90 as you said. I have seen the range 0 to 360 for longitude, but no where near as often.

What’s important is that you define latitude across a range of 360 degrees and latitude across a range of 180, since that lets you find any point on the earth.

Although I am completely ignorant of hilbert curves and don’t know what’s involved in your task, I would recommend making sure that you understand that the values of latitude and longitude typically used are geodetic. Latitude is thus the angle that a line normal to the surface of the earth makes against the equatorial plane. This line will not go through the center of the earth unless you are on the equator.