[Ovmsdev] SIM808/SIM908 GPS accuracy

Edward Cheeseman cheesemanedward at gmail.com
Tue Feb 7 14:43:05 HKT 2017

> On 7/02/2017, at 6:59 PM, HONDA S-2000 wrote:
> Finally, to satisfy my curiosity, what are the latitude and longitude angles being converted to?

> On 7/02/2017, at 12:47 PM, Edward Cheeseman wrote:
> OVMS native format:
> Appears to be signed seconds * 2048. I haven’t delved into documentation here, just what I saw in the gps2latlon().

Seconds * 3600 = degrees. So native units would be degrees * 3600 * 2048.

I think we all agree - if land or road surveying was the application better precision would be necessary.

When all we want is to know where our car is, within 30 meters is probably fine. Cars don’t hide that easy :)
I only delved down this rabbit hole because the position was 200kms off! That cause has been separately solved.

The main advantage is, given the poor little 8bit PIC doesn’t need to deal with a floating point at all, there could be a speed improvement.
A huge disadvantage is the code is not easily read.


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