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[aprssig] DAO quantified.

Wes Johnston, AI4PX wes at ai4px.com
Sun May 11 03:31:58 UTC 2008


I'm hoping this attachment goes through the list.

The pic on the left is a screen shot from aprs.fi , the right is
findu.com.  I am setting up a tracker for a club and am running it in
the back of my
car for a few days to see if I've got it setup the way I want.  Actually
another local ham and I have been getting a kick out of the fact that my
speed can vary from when one tracker transmits and the other transmits.  We
get a kick out of how the rear of my car can be going faster or slower than
the front and in a different direction.

The call of the tracker is k4scg-15 and it's running DAO on Scott Miller's
OpenTrak.
My mobile call is ai4px-9 and i'm running a d700.

The D700 transmits with a 60' (18meters) ambiguity, DAO adds digits of
precision down to 2' (60cm).

In the pic on the left, you can see the difference in location from the DAO
tracker vs my d700.  k4scg-15 is exactly in the correct spot on the north
side of the street near the mailbox.  ai4px-9 incorrectly appears in the
neighbor's driveway.

Findu does not display the added precision, so k4scg-15 appears in the same
qth as my d700.

What's great about this is that any aprs station can decode the position to
18meters.  Clients like aprs.fi and xastir can decode the 60cm positions.

By the way, this is not meant to make one web site appear better than the
other.  It was a very convenient way to show the difference between mic-e
packets and DAO enabled packets.  APRS.fi and findu just provided an easy
way to contrast the improved precision on the same photo.

-- 
Wes
---
Where there's silence, there is no Hope.
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