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[aprssig] !x! (was: IS-to-RF proposal (rev b))

40.174N 75.797W 40.174n75.797w at gmail.com
Tue Jan 3 13:58:21 UTC 2012


I don't think it was It was fear or privacy concerns that drove their
decision. The agency has valuable data, they wanted to help hams and
emcom but they needed to be able to 'control the narrative'; which to
them meant that no one else provided a long-term searchable database
of their data on the internet that they couldn't control. they did not
want the preponderance of google search result to drive users away
from their site and over to a site where the data was presented 'in
the raw' and without their contex. I have worked with a number of data
providers and as they become more internet-savvy  the long-term
presentation of their data becomes a bigger concern.

The way i read the spec, I don't think !x! can be at the beginning of
a packet due to the X1J exception:

[quote]Every APRS packet contains an APRS Data Type Identifier (DTI).
This determines the format of the remainder of the data in the
Information field, as follows: [snip] Note: There is one exception to
the requirement for the Data Type Identifier to be the first character
in the Information field — this is the Position without Timestamp
(indicated by the ! DTI). The ! character may occur anywhere up to and
including the 40th character position in the Information field. This
variability is required to support X1J TNC digipeaters which have a
string of unmodifiable text at the beginning of the field.[/quote]

In my APRS object generation code, I change any existing ! characters
in the first 40 characters to a space, and I'll pad a packet with
spaces if needed to ensure that !x! appears as or after the 41st
character.

Steve AB3LT


On Tue, Jan 3, 2012 at 4:18 AM, Heikki Hannikainen <hessu at hes.iki.fi> wrote:
> On Tue, 3 Jan 2012, Steve wrote:
>
>> On Fri, Dec 30, 2011 at 4:58 PM, Heikki Hannikainen <hessu at hes.iki.fi>
>> wrote:
>>>
>>> Someone has requested it from me a few years back, and I have implemented
>>> it
>>> in aprs.fi, but it seems like my code requires it to be in the beginning
>>> of
>>> the comment string for position packets.
>>
>>
>> Hessu, that was me. Sad story. I was sending objects with !x! in the
>> object description and the source of the data found their data via
>> google on aprs.fi. I explained to  them that I had tagged the data
>> with the no-archive flag and that it would be on the site for only a
>> short time 'as-it-happens' but not long term, which they were ok with.
>> Turned out, that wasn't the case, I lost access to the data, and they
>> stopped working with me (and I heard they stopped working with other
>> hams too), I never knew why until now. i really wish aprs.fi had
>> implemented !x! for object descriptions.
>
>
> Ouch.
>
> It is implemented for object descriptions (and items and other position
> formats), but as described above, it needs to go in the beginning of the
> comment. It might make more sense to have it in the end so it would not
> affect the readability.
>
> If the people who provided the data are afraid of that sort of thing
> happening, they're doing the right thing not letting you transmit it on
> APRS, even if aprs.fi would not be showing the data. Anyone else can record
> it off the air or APRS-IS and has every right to publish it on the Internet,
> !x! or not. Amateur radio transmissions are public by definition and there
> is no guarantee of any privacy at all.
>
> That said, I will continue to support !x! since it does serve a purpose and
> might become more popular over time.
>
>
>  - Hessu
>
>
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