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[aprssig] Re: DAO quantified.

Gregory A. Carter gcarter at openaprs.net
Tue May 13 23:17:04 UTC 2008


Since DAO support seems to be the magic topic of discussion I went ahead and
added support on OpenAPRS for it.

I have also started opening up and documenting our XML interface for
external sites to use the data in our database.  The interface reference can
be found at http://www.openaprs.net/xml.html.  Along with this move I'll be
releasing a method to embed OpenAPRS's system into a remote website using
our native javascript files and XML interface, you can expect that to happen
in about 2 weeks.  So far via XML you can look up a location in the US by
zip/city & state, view current message reports, access the KML interface for
both tractking stations and particular locations, view raw packet reports
and lookup position reports.

I've also added the FCC ULS database to our system which will auto-update
every 30 days from the FCC, now all stations displayed on the map will show
their ULS information in the popup bubble on click and will also appear in
our station info lookup page.  In a couple of days I'll have an XML
interface up for the ULS lookup as well.

And finally, I've released the C++ daemon OpenAPRS uses to inject the
APRS-IS packet to mySQL (it's on the site under OpenAPRS Daemon).  It should
compile on most UNIX variants and has several additional features for
watching packets as they come in.

If anyone has any suggestions, questions or rants/raves I'd love to hear
them, email me direct.

73,

Greg (N7NXS)
OpenAPRS.Net

On Sun, May 11, 2008 at 10:58 AM, Wes Johnston, AI4PX <wes at ai4px.com> wrote:

> Someone just asked me off list what DAO is...
>
>  DAO in a nushell is one extra digit of precision on a normal aprs
> packet.
>
> Here's a snippet from Bob's page..
>
> FORMAT:  The format of this APRS Precision-and-Datum option is the
> presence
> of a 5 byte field !DAO! appearing anywhere in the position comment field.
> This option is backwards compatible beacause the basic DDMM.HH/DDDMM.HH
> format is retained and will still be decoded by all existing applications.
> The !DAO! simply provides the additional precision down to a foot or so
> and also identifies the datum:
>
>    !DAO! - is fixed length anywhere in the position commment
>     D    - is the datum identifier (base-91)
>      A   - is the added LAtitude precision (base-91)
>       O  - is the added LOngitude precision (base-91)
>
> RECOMMENDATION:  Recommend placing this option on the END of all other
> position comment text.  This way it does not displace any human readable
> comment text that is otherwise desired to display on older systems.  This
> added option may extend beyond the existing "viewable" limit of 57 bytes
> currently in the spec since these added bytes are not used by legacy
> systems anyway.
>
> PRECISION:  There are three degrees of precision offered by this option.
>
>     1) HUMAN READABLE, Thousandths of a minute.  This is good to the
>        nearest 6 feet or so and being human readable gives even users
>        of the D7 and D700 or any other existing application the ability
>        to human read position to 3 decimal digits of Minutes.  This
>        format is identified if the Datum byte is in uppercase.
>
>     2) BASE-91.  This adds additional precision to the nearest 91/ten
>        thousandth of a minute, or about 4 decimal fractional digits of
>        a minute or about one foot.  This format is identified if the
>        datum byte is in lowercase.
>
>     3) NULL.  If the A and O bytes are SPACE characers, then they
>        are only there to fulfill the !DAO! format and imply NO ADDED
>        precision.  This is used when one wants to send DATUM info
>        but without claming added precision.  This use of space characters
>        to imply lacking digits of precision is consistent with the
>        existing APRS ambiguity system.
>
> By the way, for those of you wondering about my tag line... My 8 year old
> daughter's name is Hope.  Must be something about that missing Y
> chromosome.  Talking excessively does seem to run on that side of the aisle.
> --
> Wes
> ---
> Where there's silence, there is no Hope.
>
> _______________________________________________
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>
>
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