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ZL3AI > APRDIG 13.05.04 09:46l 258 Lines 10490 Bytes #999 (0) @ WW
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: Compromise proposal (was: Re: The APRS-WG and spec improvements.)
From: "Laurie - g6isy" <g6isy@dsl.pipex.com>
Date: Sat, 24 Apr 2004 13:00:22 +0100
X-Message-Number: 9
Henk de Groot wrote:
>Maybe we can have a nice compromise here: Allow ASCII APRS posits and
>MIC-E to be in the predominat datum that is current for some country.
>Make WGS84 mandatory for the high precision base-91 format.
Henk,
I understand what you are trying to do but I don't think that disallowing a
datum identifer in a high precision format will address the issue in all
locations.
Sorry to keep banging on about the situation in the UK but maybe I have not
explained the problem very well before. I will attempt to do so now.
Our mapping agency does not plan to issue maps to WGS84.
All high precision mapping uses our national grid system (which is used for
99% of navigation also). Our national grid is defined as being in OSGB36.
OSGB36 itself is defined as a transformation from ETRS89 which in turn is a
transform from WGS84.
The transformations are applied before our maps are published (and they
have stated this will continue to be the case). Hence all our mapping is
referenced to OSGB36, not WGS84.
The difference between OSGB36 and WGS84 is up to 300 metres and they are
diverging by about 25mm per year.
The important and practical problem we have is this.
If you want to use a GPS in the UK, and have it display your correct
position on its display, it must be set to perform a WGS84 - OSGB36
transformation. If you do this, the NEMA data is then sent as OSGB36. I
have not yet seen a GPS that will display OSGB36 but send data as WGS84. If
you insist on only allowing WGS84 on air, it means you cannot use a GPS to
accurately navigate with, we will have to have 2. One set to OSGB36 for our
own navigation purposes and another to WGS84 for APRS.
In an ideal world, yes the use of WGS84 as the only on air datum would be
desirable but in the real world, where people need to have an accurate
display on their GPS so they can see where they really are, the use of an
alternative datum is unavoidable. All I want to know, is what datum is
someone using. If it comes from a GPS without a display then it might be in
WGS84 as there are no local display issues and the transform can be applied
at the receiving client but if there is a local display then the data will
be to OSGB36 and the transform must not be applied.
I hope this shows our problem more clearly.
73 Laurie - G6ISY
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Subject: APRS+SA Programming
From: "John Troutman" <w4dcr@ctc.net>
Date: Sat, 24 Apr 2004 09:17:57 -0400
X-Message-Number: 10
Sir: About 24 hours ago I asked some assistance in programming the APRS+SA
program. The problem always goes back to the World map each time it
refreshes and I have to zoom in on my position each time the map changes.
From Map 1A to Map 2A etc. Since I have had no answer to the problem I will
seek the answer else where and I will unsubscribe to the website. Tnx. John
W4DCR
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Subject: RE: More Positionless Weather!!!!
From: "Brian Riley (maillist)" <n1bq_list@wulfden.org>
Date: Sat, 24 Apr 2004 09:31:29 -0400
X-Message-Number: 11
The T-238 TAPR weather box for the Dallas One-Wire station needs simply a
"pass-through" which could be useful for multiple other forms of telemetry.
The data is already formatted.
You need to setup Config to take a position and the other usual data. Then
have the OT read the serial port and pass through what it gets, there are
several modes of the T-238 but the most common is the 5 minute mode.
On 4/23/04 8:56 PM, "Scott Miller" <scott@3xf.com> wrote:
>>pure, but it is far closer than we have been we WILL get to the point
>>either with Byon upgrading the code or with the addition of our PIC
>>translator to do it correct.
>
>You guys are welcome to build on the OpenTracker hardware. It's not a PIC
>(don't like the critters) but it'll do the job, plus eliminate the TNC like
>the WXtrak will.
>
>I've been planning on writing weather firmware for the device all along,
>it's just a matter of getting sample data (and preferably a working station)
>to test with. Plus documentation, of course.
>
>I'm willing to write the code, but what would really help me is a
>prioritized list of weather station types that sould be supported, plus
>clear documentation on how to interface with each one. Better yet, if
>someone's already got C code for a particular station, I'll do what I can to
>adapt it.
>
>The parsing/translating code is going to have to be written one way or
>another. I've got the FSK code and support stuff written already, with
>hardware available now. And you'd be able to switch between tracker and
>weather modes instantly, no swapping chips, and no added cost.
>
>Scott
>N1VG
>
>http://n1vg.net/opentracker
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Subject: RE: More Positionless Weather!!!!
From: "Brian Riley (maillist)" <n1bq_list@wulfden.org>
Date: Sat, 24 Apr 2004 09:49:40 -0400
X-Message-Number: 12
On 4/24/04 9:31 AM, "Brian Riley (maillist)" <n1bq_list@wulfden.org> wrote:
>The T-238 TAPR weather box for the Dallas One-Wire station needs simply a
>"pass-through" which could be useful for multiple other forms of telemetry.
>The data is already formatted.
>
>You need to setup Config to take a position and the other usual data. Then
>have the OT read the serial port and pass through what it gets, there are
>several modes of the T-238 but the most common is the 5 minute mode.
Which means of course that you need an additional config to be able to tell
the OT to transmit when it gets the data as opposed to be on its own
schedule.
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Subject: Re: Compromise proposal (was: Re: The APRS-WG and spec improvements.)
From: Henk de Groot <henk.de.groot@hetnet.nl>
Date: Sat, 24 Apr 2004 19:37:30 +0200
X-Message-Number: 13
Hello Laurie,
At 13:00 24-4-2004 +0100, Laurie - g6isy wrote:
>I understand what you are trying to do but I don't think that disallowing a
>datum identifer in a high precision format will address the issue in all
>locations.
Well, the compromise allows it, only not on base-91 posits (since in the
proposal only those are strict WGS84). Base 91 positions are not human
readble anyway and will never be used "raw". When receiving those then the
client that processed this posits can do the WGS84 to OSGB36 conversion.
If you want to run the GPS with OSGB36 datum then go ahead, you have the
plain-format an MIC-E (which are the most spread anyway) to choose.
>Our mapping agency does not plan to issue maps to WGS84.
That doesn't surprise me, the Brits have a long histroy when it comes to
dealing with international standards...
>If you want to use a GPS in the UK, and have it display your correct
>position on
>its display, it must be set to perform a WGS84 - OSGB36 transformation. If you
>do this, the NEMA data is then sent as OSGB36. I have not yet seen a GPS that
Which in my proposal means that if you connect it to an APRS transmitter to
this GPS then you have to pick either the plain or MIC-E format and is not
allowed to use the Base-91 compressed format unless the transmitter
converts OSGB36 back to WGS84. I see no big problem with this restriction
and it provides at least one well defined, well specified and compatible
format without breaking the current APRS specification or any Kenwood
compatibility.
>will display OSGB36 but send data as WGS84. If you insist on only allowing
>WGS84
>on air, it means you cannot use a GPS to accurately navigate with, we will
>have
In the compromise proposal I do not; I only define WGS84 if for the base-91
compressed format. It is even in the true sprit of "compressed", its
compressed to save space so why add an extra 5 bytes?. By requiring WGS84
for base-91 you keep the packet small since you don't have to tell the
datum to anyone - you know this must be WGS84.
>I hope this shows our problem more clearly.
I understood this already, I hope you understand the compromise which gives
both sides what they want without a sacrifice to compatibility, neglegible
drawbacks while mantaining the true sprit of keeping compressed packets
accurate and small.
Kind regards,
Henk.
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Subject: Hosstraders Hamfest / SE New Hampshire - New Maps
From: "Brian Riley (maillist)" <n1bq_list@wulfden.org>
Date: Sat, 24 Apr 2004 15:26:37 -0400
X-Message-Number: 14
Hosstraders Hamfest (NH State Fairgrounds, Hopkinton, NH, 10 miles SE of
Concord along I-89 near exit 7) is fast upon us. I received a request from
K1MID for a map of that area. I have added two maps to the
APRSQuery/APRSTracking web pages ...
------
If you are looking for general APRS activity in the Southcentral and
South eastern New Hampshire area, try this;
<http://www.findu.com/cgi-bin/plot.cgi?call=*&geo=http://www.wulfden.org/map
s/SENH1.geo>
------
Come Friday and Saturday April 30/May 1 while the hamfest is on, try
this for a close-up map (only 4-6 sq miles) of who is at Hosstraders, try
this
<http://www.findu.com/cgi-bin/plot.cgi?call=*&geo=http://www.wulfden.org/map
s/SENH1.geo>
------
If you are mobile in that region you could type;
<http://www.findu.com/cgi-bin/track.cgi?line=1&call=kc1ncr&geo=http://www.wu
lfden.org/maps/SENH1.geo&start=120&length=120>
This gives you the track for KC1NCR who lives in that region for the
last five days (120= 5x24 hours) change the call, strat, and length
parameters to suit yourself, or just go to the APRSTrack webpage and use the
pulldowns;
<http://www.wulfden.org/APRSTracking.shtml>
------
A couple of weeks ago I added a map called "New Hampshire Seacoast" for
N1RUF who commutes from Dover to Beantow every day. The map covers Concord
east to the Coast and down to an E-W line through Lexington.
All of these maps have been added to the APRS Activity query on the
APRSQuery page and to the appropriate (in this case New England) selections
on the APRSTracking page.
..... ANY MORE MAP REQUESTS ????????????????
--
Cheers ... 73 de brian, n1bq, underhill center, vt, usa
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