[aprssig] APRStt 4 digit grid squares...

Robert Bruninga bruninga at usna.edu
Sun Feb 15 13:40:53 EST 2015

Thanks everyone, for all the GRID ideas.  But here is what we think we have
decided to go with for the worldwide 4 digit DTMF Grid map we will use on


It uses a table from 00 to 99 to map to the first two ALPHA characters.

Bob, WB4aPR

*From:* aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] *On
Behalf Of *George Vastianos
*Sent:* Saturday, February 14, 2015 5:13 PM
*To:* TAPR APRS Mailing List
*Subject:* [aprssig] Σχετ: proposal for APRStt grid loc. Σχετ: 60 Grid


Thanks for the correction!

I had in my mind that you have to look for the first letter on the black
row below and then look for the second letter on the black column on
left... so i wrote "Row 1st, Col 2nd" BUT THIS IS WRONG

The correct is "Col 1st, Row 2nd" that means "Find the Column of 1st letter
and then the Row of 2nd letter"

e.g.  KM = 502, NQ=536, UW=902



*Απο:* Lynn W. Deffenbaugh (Mr) <ldeffenb at homeside.to>
*Προς:* TAPR APRS Mailing List <aprssig at tapr.org>
*Στάλθηκε:* 11:57 μ.μ. Σάββατο, 14 Φεβρουαρίου 2015
*Θέμα:* Re: [aprssig] proposal for APRStt grid loc. Σχετ: 60 Grid

Pardon my literalness, but if you say "Row 1st, Col 2nd", then for KM I'd
go to row K up the right side and column M across the bottom and get 520
whereas your example says it's 502 which seems to be column K and row M?

More than one example would make it more clear for those of us that need to
see what you're talking about.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

On 2/14/2015 7:33 AM, George Vastianos wrote:

Hello Bob

IMO in APRStt the conversion between grid and numbers should be very easy
in a way that no calculation algorithm will be needed by the user and only
a small printed table will be enough. In this way with a small printed
paper in the pocket and the low cost HT anyone could define his position in
the APRS system (of course if he knows his position and if there is APRStt
infrastructure in his area...)

In the attached file (PNG picture) you can find my proposal for a simple
conversion table

the result is that you add a group of 3 number-digits for each 2 letters of
the grid

eg. KM = 502, KM17 = 50217, KM17uw = 50217902, KM17uw48 = 5021790248

based on the fact that my proposal uses only the 0-9 digits and not the
*,#,A-D this makes it compatible with the APRStt format.

The conversion table was designed in a way that the conversion from the
number to ascii will be very easy (even for 8-bit microcontrollers) and
will not require usage of memory lookup tables.

Below is a sample code (in basic style) that will convert the 3-digit
number into the Grid Square letter characters (e.g. for i=502 then Chr(C1)
becomes "K" and Chr(C2) becomes "M")


'example I=536 will print "NQ"

Dim I, X, CO1, CO2, C1, C2 As Integer
I = 536
If (I >= 100 And I < 340) Then
    CO1 = 10: CO2 = 65
ElseIf (I >= 400 And I < 640) Then
    CO1 = 40: CO2 = 75
ElseIf (I >= 700 And I < 940) Then
    CO1 = 70: CO2 = 85
End If
X = Int(I / 10)
C1 = 65 + X - CO1
If C1 < 65 Or C1 > 88 Then End 'ERROR i is outside limits
C2 = I - X * 10 + CO2
If C2 < 65 Or C2 > 88 Then End 'ERROR i is outside limits
MsgBox Chr(C1) & Chr(C2)


In the above sample code the C1 and C2 are integers that contain the ASCII
value of the 2 characters..... This proposal is not only for the satellite
app but for the APRStt in general.



P.S. The limit of 40KB in aprssig list....really sucks! i tried 3 times to
send the same email until it fits in limits. SORRY in case you received
multiple times the same message (e.g. amsat-bb)


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