[aprssig] proposal for APRStt grid loc. Σχετ: 60 Grid Square............

George Vastianos gvastianos at yahoo.gr
Sat Feb 14 06:33:11 CST 2015


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.
 
73

sv8gxc
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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