MODES OF OPERATION - APRS
APRS OVERLAY FORMAT

Updated 21 May 2011, 0200 UTC

What are Overlays?

Overlay files allow you to show specific information about specific objects on your APRS map which are not transmitted over the air to other stations.

How to use overlay files in APRSIS32
How to use overlay files in UI-VIEW32
How to use overlay files in WinAPRS
How to use overlay files in XASTIR


The format is described in the PROTOCOL.TXT and APRS101.PDF

From the UI-View Manual (UI-VIEW32V203MANUAL.pdf) Quote
The format of an overlay file is very simple. The first line is a description, subsequent lines are location lines or status text lines. Location lines consist of up to nine characters for a callsign/identifier, followed by a '!', followed by a position beacon. Status text lines consist of a callsign/identifier, a '>' , and some status text. NOTE - UI-View32 overlay files are not fully compatible with APRS overlay files, because APRS doesn't support the status text lines. However, if you create overlay files for UI-View32 and include status text, anyone wanting to use them with APRS can easily remove the status text lines.
UnQuote

How to create your own Overlay File

Create the overlay file using an ASCII text editor such as Notepad.
Notepad is great for creating short overlay files but for large files such as creating overlay files for the IRLP Nodes, I have a spreadsheet that reads in the raw data , lets me check for errors in the data manually and then when I'm happy with the raw data, the spreadsheet then creates the files for WinAPRS, UI-View, and XASTIR for me.

Overlay files are one line per object except for UI-View and APRSIS32.
With UI-View and APRSISCE you can have a two lines to convey more information.

Included with the overlay files I also add a text readme file listing the overlay files, explaining where the files need to be located, and any other information that the APRS operator should be aware of before using the file. XASTAIR users must turn OFF Object/Item transmit before using an ovelay otherwise all the objects in the overlay get transmitted out over the APRS network!

Format for a one line overlay file for WinAPRS, UI-View, APRSIS32

* 144 MHZ IRLP Nodes Callsign overlay for APRS
* irlp.net node data: 08/12/2008
* This file created using irlpnodelist-aprs.xls by CJ Chapman, VA3KGB
VE7RHS!4916.19N/12315.00WnNode 1000,145.270,T100.0
VE7ISC!4913.64N/12358.45WnNode 1003,146.640(-600)
VE7VIC!4825.80N/12335.99WnNode 1030,146.840(-600),T100.00
VE7BYN!5049.52N/11859.48WnNode 1041,147.570
VE7KJA!5035.03N/12705.61WnNode 1064,146.445

The Asterisk (*) denotes that this is a comment and is ignored by the APRS program
The APRS protocol calls for the first line to be a comment.
I usually add comment lines to identify what the overlay file is used for, the date the file was created, and the spreadsheet or source data that was used to generate the file.
Each line is a separate Object.

The format using one line as an example is:

VE7RHS!4916.19N/12315.00WnNode 1000,145.270,T100.0


VE7RHS - The callsign (or identifying label) should be 9 characters or less.

! - The (!) tells the system not to send the object out as an APRS message.

4916.19N - The Lat is in degrees and decimal minutes format (49°16.19' N) stripping out the degree and minute characters and is to 2 decimal places.

/ - In between the Lat and Long is the symbol which identifies which symbol table to use for the icon to be displayed.

12315.00W - The Long is in degrees and decimal minutes format (123°15.00' E) stripping out the degree and minute characters and is to 2 decimal places.

n
- The Icon is from APRS Icon tables and uses the aplha/numeric character in conjucntion with the Primary/Alt table symbol to identify the graphical icon to display.

Node 1000,145.270,T100.0 - The comment field should be kept short, and in this example indicates the IRLP NODE ID, the Frequency and Tone required. Commas (,) are used to separate items within the comment. In the comment field using a spreadsheet to build the overlay files there will be comma with a space between them indicating that the source file had no information for that portion of the comment. If building the file by hand you can delete the space(s) and extra comma(s).

Format for a two line overlay file for UI-View and APRSIS32

* 144 MHZ IRLP Nodes Callsigns with Cities overlay for UI-View or APRSIS32
* irlp.net node data: 08/12/2008
* This file created using irlpnodelist-aprs.xls by CJ Chapman, VA3KGB
VE7RHS!4916.19N/12315.00WnNode 1000,145.270,T100.0
VE7RHS> IRLP Node: 1000, Vancouver, BC, Canada
VE7ISC!4913.64N/12358.45WnNode 1003,146.640(-600)
VE7ISC> IRLP Node: 1003, Nanaimo, BC, Canada
VE7VIC!4825.80N/12335.99WnNode 1030,146.840(-600),T100.00
VE7VIC> IRLP Node: 1030, Victoria, BC, Canada

The format for the first line is as per the one line format above.
The format for the second line as an example is:
VE7RHS!4916.19N/12315.00WnNode 1000,145.270,T100.0
VE7RHS> IRLP Node: 1000, Vancouver, BC, Canada


VE7RHS - Callsign will be exactly the same as the first line
> - Comment identifier
IRLP Node: 1000, Vancouver, BC, Canada - Comment field again is short and in this example indicated that it is IRLP Node 1000 located in Vancouver BC Canada. (Commas (,) separate the items in the comment.


Format for a one line overlay file for XASTIR
# 144 MHZ IRLP Node Callsign overlay for Xastir
# irlp.net node data: 08/12/2008
# This file created using irlpnodelist-aprs.xls by CJ Chapman, VA3KGB
# NOTE: These APRS Items will become part of your locally owned/transmitted
# objects. Turn Off Object/Item transmit before bringing this file in.
NOCALL>APRS:)VE7RHS !4916.19N/12315Wn Node 1000, 145.270,T100.0, Vancouver, BC, Canada
NOCALL>APRS:)VE7ISC !4913.64N/12358.45Wn Node 1003, 146.640(-600), Nanaimo, BC, Canada
NOCALL>APRS:)VE7VIC !4825.8N/12335.99Wn Node 1030, 146.840(-600),T100.00, Victoria, BC, Canada
NOCALL>APRS:)VE7BYN !5049.52N/11859.48Wn Node 1041, 147.570, Sicamous, BC, Canada

Xastir uses a slightly different formatting and is saved as a .log file.

The crosshatch (#) is used to identify comment lines to be ignored.
In XASTIR an object is Owned by callsign. For ovelay files being used locally the default NOCALL can be used.

The start of every object line will using NOCALL for example will be:
NOCALL>APRS:)

The format using one line as an example is: NOCALL>APRS:)VE7RHS !4916.19N/12315Wn Node 1000, 145.270,T100.0, Vancouver, BC, Canada


NOCALL>APRS:) - is the preamble for each object.

VE7RHS - Callsign field is exactly 9 (nine) characters and use spaces to pad the callsign to 9 characters.

! - The (!) tells the system normally not to send the object out as an APRS message but since the overlay file is stored as .log file Transmit Objects/Items must be turned off manually.

4916.19N - The Lat is in degrees and decimal minutes format (49°16.19' N) stripping out the degree and minute characters and is to 2 decimal places.

/ - In between the Lat and Long is the symbol which identifies which symbol table to use for the icon to be displayed.

12315.00W - The Long is in degrees and decimal minutes format (123°15.00' E) stripping out the degree and minute characters and is to 2 decimal places.

n
- The Icon is from APRS Icon tables and uses the aplha/numeric character in conjucntion with the Primary/Alt table symbol to identify the graphical icon to display.

Space - A space character is required beyween the Icon and the comments
Node 1000, 145.270,T100.0, Vancouver, BC, Canada - Comments in this example The IRLP Node ID, Frequecy, Tone, and location



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