WA8LMF Mirror of WB4APR Website - 21 July 2008 Using TH-D7 manual Positions

Rapid Manual Positioning without GPS

Using the TH-D7 to manually enter positions

During a local event(see page) over 5 square miles with many fixed sites of interest, we had over 10 users with TH-D7 APRS HT's. But because the event was grueling and dirty and physical, we did not want to risk having GPS's and their wires and cables encumbering the participants. Thus we devised two schemes to allow them to rapidly report their position at any of the numbered points in the event.

GRID METHOD: Two methods were used. First, we prepared a printed map with a grid overlay. The users could easily see their coordinates and usually only enter the least-significant two digits of LAT/LONG to locate themselves anywhere on the map as shown below:

TABLE METHOD: This second method can be used to place a station (or object) in the vicinity of any of up to 999 pre-tabled positions, with only the simple entry of a 3 digit number. We did this by declaring the area of N40,00 and W40,00 out in the middle of the Atlantic Ocean as special and then using the hundredths digits to allow entry of the pre-identified locations. Typically, we use the first digit as a "table" selection and then the other two digits are the selection in that table. Many events have so few points, that a table of 0, and then just 2 digits can be used. For example, using the POS key on the D7 radio and entering this location would place the user in the vicinity of location number 23:
N40 00.00 <== the .00 indicates table 0 and 0 ambiguity
W40 00.23 <== the .23 here indicates location 23 in table 0

See the POINTS.TXT file which details this system

POINTS.TBL File: The locations of all the points to be used is trivial to generate. Simply using APRSdos, move the cursor around the map and use the INPUT-ADD command to create an object at that location. Then save this as a .HST history file. Then simply edit in the 3 digit number for each object in the file and save it as a POINTS.TBL file and you are done.
See the POINTS.TBL file which is an example POINT file.

To all observers of the result, they can see no distinction between the positions of stations that used GPS, or the GRID method, or the TABLE method. All positions are valid and useful. Though typically, the manual methods should include a degree of ambiguity so that only their presence in the vicinity of the position is conveyed to the viewer. .

The Naval Academy is a registered user of APRS and WinAPRS. The purpose of this web page is to show several applications currently in use at this site and should not be considered as an advertisement or an endorsement of any commercial product.

WA8LMF Mirror of WB4APR Website - 21 July 2008