[Xastir] Here's a puzzle: Map metadata in map border?

[William McKeehan]

I'll take a stab at it.

The code that you are looking at is only called when not in UTM mode. Have a
look at draw_grid()


-- 
William McKeehan
KI4HDU
http://mckeehan.homeip.net


On Mon, July 7, 2008 6:16 pm, Tom Russo wrote:
> Ok, so I usually run my station with coordinate system UTM, since that's
> what I like to use most often.  But sometimes I need to switch to Lat/Lon
> in DMS or DDMM.MM format when working with some groups who need things that
> way.
>
> I just this moment noticed something truly bizarre about how Xastir displays
> the screen extents in its map border (enabled with Map->Enable Map Border and
> Enable Map Grid).
>
> With UTM, the extents appear to be displayed correctly, but with lat/lon
> the extents displayed are both (roughly) the coordinates of the lower right
> corner.  See for example these two screen shots, which differ only by the
> setting of coordinate system:
>  http://www.swcp.com/~russo/imgs/utm.jpg
>  http://www.swcp.com/~russo/imgs/ll.jpg
>
> Note that the lat/lon coordinates displayed for upper left corner are the
> same as the lat/lon coordinates for the lower right.  That's just plain
> wrong.
>
> What's puzzling, though, is the code for this, in maps.c:
>
>
>         // Put metadata in top border.
>         // find location of upper left corner of map, convert to Lat/Long
>         convert_lon_l2s(xx2, grid_label1, sizeof(grid_label1),
> coordinate_format
> );
>         convert_lat_l2s(yy2, grid_label2, sizeof(grid_label2),
> coordinate_format
> );
>         xastir_snprintf(grid_label,
>             sizeof(grid_label),
>             "%s %s",
>             grid_label1,grid_label2);
>         // find location of lower right corner of map, convert to Lat/Long
>         convert_lon_l2s(xx2, grid_label1, sizeof(grid_label1),
> coordinate_format
> );
>         convert_lat_l2s(yy2, grid_label2, sizeof(grid_label2),
> coordinate_format
> );
>
> Note that both sets of "convert_lon_l2s" are working on the same pair of
> coordinates, xx2 and yy2, with nothing intervening to change them.  In earlier
> code we have:
>
>     // Find xastir coordinates of upper left and lower right corners.
>     xx = NW_corner_longitude  + (border_width * scale_x);
>     yy = NW_corner_latitude   + (border_width * scale_y);
>     xx2 = NW_corner_longitude  + ((screen_width - border_width) * scale_x);
>     yy2 = NW_corner_latitude   + ((screen_height - border_width) * scale_y);
>
>
> It *looks* like the two pairs of convert_lon_l2s should be working on
> xx,yy and xx2,yy2 instead, but that doesn't explain at all how the UTM version
> of this code actually produces a banner at the top that is correct.  They
> should all be wrong.
>
> Can anyone spot what's going on here?
>
> --
> Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
> Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM
>  "It's so simple to be wise: just think of something stupid to say and
>   then don't say it."  --- Sam Levinson
>
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