Two faults reported from in front of the window, both of them the map saying
something confidently and wrongly.
Tiles that did not arrive. Resizing the window does not refetch the map: the
window deliberately fetches more world than it shows, so a resize still fits
inside what is in hand and gets stretched to the new size. It refetches when
the view leaves that box, which is what a new station does -- and that fetch
asks a volunteer-funded server for a hundred tiles that have never been on
this disk, all at once, at the sharper zoom the bigger window chose. Some of
them are refused.
What the window did with a refusal was draw it. A tile that never arrived
leaves its square of the canvas black, and black is not a neutral colour
here: the brightness is inverted on the way in, because a printed map is ink
on paper and this picture is the other way round. So the darkest possible
square came out as the brightest thing on the picture, a glowing rectangle
where the map should be. Measured on a reproduction, one missing tile in
eighteen put thirteen thousand pixels at full brightness -- and dragged the
floor of the map's own contrast down to black with it, so thirteen thousand
four hundred and ninety pixels changed in all: the whole map was redrawn
dimmer to make room for a square that was not there. Then it was kept, cached
under the view it was fetched for, until the view moved again.
So the missing squares are asked for again at once, and only those, the rest
being on the disk by then; what is still missing is drawn as bare ground and
left out of the reckoning when the darkest and brightest of the map are worked
out, which puts the same reproduction at two pixels changed rather than
thirteen thousand four hundred and ninety, a hairline where a cell is averaged
over part of a tile and part of nothing; and the map is kept as provisional
rather than as the last word, asked for again half a minute later, four
attempts in all, each retrying its own misses once.
Found while measuring that: the politeness pause between requests was being
paid on every tile, including the ones read straight back off the disk. Two
hundred and twenty tiles at an eighth of a second is twenty-six seconds of
sleeping to redraw a view that was entirely cached, and it would have made
asking again for three missing squares cost the wait for the two hundred that
were not. The constant's own comment already said it should only be paid on a
tile that was not already there. Now it is.
The APRS map's units. Setting imperial changed nothing at all about the
window: the unit it measures in was hardcoded to kilometres, and that one
value drives the ring labels and the scale along the bottom; and --radius was
always read as kilometres, so the rings were not merely mislabelled, they were
at the wrong distance from the flag. A ring is what a distance gets judged
against by eye, and one labelled in a unit it was not drawn in is a wrong
answer given confidently. The aircraft side has done this properly all along
-- a radius read in whatever unit the speeds are in, and no unit suffix on the
setting because the suffix belongs to the other setting -- so this now mirrors
it exactly. At --radius 100 in imperial the outermost ring stands seventy-
five statute miles from the flag and says so, where it used to stand seventy-
five kilometres and say kilometres whatever you had asked for.
Twenty-one new tests against sixteen deliberately broken builds. One
survived, and removing what it broke was the right answer rather than
strengthening a test: a check that the remembered request still matched the
map in hand could not be made to fail, a request for a different view being
taken up only after the slot it guards is already full. The tests do not
trust the drawing to mark its own homework -- the one that matters walks north
from the flag by each ring's radius and measures the great-circle distance
with a haversine written in the test, then checks that against the printed
label. Full suite 2685 passed. Built as 2026-09-21_03.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
Three things wrong with the window, all reported from the chair in front of
it, and all three the same kind of wrong: the map had been handed the aircraft
map's furniture and nobody had checked which bits of it were about aircraft.
The empty screen said "listening on 1090 MHz" and went on to explain that an
aeroplane is placed once an even and an odd position frame have both arrived.
That sentence was true of the window it was written for and false of every
word in this one. What has to arrive before a mark can be placed is a fact
about the signal rather than about the window, so it is now a thing the window
is told: an aeroplane still says what an aeroplane needs, a station says that
most of them mention where they are every few minutes, and left unsaid the
words follow whatever channel the window was given rather than naming 1090
from memory.
There was no red flag. The flag is drawn where the receiver was actually told
it is, and this section has its own --at that had never been filled in -- but
the aircraft section's had, by the same person, about the same aerial, on the
same roof. One aerial does not move because the receiver was pointed at a
different band, so a position set on either side now serves both, this
section's own winning where it has one because two receivers in two places is
exactly what a separate setting is for. It says out loud which it used, an
inherited position being a convenience right up until somebody has moved and
changed only one of them. The flag, the range rings and every distance and
bearing all come from the same answer, so all four arrive together.
The boxes drew a station's position and never wrote it down. A mark on a map
shows where something is; the figures are what gets read out over the air,
copied into a log or typed into something else. They are also the only place
the doubt shows: a station that blanks its minutes is somewhere inside a
two-degree square, the diamond is as definite there as it is anywhere, and
only "49.0000N 72.0000W +/-340 km" admits it.
Twelve new tests against six deliberately broken builds. One survived, and
it is the one that matters: with the drawing code changed back to print
aeroplanes at 1090 MHz, every test still passed, because they all read the
sentence off the object and none of them read the pixels. That is the
reported fault exactly -- a window that holds one sentence and paints another
-- and the suite could not see it. It reads the picture now, cropped below
the header, whose ticking clock has made a test pass for the wrong reason
twice already this session. Full suite 2664 passed. Built as
2026-09-21_02.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
The same window the aircraft use, given marks that are not aeroplanes. It
already knew how to fetch a map, place an information box where it covers
nothing, glide it when its owner moves, draw range rings, put a flag where
the aerial stands and a scale along the bottom -- and not one of those has
anything to do with aviation. What it did not know is that a mark might not
fade, might not point anywhere, and might be coloured by what it is rather
than by how high it is. Those are three hooks rather than a second window,
and the aircraft map is untouched: every one of them defaults to exactly what
an aeroplane does.
Nothing fades, which is the difference asked for and the right one. An
aeroplane that stops transmitting has flown out of range, and drawing it an
hour later where it was would be drawing something that is certainly not
there. A fixed amateur station that stops transmitting is still exactly
where it was -- it beacons every half hour, and the gaps are silence rather
than absence. So the picture accumulates and an evening of listening fills a
map. Marks are ordered most-recently-heard first, because that is the order
the boxes are laid out in and an accumulating map has more marks on it than
it has room for boxes.
Marks are drawn by what they are: something moving as a body with a stalk
pointing where it is going, and anything fixed as a diamond, which is the one
shape on the picture with no front -- a house that beacons twice an hour is a
place, and a triangle would have it pointing north for no reason. Colours
come off the altitude ramp, not because a station has an altitude but because
that ramp is the one set of colours all five themes define: warm to cold on
the default map, dim to bright on the phosphor ones, so a digipeater stays
distinguishable from a car everywhere without a colour being named here.
The box says what the station is, how far off and in which bearing, what it
is doing if it is moving, its altitude, its weather, its status, the
digipeaters it came through, how many packets and how many of those arrived
directly, and how strongly. The heading prints the callsign once: an
aeroplane has two names and the heading was built for that.
Reachable both ways, as everything here is -- --window on the command line, w
in the menu -- with the same eight map settings the aircraft side has.
Forty new tests against nine deliberately broken builds. Two of them survived
the first attempt, and both for the same reason: they asked whether the
rendered frames differed rather than whether the symbol did, and the strip
along the top carries a running clock, so two frames taken a millisecond apart
differ by a few hundred pixels whatever is on the map. They now crop to the
mark. That is the second time this session that a ticking header has made a
test pass for the wrong reason. Full suite 2652 passed. Built as
2026-09-21_01.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
The region was in the menu, in the receiver group, between the sample rate and
the invented channel. That is the wrong place for it. It is the setting that
decides whether anything is heard at all, and being on the wrong one sounds
exactly like having no aerial, so it does not belong a level down among the
things that make a working receiver work slightly better.
It is now on the front page of the APRS menu, named as well as numbered, and
so is the Listen line: "north-america 144.39 MHz" rather than "144.39 MHz",
because the number alone does not say whether it is the right one and the name
alone does not say what will be tuned. A channel that is no region's says so
rather than claiming one.
The region and the frequency are separate settings -- somebody may want a
local packet network on neither -- which means they can be made to disagree.
Every place that chooses a region now goes through one function, so they
cannot.
And there is a search. `bandsaunter aprs --find-channel`, or f in the menu,
listens on each region's channel in turn and prints what was on each, then
offers to use the busiest. This answers the one question about APRS that
cannot be answered on any single frequency, because the answer *is* a
frequency: somebody who has just plugged a dongle in cannot tell a wrong
channel from a dead aerial, and that is worth a minute of listening rather
than an evening of doubt.
What it does not do is claim more than it found. A quiet channel is not proof
of an empty one -- a fixed station beacons every half hour -- so what it finds
is traffic, and when every channel comes back silent it says that this is not
the same as an empty band and points at the aerial instead.
The invented channel now honours tuning, and only carries its stations on its
own frequency. Without that the search would pass on a simulated band having
never searched anything, which is the kind of test that is worse than none.
Sixteen new tests against six deliberately broken builds. The three that
searched a whole simulated band were doing the same expensive thing three
times over and now build their results directly, leaving one real end-to-end
search; that file went from nine and a half minutes to two. Full suite 2612
passed. Built as 2026-09-20_03.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
A third section, alongside the aircraft and the weather sensors, and for the
same reason as both: a scan stops on a signal, records it and moves on, while
APRS is a two-second transmission every few minutes from a hundred stations
sharing one frequency. A sweep catches whichever happened to key up as it
passed. `bandsaunter aprs` parks on the channel and catches all of them;
`bandsaunter packets` reads a log back.
Four layers, three of them new.
The link layer was already here, opportunistically, in the generic decoder --
a correlator, NRZI, HDLC and a checksum, run on whatever a scan happened to
record. It is now a receiver. What had to change is the state that survives
a block boundary: the tail of the audio so the correlators see no edge, the
phase of the sampling loop so a bit is not lost where one block meets the
next, the tone the line was last at, and the bits themselves. A packet is
most of a second and a block is about one, so frames straddling the boundary
are not an edge case, they are most of them.
Above that, the APRS information field, which is not one format but about
twenty, chosen by the first character and accreted over thirty years.
Positions uncompressed and compressed; Mic-E, which every Kenwood and Yaesu
mobile sends and which hides the latitude inside the destination callsign
because in 1995 those six bytes were carrying the word "APRS" and nothing
else; weather with a position and without; messages, acknowledgements,
rejections and bulletins; objects and items; status; telemetry; third-party
traffic, credited to whoever originally sent it rather than to the gateway.
Course and speed, altitude, power and antenna height, range and the precision
extension, all of which ride in the comment. Every one has a writer beside
its reader, so a packet goes in and the same packet comes out.
Above that the section: a registry of who is out there and what each last
said of each kind, distances and bearings from --at, a log keeping the whole
frame under whatever was made of it, a spreadsheet, a map, and a channel full
of stations that are not there for --simulate.
One rule is worth naming because it is the difference between a decoder and a
liar. A packet whose format does not match what its first character promised
comes back as unparsed with its text intact. Thirteen characters of a
*malformed* uncompressed position are perfectly good base-91, so trying one
format and falling back to the other does not fail on a bad packet -- it
succeeds, as a confident and completely different place, usually a thousand
miles away. The specification makes the two unambiguous, a leading digit
always meaning uncompressed, and the rule is read rather than guessed at.
Two faults found by building it, both by measurement rather than by reading
the code again. The framer handed back frames it had already reported,
because it trimmed its buffer to before them rather than after -- every packet
counted twice, for ever, which only shows up once the same signal is read
across more than one block. And the invented channel truncated a
transmission at the end of the block it began in rather than carrying the
remainder over, which was invisible for as long as the simulated clock
advanced in exact seconds and put every transmission at a block boundary; the
moment it was paced against a real clock, nothing decoded at all.
204 new tests against seven deliberately broken builds, one of which survived
until a test was written for the case it actually breaks. Full suite 2597
passed. Built as 2026-09-20_02.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
The Dust Council