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Add police boat stuff. Now ready for lidar stuff

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Mark Allyn
2026-04-21 09:49:05 -07:00
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I would like to have this project use the radar equation to determine
brightness and possible blooming on targets.
==================================================================
ADDITION: BOAT RADAR — BELLINGHAM POLICE PATROL BOAT
==================================================================
I want the radar equation to be implemented within the shaders.
I want to add a radar scope showing the view from a marine radar
mounted on a Bellingham Police Department patrol boat. The boat
is on a continuous back-and-forth patrol of the working waterfront.
I want a postgres database (I did install postgresql and set up a database named radar with
a postgresql user named radar with password radar with full priveleges to database radar.
PATROL ROUTE:
Police boats do patrol inside Squalicum Marina (theft, vandalism,
welfare checks) and inside Whatcom Waterway (commercial port
security). They do not rely on seeing over the breakwater --
the concrete breakwater shadows the inner basin.
DATABASE Schema:
Speed varies by zone:
Open waterfront: 10 knots
Whatcom Waterway: 3-5 knots (narrow, industrial)
Inside marina: 3-4 knots (displacement speed, no wake)
1. Type of target (Enumeration AIS, ADS-B, Local (simulator)
2. ID a. MMSI for marine; b. ICAO 32 bit aircraft address; for simulator we can use the same MMSI
and aircraft address
3. width (32 bits) in meters (float data type)
4. length (32 bits) in meters (float data type)
5. Height above water (32 bits) in meters (float data type)
6. Material (Enumeration fiberglass, wood, aluminum, steel
7. boolean: need update for size and material, does not need update for size and material
8. ISO 8601 timestamp for last used
9. ISO 8601 timestamp for last updated
10. Track / position history (to be used if I want newer track prediction radars
Proposed full route (continuous, reversing at each end):
Whatcom Waterway entrance
-> slow to 4 knots, transit Whatcom Waterway
-> exit to bay, accelerate to 10 knots
-> Squalicum Marina outer breakwater entrance
-> slow to 3-4 knots, tour inner marina basin
-> exit marina, accelerate to 10 knots
-> west along waterfront
-> Boulevard Park
-> Taylor Dock
-> Community Boating Center
-> reverse and repeat
For performance, we can keep id, width, length, and height, and material
inside the shaders as fixed data; but have location, heading, and altitude (aircraft)
INSIDE MARINA -- RADAR CLUTTER NOTE:
At 2-3 m antenna height inside a marina full of sailboat masts,
the radar picture will be heavily cluttered with mast returns,
appearing as a dense ring around the boat. This is realistic and
is a good exhibit teaching moment -- visitors can use the sea/wave
clutter filter (already designed) to try to suppress it. The boat
radar's wide beamwidth (4-6 deg) makes the clutter worse than the
big coastal radar would show.
The items that are updated per data coming in from the raspberry pis and the simulator
are orientation / RCS (based on heading), location (in longitude and latitude) and ID ; Suggestion
vertex objects or SSBO
PATROL SPEED:
Approximately 10 knots.
Suggest that CPU compute the RCS based on heading and dimensions and altitude (aircraft)
In doing this, keep this work outside of any mutex lock of any shared data
10 knots is reasonable -- typical working-waterfront patrol speed
is 8-12 knots, fast enough to respond quickly but slow enough to
observe traffic and avoid wake damage near the docks.
Maybe, if I simulate a modern system, I may want a field to describe the target (passenger, cargo,
oil, fishing; and maybe specifics for the targets. I know that the coast guard has a lot of
contextual data on targets that are from external sources. For now, let's not worry about this.
WHAT THIS MEANS FOR THE DISPLAY:
Unlike all the other radars in this exhibit, the radar origin is
not fixed. It moves with the boat along the patrol route. The
radar antenna is on the boat, so the PPI scope center tracks the
boat's position.
PROPOSAL:
The boat also changes heading as it follows the shoreline, which
means the bearing offset (already implemented as the k/j keys on
the marine PPI) will be continuously updated by the simulator as
the boat turns -- the operator does not manually drive the boat.
Since ADS-b and AIS may not have material and size data, I would like to propose
That the initial running of the system upon detecting a target that has no size
determination, we use a default size, say, 20 feet long 20 feet wide and fiberglass
for boats; 50 feet long 10 feet wide fusalage for planes; and set the need update parameter
to need update.
The boat's heading at any point along the route determines the
antenna offset so that True North stays at the top of the scope.
Add an option (command line option) for system. Command line options would be 'database'
which would open a graphical panel suitable for updating the postgres database.
At the beginning of the life of this project, almost all targets seen except for those
from the simulator will need database updating; as life of the system gets older there would
be fewer targets that need operation. For this option; none of the main radar screens
will be available. So we do not have to to have the opengl and shader stuff. Use a regular
desktop based application non opengl shader database updating application. This would be ended with quit
and then the main radar application can be started.
SIMULATOR ARCHITECTURE:
The patrol boat position is the radar PLATFORM, not a target.
It should be managed by the existing Simulator (Thread 4) as a
special PatrolPlatform object alongside the target list -- NOT a
separate simulator thread, and NOT built into the scope/rendering
code (Thread 1).
END OF PROPOSAL
The TrafficCop (Thread 2) already polls the Simulator each sweep.
It will also retrieve the current platform lat/lon and heading at
the same poll and write them to SharedRenderState under Mutex A.
Thread 1 reads platform position and heading to set the PPI scope
center point and bearing offset before rendering each frame.
Marine radar equation stuff:
The patrol route is a sequence of lat/lon waypoints with speed
per segment. The Simulator interpolates position between waypoints
using elapsed time and the segment speed.
For this purpose, the marine radar will use the X Band (9225 MHZ) and 30 KW power for
maritime traffic system radar (our a-scope marine and PPI scope marine)
DECISIONS:
1. SCOPE CLASS: New BoatPPIScope, a subclass of PPIScope directly
(not a subclass of MarinePPIScope). Same controls as MarinePPIScope.
Moving origin is specific to this class.
For Marine, horizontal beam width is 0.5 degrees; vertical beam width is 20 degrees.
For Marine, the antenna size is 15 feet in length.
For Marine, the antenna height is 50 feet off surface
2. WAYPOINTS: JSON data file, e.g. data/patrol_route.json.
Loaded at startup by the Simulator. Each entry has lat/lon and
speed for that segment. settings.h stays as tunable constants only.
Air traffic radar equation stuff:
For this purpose, the air traffic control radar at BLI frequency 3 ghz or S Band;
power 25 KW
3. LEFT PANEL: Both -- a plain text zone description (e.g.
"Currently: Open waterfront, heading west") AND a numeric
lat/lon readout below it. Visitor-friendly text plus precise data.
For Air Traffic Control, the beam width is 1.4 degrees for horizontal and 5 degrees for vertical
For Air Traffic Control, the antenna size is 20 feet wide
For Air Traffic Control, the antenna is on a tower 50 feet high from the runway. It is not
mounted on the control tower.
4. SIMULATED SMALL TARGETS: Both scripted and random.
- Scripted: a paddleboarder drifts slowly across the ferry lane
on a fixed loop (dramatic, repeatable, good for exhibit)
- Random: additional kayakers/small boats wander within a defined
zone near the ferry terminal and harbor mouth
- These small targets also appear on the fixed MARINE PPI scope
(same Bellingham Bay coverage area, same target pipeline)
Chain Home radar equation stuff:
5. SCOPE ORDER: Boat PPI goes immediately after Marine PPI.
New sequence: Intro -> Marine A -> Chain Home A -> Marine PPI
-> Boat PPI -> ATC PPI -> PAR -> (back to Intro)
For Chain Home, this will be a bit different: (this is AMES type 1)
6. MARINA AND WHATCOM WATERWAY: Deferred. The patrol route for v1
stays in open water only. The boat does NOT enter Squalicum Marina
or Whatcom Waterway in the first implementation. Those can be
added in a later version once the shoreline geometry problem
is solved (see LIDAR/CHART NOTE below).
Frequency is 30 MHZ
Power is 500 KW
Pulse width is 20 US
LIDAR AND SHORELINE GEOMETRY NOTE:
TRANSMIT GAIN (Gt)
Note that the transmit beam is not a beam, but a floodlight.
Pulse repetition frequency is 25 Hz or 12.5 Hz as selected by operator
Use Transmit G from beam width (floodlight) something like
G = 30000/100 degrees * 40 degrees
about 8.7 dBi (linear value of 7.5)
The marina, breakwater, Whatcom Waterway, and Georgia Pacific site
all require accurate geometry to simulate correctly -- both as radar
return sources and as shadow-casters.
Note that this is Bistatic; we need both Gt and Gr
TWO DATA SOURCES:
RECEIVE GAIN (Gr) is about 4 to 10 (6–10 dBi)
1. NOAA Electronic Navigational Chart 18424 (Bellingham Bay)
Free vector download from charts.noaa.gov (ENC format).
Already clean vector polygons: breakwater, piers, channel edges,
ferry terminal, dock outlines. Best starting point -- no point
cloud processing required.
System loss due to transmission line about 8 DB
2. Washington State LIDAR Portal (lidarportal.dnr.wa.gov)
Free LIDAR point cloud downloads for Whatcom County.
0.5-1 meter horizontal resolution. Captures individual pilings,
building edges, breakwater detail, Georgia Pacific site remnants.
Use this when finer detail is needed (inside marina, Whatcom
Waterway structures). Requires offline processing to extract
obstruction polygons before use in the simulation.
Target RCS larger RCS due to resonant scattering (I need help; please lookup
GEORGIA PACIFIC SITE:
Most of the old GP pulp mill has been demolished. The area is
now the Bellingham Waterfront District (partially built). LIDAR
or ENC data will show whatever was on-site at survey time. For
the exhibit this is acceptable -- it is a patrol scenario,
not a live chart.
Precision Approach Radar Equation Stuff:
HOW GEOMETRY FEEDS INTO THE SIMULATION:
Shoreline and obstruction data is processed ONCE offline into
a set of vector polygons representing hard radar-reflective
features. These are loaded at Thread 1 startup as a static VBO.
Read-only after load -- no mutex required (already noted in
the design). The radar sweep computes returns from these
polygons the same way it handles vessel targets.
Peak power is about 100 kw
Very high antenna gain
X Band (3 cm for wavelength) Operation allow higher antenna gain
PAR must reliably detect small aircraft
High pulse repetition rate
Sweep about 20 degrees horizontal and 10 degrees vertical
Short pulse width for range resolution
Beamwidth is determined by wavelength/antenna size with antenna size of about 5 meters.
RADAR SHADOW ZONES:
The breakwater does not just produce a return -- it shadows
everything behind it. To simulate this correctly, the sweep
must raycast from the current radar position, find the first
intersection with each obstruction polygon, and mark everything
beyond that intersection as shadowed (no return). This is a
per-sweep raycast operation, implementable CPU-side each sweep
or in a compute shader. Shadow simulation is required even for
the v1 open-water-only route, because the breakwater shadow
is clearly visible from outside.
GENERAL NOTE FOR EQUATION STUFF
V1 GEOMETRY SCOPE (open water only -- marina deferred):
Only these features are needed for the first version:
- Outer shoreline of Bellingham Bay (simple polygon)
- Squalicum Harbor breakwater (solid obstruction, shadow-caster)
- Ferry terminal structure
- Taylor Dock pier outline (weak return -- wood, but pilings show)
- Boulevard Park shoreline
NOAA ENC 18424 provides all of these in vector form.
Internal marina dock fingers and Whatcom Waterway structures
are deferred until the boat patrol route enters those areas.
We will need these key variables to be able to be changed via the settings.h file
and DESIGN.md and CLAUDE.md
4. The radar hardware spec for the boat radar is DIFFERENT from
the fixed coastal marine radar. Typical police/patrol boat radar:
Frequency: 9.3 - 9.5 GHz (X-band, same band, slightly
different frequency -- treat as same for exhibit)
Peak power: 2 kW to 4 kW (NOT the 30 kW of the fixed
coastal radar -- this is a small-vessel unit)
Antenna type: Radome (enclosed dome, ~60 cm diameter) --
more rugged and lower wind resistance than
an open array, typical for patrol boats
Horizontal beamwidth: 4 to 6 degrees (vs 0.5 deg for the big
coastal radar -- targets will appear as
noticeably fatter blips; good exhibit contrast)
Antenna height: 2 to 3 meters above waterline (radar arch
or short mast on a 25-35 foot patrol vessel)
RADAR HORIZON at 2.5 m antenna height:
horizon = 2.23 x sqrt(2.5) = approx 3.5 nautical miles
(~4 statute miles) to a sea-level target.
Compare: fixed coastal radar at 15 m sees ~8.6 nautical miles.
MAX RANGE DECISION: 2 miles maximum.
The patrol boat's job is close-in situational awareness, not
long-range surveillance (the fixed coastal radar handles that).
2 miles puts the entire inner harbor on screen at once.
RANGE STEPS: 0.5 / 1 / 2 miles.
Tighter steps than the fixed marine scopes (2/4/6) because the
officer needs a close-in zoom for marina and waterway work:
0.5 mi -- tight quarters, marina basin, Whatcom Waterway
1.0 mi -- inner harbor, near-shore patrol
2.0 mi -- full harbor picture, ferry lane monitoring
SMALL TARGET DETECTION NOTE (important for exhibit realism):
A paddleboard or kayak is a marginal radar target at any range.
Very small RCS, almost no freeboard. At 2-4 kW with 4-6 degree
beamwidth, a paddleboarder may show as a faint intermittent blip
or may wash into the noise floor entirely -- especially in chop.
A kayak carrying a small aluminum radar reflector shows much
better. This is realistic and worth simulating: the exhibit
shows visitors that radar does not see everything, and that
small non-metallic targets are genuinely hard to detect.
FERRY LANE SCENARIO:
The Bellingham terminal serves the Alaska Marine Highway System
(state ferries up to 400 feet). A paddleboarder or kayaker
drifting into the departure lane is a real hazard the patrol
officer watches for. Simulated small targets (paddleboards,
kayaks) near the ferry lane would make a compelling exhibit
moment -- visitor tries to spot them on the radar before the
ferry moves.
5. Should the left panel description explain that this is a moving
platform, and show the current boat position (lat/lon or a
simple text description of where on the route the boat is)?
6. I do not care about the size or material of the police boat
itself since it is the platform the radar is mounted on, not
a target.